globe_index.c

#include "readsb.h"
#define STATE_SAVE_MAGIC (0x7ba09e63757314ceULL)
#define STATE_SAVE_MAGIC_END (STATE_SAVE_MAGIC + 1)
#define LZO_MAGIC (0xf7413cc6eaf227dbULL)

static const char zstd_magic[] = { 0x28, 0xb5, 0x2f, 0xfd };

static void mark_legs(traceBuffer tb, struct aircraft *a, int start, int recent);
static void traceCleanupNoUnlink(struct aircraft *a);
static traceBuffer reassembleTrace(struct aircraft *a, int numPoints, int64_t after_timestamp, threadpool_buffer_t *buffer);
static void resizeTraceCurrent(struct aircraft *a, int64_t now);

void init_globe_index() {
    struct tile *s_tiles = Modes.json_globe_special_tiles = cmalloc(GLOBE_SPECIAL_INDEX * sizeof(struct tile));
    memset(s_tiles, 0, GLOBE_SPECIAL_INDEX * sizeof(struct tile));
    int count = 0;

    // Arctic
    s_tiles[count++] = (struct tile) {
        60, -126,
        90, 0
    };
    s_tiles[count++] = (struct tile) {
        60, 0,
        90, 150
    };

    // Alaska and Chukotka
    s_tiles[count++] = (struct tile) {
        51, 150,
        90, -126
    };
    // North Pacific
    s_tiles[count++] = (struct tile) {
        9, 150,
        51, -126
    };

    // Northern Canada
    s_tiles[count++] = (struct tile) {
        51, -126,
        60, -69
    };

    // Northwest USA
    s_tiles[count++] = (struct tile) {
        45, -120,
        51, -114
    };
    s_tiles[count++] = (struct tile) {
        45, -114,
        51, -102
    };
    s_tiles[count++] = (struct tile) {
        45, -102,
        51, -90
    };
    // Eastern Canada
    s_tiles[count++] = (struct tile) {
        45, -90,
        51, -75
    };

    s_tiles[count++] = (struct tile) {
        45, -75,
        51, -69
    };
    // Balkan
    s_tiles[count++] = (struct tile) {
        42, 12,
        48, 18
    };
    s_tiles[count++] = (struct tile) {
        42, 18,
        48, 24
    };
    // Poland
    s_tiles[count++] = (struct tile) {
        48, 18,
        54, 24
    };
    // Sweden
    s_tiles[count++] = (struct tile) {
        54, 12,
        60, 24
    };
    // Denmark
    s_tiles[count++] = (struct tile) {
        54, 3,
        60, 12
    };
    // Northern UK
    s_tiles[count++] = (struct tile) {
        54, -9,
        60, 3
    };

    // Golfo de Vizcaya / Bay of Biscay
    s_tiles[count++] = (struct tile) {
        42, -9,
        48, 0
    };

    // West Russia
    s_tiles[count++] = (struct tile) {
        42, 24,
        51, 51
    };
    s_tiles[count++] = (struct tile) {
        51, 24,
        60, 51
    };

    // Central Russia
    s_tiles[count++] = (struct tile) {
        30, 51,
        60, 90
    };

    // East Russia
    s_tiles[count++] = (struct tile) {
        30, 90,
        60, 120
    };
    // Koreas and Japan and some Russia
    s_tiles[count++] = (struct tile) {
        30, 120,
        39, 129
    };
    s_tiles[count++] = (struct tile) {
        30, 129,
        39, 138
    };
    s_tiles[count++] = (struct tile) {
        30, 138,
        39, 150
    };
    s_tiles[count++] = (struct tile) {
        39, 120,
        60, 150
    };
    // Vietnam
    s_tiles[count++] = (struct tile) {
        9, 90,
        21, 111
    };

    // South China
    s_tiles[count++] = (struct tile) {
        21, 90,
        30, 111
    };

    // South China and ICAO special use
    s_tiles[count++] = (struct tile) {
        9, 111,
        24, 129
    };
    s_tiles[count++] = (struct tile) {
        24, 111,
        30, 120
    };
    s_tiles[count++] = (struct tile) {
        24, 120,
        30, 129
    };

    // mostly pacific south of Japan
    s_tiles[count++] = (struct tile) {
        9, 129,
        30, 150
    };


    // Persian Gulf / Arabian Sea
    s_tiles[count++] = (struct tile) {
        9, 51,
        30, 69
    };

    // India
    s_tiles[count++] = (struct tile) {
        9, 69,
        30, 90
    };

    // South Atlantic / South Africa
    s_tiles[count++] = (struct tile) {
        -90, -30,
        9, 51
    };
    //Indian Ocean
    s_tiles[count++] = (struct tile) {
        -90, 51,
        9, 111
    };

    // Australia
    s_tiles[count++] = (struct tile) {
        -90, 111,
        -18, 160
    };
    s_tiles[count++] = (struct tile) {
        -18, 111,
        9, 160
    };

    // South Pacific and NZ
    s_tiles[count++] = (struct tile) {
        -90, 160,
        -42, -90
    };
    s_tiles[count++] = (struct tile) {
        -42, 160,
        9, -90
    };

    // North South America
    s_tiles[count++] = (struct tile) {
        -9, -90,
        9, -42
    };

    // South South America
    // west
    s_tiles[count++] = (struct tile) {
        -90, -90,
        -9, -63
    };
    // east
    s_tiles[count++] = (struct tile) {
        -21, -63,
        -9, -42
    };
    s_tiles[count++] = (struct tile) {
        -90, -63,
        -21, -42
    };

    s_tiles[count++] = (struct tile) {
        -90, -42,
        9, -30
    };

    // Guatemala / Mexico
    s_tiles[count++] = (struct tile) {
        9, -126,
        33, -117
    };
    s_tiles[count++] = (struct tile) {
        9, -117,
        30, -102
    };
    // western gulf + east mexico
    s_tiles[count++] = (struct tile) {
        9, -102,
        27, -90
    };
    // Eastern Gulf of Mexico
    s_tiles[count++] = (struct tile) {
        24, -90,
        30, -84
    };

    // south of jamaica
    s_tiles[count++] = (struct tile) {
        9, -90,
        18, -69
    };

    // Cuba / Haiti
    s_tiles[count++] = (struct tile) {
        18, -90,
        24, -69
    };

    // Mediterranean
    s_tiles[count++] = (struct tile) {
        36, 6,
        42, 18
    };
    s_tiles[count++] = (struct tile) {
        36, 18,
        42, 30
    };

    // North Africa
    s_tiles[count++] = (struct tile) {
        9, -9,
        39, 6
    };
    s_tiles[count++] = (struct tile) {
        9, 6,
        36, 30
    };

    // Middle East
    s_tiles[count++] = (struct tile) {
        9, 30,
        42, 51
    };

    // west of Bermuda
    s_tiles[count++] = (struct tile) {
        24, -75,
        39, -69
    };
    // North Atlantic
    s_tiles[count++] = (struct tile) {
        9, -69,
        30, -33
    };
    s_tiles[count++] = (struct tile) {
        30, -69,
        60, -33
    };
    s_tiles[count++] = (struct tile) {
        9, -33,
        30, -9
    };
    s_tiles[count++] = (struct tile) {
        30, -33,
        60, -9
    };

    Modes.specialTileCount = count;

    if (count + 1 >= GLOBE_SPECIAL_INDEX)
        fprintf(stderr, "increase GLOBE_SPECIAL_INDEX please!\n");

    Modes.json_globe_indexes = cmalloc(GLOBE_MAX_INDEX * sizeof(int32_t));
    memset(Modes.json_globe_indexes, 0, GLOBE_MAX_INDEX * sizeof(int32_t));
    Modes.json_globe_indexes_len = 0;
    for (int i = 0; i <= GLOBE_MAX_INDEX; i++) {
        if (i == Modes.specialTileCount)
            i = GLOBE_MIN_INDEX;

        if (i >= GLOBE_MIN_INDEX) {
            int index_index = globe_index_index(i);
            if (index_index != i) {

                if (index_index >= GLOBE_MIN_INDEX) {
                    fprintf(stderr, "weird globe index: %d\n", i);
                }
                continue;
            }
        }
        Modes.json_globe_indexes[Modes.json_globe_indexes_len++] = i;
    }
    // testing out of bounds
    /*
    for (double lat = -90; lat < 90; lat += 0.5) {
        for (double lon = -180; lon < 180; lon += 0.5) {
            globe_index(lat, lon);
        }
    }
    */
}
void cleanup_globe_index() {
    free(Modes.json_globe_indexes);
    Modes.json_globe_indexes = NULL;

    free(Modes.json_globe_special_tiles);
    Modes.json_globe_special_tiles = NULL;
}

int globe_index(double lat_in, double lon_in) {
    int grid = GLOBE_INDEX_GRID;
    int lat = grid * ((int) ((lat_in + 90) / grid)) - 90;
    int lon = grid * ((int) ((lon_in + 180) / grid)) - 180;

    struct tile *tiles = Modes.json_globe_special_tiles;

    for (int i = 0; tiles[i].south != 0 || tiles[i].north != 0; i++) {
        struct tile tile = tiles[i];
        if (lat >= tile.south && lat < tile.north) {
            if (tile.west < tile.east && lon >= tile.west && lon < tile.east) {
                return i;
            }
            if (tile.west > tile.east && (lon >= tile.west || lon < tile.east)) {
                return i;
            }
        }
    }


    int i = (lat + 90) / grid;
    int j = (lon + 180) / grid;

    int res = (i * GLOBE_LAT_MULT + j + GLOBE_MIN_INDEX);
    if (res > GLOBE_MAX_INDEX) {
        fprintf(stderr, "globe_index: %d larger than GLOBE_MAX_INDEX: %d grid: %d,%d input: %.2f,%.2f\n",
                res, GLOBE_MAX_INDEX, lat, lon, lat_in, lon_in);
        return 0;
    }
    return res;
    // highest number returned: globe_index(90, 180)
    // first 1000 are reserved for special use
}

int globe_index_index(int index) {
    double lat = ((index - GLOBE_MIN_INDEX) /  GLOBE_LAT_MULT) * GLOBE_INDEX_GRID - 90;
    double lon = ((index - GLOBE_MIN_INDEX) % GLOBE_LAT_MULT) * GLOBE_INDEX_GRID - 180;
    return globe_index(lat, lon);
}

static void sprintDateDir(char *base_dir, struct tm *utc, char *dateDir) {
    char tstring[100];
    strftime (tstring, 100, TDATE_FORMAT, utc);
    snprintf(dateDir, PATH_MAX * 3/4, "%s/%s", base_dir, tstring);
}
static void createDateDir(char *base_dir, struct tm *utc, char *dateDir) {
    if (!strcmp(TDATE_FORMAT, "%Y/%m/%d")) {
        char yy[100];
        char mm[100];
        strftime (yy, 100, "%Y", utc);
        strftime (mm, 100, "%m", utc);
        char pathbuf[PATH_MAX];

        snprintf(pathbuf, PATH_MAX, "%s/%s", base_dir, yy);
        mkdir_error(pathbuf, 0755, stderr);

        snprintf(pathbuf, PATH_MAX, "%s/%s/%s", base_dir, yy, mm);
        mkdir_error(pathbuf, 0755, stderr);
    }
    sprintDateDir(base_dir, utc, dateDir);

    //fprintf(stderr, "making sure directory exists: %s\n", dateDir);

    mkdir_error(dateDir, 0755, stderr);
}

static void scheduleMemBothWrite(struct aircraft *a, int64_t schedTime) {
    a->trace_next_mw = schedTime;
    a->trace_writeCounter = 0xc0ffee;
}

// return first index at or after timestamp, return tb.len if all indexes are before the timestamp
static int first_index_ge_timestamp(traceBuffer tb, int64_t timestamp) {
    int start = 0;
    int end = tb.len - 1;
    while (start + 32 < end) {
        int pivot = (start + end) / 2 + 1;
        int64_t pivot_ts = getState(tb.trace, pivot)->timestamp;
        if (pivot_ts < timestamp) {
            start = pivot + 1;
        } else {
            end = pivot;
        }
    }
    for (int i = start; i <= end; i++) {
        if (getState(tb.trace, i)->timestamp >= timestamp) {
            return i;
        }
    }
    return tb.len;
}

void traceWrite(struct aircraft *a, threadpool_threadbuffers_t *buffer_group) {
    struct char_buffer recent;
    struct char_buffer full;
    struct char_buffer hist;
    char filename[PATH_MAX];
    //static uint32_t count2, count3, count4;

    recent.len = 0;
    full.len = 0;
    hist.len = 0;

    int trace_write = a->trace_write;

    if (Modes.replace_state_inhibit_traces_until) {
        trace_write &= WRECENT;
        a->trace_write &= ~WRECENT;
    } else {
        a->trace_write = 0;
    }

    if (a->trace_len == 0) {
        return;
    }

    int64_t now = mstime();

    int recent_points = Modes.traceRecentPoints;
    int memThreshold = recent_points - 2;
    if (a->trace_writeCounter >= memThreshold) {
        trace_write |= WMEM;
        trace_write |= WRECENT;
    }

    int focus = (a->addr == Modes.leg_focus);

    if (Modes.trace_hist_only) {
        int hist_only_mask = WPERM | WMEM | WRECENT;

        if (Modes.trace_hist_only & 8) {
            hist_only_mask = WPERM;
            if (Modes.trace_hist_only == 10) {
                if (a->trace_writeCounter > 0 && now > a->trace_next_mw) {
                    a->trace_next_mw = now + 5 * MINUTES;
                    trace_write |= WRECENT;
                    hist_only_mask |= WRECENT;
                    a->trace_writeCounter = 0;
                }
            } else {
                if (a->trace_writeCounter > recent_points) {
                    hist_only_mask |= WRECENT;
                    a->trace_writeCounter = 0;
                }
            }
            if (now > a->trace_next_mw) {
                hist_only_mask |= WMEM;
            }
        }

        if (Modes.trace_hist_only & 1)
            hist_only_mask &= ~ WRECENT;
        if (Modes.trace_hist_only & 2)
            hist_only_mask &= ~ WMEM;


        trace_write &= hist_only_mask;
    }
    traceBuffer tb = { 0 };

    if (buffer_group->buffer_count < 2) {
        static int64_t antiSpam;
        if (now > antiSpam) {
            antiSpam = now + 5 * SECONDS;
            fprintf(stderr, "<3> FATAL: traceWrite: insufficient buffer_count\n");
        }
        exit(1);
    }

    threadpool_buffer_t *reassemble_buffer = &buffer_group->buffers[0];
    threadpool_buffer_t *generate_buffer = &buffer_group->buffers[1];

    if ((trace_write & (WPERM | WMEM))) {
        tb = reassembleTrace(a, -1, -1, reassemble_buffer);
    } else {
        tb = reassembleTrace(a, 2 * recent_points, -1, reassemble_buffer);
    }

    int startFull = 0;
    if ((Modes.trace_hist_only & 8) && (trace_write & WMEM)) {
        startFull = first_index_ge_timestamp(tb, now - GLOBE_MEM_IVAL);
    } else {
        startFull = first_index_ge_timestamp(tb, now - Modes.keep_traces);
    }

    if (startFull >= tb.len) {
        //do not write trace if all data is older than keep_traces
        trace_write = 0;
    }

    if ((trace_write & WRECENT)) {
        mark_legs(tb, a, imax(0, tb.len - 4 * recent_points), 1);

        // statistics
        atomic_fetch_add(&Modes.recentTraceWrites, 1);

        // prepare the data for the trace_recent file in /run
        recent = generateTraceJson(a, tb, -2, -2, generate_buffer, 0);

        //if (Modes.debug_traceCount && ++count2 % 1000 == 0)
        //    fprintf(stderr, "recent trace write: %u\n", count2);

        if (recent.len > 0) {
            snprintf(filename, 256, "traces/%02x/trace_recent_%s%06x.json", a->addr % 256, (a->addr & MODES_NON_ICAO_ADDRESS) ? "~" : "", a->addr & 0xFFFFFF);

            writeJsonToGzip(Modes.json_dir, filename, recent, 1);
        }
    }

    if (trace_write && a->addr == TRACE_FOCUS)
        fprintf(stderr, "mw: %.0f, perm: %.0f, count: %d %x\n",
                ((int64_t) a->trace_next_mw - (int64_t) now) / 1000.0,
                ((int64_t) a->trace_next_perm - (int64_t) now) / 1000.0,
                a->trace_writeCounter, a->trace_writeCounter);

    int memWritten = 0;
    // prepare the data for the trace_full file in /run
    if ((trace_write & WMEM)) {
        if (a->trace_writeCounter > 0) {
            memWritten = a->trace_writeCounter;
            //if (Modes.debug_traceCount && ++count3 % 1000 == 0)
            //    fprintf(stderr, "memory trace writes: %u\n", count3);
            if (a->addr == TRACE_FOCUS)
                fprintf(stderr, "full\n");

            int64_t before = mono_milli_seconds();

            mark_legs(tb, a, 0, 0);

            int64_t elapsed = mono_milli_seconds() - before;
            if (elapsed > 2 * SECONDS || focus) {
                fprintf(stderr, "%06x mark_legs() took %.1f s!\n", a->addr, elapsed / 1000.0);
            }

            // statistics
            atomic_fetch_add(&Modes.fullTraceWrites, 1);

            full = generateTraceJson(a, tb, startFull, -1, generate_buffer, 0);

            if (full.len > 0) {
                snprintf(filename, 256, "traces/%02x/trace_full_%s%06x.json", a->addr % 256, (a->addr & MODES_NON_ICAO_ADDRESS) ? "~" : "", a->addr & 0xFFFFFF);

                writeJsonToGzip(Modes.json_dir, filename, full, 5);
            }
        }

        if (a->trace_writeCounter >= 0xc0ffee) {
            a->trace_next_mw = now + random() % (GLOBE_MEM_IVAL * 9 / 8);
            a->trace_writeCounter = random() % memThreshold;
        } else {
            a->trace_next_mw = now + GLOBE_MEM_IVAL + random() % (GLOBE_MEM_IVAL / 8);
            a->trace_writeCounter = 0;
        }
    }

    int permWritten = 0;
    // prepare writing the permanent history
    // until 20 min after midnight we only write permanent traces for the previous day
    if ((trace_write & WPERM)) {
        int64_t endStamp = 0;

        // fiftyfive_ago changes day 55 min after midnight: stop writing the previous days traces
        // fiftysix_ago changes day 56 min after midnight: allow webserver to read the previous days traces (see checkNewDay function)
        // this is in seconds, not milliseconds
        time_t fiftyfive_time = now / 1000 - 55 * 60;

        struct tm fiftyfive;
        gmtime_r(&fiftyfive_time, &fiftyfive);

        if (!Modes.globe_history_dir) {
            // push timer back in perm_done
            goto perm_done;
        }

        if (a->addr == TRACE_FOCUS) {
            fprintf(stderr, "perm\n");
        }

        struct tm tm_daystart = fiftyfive;
        tm_daystart.tm_sec = 0;
        tm_daystart.tm_min = 0;
        tm_daystart.tm_hour = 0;

        time_t epoch_daystart = timegm(&tm_daystart);

        int64_t start_of_day = 1000 * (int64_t) epoch_daystart;
        int64_t end_of_day = 1000 * (int64_t) (epoch_daystart + 86400);

        int start = first_index_ge_timestamp(tb, start_of_day);
        int end = first_index_ge_timestamp(tb, end_of_day) - 1;
        // end == -1 means we have no data before end_of_day thus we do not write the trace

        if (start < 0 || end < 0 || end < start) {
            goto perm_done;
        }

        struct state *startState = getState(tb.trace, start);
        struct state *endState = getState(tb.trace, end);
        endStamp = endState->timestamp;

        // only write permanent trace if we haven't already written up to the last timestamp
        if (a->trace_perm_last_timestamp == endStamp) {
            goto perm_done;
        }
        // don't write permanent trace for non icao traces that are on the ground
        if ((a->addr & MODES_NON_ICAO_ADDRESS) &&
                (
                 (startState->on_ground || !startState->baro_alt_valid)
                 && (endState->on_ground || !endState->baro_alt_valid)
                )
           ) {
            goto perm_done;
        }

        static int64_t antiSpam;
        if (fiftyfive.tm_hour == 23 && fiftyfive.tm_min > 50 && now > antiSpam) {
            antiSpam = now + 30 * SECONDS;
            fprintf(stderr, "<3>%06x permanent trace written for yesterday was written successfully but a bit late,"
                    "persistent traces for the previous UTC day are in danger of not all getting done!"
                    "consider alloting more CPU cores or increasing json-trace-interval!\n",
                    a->addr);
        }

        int64_t before = mono_milli_seconds();

        mark_legs(tb, a, 0, 0);

        int64_t elapsed = mono_milli_seconds() - before;
        if (elapsed > 2 * SECONDS || focus) {
            fprintf(stderr, "%06x mark_legs() took %.1f s!\n", a->addr, elapsed / 1000.0);
        }

        // statistics
        atomic_fetch_add(&Modes.permTraceWrites, 1);

        hist = generateTraceJson(a, tb, start, end, generate_buffer, start_of_day);
        if (hist.len > 0) {
            permWritten = 1;
            char tstring[100];
            strftime (tstring, 100, TDATE_FORMAT, &fiftyfive);

            snprintf(filename, PATH_MAX, "%s/traces/%02x/trace_full_%s%06x.json", tstring, a->addr % 256, (a->addr & MODES_NON_ICAO_ADDRESS) ? "~" : "", a->addr & 0xFFFFFF);
            filename[PATH_MAX - 101] = 0;

            writeJsonToGzip(Modes.globe_history_dir, filename, hist, 9);

            //if (Modes.debug_traceCount && ++count4 % 100 == 0)
            //    fprintf(stderr, "perm trace writes: %u\n", count4);
        }

perm_done:
        if (fiftyfive.tm_hour == 23) {
            a->trace_next_perm = now + GLOBE_PERM_IVAL / 8 + random() % (GLOBE_PERM_IVAL / 1);
        } else {
            a->trace_next_perm = now + GLOBE_PERM_IVAL / 1 + random() % (GLOBE_PERM_IVAL / 8);
        }
        // note what we have written to disk
        a->trace_perm_last_timestamp = endStamp;
    }

    if (Modes.debug_traceCount) {
        static uint32_t timedCount, pointsCount, permCount;
        int timed = 0;
        int byCounter = 0;
        if (permWritten || (memWritten && memWritten < 0xc0ffee)) {
            pthread_mutex_lock(&Modes.traceDebugMutex);
            {
                if (permWritten) {
                    permCount++;
                }
                if (memWritten && memWritten < 0xc0ffee) {
                    if (memWritten >= memThreshold) {
                        byCounter = 1;
                        pointsCount++;
                    } else {
                        timed = 1;
                        timedCount++;
                    }
                }
            }
            pthread_mutex_unlock(&Modes.traceDebugMutex);

            int print = 0;
            if (timed && timedCount % 500 == 0) {
                fprintf(stderr, "full_time  :%6d", timedCount);
                print = 1;
            }
            if (byCounter && pointsCount % 500 == 0) {
                fprintf(stderr, "full_points:%6d", pointsCount);
                print = 1;
            }
            if (permWritten && permCount % 500 == 0) {
                fprintf(stderr, "perm       :%6d", permCount);
                print = 1;
            }

            if (print) {
                fprintf(stderr, " hex: %06x mw: %6.0f, perm: %6.0f, count: %4d / %4d (%4x) \n",
                        a->addr,
                        ((int64_t) a->trace_next_mw - (int64_t) now) / 1000.0,
                        ((int64_t) a->trace_next_perm - (int64_t) now) / 1000.0,
                        a->trace_writeCounter,
                        recent_points,
                        a->trace_writeCounter);
            }
        }
    }


    if (0 && a->addr == TRACE_FOCUS)
        fprintf(stderr, "mw: %.0f, perm: %.0f, count: %d\n",
                ((int64_t) a->trace_next_mw - (int64_t) now) / 1000.0,
                ((int64_t) a->trace_next_perm - (int64_t) now) / 1000.0,
                a->trace_writeCounter);
}

static void free_aircraft_range(int start, int end) {
    for (int j = start; j < end; j++) {
        struct aircraft *a = Modes.aircraft[j], *na;
        /* Go through tracked aircraft chain and free up any used memory */
        while (a) {
            na = a->next;
            if (a) {
                traceCleanupNoUnlink(a);
                free(a);
            }
            a = na;
        }
    }
}

static void save_blobs(void *arg, threadpool_threadbuffers_t *threadbuffers) {
    task_info_t *info = (task_info_t *) arg;
    for (int j = info->from; j < info->to; j++) {
        //fprintf(stderr, "save_blob(%d)\n", j);

        save_blob(j, &threadbuffers->buffers[0], &threadbuffers->buffers[1]);

        if (Modes.free_aircraft) {
            int stride = AIRCRAFT_BUCKETS / STATE_BLOBS;
            int start = stride * j;
            int end = start + stride;
            free_aircraft_range(start, end);
        }
    }
}

static size_t memcpySize(void *dest, const void *src, size_t n) {
    memcpy(dest, src, n);
    return n;
}
static int roundUp8(int value) {
    return ((value + 7) / 8) * 8;
}

static int load_aircraft(char **p, char *end, int64_t now, threadpool_buffer_t *passbuffer) {
    static int size_changed;

    ssize_t newSize = sizeof(struct aircraft);

    if (end - *p < (int) sizeof(uint64_t)) {
        return -1;
    }

    uint64_t tmp_u64;
    *p += memcpySize(&tmp_u64, *p, sizeof(tmp_u64));
    ssize_t oldSize = tmp_u64;

    if (end - *p < oldSize) {
        return -1;
    }

    struct aircraft *source = (struct aircraft *) *p;

    struct aircraft *a = aircraftGet(source->addr);
    if (a) {
        if (0 && oldSize != newSize) {
            fprintf(stderr, "%06x size mismatch when replacing aircraft data, aborting!\n", source->addr);
            return -1;
        }
        //fprintf(stderr, "%06x aircraft already exists, overwriting old data\n", source->addr);
        //freeAircraft(a);
        quickRemove(a);

        // remove from active list if on it
        if (a->onActiveList) {
            ca_remove(&Modes.aircraftActive, a);
        }
        // remove from the globeList
        set_globe_index(a, -5);

        traceCleanupNoUnlink(a);
    } else {
        a = aircraftCreate(source->addr);
    }

    struct aircraft *preserveNext = a->next;

    memcpy(a, *p, imin(oldSize, newSize));
    *p += oldSize;

    a->next = preserveNext;

    if (!size_changed && oldSize != newSize) {
        size_changed = 1;
        fprintf(stderr, "sizeof(struct aircraft) has changed from %ld to %ld bytes, this means the code changed and if the coder didn't think properly might result in bad aircraft data. If your map doesn't have weird stuff ... probably all good and just an upgrade.\n",
                (long) oldSize, (long) newSize);
        Modes.writeInternalState = 1; // immediately write in the new format
    }

    // if we are loading this data via the replace_state mechanism, make sure we write the permanent trace again
    if (Modes.replace_state_blob) {
        a->trace_perm_last_timestamp = 0;
    }

    aircraftZeroTail(a);

    // just in case we have bogus values saved, make sure they time out
    if (a->seen_pos > now + 1 * MINUTES)
        a->seen_pos = now - 26 * HOURS;
    if (a->seen > now + 1 * MINUTES)
        a->seen = now - 26 * HOURS;

    if (a->globe_index > GLOBE_MAX_INDEX)
        a->globe_index = -5;

    if (a->addrtype_updated > now)
        a->addrtype_updated = now;

    if (a->trace_next_perm < now) {
        a->trace_next_perm = now + 1 * MINUTES + random() % (5 * MINUTES);
    } else if (a->trace_next_perm - now > GLOBE_PERM_IVAL) {
        a->trace_next_perm = now + 5 * MINUTES + random() % GLOBE_PERM_IVAL;
    }

    int new_index = a->globe_index;
    a->globe_index = -5;
    if (a->pos_reliable_valid.source != SOURCE_INVALID) {
        set_globe_index(a, new_index);
    }
    if (a->onActiveList) {
        a->onActiveList = 1;
        ca_add(&Modes.aircraftActive, a);
    }
    updateValidities(a, now);

    // make sure we don't think an extra position is still buffered in the trace memory
    a->tracePosBuffered = 0;


    // set trace pointers to zero before loading the trace
    a->trace_current_max = 0;
    a->trace_current = NULL;
    a->trace_chunks = NULL;

    // recalculate overall trace chunk size
    a->trace_chunk_overall_bytes = 0;

    int discard_trace = 0;

    // check that the trace meta data make sense before loading it
    if (a->trace_len > 0) {
        if (a->trace_len > Modes.traceMax) {
            fprintf(stderr, "%06x unexpectedly long trace: %d!\n", a->addr, a->trace_len);
        }

        uint64_t tmp_u64;
        *p += memcpySize(&tmp_u64, *p, sizeof(tmp_u64));
        ssize_t oldFourStateSize = tmp_u64;

        if (oldFourStateSize != sizeof(fourState)) {
            fprintf(stderr, "%06x sizeof(fourState) / SFOUR definition has changed, aborting state loading!\n", a->addr);
            traceCleanupNoUnlink(a);
            return -1;
        }

        int checkNo = 0;
#define checkSize(size) if (++checkNo && ((end - *p < (ssize_t) size) || size < 0)) { fprintf(stderr, "loadAircraft: checkSize failed for hex %06x checkNo %d size %lld\n", a->addr, checkNo, (long long) size); traceCleanupNoUnlink(a); return -1; }

        if (a->trace_chunk_len > 0) {
            a->trace_chunks = cmalloc(a->trace_chunk_len * sizeof(stateChunk));
        } else {
            a->trace_chunk_len = 0;
        }
        for (int k = 0; k < a->trace_chunk_len; k++) {
            stateChunk *chunk = &a->trace_chunks[k];
            checkSize(sizeof(stateChunk));
            *p += memcpySize(chunk, *p, sizeof(stateChunk));

            checkSize(chunk->compressed_size);
            chunk->compressed = cmalloc(chunk->compressed_size);
            a->trace_chunk_overall_bytes += chunk->compressed_size;
            *p += memcpySize(chunk->compressed, *p, chunk->compressed_size);

            ssize_t padBytes = roundUp8(chunk->compressed_size) - chunk->compressed_size;
            *p += padBytes;

            if (chunk->numStates % SFOUR != 0) {
                fprintf(stderr, "<3> %06x load_aircraft: (chunk->numStates %% SFOUR != 0) ..... this would cause issues, throwing away trace data!\n", a->addr);
                discard_trace = 1;
            }
        }
        resizeTraceCurrent(a, now);
        if (a->trace_current_len) {
            checkSize(stateBytes(a->trace_current_len));
            *p += memcpySize(a->trace_current, *p, stateBytes(a->trace_current_len));
        }
#undef checkSize

        if (!Modes.keep_traces) {
            traceCleanupNoUnlink(a);
            return 0;
        }

        traceMaintenance(a, now, passbuffer);

        if (a->addr == Modes.leg_focus) {
            a->trace_next_perm = now;
            scheduleMemBothWrite(a, now);
            fprintf(stderr, "leg_focus: %06x trace len: %d\n", a->addr, a->trace_len);
            a->trace_write |= WRECENT;
            a->trace_write |= WPERM;
            a->trace_write |= WMEM;
        }

        // write traces into /run/readsb so they are present for the webinterface
        if (a->pos_reliable_valid.source != SOURCE_INVALID || (now - a->seenPosReliable) < 15 * MINUTES) {
            // write these trace immediately
            a->trace_writeCounter = 0xc0ffee;
            a->trace_write |= WRECENT;
            a->trace_write |= WMEM;
        }
    } else {
        traceCleanupNoUnlink(a);
    }
    if (discard_trace) {
        traceCleanupNoUnlink(a);
    }

    return 0;
}

static void utc_string_from_ms(int64_t ts, char *target) {
    time_t time = ts / 1000;
    struct tm utc;
    gmtime_r(&time, &utc);
    strftime (target, 100, "%H:%M:%S", &utc);
}

static void mark_legs(traceBuffer tb, struct aircraft *a, int start, int recent) {
    if (tb.len < 20)
        return;
    if (start < 0) {
        start = 0;
    }

    int high = 0;
    int low = 100000;

    struct timespec watch = { 0 };
    int64_t elapsed1 = 0;
    int64_t elapsed2 = 0;

    int focus = (a->addr == Modes.leg_focus && !recent);

    if (!recent) {
        startWatch(&watch);
    }

    int last_five_init_alt = 0;
    struct state *startState = getState(tb.trace, start);
    if (startState->baro_alt_valid) {
        last_five_init_alt = startState->baro_alt / _alt_factor;
    }

    int last_five[5];
    uint32_t five_pos = 0;
    for (int i = 0; i < 5; i++) { last_five[i] = last_five_init_alt; }

    int32_t last_air_alt = INT32_MIN;

    double sum = 0;
    int count = 0;

    struct state *new_leg = NULL;

    int increment = SFOUR;
    if (tb.len > 256 * SFOUR) {
        increment = 4 * SFOUR;
    }
    float inverse_alt_factor = 1 / _alt_factor;
    for (int i = start - (start % SFOUR); i < tb.len; i += increment) {
        struct state *curr = getState(tb.trace, i);
        int on_ground = curr->on_ground;
        int altitude_valid = curr->baro_alt_valid;
        int altitude = curr->baro_alt * inverse_alt_factor;

        if (!altitude_valid && curr->geom_alt_valid) {
            altitude_valid = 1;
            altitude = curr->geom_alt * inverse_alt_factor;
        }

        if (on_ground || !altitude_valid) {
            if (last_air_alt == INT32_MIN) {
                int avg = 0;
                for (int i = 0; i < 5; i++) avg += last_five[i];
                avg /= 5;
                last_air_alt = avg;
            }
            altitude = last_air_alt;
        } else {
            last_air_alt = INT32_MIN;
            last_five[five_pos] = altitude;
            five_pos = (five_pos + 1) % 5;
        }

        sum += altitude;
        count++;
    }

    int threshold = (int) (sum / (double) (count * 3));


    if (!recent) {
        elapsed1 = lapWatch(&watch);
    }
    if (focus) {

        fprintf(stderr, "--------------------------\n");
        fprintf(stderr, "start: %d\n", start);
        fprintf(stderr, "trace_len: %d\n", tb.len);
        fprintf(stderr, "threshold: %d\n", threshold);
    }


    if (threshold > 2500)
        threshold = 2500;
    if (threshold < 200)
        threshold = 200;

    high = 0;
    low = 100000;

    int64_t major_climb = 0;
    int64_t major_descent = 0;
    int major_climb_index = 0;
    int major_descent_index = 0;
    int64_t last_high = 0;
    int64_t last_low = 0;

    int last_high_index = 0;
    int last_low_index = 0;

    int64_t last_airborne = 0;
    int64_t last_ground = 0;
    int64_t last_ground_index = 0;
    int64_t first_ground = 0;
    int64_t first_ground_index = 0;

    int last_5min_gap_index = -1;
    struct state last_5min_gap_state = { 0 };
    int last_10min_gap_index = -1;

    int was_ground = 0;

    last_air_alt = INT32_MIN;
    for (int i = 0; i < 5; i++) { last_five[i] = last_five_init_alt; }
    five_pos = 0;

    int32_t counter1 = 0;
    int32_t counter2 = 0;
    int32_t counter3 = 0;
    int32_t counter4 = 0;
    int32_t counter5 = 0;

    if (start < 1) {
        start = 1;
    }
    int prev_index = start - 1;
    struct state *state = getState(tb.trace, prev_index);
    int state_index = prev_index;
    struct state *prev;
    for (int index = start; index < tb.len; index++) {
        prev = state;
        prev_index = state_index;

        state = getState(tb.trace, index);
        state_index = index;

        int64_t elapsed = state->timestamp - prev->timestamp;

        if (elapsed < 5 * SECONDS) {
            state = prev;
            state_index = prev_index;
            continue;
        }

        if (elapsed > 5 * MINUTES) {
            last_5min_gap_index = state_index;
            last_5min_gap_state = *state;
            if (focus) {
                fprintf(stderr, "5 min gap detected with index %d\n", state_index);
            }
            if (elapsed > 10 * MINUTES) {
                last_10min_gap_index++; // shut up unused var
                last_10min_gap_index = state_index;
            }
        }

        int on_ground = state->on_ground;
        int altitude_valid = state->baro_alt_valid;
        int altitude = state->baro_alt * inverse_alt_factor;

        if (!altitude_valid && state->geom_alt_valid) {
            altitude_valid = 1;
            altitude = state->geom_alt * inverse_alt_factor;
        }

        if (on_ground || !altitude_valid) {
            if (last_air_alt == INT32_MIN) {
                int avg = 0;
                for (int i = 0; i < 5; i++) avg += last_five[i];
                avg /= 5;
                last_air_alt = avg;
            }
            altitude = last_air_alt;
        } else {
            last_air_alt = INT32_MIN;
            last_five[five_pos] = altitude;
            five_pos = (five_pos + 1) % 5;
        }

        if (on_ground || was_ground) {
            // count the last point in time on ground to be when the aircraft is received airborn after being on ground
            if (state->timestamp > last_ground + 5 * MINUTES) {
                first_ground = state->timestamp;
                first_ground_index = index;
            }
            last_ground = state->timestamp;
            last_ground_index = index;
        } else {
            last_airborne = state->timestamp;
        }

        if (was_ground) {
            low = altitude;
            high = altitude;
        }

        if (altitude >= high) {
            high = altitude;
            if (0 && focus) {
                time_t nowish = state->timestamp/1000;
                struct tm utc;
                gmtime_r(&nowish, &utc);
                char tstring[100];
                strftime (tstring, 100, "%H:%M:%S", &utc);
                fprintf(stderr, "high: %d %s\n", altitude, tstring);
            }
        }
        if (!on_ground && major_descent && last_ground >= major_descent
                && last_ground > first_ground + 1 * MINUTES
                && state->timestamp > last_ground + 15 * SECONDS
                && high - low > 200) {
            // fake major_climb after takeoff ... bit hacky
            high = low + threshold + 1;
            last_high = state->timestamp;
            last_high_index = index;
            last_low = last_ground;
            last_low_index = last_ground_index;
        }
        if (altitude <= low) {
            low = altitude;
        }

        if (abs(low - altitude) < threshold * 1 / 3) {
            last_low = state->timestamp;
            last_low_index = index;
        }
        if (abs(high - altitude) < threshold * 1 / 3) {
            last_high = state->timestamp;
            last_high_index++;
            last_high_index = index;
            if (0 && focus) {
                time_t nowish = state->timestamp/1000;
                struct tm utc;
                gmtime_r(&nowish, &utc);
                char tstring[100];
                strftime (tstring, 100, "%H:%M:%S", &utc);
                fprintf(stderr, "last_high: %d %s\n", altitude, tstring);
            }
        }

        if (high - low > threshold) {
            if (last_high > last_low) {
                // only set new major climb time if this is after a major descent.
                // then keep that time associated with the climb
                // still report continuation of thta climb
                if (major_climb <= major_descent) {
                    int bla = imin(tb.len - 1, last_low_index + 3);
                    major_climb = getState(tb.trace, bla)->timestamp;
                    major_climb_index = bla;
                }
                if (focus) {

                    char climbString[100];
                    utc_string_from_ms(major_climb, climbString);

                    char tstring[100];
                    utc_string_from_ms(state->timestamp, tstring);

                    fprintf(stderr, "%s climb: %d %s high: %d low:%d index: %d\n", tstring, altitude, climbString, high, low, major_climb_index);
                }
                low = high - threshold * 9/10;
            } else if (last_low > last_high) {
                int k = imax(0, last_low_index - 3);
                for (; k > 0; k--) {
                    counter1++;
                    struct state *st = getState(tb.trace, k);
                    if (0 && focus) {
                        fprintf(stderr, "k: %d %d %d %d\n", k, (int) (st->baro_alt / _alt_factor), st->baro_alt_valid, st->on_ground);
                    }
                    if (st->baro_alt_valid && !st->on_ground) {
                        break;
                    }
                }
                if (k < 0) {
                    fprintf(stderr, "look screwed up. Thaeth5g\n");
                    // because it's easy to mess up the logic of k decreasing after the last loop
                    k = 0;
                }

                major_descent = getState(tb.trace, k)->timestamp;
                major_descent_index = k;
                if (focus) {
                    char descString[100];
                    utc_string_from_ms(major_descent, descString);

                    char tstring[100];
                    utc_string_from_ms(state->timestamp, tstring);

                    fprintf(stderr, "%s desc: %d %s index: %d\n", tstring, altitude, descString, major_descent_index);
                }
                high = low + threshold * 9/10;
            }
        }
        int leg_now = 0;
        if (
                (major_descent && (on_ground || was_ground) && elapsed > 25 * 60 * 1000) ||
                (major_descent && on_ground && state->timestamp > last_airborne + 45 * 60 * 1000)
           )
        {
            if (focus) {
                fprintf(stderr, "ground leg (on ground and time between reception > 25 min)\n");
            }
            leg_now = 1;
        }

        int max_leg_alt = 20000;
        // disable .... let's see if we really need it
        if (0 && elapsed > 30 * 60 * 1000 && (state->on_ground || !state->baro_alt_valid || (state->baro_alt_valid && state->baro_alt / _alt_factor < max_leg_alt))) {
            double distance = greatcircle(
                    (double) state->lat * 1e-6,
                    (double) state->lon * 1e-6,
                    (double) prev->lat * 1e-6,
                    (double) prev->lon * 1e-6,
                    0
                    );
            if (distance < 10E3 * (elapsed / (30 * 60 * 1000.0)) && distance > 1) {
                leg_now = 1;
                if (focus) {
                    fprintf(stderr, "time/distance leg, elapsed: %0.fmin, distance: %0.f\n", elapsed / (60 * 1000.0), distance / 1000.0);
                }
            }
        }

        int leg_float = 0;
        if (major_climb && major_descent && major_climb > major_descent + 12 * MINUTES) {
            if (last_5min_gap_index >= 0 && last_5min_gap_index >= major_descent_index) {
                struct state *st = &last_5min_gap_state;
                if (focus) {
                    fprintf(stderr, "checking for: float leg: 5 minutes between descent / climb, 5 minute reception gap in between somewhere\n");
                }
                if (st->on_ground || !st->baro_alt_valid || (st->baro_alt_valid && st->baro_alt / _alt_factor < max_leg_alt)) {
                    leg_float = 1;
                    if (focus) {
                        fprintf(stderr, "float leg: 5 minutes between descent / climb, 5 minute reception gap in between somewhere\n");
                    }
                }
            }
        }
        if (major_climb && major_descent
                && major_climb > major_descent + 1 * MINUTES
                && last_ground >= major_descent
                && last_ground > first_ground + 1 * MINUTES
           ) {
            leg_float = 1;
            if (focus) {
                fprintf(stderr, "float leg: 1 minutes between descent / climb, 1 minute on ground\n");
            }
        }


        if (leg_float || leg_now)
        {
            int64_t leg_ts = 0;

            if (leg_now) {
                new_leg = state;
                for (int k = prev_index + 1; k < index; k++) {
                    counter2++;
                    struct state *state = getState(tb.trace, k);
                    struct state *last = getState(tb.trace, k - 1);

                    if (state->timestamp > last->timestamp + 5 * MINUTES) {
                        new_leg = state;
                        break;
                    }
                }
            } else if (major_descent_index + 1 == major_climb_index) {
                new_leg = getState(tb.trace, major_climb_index);
            } else {
                for (int i = major_climb_index; i > major_descent_index; i--) {
                    counter3++;
                    struct state *state = getState(tb.trace, i);
                    struct state *last = getState(tb.trace, i - 1);

                    if (state->timestamp > last->timestamp + 5 * 60 * 1000) {
                        new_leg = state;
                        break;
                    }
                }
                if (last_ground > major_descent) {
                    int64_t half = first_ground + (last_ground - first_ground) / 2;
                    for (int i = first_ground_index + 1; i <= last_ground_index; i++) {
                        counter4++;
                        struct state *state = getState(tb.trace, i);

                        if (state->timestamp > half) {
                            new_leg = state;
                            break;
                        }
                    }
                } else {
                    int64_t half = major_descent + (major_climb - major_descent) / 2;
                    for (int i = major_descent_index + 1; i < major_climb_index; i++) {
                        counter5++;
                        struct state *state = getState(tb.trace, i);

                        if (state->timestamp > half) {
                            new_leg = state;
                            break;
                        }
                    }
                }
            }

            if (new_leg) {
                leg_ts = new_leg->timestamp;
                new_leg->leg_marker = 1;
                // set leg marker
            }

            major_climb = 0;
            major_climb_index = 0;
            major_descent = 0;
            major_descent_index = 0;
            low += threshold;
            high -= threshold;

            if (new_leg && new_leg->on_ground) {
                // reset low / high completely
                high = 0;
                low = 100000;
            }

            if (focus) {
                if (new_leg) {
                    time_t nowish = leg_ts/1000;
                    struct tm utc;
                    gmtime_r(&nowish, &utc);
                    char tstring[100];
                    strftime (tstring, 100, "%H:%M:%S", &utc);
                    fprintf(stderr, "leg: %s\n", tstring);
                } else {
                    time_t nowish = state->timestamp/1000;
                    struct tm utc;
                    gmtime_r(&nowish, &utc);
                    char tstring[100];
                    strftime (tstring, 100, "%H:%M:%S", &utc);
                    fprintf(stderr, "resetting major_c/d without leg: %s\n", tstring);
                }
            }
        }

        was_ground = on_ground;
    }
    if (!recent) {
        elapsed2 = lapWatch(&watch);
    }
    if (focus || ((elapsed1 > 50 || elapsed2 > 50) && counter1 + counter2 + counter3 + counter4 + counter5 > 2000)) {
        fprintf(stderr, "%06x mark_legs loop1: %.3f loop2: %.3f counter1 %d counter2 %d counter3 %d counter4 %d counter5 %d\n",
                a->addr, elapsed1 / 1000.0, elapsed2 / 1000.0,
                counter1,
                counter2,
                counter3,
                counter4,
                counter5);
    }
}

void ca_lock_read(struct craftArray *ca) {
    pthread_mutex_lock(&ca->read_mutex);

    if (ca->reader_count == 0) {
        pthread_mutex_lock(&ca->write_mutex);
    }
    ca->reader_count++;
    if (0 && ca->reader_count > 1) {
        fprintf(stderr, "ca->reader_count %d\n", ca->reader_count);
    }

    pthread_mutex_unlock(&ca->read_mutex);
}

void ca_unlock_read(struct craftArray *ca) {
    pthread_mutex_lock(&ca->read_mutex);

    ca->reader_count--;
    if (ca->reader_count == 0) {
        pthread_mutex_unlock(&ca->write_mutex);
    }
    //fprintf(stderr, "ca->reader_count %d\n", ca->reader_count);

    pthread_mutex_unlock(&ca->read_mutex);
}

void ca_init (struct craftArray *ca) {
    memset(ca, 0x0, sizeof(struct craftArray));
    pthread_mutex_init(&ca->change_mutex, NULL);
    pthread_mutex_init(&ca->read_mutex, NULL);
    pthread_mutex_init(&ca->write_mutex, NULL);
}

void ca_destroy (struct craftArray *ca) {
    if (ca->list) {
        sfree(ca->list);
    }

    pthread_mutex_destroy(&ca->change_mutex);
    pthread_mutex_destroy(&ca->read_mutex);
    pthread_mutex_destroy(&ca->write_mutex);

    memset(ca, 0x0, sizeof(struct craftArray));
}

void ca_add (struct craftArray *ca, struct aircraft *a) {
    pthread_mutex_lock(&ca->change_mutex);

    if (ca->len == ca->alloc) {
        pthread_mutex_lock(&ca->write_mutex);
        if (ca->len == ca->alloc) {
            ca->alloc = ca->alloc * 2 + 16;
            ca->list = realloc(ca->list, ca->alloc * sizeof(struct aircraft *));
            if (!ca->list) {
                fprintf(stderr, "ca_add(): out of memory!\n");
                exit(1);
            }
        }
        pthread_mutex_unlock(&ca->write_mutex);
    }

    int duplicate = 0;
    for (int i = 0; i < ca->len; i++) {
        if (unlikely(a == ca->list[i])) {
            fprintf(stderr, "<3>hex: %06x, ca_add(): double add!\n", a->addr);
            duplicate = 1;
        }
    }

    if (!duplicate) {
        ca->list[ca->len] = a;  // add at the end
        ca->len++;
    }

    pthread_mutex_unlock(&ca->change_mutex);
}

void ca_remove (struct craftArray *ca, struct aircraft *a) {
    pthread_mutex_lock(&ca->change_mutex);

    int found = 0;
    for (int i = 0; i < ca->len; i++) {
        if (ca->list[i] == a) {
            // replace with last element in array

            ca->list[i] = ca->list[ca->len - 1];
            ca->list[ca->len - 1] = NULL;

            ca->len--;
            i--;

            found++;
        }
    }
    if (found == 0) {
        fprintf(stderr, "<3>hex: %06x, ca_remove(): pointer not in array!\n", a->addr);
    } else if (found > 1) {
        fprintf(stderr, "<3>hex: %06x, ca_remove(): pointer removed %d times!\n", a->addr, found);
    }

    pthread_mutex_unlock(&ca->change_mutex);
}

void set_globe_index (struct aircraft *a, int new_index) {

    if (!Modes.json_globe_index)
        return;

    int old_index = a->globe_index;
    a->globe_index = new_index;

    if (old_index == new_index)
        return;
    if (new_index > GLOBE_MAX_INDEX || old_index > GLOBE_MAX_INDEX) {
        fprintf(stderr, "hex: %06x, old_index: %d, new_index: %d, GLOBE_MAX_INDEX: %d\n",
                a->addr, old_index, new_index, GLOBE_MAX_INDEX);
        return;
    }
    if (old_index >= 0) {
        ca_remove(&Modes.globeLists[old_index], a);
    }
    if (new_index >= 0) {
        ca_add(&Modes.globeLists[new_index], a);
    }
}

static void traceUnlink(struct aircraft *a) {
    char filename[PATH_MAX];

    if (!Modes.json_globe_index || !Modes.json_dir)
        return;

    snprintf(filename, 1024, "%s/traces/%02x/trace_recent_%s%06x.json", Modes.json_dir, a->addr % 256, (a->addr & MODES_NON_ICAO_ADDRESS) ? "~" : "", a->addr & 0xFFFFFF);
    unlink(filename);

    snprintf(filename, 1024, "%s/traces/%02x/trace_full_%s%06x.json", Modes.json_dir, a->addr % 256, (a->addr & MODES_NON_ICAO_ADDRESS) ? "~" : "", a->addr & 0xFFFFFF);
    unlink(filename);

    //fprintf(stderr, "unlink %06x: %s\n", a->addr, filename);
}

static stateChunk *resizeTraceChunks(struct aircraft *a, int newLen) {
    int oldLen = a->trace_chunk_len;

    if (oldLen < 0 || newLen < 0) {
        fprintf(stderr, "resizeTraceChunks: oldLen < 0 || newLen < 0 ... this is a fatal error, exiting.\n");
        exit(1);
    }
    if (oldLen > 0 && !a->trace_chunks) {
        fprintf(stderr, "resizeTraceChunks: oldLen > 0 && !a->trace_chunks ... this is a fatal error, exiting.\n");
        exit(1);
    }

    a->trace_chunk_len = newLen;
    if (newLen == 0) {
        sfree(a->trace_chunks);
        return NULL;
    }
    if (oldLen == newLen) {
        fprintf(stderr, "resizeTraceChunks: oldLen == newLen ... this is weird but shouldn't be an issue\n");
    }

    int maxLen = INT_MAX / sizeof(stateChunk);
    if (maxLen < newLen || maxLen < oldLen) {
        fprintf(stderr, "resizeTraceChunks: wat? overflow3? this can't happen, shut up old gcc\n");
        exit(1);
    }

    int newBytes = newLen * sizeof(stateChunk);
    int oldBytes = oldLen * sizeof(stateChunk);

    stateChunk *new = cmalloc(newBytes);
    if (!new) {
        return NULL;
    }

    if (oldLen > newLen) {
        int shrinkByLen = oldLen - newLen;
        if (shrinkByLen < 0) {
            fprintf(stderr, "resizeTraceChunks: wat? overflow1? this can't happen, shut up old gcc\n");
            exit(1);
        }

        memcpy(new, a->trace_chunks + shrinkByLen, newBytes);
    } else {
        int growByBytes = newBytes - oldBytes;
        if (growByBytes < 0) {
            fprintf(stderr, "resizeTraceChunks: wat? overflow2? this can't happen, shut up old gcc\n");
            exit(1);
        }

        memcpy(new, a->trace_chunks, oldBytes);
        memset(new + oldLen, 0x0, growByBytes);
    }

    sfree(a->trace_chunks);

    a->trace_chunks = new;

    if (newLen > oldLen) {
        return &a->trace_chunks[a->trace_chunk_len - 1];
    } else {
        return NULL;
    }
}

static void tracePrune(struct aircraft *a, int64_t now) {
    if (a->trace_len <= 0) {
        traceCleanup(a);
        return;
    }

    int64_t keep_after = now - Modes.keep_traces;

    if (a->trace_current_len > 0 && getState(a->trace_current, a->trace_current_len - 1)->timestamp < keep_after) {
        traceCleanup(a);
        return;
    }

    int deletedChunks = 0;

    for (int k = 0; k < a->trace_chunk_len; k++) {
        stateChunk *chunk = &a->trace_chunks[k];
        if (chunk->lastTimestamp >= keep_after) {
            break;
        }

        deletedChunks++;
        a->trace_len -= chunk->numStates;
        a->trace_chunk_overall_bytes -= chunk->compressed_size;

        sfree(chunk->compressed);
    }

    if (deletedChunks > 0) {
        if (0 && Modes.verbose) {
            fprintf(stderr, "%06x deleting %d chunks\n", a->addr, deletedChunks);
        }
        resizeTraceChunks(a, a->trace_chunk_len - deletedChunks);
    }

    int deleteFs = 0;
    for (int k = 0; k < a->trace_current_len / SFOUR; k++) {
        fourState *fs = &a->trace_current[k];
        int64_t ts = fs->no[SFOUR - 1].timestamp;
        if (ts >= keep_after) {
            break;
        }
        deleteFs++;
    }
    if (deleteFs * SFOUR >= Modes.traceReserve) {
        if (0 && Modes.verbose) {
            fprintf(stderr, "%s%06x tracePrune a->trace_current: %d\n",
                    ((a->addr & MODES_NON_ICAO_ADDRESS) ? "." : ". "), a->addr, SFOUR * deleteFs);
        }
        a->trace_current_len -= SFOUR * deleteFs;
        a->trace_len -= SFOUR * deleteFs;
        // keep buffered position intact -> +1
        memmove(a->trace_current, a->trace_current + deleteFs, stateBytes(a->trace_current_len + 1));
    }
}

int traceUsePosBuffered(struct aircraft *a) {
    if (a->tracePosBuffered) {
        a->tracePosBuffered = 0;
        // bookkeeping:
        a->trace_len++;
        a->trace_current_len++;
        a->trace_write |= WRECENT;
        a->trace_writeCounter++;
        return 1;
    } else {
        return 0;
    }
}

static void destroyTraceCache(struct traceCache *cache) {
    if (!cache) {
        return;
    }
    sfree(cache->entries);
    memset(cache, 0x0, sizeof(struct traceCache));
}


static void traceCleanupNoUnlink(struct aircraft *a) {
    if (a->trace_chunks) {
        for (int k = 0; k < a->trace_chunk_len; k++) {
            sfree(a->trace_chunks[k].compressed);
        }
    }
    sfree(a->trace_chunks);
    a->trace_chunk_len = 0;
    a->trace_chunk_overall_bytes = 0;

    sfree(a->trace_current);
    a->trace_current_max = 0;
    a->trace_current_len = 0;

    a->tracePosBuffered = 0;
    a->trace_len = 0;

    destroyTraceCache(&a->traceCache);
}

void traceCleanup(struct aircraft *a) {
    if (a->trace_current) {
        traceUnlink(a);
    }
    traceCleanupNoUnlink(a);
}

// reconstruct at least the last numPoints points from trace chunks / current_trace
// numPoints < 0 => all data / whole trace
static traceBuffer reassembleTrace(struct aircraft *a, int numPoints, int64_t after_timestamp, threadpool_buffer_t *buffer) {
    int firstChunk = 0;

    int currentLen = a->trace_current_len;
    int allocLen = currentLen;

    if (numPoints >= 0) {
        firstChunk = a->trace_chunk_len;
        for (int k = a->trace_chunk_len - 1; k >= 0 && allocLen < numPoints; k--) {
            stateChunk *chunk = &a->trace_chunks[k];
            allocLen += chunk->numStates;
            firstChunk = k;
        }
    } else if (after_timestamp > 0) {
        firstChunk = a->trace_chunk_len;
        for (int k = a->trace_chunk_len - 1; k >= 0; k--) {
            stateChunk *chunk = &a->trace_chunks[k];
            if (after_timestamp > chunk->lastTimestamp) {
                break;
            }
            allocLen += chunk->numStates;
            firstChunk = k;
        }
    } else {
        for (int k = 0; k < a->trace_chunk_len; k++) {
            stateChunk *chunk = &a->trace_chunks[k];
            allocLen += chunk->numStates;
        }
    }

    traceBuffer tb = { 0 };

    //fprintf(stderr, "allocLen %ld fourStates %ld stateBytes %ld\n", (long) allocLen, (long) getFourStates(allocLen), (long) stateBytes(allocLen));
    tb.trace = check_grow_threadpool_buffer_t(buffer, stateBytes(allocLen));

    fourState *tp = tb.trace;


    int actual_len = 0;
    for (int k = firstChunk; k < a->trace_chunk_len; k++) {
        stateChunk *chunk = &a->trace_chunks[k];
        actual_len += chunk->numStates;
        if (actual_len > allocLen) { fprintf(stderr, "remakeTrace buffer overflow, bailing eex5ioBu\n"); exit(1); }

        lzo_uint uncompressed_len = stateBytes(chunk->numStates);

        if (memcmp(zstd_magic, chunk->compressed, sizeof(zstd_magic)) == 0) {
            if (!buffer->dctx) {
                buffer->dctx = ZSTD_createDCtx();
            }
            size_t res = ZSTD_decompressDCtx(buffer->dctx, tp, uncompressed_len, chunk->compressed, chunk->compressed_size);
            if (ZSTD_isError(res)) {
                fprintf(stderr, "reassembleTrace() zstd error: %s\n", ZSTD_getErrorName(res));
                tb.len = 0;
                traceCleanup(a);
                return tb;
            }
        } else {
            //fprintf(stderr, "reassembleTrace(%06x %d %ld): chunk %d trace_chunk_len %d compressed_size %d uncompressed_size %d outAlloc %d allocLen %d numStates %d trace_current_len %d\n",
            //        a->addr, numPoints, (long) after_timestamp, k, a->trace_chunk_len,
            //        chunk->compressed_size, (int) uncompressed_len, (int) stateBytes(allocLen), allocLen, (int) chunk->numStates, currentLen);

            int res = lzo1x_decompress_safe(chunk->compressed, chunk->compressed_size, (unsigned char*) tp, &uncompressed_len, NULL);

            //fprintf(stderr, "reassembleTrace(%06x %d %ld): chunk %d trace_chunk_len %d compressed_size %d uncompressed_size %d outAlloc %d allocLen %d numStates %d trace_current_len %d\n",
            //        a->addr, numPoints, (long) after_timestamp, k, a->trace_chunk_len,
            //        chunk->compressed_size, (int) uncompressed_len, (int) stateBytes(allocLen), allocLen, (int) chunk->numStates, currentLen);

            if (res != LZO_E_OK) {
                fprintf(stderr, "reassembleTrace(%06x %d %ld): decompress failure chunk %d trace_chunk_len %d compressed_size %d uncompressed_size %d\n",
                        a->addr, numPoints, (long) after_timestamp, k, a->trace_chunk_len,
                        chunk->compressed_size, (int) uncompressed_len);
                tb.len = 0;
                traceCleanup(a);
                return tb;
            }
        }

        tp += getFourStates(chunk->numStates);
    }

    actual_len += currentLen;

    if (actual_len > allocLen) { fprintf(stderr, "remakeTrace buffer overflow, bailing eex5ioBu with actual_len %d allocLen %d\n", actual_len, allocLen); exit(1); }

    if (a->trace_current_len > 0) {
        memcpy(tp, a->trace_current, stateBytes(currentLen));
    }
    // tp is not incremented here as it's not used anymore after this.
    tb.len = actual_len;
    return tb;
}

static float recompressStateChunk(struct stateChunk *chunk, threadpool_buffer_t *passbuffer) {
    if (!passbuffer->dctx) {
        passbuffer->dctx = ZSTD_createDCtx();
    }
    int uncompressed_len = stateBytes(chunk->numStates);
    int maxSize = ZSTD_compressBound(uncompressed_len);
    int totalBuffer = uncompressed_len + maxSize;
    char *uncompressed = check_grow_threadpool_buffer_t(passbuffer, totalBuffer);
    char *compressed = uncompressed + uncompressed_len;

    size_t res = ZSTD_decompressDCtx(passbuffer->dctx, uncompressed, uncompressed_len, chunk->compressed, chunk->compressed_size);
    if (ZSTD_isError(res)) {
        fprintf(stderr, "recompress(): Corrupt trace chunk: zstd error: %s\n", ZSTD_getErrorName(res));
        return 0.0f;
    }

    if (!passbuffer->cctx) {
        passbuffer->cctx = ZSTD_createCCtx();
    }
    size_t compressedSize = ZSTD_compressCCtx(
            passbuffer->cctx,
            compressed, maxSize,
            uncompressed, uncompressed_len,
            2);

    if (ZSTD_isError(compressedSize)) {
        fprintf(stderr, "recompress() zstd error: %s\n", ZSTD_getErrorName(compressedSize));
        return 0.0f;
    }

    float recompressSavings = 0;
    if (chunk->compressed_size == 0) {
        fprintf(stderr, "chunk->compressed_size == 0\n");
    } else {
        recompressSavings = (float) (chunk->compressed_size - (int) compressedSize) / (float) chunk->compressed_size;
    }

    if (recompressSavings > 100) {
        fprintf(stderr, "savings %4.1f old %lld new %lld\n",
                recompressSavings * 100.0f,
                (long long) chunk->compressed_size,
                (long long) compressedSize);
    }

    sfree(chunk->compressed);
    chunk->compressed = cmalloc(compressedSize);

    memcpy(chunk->compressed, compressed, compressedSize);
    chunk->compressed_size = compressedSize;

    return recompressSavings;
}



static int minCurrentPoints() {
    return alignSFOUR(8);
}
static int64_t traceChunkDuration() {
    return 120 * MINUTES;
}


static int compressChunk(fourState *source, int pointCount, threadpool_buffer_t *passbuffer, struct aircraft *a) {
    int64_t now = mstime();
    int64_t before = 0;
    if (Modes.verbose) { before = nsThreadTime(); };

    if (pointCount < SFOUR || pointCount % SFOUR != 0) {
        fprintf(stderr, "eeZ2avaH\n");
        return 0;
    }

    stateChunk *target = NULL;

    int64_t chunkDuration = traceChunkDuration();

    stateChunk *lastChunk = NULL;

    int extending = 0;

    if (a->trace_chunk_len > 0) {
        lastChunk = &a->trace_chunks[a->trace_chunk_len - 1];

        int k = 0;
        while(k < pointCount / SFOUR) {
            int64_t ts2 = getState(source, k * SFOUR + (SFOUR - 1))->timestamp;
            int64_t diff_last = ts2 - lastChunk->firstTimestamp;

            // minimize duration of last and next chunk
            if (diff_last > chunkDuration) {
                break;
            }
            k++;
        }
        extending = k * SFOUR;

        if (extending && lastChunk->compressed_size > Modes.traceChunkMaxBytes) {
            // make new chunk if the last one is pretty big already
            extending = 0;
        }

        if (extending && memcmp(zstd_magic, lastChunk->compressed, sizeof(zstd_magic)) != 0) {
            extending = 0;
        }
        if (extending < Modes.traceChunkPoints / 4) {
            extending = 0;
        }
    }

    int newBytes = 0;
    if (extending) {
        pointCount = extending;
        // add to existing chunk

        // do some bookkeeping, we add the compressed size of the newly compressed chunk back to it
        a->trace_chunk_overall_bytes -= lastChunk->compressed_size;

        // tell rest of the code to write new details into existing stateChunk struct
        target = lastChunk;
        lastChunk = NULL;

        target->numStates = target->numStates + pointCount;
        // target->firstTimestamp stays the same
        target->lastTimestamp = getState(source, pointCount - 1)->timestamp;

        newBytes = stateBytes(pointCount);
    } else {
        // disable, not worth it
        if (0 && lastChunk && memcmp(zstd_magic, lastChunk->compressed, sizeof(zstd_magic)) == 0) {
            // recompress finished buffer
            recompressStateChunk(lastChunk, passbuffer);
        }

        // make new chunk
        target = resizeTraceChunks(a, a->trace_chunk_len + 1);

        if (!target) {
            fprintf(stderr, "%06x compressChunk error, resizeTraceChunks returned NULL, treat this as fatal and exit.\n", a->addr);
            setExit(2);
            return 0;
        }

        target->numStates = pointCount;
        target->firstTimestamp = getState(source, 0)->timestamp;
        target->lastTimestamp = getState(source, pointCount - 1)->timestamp;

        newBytes = stateBytes(pointCount);
    }
    size_t compressedSize = 0;
    if (1) {

        if (!passbuffer->cctx) {
            passbuffer->cctx = ZSTD_createCCtx();
        }

        //fprintf(stderr, "pbuffer->size: %ld src.len %ld\n", (long) pbuffer->size, (long) src.len);

        if (0 && Modes.json_dir) {
            char path[1024];
            snprintf(path, 1024, "%s/tracechunk_samples/%06x", Modes.json_dir, a->addr);
            int fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
            if (fd >= 0) {
                check_write(fd, source, newBytes, path);
                close(fd);
            }
        }

        /*
         * size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
         void* dst, size_t dstCapacity,
         const void* src, size_t srcSize,
         int compressionLevel);
         */

        int maxSize = ZSTD_compressBound(newBytes);
        int totalBuffer = maxSize;
        if (extending) {
            totalBuffer += target->compressed_size;
        }
        char *compressed = check_grow_threadpool_buffer_t(passbuffer, totalBuffer);

        if (extending) {
            memcpy(compressed, target->compressed, target->compressed_size);
            sfree(target->compressed);
            compressed += target->compressed_size;
        }

        compressedSize = ZSTD_compressCCtx(
                passbuffer->cctx,
                compressed, maxSize,
                source, newBytes,
                2);

        if (ZSTD_isError(compressedSize)) {
            fprintf(stderr, "compressChunk() zstd error: %s\n", ZSTD_getErrorName(compressedSize));
            exit(1);
        }

    } else {
        int temp_alloc = newBytes + newBytes / 16 + 64 + 3; // from mini lzo example: upper bound of compressed size
        unsigned char lzo_work[LZO1X_1_MEM_COMPRESS];
        check_grow_threadpool_buffer_t(passbuffer, temp_alloc);

        lzo_uint compressed_len = 0;
        //lzo1x_1_compress        ( const lzo_bytep src, lzo_uint  src_len, lzo_bytep dst, lzo_uintp dst_len, lzo_voidp wrkmem );
        int res = lzo1x_1_compress((unsigned char *) source, newBytes, passbuffer->buf, &compressed_len, lzo_work);

        if (res != LZO_E_OK) { fprintf(stderr, "lzo1x_1_compress error Theij8ah\n"); exit(1); }
        if (compressed_len < 1) { fprintf(stderr, "compressChunk len < 1\n"); exit(1); }

        compressedSize = compressed_len;
    }

    if (extending) {
        target->compressed_size = target->compressed_size + compressedSize;
    } else {
        target->compressed_size = compressedSize;
    }
    target->compressed = cmalloc(target->compressed_size);
    memcpy(target->compressed, passbuffer->buf, target->compressed_size);

    a->trace_chunk_overall_bytes += target->compressed_size;


    if (Modes.verbose) {
        int64_t after = nsThreadTime();
        fprintf(stderr, "%s%06x compressChunk: cpu: %7.3f ms compressed: %8d chunks %3d ratio %5.2f lp %5.1fh chunkTime %5.1fh %5d %5d\n",
                ((a->addr & MODES_NON_ICAO_ADDRESS) ? "." : ". "),
                a->addr, (after - before) * 1e-6, target->compressed_size, a->trace_chunk_len, stateBytes(target->numStates) / (double) target->compressed_size,
                (now - (getState(a->trace_current, a->trace_current_len - 1))->timestamp) / (double) HOURS,
                (target->lastTimestamp - target->firstTimestamp) / (double) HOURS,
                target->numStates, extending);
    }

    return pointCount;
}

static void setTrace(struct aircraft *a, fourState *source, int len, threadpool_buffer_t *passbuffer) {
    if (len == 0) {
        traceCleanup(a);
        return;
    }
    int64_t now = mstime();

    //fprintf(stderr, "%06x setTrace, len %ld fourStates %ld stateBytes %ld\n", a->addr, (long) len, (long) getFourStates(len), (long) stateBytes(len));

    traceCleanupNoUnlink(a);

    a->trace_len = len;

    fourState *p = source;
    int chunkSize = alignSFOUR(Modes.traceChunkPoints);
    while (len > chunkSize + minCurrentPoints()) {
        int res = compressChunk(p, chunkSize, passbuffer, a);

        len -= res;
        p += res / SFOUR;
        //fprintf(stderr, "setTrace reduce len: %ld\n", (long) len);
    }

    a->trace_current_len = len;
    resizeTraceCurrent(a, now);
    if (a->trace_current_max < a->trace_current_len) {
        fprintf(stderr, "%06x setTrace error, insufficient current trace, discarding some data\n", a->addr);
        a->trace_current_len = 0;
    } else if (a->trace_current_len > 0) {
        //fprintf(stderr, "%06x setTrace current memcpy, len %ld fourStates %ld stateBytes %ld\n", a->addr, (long) len, (long) getFourStates(len), (long) stateBytes(len));
        // keep buffered position intact -> +1
        memcpy(a->trace_current, p, stateBytes(a->trace_current_len + 1));
    }

}

static int get_nominal_trace_current_points(struct aircraft *a, int64_t now) {
    if (now - a->seenPosReliable > 60 * MINUTES) {
        return alignSFOUR(Modes.traceReserve) + minCurrentPoints() + SFOUR;
    } else {
        return alignSFOUR(Modes.traceReserve + Modes.traceChunkPoints);
    }
}

static void resizeTraceCurrent(struct aircraft *a, int64_t now) {
    int newPoints = get_nominal_trace_current_points(a, now);
    int minPoints = alignSFOUR(a->trace_current_len + Modes.traceReserve);
    if (newPoints < minPoints) {
        newPoints = minPoints;
    }
    if (newPoints == a->trace_current_max && a->trace_current) {
        if (0 && Modes.verbose) {
            fprintf(stderr, "len %d max %d\n", a->trace_current_len, a->trace_current_max);
        }
        return;
    }
    int newBytes = stateBytes(newPoints);
    fourState *new = cmalloc(newBytes);

    memset(new, 0x0, newBytes);

    if (a->trace_current) {
        memcpy(new, a->trace_current, stateBytes(a->trace_current_len + 1)); // 1 extra for buffered pos
        sfree(a->trace_current);
    }

    a->trace_current = new;
    a->trace_current_max = newPoints;
}

static void compressCurrent(struct aircraft *a, threadpool_buffer_t *passbuffer) {
    int keep = minCurrentPoints();
    int chunkPoints = ((a->trace_current_len - keep) / SFOUR) * SFOUR;
    int newLen = a->trace_current_len - chunkPoints;
    if (chunkPoints < SFOUR || newLen < keep) {
        return;
    }
    if (chunkPoints % SFOUR != 0) {
        fprintf(stderr, "<3> %06x compressCurrent: error: (chunkPoints %% SFOUR != 0)\n", a->addr);
        return;
    }
    if (a->trace_current_len < chunkPoints) {
        fprintf(stderr, "<3> %06x compressCurrent: error: trace_current_len < chunkPoints\n", a->addr);
        return;
    }

    // return actually compressed points
    int res = compressChunk(a->trace_current, chunkPoints, passbuffer, a);

    // current_len + 1 to account for the buffered position
    int oldBytes = stateBytes(a->trace_current_len + 1);
    a->trace_current_len -= res;
    int newBytes = stateBytes(a->trace_current_len + 1);

    int diffBytes = stateBytes(res);
    char *src = ((char *) a->trace_current) + diffBytes;
    char *dest = (char *) a->trace_current;

    if (newBytes + diffBytes != oldBytes) {
        fprintf(stderr, "<3> %06x compressCurrent very wrong, very bad!\n", a->addr);
    }

    memmove(dest, src, newBytes);
}

void traceMaintenance(struct aircraft *a, int64_t now, threadpool_buffer_t *passbuffer) {
    // free trace cache for inactive aircraft
    if (a->traceCache.entries && now - a->seenPosReliable > TRACE_CACHE_LIFETIME) {
        //fprintf(stderr, "%06x free traceCache\n", a->addr);
        destroyTraceCache(&a->traceCache);
    }

    //fprintf(stderr, "%06x\n", a->addr);

    if (a->trace_len == 0) {
        return;
    }
    // throw out old data if older than keep_trace or trace is getting full
    tracePrune(a, now);

    if (a->trace_len == 0) {
        return;
    }

    if (Modes.json_globe_index) {
        if (now > a->trace_next_perm)
            a->trace_write |= WPERM;
        if (now > a->trace_next_mw)
            a->trace_write |= WMEM;
    }

    // on day change write out the traces for yesterday
    // for which day and which time span is written is determined by traceday
    if (a->traceWrittenForYesterday != Modes.triggerPermWriteDay) {
        a->traceWrittenForYesterday = Modes.triggerPermWriteDay;
        if (a->addr == TRACE_FOCUS)
            fprintf(stderr, "schedule_perm\n");

        a->trace_next_perm = now + random() % (5 * MINUTES);
    }

    if (a->trace_current_len > 0) {
        // reset trace_current allocation to nominal size if possible / necessary
        if (a->trace_current_max != get_nominal_trace_current_points(a, now)) {
            resizeTraceCurrent(a, now);
        }


        if ((a->trace_current_len >= Modes.traceChunkPoints + Modes.traceReserve / 4)) {
            compressCurrent(a, passbuffer);
        }

        if (a->trace_current_len > Modes.traceChunkPoints / 4) {
            struct state *firstCurrent = getState(a->trace_current, 0);
            struct state *lastCurrent = getState(a->trace_current, a->trace_current_len - 1);
            if (lastCurrent->timestamp - firstCurrent->timestamp > traceChunkDuration()) {
                compressCurrent(a, passbuffer);
            }
        }
    }
}


int traceAdd(struct aircraft *a, struct modesMessage *mm, int64_t now, int stale) {
    if (!Modes.keep_traces)
        return 0;

    int traceDebug = (a->addr == Modes.trace_focus);

    int save_state_no_buf = 0;
    int posUsed = 0;
    int bufferedPosUsed = 0;
    double distance = 0;
    int64_t elapsed = 0;
    int64_t elapsed_buffered = 0;
    int duplicate = 0;
    float speed_diff = 0;
    float track_diff = 0;
    float baro_rate_diff = 0;
    struct state *last = NULL;

    int64_t max_elapsed = Modes.json_trace_interval;
    int64_t min_elapsed = imin(250, max_elapsed / 4);

    float turn_density = 5.0;
    float max_speed_diff = 5.0;

    int alt = a->baro_alt;
    int alt_valid = altBaroReliableTrace(now, a);

    if (alt_valid && a->baro_alt > 10000) {
        max_speed_diff *= 2;
    }

    if (Modes.json_trace_interval > 5 * SECONDS) {
        if (a->pos_reliable_valid.source == SOURCE_MLAT) {
            min_elapsed = 1500;
            max_elapsed /= 2;
        }
    }
    // some towers on MLAT .... create unnecessary data
    // only reduce data produced for configurations with trace interval more than 5 seconds, others migh want EVERY DOT :)
    if (a->squawk_valid.source != SOURCE_INVALID && a->squawk == 0x7777) {
        min_elapsed = max_elapsed;
    }

    int on_ground = 0;
    float track = -1;
    if (trackVState(now, &a->track_valid, &a->pos_reliable_valid) && a->track_valid.source != SOURCE_MLAT) {
        track = a->track;
    } else {
        track = -1;
    }

    int agValid = 0;
    if (trackDataValid(&a->airground_valid)) {
        agValid = 1;
        if (a->airground == AG_GROUND) {
            on_ground = 1;
            if (trackVState(now, &a->true_heading_valid, &a->pos_reliable_valid)) {
                track = a->true_heading;
            } else {
                track = -1;
            }
        }
    }

    if (a->trace_current_len == 0)
        goto save_state;

    last = getState(a->trace_current, a->trace_current_len - 1);

    if (now >= last->timestamp) {
        elapsed = now - last->timestamp;
    }

    struct state *buffered = NULL;

    if (a->tracePosBuffered) {
        buffered = getState(a->trace_current, a->trace_current_len);
        elapsed_buffered = (int64_t) buffered->timestamp - (int64_t) last->timestamp;
    }

    if (elapsed_buffered < 0) {
        fprintf(stderr, "%06x traceAdd len: %d current_len %d elapsed: %.3f elapsed_buffered %.3f mstime: %.3f now: %.3f last->timesatmp: %.3f\n",
                a->addr, a->trace_len, a->trace_current_len, elapsed / 1000.0, elapsed_buffered / 1000.0, mstime() / 1000.0, now / 1000.0, last->timestamp / 1000.0);
        buffered = NULL;
        a->tracePosBuffered = 0;
        elapsed_buffered = 0;
    }

    if (elapsed < 0) {
        fprintf(stderr, "%06x traceAdd elapsed: %.3f elapsed_buffered %.3f mstime: %.3f now: %.3f last->timesatmp: %.3f\n",
                a->addr, elapsed / 1000.0, elapsed_buffered / 1000.0, mstime() / 1000.0, now / 1000.0, last->timestamp / 1000.0);
    }

    int32_t new_lat = (int32_t) nearbyint(a->lat * 1E6);
    int32_t new_lon = (int32_t) nearbyint(a->lon * 1E6);
    duplicate = (elapsed < 1 * SECONDS && new_lat == last->lat && new_lon == last->lon);

    int last_alt = last->baro_alt / _alt_factor;
    int last_alt_valid = last->baro_alt_valid;

    int alt_diff = 0;
    if (last_alt_valid && alt_valid) {
        alt_diff = abs(a->baro_alt - last_alt);
    }

    if (trackDataValid(&a->gs_valid) && last->gs_valid && a->gs_valid.source != SOURCE_MLAT) {
        speed_diff = fabs(last->gs / _gs_factor - a->gs);
    }

    if (trackDataValid(&a->baro_rate_valid) && last->baro_rate_valid && a->baro_rate_valid.source != SOURCE_MLAT) {
        baro_rate_diff = fabs(last->baro_rate / _rate_factor - a->baro_rate);
    }

    // keep the last air ground state if the current isn't valid
    if (!agValid && !alt_valid) {
        on_ground = last->on_ground;
    }
    if (on_ground) {
        // just do this twice so we cover the first point in a trace as well as using the last airground state
        if (trackVState(now, &a->true_heading_valid, &a->pos_reliable_valid)) {
            track = a->true_heading;
        } else {
            track = -1;
        }
    }

    float last_track = last->track / _track_factor;
    if (last->track_valid && track > -1) {
        track_diff = fabs(norm_diff(track - last_track, 180));
    }


    distance = greatcircle(last->lat / 1E6, last->lon / 1E6, a->lat, a->lon, 0);

    if (distance < 5)
        traceDebug = 0;

    if (traceDebug) {
        fprintf(stderr, "%11.6f,%11.6f %5.1fs d:%5.0f a:%6d D%4d s:%4.0f D%3.0f t: %5.1f D%5.1f ",
                a->lat, a->lon,
                elapsed / 1000.0,
                distance, alt, alt_diff, a->gs, speed_diff, a->track, track_diff);
    }

    if (speed_diff >= max_speed_diff) {
        if (traceDebug) {
            fprintf(stderr, "speed_change: %0.1f %0.1f -> %0.1f", speed_diff, last->gs / _gs_factor, a->gs);
        }

        if (buffered && last->gs == buffered->gs) {
            save_state_no_buf = 1;
        } else {
            goto save_state;
        }
    }

    if (baro_rate_diff >= 450) {
        if (traceDebug) {
            fprintf(stderr, "baro_rate_change: %0.0f %0.0f -> %0.0f", baro_rate_diff, last->baro_rate / _rate_factor, (double) a->baro_rate);
        }

        goto save_state;
    }

    // record ground air state changes precisely
    if (on_ground != last->on_ground) {
        goto save_state;
    }

    // record non moving targets every 5 minutes
    if (elapsed > 10 * max_elapsed) {
        goto save_state;
    }

    if (alt_valid && !last_alt_valid) {
        goto save_state;
    }

    // check altitude change before minimum interval
    if (alt_diff > 0) {

        int max_diff = 250;

        if (alt <= 7000) {
            if (buffered && last->baro_alt == buffered->baro_alt) {
                max_diff = 200; // for transponders with 100 ft altitude increments
            } else {
                max_diff = 100;
            }
        } else if (alt <= 12000) {
            max_diff = 200;
        } else {
            max_diff = 400;
        }

        if (alt_diff >= max_diff) {
            if (traceDebug) fprintf(stderr, "alt_change1: %d -> %d", last_alt, alt);
            if (alt_diff == max_diff || (buffered && last->baro_alt == buffered->baro_alt)) {
                save_state_no_buf = 1;
            } else {
                goto save_state;
            }
        }

        int base = 800;
        if (alt <= 7000) {
            base = 125;
        } else if (alt <= 12000) {
            base = 250;
        }
        int64_t too_long = ((max_elapsed / 4) * base / (float) alt_diff);
        if (alt_diff >= 25 && elapsed > too_long) {
            if (traceDebug) fprintf(stderr, "alt_change2: %d -> %d, %5.1f", last_alt, alt, too_long / 1000.0);
            save_state_no_buf = 1;
        }
    }

    // don't record unnecessary many points
    if (elapsed < min_elapsed)
        goto no_save_state;

    // even if the squawk gets invalid we continue to record more points
    if (a->squawk == 0x7700) {
        goto save_state;
    }

    // record trace precisely if we have a TCAS advisory
    if (trackDataValid(&a->acas_ra_valid) && trackDataAge(now, &a->acas_ra_valid) < 15 * SECONDS) {
        goto save_state;
    }

    if (!on_ground && elapsed > max_elapsed) // default 30000 ms
        goto save_state;

    // SS2
    if (a->addr == 0xa19b53 && elapsed > max_elapsed / 4)
        goto save_state;

    if (stale) {
        // save a point if reception is spotty so we can mark track as spotty on display
        goto save_state;
    }

    if (on_ground) {
        if (elapsed > 4 * max_elapsed) {
            goto save_state;
        }
        if (distance > 10 && elapsed > max_elapsed) {
            goto save_state;
        }
        if (a->gs > 5 && elapsed > max_elapsed / 2) {
            goto save_state;
        }

        if (distance * track_diff > 130) {
            if (traceDebug) fprintf(stderr, "track_change: %0.1f %0.1f -> %0.1f", track_diff, last_track, a->track);
            goto save_state;
        }

        if (distance > 50)
            goto save_state;
    }

    if (track_diff > 0.5
            && (elapsed / 1000.0 * track_diff * turn_density > 100.0)
       ) {
        if (traceDebug) fprintf(stderr, "track_change: %0.1f %0.1f -> %0.1f", track_diff, last_track, a->track);
        goto save_state;
    }

    if (save_state_no_buf) {
        goto save_state_no_buf;
    }

    goto no_save_state;

save_state:


    if (Modes.debug_position_timing && last && elapsed < 10) {
        fprintf(stderr, "%06x elapsed < 10 ms: %11.6f,%11.6f -> %11.6f,%11.6f %lldms d:%5.0f s: %4.0f sc: %4.0f\n",
                a->addr,
                last->lat * 1e-6, last->lon * 1e-6,
                a->lat, a->lon,
                (long long) elapsed,
                distance, a->gs, (distance * 1000 / elapsed) * (3600.0f/1852.0f));
    }
    if (elapsed_buffered && elapsed_buffered < 10) {
    }

    // always try using the buffered position instead of the current one
    // this should provide a better picture of changing track / speed / altitude

    if (elapsed > max_elapsed || 2 * elapsed_buffered > elapsed || elapsed_buffered > 2700) {
        if (traceUsePosBuffered(a)) {
            if (traceDebug) fprintf(stderr, " buffer\n");
            // in some cases we want to add the current point as well
            // if not, the current point will be put in the buffer
            traceAdd(a, mm, now, stale);
            // return so the point isn't used a second time or put in the buffer
            return 1;
        }
    }

save_state_no_buf:
    posUsed = 1;
    //fprintf(stderr, "traceAdd: %06x elapsed: %8.1f s distance: %8.3f km\n", a->addr, elapsed / 1000.0, distance / 1000.0);

no_save_state:


    if (duplicate) {
        // don't put a duplicate position in the buffer and don't use it for the trace
        return 0;
    }

    if (!a->trace_current) {
        resizeTraceCurrent(a, now);
        scheduleMemBothWrite(a, now); // rewrite full history file
        a->trace_next_perm = now + GLOBE_PERM_IVAL / 2; // schedule perm write

        //fprintf(stderr, "%06x: new trace\n", a->addr);
    }

    // current_len still needs to be a usable index after being incremented
    if (a->trace_current_len + 1 >= a->trace_current_max - 1) {
        static int64_t antiSpam;
        if (Modes.debug_traceAlloc || now > antiSpam + 5 * SECONDS) {
            double elapsed_seconds = elapsed * 0.001;
            fprintf(stderr, "%06x trace_current_max insufficient (%d/%d) %11.6f,%11.6f %5.1fs d:%5.0f s: %4.0f sc: %4.0f\n",
                    a->addr,
                    a->trace_current_len, a->trace_current_max,
                    a->lat, a->lon,
                    elapsed_seconds,
                    distance, a->gs, (distance / elapsed_seconds) * (3600.0f/1852.0f));
            antiSpam = now;
            //displayModesMessage(mm);
        }
        return 0;
    }

    struct state *new = getState(a->trace_current, a->trace_current_len);

    to_state(a, new, now, on_ground, track, stale);

    // trace_all stuff:
    struct state_all *new_all = getStateAll(a->trace_current, a->trace_current_len);
    if (new_all) {
        to_state_all(a, new_all, now);
    }

    if (posUsed) {
        if (traceDebug) fprintf(stderr, " normal\n");
        a->tracePosBuffered = 0;
        // bookkeeping:
        a->trace_len++;
        a->trace_current_len++;
        a->trace_write |= WRECENT;
        a->trace_writeCounter++;
    } else {
        a->tracePosBuffered = 1;
    }

    if (traceDebug && !posUsed && !bufferedPosUsed) fprintf(stderr, " none\n");

    return posUsed || bufferedPosUsed;
}

void save_blob(int blob, threadpool_buffer_t *pbuffer1, threadpool_buffer_t *pbuffer2) {
    if (!Modes.state_dir)
        return;
    //static int count;
    //fprintf(stderr, "Save blob: %02x, count: %d\n", blob, ++count);
    if (blob < 0 || blob > STATE_BLOBS) {
        fprintf(stderr, "save_blob: invalid argument: %02x", blob);
        return;
    }

    int gzip = 0;
    int lzo = 0;
    int zst = 1;

    char filename[PATH_MAX];
    char tmppath[PATH_MAX];
    if (zst) {
        snprintf(filename, 1024, "%s/blob_%02x.zstl", Modes.state_dir, blob);
    } else if (lzo) {
        snprintf(filename, 1024, "%s/blob_%02x.lzol", Modes.state_dir, blob);
    } else if (gzip) {
        snprintf(filename, 1024, "%s/blob_%02x.gz", Modes.state_dir, blob);
    } else {
        snprintf(filename, 1024, "%s/blob_%02x", Modes.state_dir, blob);
    }
    snprintf(tmppath, PATH_MAX, "%s.readsb_tmp", filename);

    int fd = open(tmppath, O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (fd < 0) {
        fprintf(stderr, "open failed:");
        perror(tmppath);
        return;
    }
    gzFile gzfp = NULL;
    if (gzip) {
        int res;
        gzfp = gzdopen(fd, "wb");
        if (!gzfp) {
            fprintf(stderr, "gzdopen failed:");
            perror(tmppath);
            close(fd);
            return;
        }
        if (gzbuffer(gzfp, GZBUFFER_BIG) < 0)
            fprintf(stderr, "gzbuffer fail");
        res = gzsetparams(gzfp, 1, Z_FILTERED);
        if (res < 0)
            fprintf(stderr, "gzsetparams fail: %d", res);
    }

    int stride = AIRCRAFT_BUCKETS / STATE_BLOBS;
    int start = stride * blob;
    int end = start + stride;

    int alloc = Modes.state_chunk_size;

    unsigned char *buf = check_grow_threadpool_buffer_t(pbuffer1, alloc);
    unsigned char *p = buf;

    //fprintf(stderr, "buf %p p %p \n", buf, p);

    lzo_uint compressed_len = 0;
    unsigned char *lzo_out = NULL;
    unsigned char lzo_work[LZO1X_1_MEM_COMPRESS];
    int lzo_out_alloc;
    int lzo_header_len = 2 * sizeof(uint64_t);
    if (lzo) {
        lzo_out_alloc = lzo_header_len + alloc + alloc / 16 + 64 + 3; // from mini lzo example
        lzo_out = check_grow_threadpool_buffer_t(pbuffer2, lzo_out_alloc);
    }

    char *zst_out = NULL;
    int zst_out_alloc;
    int zst_header_len = 2 * sizeof(uint32_t);
    if (zst) {
        if (!pbuffer2->cctx) {
            pbuffer2->cctx = ZSTD_createCCtx();
        }
        zst_out_alloc = ZSTD_compressBound(alloc);
        zst_out = check_grow_threadpool_buffer_t(pbuffer2, zst_out_alloc + zst_header_len);
    }

    int chunk_ac_count = 0;

    struct aircraft copyback;
    struct aircraft *copy = &copyback;
    for (int j = start; j < end; j++) {
        for (struct aircraft *a = Modes.aircraft[j]; a || (j == end - 1); a = a->next) {
            int size_state = 0;
            if (!a) {
                copy = NULL;
            } else {
                // work on local copy of aircraft for traceUsePosBuffered
                memcpy(copy, a, sizeof(struct aircraft));

                traceUsePosBuffered(copy);

                size_state += sizeof(struct aircraft);
                if (copy->trace_chunk_len > 0 && copy->trace_chunks == NULL) {
                    fprintf(stderr, "<3> %06x trace corrupted, copy->trace_chunks is NULL but copy->trace_chunk_len > 0\n", copy->addr);
                }
                for (int k = 0; k < copy->trace_chunk_len; k++) {
                    stateChunk *chunk = &copy->trace_chunks[k];
                    size_state += sizeof(stateChunk);
                    size_state += roundUp8(chunk->compressed_size);
                }
                size_state += stateBytes(copy->trace_current_len);

                // add space for 2 magic constants / 2 struct sizes
                size_state += 4 * sizeof(uint64_t);
            }

            if (!copy || (p + size_state > buf + alloc)) {
                //fprintf(stderr, "save_blob writing %d bytes (buffer %p alloc %d)\n", (int) ((p - buf)), p, alloc);

                uint64_t magic_end = STATE_SAVE_MAGIC_END;
                memcpy(p, &magic_end, sizeof(magic_end));
                p += sizeof(magic_end);

                if (p > buf + alloc) {
                    fprintf(stderr, "save_blob: overran buffer! %ld\n", (long) (p - (buf + alloc)));
                }

                if (zst) {
                    uint32_t uncompressed_len = p - buf;

                    /*
                     * size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
                     void* dst, size_t dstCapacity,
                     const void* src, size_t srcSize,
                     int compressionLevel);
                     */

                    size_t compressedSize = ZSTD_compressCCtx(pbuffer2->cctx,
                            zst_out + zst_header_len, zst_out_alloc,
                            buf, uncompressed_len,
                            1);

                    if (ZSTD_isError(compressedSize)) {
                        fprintf(stderr, "save_blob() zstd error: %s\n", ZSTD_getErrorName(compressedSize));
                        goto error;
                    }

                    uint32_t compressed_len = compressedSize;

                    // write header

                    memcpy(zst_out, &compressed_len, sizeof(uint32_t));
                    memcpy(zst_out + sizeof(uint32_t), &uncompressed_len, sizeof(uint32_t));

                    // end header

                    check_write(fd, zst_out, compressed_len + zst_header_len, tmppath);
                } else if (lzo) {
                    int res = lzo1x_1_compress(buf, p - buf, lzo_out + lzo_header_len, &compressed_len, lzo_work);

                    //fprintf(stderr, "%d %08lld\n", blob, (long long) compressed_len);

                    if (res != LZO_E_OK) {
                        fprintf(stderr, "lzo1x_1_compress error, couldn't save state blob: %s\n", filename);
                        goto error;
                    }

                    // write header
                    uint64_t lzo_magic = LZO_MAGIC;
                    memcpy(lzo_out, &lzo_magic, sizeof(uint64_t));
                    uint64_t compressed_len_64 = compressed_len;
                    memcpy(lzo_out + sizeof(uint64_t), &compressed_len_64, sizeof(uint64_t));
                    // end header

                    check_write(fd, lzo_out, compressed_len + lzo_header_len, tmppath);
                } else if (gzip) {
                    writeGz(gzfp, buf, p - buf, tmppath);
                } else {
                    check_write(fd, buf, p - buf, tmppath);
                }

                if (size_state > alloc) {
                    int old_alloc = alloc;
                    alloc = imax(2 * size_state, Modes.state_chunk_size);
                    if (alloc > Modes.state_chunk_size) {
                        Modes.state_chunk_size = alloc; // increase chunk size for later invocations
                        fprintf(stderr, "%06x: Increasing state_chunk_size to %d! chunk_ac_count %d size_state %d old_alloc %d\n",
                                copy->addr, (int) alloc, chunk_ac_count, (int) size_state, (int) old_alloc);
                    }


                    buf = check_grow_threadpool_buffer_t(pbuffer1, alloc);
                    p = buf;

                    if (lzo) {
                        lzo_out_alloc = lzo_header_len + alloc + alloc / 16 + 64 + 3; // from mini lzo example
                        lzo_out = check_grow_threadpool_buffer_t(pbuffer2, lzo_out_alloc);
                    }
                }

                p = buf;
                chunk_ac_count = 0;
            }

            if (!copy) {
                break;
            }

            if (p + size_state > buf + alloc) {
                fprintf(stderr, "<3> %06x: Couldn't write internal state, check save_blob code! chunk_ac_count %d size_state %d alloc %d\n", copy->addr, chunk_ac_count, (int) size_state, alloc);
                continue;
            }

            chunk_ac_count++;

            uint64_t magic = STATE_SAVE_MAGIC;
            p += memcpySize(p, &magic, sizeof(magic));
            uint64_t size_aircraft = sizeof(struct aircraft);
            p += memcpySize(p, &size_aircraft, sizeof(size_aircraft));

            aircraftZeroTail(copy);
            p += memcpySize(p, copy, sizeof(struct aircraft));
            if (copy->trace_len > 0) {

                uint64_t fourState_size = sizeof(fourState);
                p += memcpySize(p, &fourState_size, sizeof(fourState_size));

                for (int k = 0; k < copy->trace_chunk_len; k++) {
                    stateChunk *chunk = &copy->trace_chunks[k];
                    p += memcpySize(p, chunk, sizeof(stateChunk));

                    p += memcpySize(p, chunk->compressed, chunk->compressed_size);
                    ssize_t padBytes = roundUp8(chunk->compressed_size) - chunk->compressed_size;
                    if (padBytes > 0) {
                        memset(p, 0x0, padBytes);
                        p += padBytes;
                    } else if (padBytes < 0) {
                        fprintf(stderr, "padBytes %ld roundUp8 %ld compressed_size %ld\n", (long) padBytes, (long) roundUp8(chunk->compressed_size), (long) chunk->compressed_size);
                    }
                }
                p += memcpySize(p, copy->trace_current, stateBytes(copy->trace_current_len));
            }
        }
    }

    if (gzfp)
        gzclose(gzfp);
    else if (fd != -1)
        close(fd);

    if (rename(tmppath, filename) == -1) {
        fprintf(stderr, "save_blob rename(): %s -> %s", tmppath, filename);
        perror("");
        unlink(tmppath);
    }
    goto out;
error:
    if (gzfp)
        gzclose(gzfp);
    else if (fd != -1)
        close(fd);
    unlink(tmppath);
out:
    ;
}

static int load_aircrafts(char *p, char *end, char *filename, int64_t now, threadpool_buffer_t *passbuffer) {
    int count = 0;
    while (end - p > 0) {
        uint64_t value = 0;
        if (end - p >= (long) sizeof(value)) {
            p += memcpySize(&value, p, sizeof(value));
        }

        if (value != STATE_SAVE_MAGIC) {
            if (value != STATE_SAVE_MAGIC_END) {
                fprintf(stderr, "Incomplete state file (or state format was changed and is incompatible with new format): %s\n", filename);
                return -1;
            }
            break;
        }
        load_aircraft(&p, end, now, passbuffer);
        count++;
    }
    return count;
}

void load_blob(char *blob, threadpool_threadbuffers_t * buffer_group) {
    int64_t now = mstime();
    int fd = -1;
    struct char_buffer cb;
    char *p;
    char *end;
    int lzo = 0;
    int zst = 0;
    char filename[1024];

    snprintf(filename, 1024, "%s.zstl", blob);
    fd = open(filename, O_RDONLY);
    if (fd != -1) {
        zst = 1;
        cb = readWholeFile(fd, filename);
        close(fd);
    } else {
        Modes.writeInternalState = 1; // not the primary load method, immediately write state
        snprintf(filename, 1024, "%s.lzol", blob);
        fd = open(filename, O_RDONLY);
        if (fd != -1) {
            lzo = 1;
            cb = readWholeFile(fd, filename);
            close(fd);
            unlink(filename); // moving to zst
        } else {
            snprintf(filename, 1024, "%s.gz", blob);
            gzFile gzfp = gzopen(filename, "r");
            if (gzfp) {
                cb = readWholeGz(gzfp, filename);
                gzclose(gzfp);
                unlink(filename); // moving to lzo
            } else {
                fd = open(blob, O_RDONLY);
                if (fd == -1) {
                    fprintf(stderr, "missing state blob:");
                    snprintf(filename, 1024, "%s[.gz/.lzol/.zstl]", blob);
                    perror(filename);
                    return;
                }
                cb = readWholeFile(fd, filename);
                close(fd);
                unlink(filename); // moving to lzo
            }
        }
    }
    if (!cb.buffer)
        return;
    p = cb.buffer;
    end = p + cb.len;

    threadpool_buffer_t *pb1 = &buffer_group->buffers[0];
    threadpool_buffer_t *pb2 = &buffer_group->buffers[1];

    if (zst) {
        while (end - p > 0) {
            if (end - p < 2 * (ssize_t) sizeof(uint32_t)) {
                fprintf(stderr, "Corrupt state file (too small): %s\n", filename);
                goto out;
            }
            uint32_t compressed_len = *((uint32_t *) p);
            p += sizeof(compressed_len);

            uint32_t uncompressed_len = *((uint32_t *) p);
            p += sizeof(uncompressed_len);

            if (end - p < (ssize_t) compressed_len) {
                fprintf(stderr, "Corrupt state file (smaller than compressed_len): %s\n", filename);
                goto out;
            }

            if (!pb1->dctx) {
                pb1->dctx = ZSTD_createDCtx();
            }

            char *uncompressed = check_grow_threadpool_buffer_t(pb1, uncompressed_len);
            char *compressed = p;

            size_t res = ZSTD_decompressDCtx(pb1->dctx, uncompressed, uncompressed_len, compressed, compressed_len);
            if (ZSTD_isError(res)) {
                fprintf(stderr, "Corrupt state file %s zstd error: %s\n", filename, ZSTD_getErrorName(res));
                goto out;
            }

            if (load_aircrafts(uncompressed, uncompressed + uncompressed_len, filename, now, pb2) < 0) {
                goto out;
            }
            p += compressed_len;
        }
    } else if (lzo) {
        int lzo_out_alloc = Modes.state_chunk_size_read;

        char *lzo_out = check_grow_threadpool_buffer_t(pb1, lzo_out_alloc);

        lzo_uint uncompressed_len = 0;
        int res = 0;
        while (end - p > 0) {
            uint64_t value = 0;
            uint64_t compressed_len = 0;
            if (end - p >= (long) (sizeof(value) + sizeof(compressed_len))) {
                p += memcpySize(&value, p, sizeof(value));

                p += memcpySize(&compressed_len, p, sizeof(compressed_len));
            }
            //fprintf(stderr, "%d %08lld\n", blob, (long long) compressed_len);

            if (value != LZO_MAGIC) {
                fprintf(stderr, "Corrupt state file (LZO_MAGIC wrong): %s\n", filename);
                goto out;
            }

decompress:
            uncompressed_len = lzo_out_alloc;
            res = lzo1x_decompress_safe((unsigned char*) p, compressed_len, (unsigned char*) lzo_out, &uncompressed_len, NULL);
            if (res != LZO_E_OK) {
                lzo_out_alloc = imax(2 * lzo_out_alloc, Modes.state_chunk_size_read);
                lzo_out_alloc = imax(lzo_out_alloc, 2 * compressed_len);
                if (lzo_out_alloc > Modes.state_chunk_size_read) {
                    Modes.state_chunk_size_read = lzo_out_alloc; // also increase chunk size for later invocations
                    fprintf(stderr, "decompression failed, trying larger buffer (%d): %s\n", lzo_out_alloc, filename);
                }
                if (lzo_out_alloc > 256 * 1024 * 1024 || !lzo_out) {
                    fprintf(stderr, "Corrupt state file (decompression failure): %s\n", filename);
                    goto out;
                }

                lzo_out = check_grow_threadpool_buffer_t(pb1, lzo_out_alloc);
                goto decompress;
            }

            if (load_aircrafts(lzo_out, lzo_out + uncompressed_len, filename, now, pb2) < 0) {
                goto out;
            }
            p += compressed_len;
        }
    } else {
        load_aircrafts(p, end, filename, now, pb2);
    }

out:
    sfree(cb.buffer);
}

static void load_blobs(void *arg, threadpool_threadbuffers_t * buffer_group) {
    task_info_t *info = (task_info_t *) arg;

    for (int j = info->from; j < info->to; j++) {
        char blob[1024];
        snprintf(blob, 1024, "%s/blob_%02x", Modes.state_dir, j);
        load_blob(blob, buffer_group);
    }
}

static inline void heatmapCheckAlloc(struct heatEntry **buffer, int64_t **slices, int64_t *alloc, int64_t len) {
    if (!*buffer || len + 8 >= *alloc) {
        *alloc += 8;
        *alloc *= 3;
        *buffer = realloc(*buffer, *alloc * sizeof(struct heatEntry));
        *slices = realloc(*slices, *alloc * sizeof(int64_t));
        if (!*buffer || !*slices) {
            fprintf(stderr, "<3> FATAL: handleHeatmap not enough memory, trying to allocate %lld bytes\n",
                    (long long) (*alloc * sizeof(struct heatEntry)));
            exit(1);
        }
    }
}

static void checkMiscBreak() {
    // take a break now and then and let maintenance functions run
    // wait in 50 ms increments
    while (priorityTasksPending()) {
        struct timespec ts;
        clock_gettime(CLOCK_REALTIME, &ts);
        threadTimedWait(&Threads.misc, &ts, 50);
    }
}


int handleHeatmap(int64_t now) {
    if (!Modes.heatmap)
        return 0;

    time_t nowish = (now - 30 * MINUTES)/1000;
    struct tm utc;
    gmtime_r(&nowish, &utc);
    int half_hour = utc.tm_hour * 2 + utc.tm_min / 30;

    if (Modes.heatmap_current_interval < -1) {
        Modes.heatmap_current_interval++;
        return 0;
        // startup delay before first time heatmap is written
    }

    // don't write on startup when persistent state isn't enabled
    if (!Modes.state_dir && Modes.heatmap_current_interval < 0) {
        Modes.heatmap_current_interval = half_hour;
        return 0;
    }
    // only do this every 30 minutes.
    if (half_hour == Modes.heatmap_current_interval)
        return 0;

    Modes.heatmap_current_interval = half_hour;

    utc.tm_hour = half_hour / 2;
    utc.tm_min = 30 * (half_hour % 2);
    utc.tm_sec = 0;
    int64_t start = 1000 * (int64_t) (timegm(&utc));
    int64_t end = start + 30 * MINUTES;
    int64_t num_slices = (int)((30 * MINUTES) / Modes.heatmap_interval);


    char pathbuf[PATH_MAX];
    char tmppath[PATH_MAX];
    int64_t len = 0;
    int64_t len2 = 0;
    int64_t alloc = (50 + Modes.globalStatsCount.readsb_aircraft_with_position) * num_slices;
    struct heatEntry *buffer = NULL;
    int64_t *slices = NULL;

    heatmapCheckAlloc(&buffer, &slices, &alloc, len);

    threadpool_buffer_t passbuffer = { 0 };

    for (int j = 0; j < AIRCRAFT_BUCKETS; j++) {
        checkMiscBreak();
        for (struct aircraft *a = Modes.aircraft[j]; a; a = a->next) {
            if ((a->addr & MODES_NON_ICAO_ADDRESS) && a->airground == AG_GROUND) continue;
            if (a->trace_len == 0) continue;

            traceBuffer tb = reassembleTrace(a, -1, start, &passbuffer);
            int64_t next = start;
            int64_t slice = 0;
            uint32_t squawk = 0x8888; // impossible squawk
            uint64_t callsign = 0; // quackery

            int64_t callsign_interval = imax(Modes.heatmap_interval, 1 * MINUTES);
            int64_t next_callsign = start;

            for (int i = 0; i < tb.len; i++) {
                struct state *state = getState(tb.trace, i);
                if (state->timestamp > end)
                    break;
                struct state_all *all = getStateAll(tb.trace, i);
                if (state->timestamp >= start && all) {
                    uint64_t *cs = (uint64_t *) &(all->callsign);
                    if (state->timestamp >= next_callsign || *cs != callsign || squawk != all->squawk) {

                        next_callsign = state->timestamp + callsign_interval;
                        callsign = *cs;
                        squawk = all->squawk;

                        uint32_t s = all->squawk;
                        int32_t d = (s & 0xF) + 10 * ((s & 0xF0) >> 4) + 100 * ((s & 0xF00) >> 8) + 1000 * ((s & 0xF000) >> 12);
                        buffer[len].hex = a->addr;
                        buffer[len].lat = (1 << 30) | d;

                        memcpy(&buffer[len].lon, all->callsign, 8);

                        //if (a->addr == Modes.leg_focus) {
                        //    fprintf(stderr, "squawk: %d %04x\n", d, s);
                        //}

                        slices[len] = slice;
                        len++;
                        heatmapCheckAlloc(&buffer, &slices, &alloc, len);
                    }
                }
                if (state->timestamp < next)
                    continue;

                if (!state->baro_alt_valid && !state->geom_alt_valid)
                    continue;

                while (state->timestamp > next + Modes.heatmap_interval) {
                    next += Modes.heatmap_interval;
                    slice++;
                }

                uint32_t addrtype_5bits = ((uint32_t) state->addrtype) & 0x1F;

                buffer[len].hex = a->addr | (addrtype_5bits << 27);
                buffer[len].lat = state->lat;
                buffer[len].lon = state->lon;

                // altitude encoded in steps of 25 ft ... file convention
                if (state->on_ground)
                    buffer[len].alt = -123; // on ground
                else if (state->baro_alt_valid)
                    buffer[len].alt = nearbyint(state->baro_alt / (_alt_factor * 25.0f));
                else if (state->geom_alt_valid)
                    buffer[len].alt = nearbyint(state->geom_alt / (_alt_factor * 25.0f));
                else
                    buffer[len].alt = 0;

                if (state->gs_valid)
                    buffer[len].gs = nearbyint(state->gs / _gs_factor * 10.0f);
                else
                    buffer[len].gs = -1; // invalid

                slices[len] = slice;

                len++;
                heatmapCheckAlloc(&buffer, &slices, &alloc, len);

                next += Modes.heatmap_interval;
                slice++;

            }
        }
    }

    free_threadpool_buffer(&passbuffer);

    struct heatEntry *buffer2 = cmalloc(alloc * sizeof(struct heatEntry));
    ssize_t indexSize = num_slices * sizeof(struct heatEntry);
    struct heatEntry *index = cmalloc(indexSize);

    if (!buffer2 || !index) {
        return 0;
    }

    //////////// UNLOCK MISC
    pthread_mutex_unlock(&Threads.misc.mutex);
    //////////// UNLOCK MISC

    memset(index, 0, indexSize); // avoid having to set zero individually

    for (int i = 0; i < num_slices; i++) {
        struct heatEntry specialSauce = (struct heatEntry) {0};
        int64_t slice_stamp = start + i * Modes.heatmap_interval;
        specialSauce.hex = 0xe7f7c9d;
        specialSauce.lat = slice_stamp >> 32;
        specialSauce.lon = slice_stamp & ((1ULL << 32) - 1);
        specialSauce.alt = Modes.heatmap_interval;

        index[i].hex = len2 + num_slices;
        buffer2[len2++] = specialSauce;

        for (int k = 0; k < len; k++) {
            if (slices[k] == i)
                buffer2[len2++] = buffer[k];
        }
    }
    char *base_dir = Modes.globe_history_dir;
    if (Modes.heatmap_dir) {
        base_dir = Modes.heatmap_dir;
    }

    mkdir_error(base_dir, 0755, stderr);

    char dateDir[PATH_MAX * 3/4];

    createDateDir(base_dir, &utc, dateDir);

    snprintf(pathbuf, PATH_MAX, "%s/heatmap", dateDir);
    mkdir_error(pathbuf, 0755, stderr);

    snprintf(pathbuf, PATH_MAX, "%s/heatmap/%02d.bin.ttf", dateDir, half_hour);
    snprintf(tmppath, PATH_MAX, "%s.readsb_tmp", pathbuf);

    //fprintf(stderr, "%s using %d positions\n", pathbuf, len);

    int fd = open(tmppath, O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (fd < 0) {
        perror(tmppath);
    } else {
        int res;
        gzFile gzfp = gzdopen(fd, "wb");
        if (!gzfp)
            fprintf(stderr, "heatmap: gzdopen fail");
        if (gzbuffer(gzfp, GZBUFFER_BIG) < 0)
            fprintf(stderr, "gzbuffer fail");
        res = gzsetparams(gzfp, 9, Z_DEFAULT_STRATEGY);
        if (res < 0)
            fprintf(stderr, "gzsetparams fail: %d", res);
        writeGz(gzfp, index, indexSize, tmppath);

        ssize_t toWrite = len2 * sizeof(struct heatEntry);
        writeGz(gzfp, buffer2, toWrite, tmppath);

        gzclose(gzfp);
    }
    if (rename(tmppath, pathbuf) == -1) {
        fprintf(stderr, "heatmap rename(): %s -> %s", tmppath, pathbuf);
        perror("");
    }

    free(index);
    free(buffer);
    free(buffer2);
    free(slices);

    //////////// LOCK MISC
    pthread_mutex_lock(&Threads.misc.mutex);
    //////////// LOCK MISC

    return 1;
}

static void compressACAS(char *dateDir) {
    char filename[PATH_MAX];
    snprintf(filename, PATH_MAX, "%s/acas/acas.csv", dateDir);
    gzipFile(filename);
    unlink(filename);

    snprintf(filename, PATH_MAX, "%s/acas/acas.json", dateDir);
    gzipFile(filename);
    unlink(filename);
}

void checkNewDay(int64_t now) {
    if (!Modes.globe_history_dir || !Modes.json_globe_index)
        return;

    static int64_t next_check;
    if (now < next_check) {
        return;
    }
    next_check = now + 5 * SECONDS;

    char filename[PATH_MAX];
    char dateDir[PATH_MAX * 3/4];

    // at 15 min past midnight, start a permanent write of all traces
    // create the new directory for writing traces
    // prevent the webserver from reading it until they are in a finished state
    time_t fifteenAgo = (now - 15 * MINUTES) / 1000; // in seconds
    struct tm utcFifteenAgo;
    gmtime_r(&fifteenAgo, &utcFifteenAgo);

    if (utcFifteenAgo.tm_mday != Modes.triggerPermWriteDay) {
        Modes.triggerPermWriteDay = utcFifteenAgo.tm_mday;

        createDateDir(Modes.globe_history_dir, &utcFifteenAgo, dateDir);

        snprintf(filename, PATH_MAX, "%s/traces", dateDir);
        int err = mkdir_error(filename, 0755, stderr);

        if (Modes.trace_hist_only) {
            chmod(filename, 0755);
        }

        // if the directory exists we assume we already have created the subdirectories
        // if the directory couldn't be created no need to try and create subdirectories it won't work.
        if (!err) {
            for (int i = 0; i < 256; i++) {
                snprintf(filename, PATH_MAX, "%s/traces/%02x", dateDir, i);
                mkdir_error(filename, 0755, stderr);
            }
        }
    }

    // fiftyfive_ago changes day 55 min after midnight: stop writing the previous days traces
    // fiftysix_ago changes day 56 min after midnight: allow webserver to read the previous days traces (see checkNewDay function)
    // this is in seconds, not milliseconds
    time_t fiftysix_ago = now / 1000 - 56 * 60;
    struct tm utcFiftySixAgo;
    gmtime_r(&fiftysix_ago, &utcFiftySixAgo);

    if (utcFiftySixAgo.tm_mday != Modes.traceDay) {
        Modes.traceDay = utcFiftySixAgo.tm_mday;
        time_t yesterday = now / 1000 - 24 * 3600;
        struct tm tm_yesterday;
        gmtime_r(&yesterday, &tm_yesterday);

        createDateDir(Modes.globe_history_dir, &tm_yesterday, dateDir); // doesn't usually create a directory ... but use the function anyhow worst that can happen is an empty directory for yesterday

        snprintf(filename, PATH_MAX, "%s/traces", dateDir);
        chmod(filename, 0755);

        compressACAS(dateDir);
    }
}

void checkNewDayAcas(int64_t now) {
    if (!Modes.globe_history_dir || !Modes.json_globe_index)
        return;

    struct tm utc;
    time_t time = now / 1000;
    gmtime_r(&time, &utc);

    if (utc.tm_mday != Modes.acasDay) {
        Modes.acasDay = utc.tm_mday;

        char filename[PATH_MAX];
        char dateDir[PATH_MAX * 3/4];

        createDateDir(Modes.globe_history_dir, &utc, dateDir);

        snprintf(filename, PATH_MAX, "%s/acas", dateDir);
        mkdir_error(filename, 0755, stderr);

        if (Modes.acasFD1 > -1)
            close(Modes.acasFD1);
        if (Modes.acasFD2 > -1)
            close(Modes.acasFD2);


        if (Modes.enableAcasCsv) {
            snprintf(filename, PATH_MAX, "%s/acas/acas.csv", dateDir);
            Modes.acasFD1 = open(filename, O_WRONLY | O_CREAT | O_APPEND, 0644);
            if (Modes.acasFD1 < 0) {
                fprintf(stderr, "open failed:");
                perror(filename);
            }
        }

        if (Modes.enableAcasJson) {
            snprintf(filename, PATH_MAX, "%s/acas/acas.json", dateDir);
            Modes.acasFD2 = open(filename, O_WRONLY | O_CREAT | O_APPEND, 0644);
            if (Modes.acasFD2 < 0) {
                fprintf(stderr, "open failed:");
                perror(filename);
            }
        }
    }
}

void writeRangeDirs() {
    if (!Modes.state_dir || !Modes.outline_json) {
        return;
    }

    char pathbuf[PATH_MAX];
    snprintf(pathbuf, PATH_MAX, "%s/rangeDirs.gz", Modes.state_dir);
    gzFile gzfp = gzopen(pathbuf, "wb");
    if (gzfp) {
        writeGz(gzfp, &Modes.lastRangeDirHour, sizeof(Modes.lastRangeDirHour), pathbuf);
        writeGz(gzfp, Modes.rangeDirs, sizeof(Modes.rangeDirs), pathbuf);
        gzclose(gzfp);
    }
}
static void writeInternalMiscTask(void *arg, threadpool_threadbuffers_t * buffers) {
    MODES_NOTUSED(arg);
    MODES_NOTUSED(buffers);

    writeRangeDirs();
}

static void readInternalMiscTask(void *arg, threadpool_threadbuffers_t * buffers) {
    MODES_NOTUSED(arg);
    MODES_NOTUSED(buffers);

    if (Modes.state_dir && Modes.outline_json) {
        char pathbuf[PATH_MAX];
        struct char_buffer cb;
        snprintf(pathbuf, PATH_MAX, "%s/rangeDirs.gz", Modes.state_dir);
        gzFile gzfp = gzopen(pathbuf, "r");
        if (gzfp) {
            cb = readWholeGz(gzfp, pathbuf);
            gzclose(gzfp);
            if (cb.len == sizeof(Modes.lastRangeDirHour) + sizeof(Modes.rangeDirs)) {
                fprintf(stderr, "actual range outline, read bytes: %zu\n", cb.len);

                char *p = cb.buffer;
                memcpy(&Modes.lastRangeDirHour, p, sizeof(Modes.lastRangeDirHour));
                p += sizeof(Modes.lastRangeDirHour);
                memcpy(Modes.rangeDirs, p, sizeof(Modes.rangeDirs));
            }
            free(cb.buffer);
        }
    }
}

void writeInternalState() {
    struct timespec watch;

    if (Modes.state_dir) {
        fprintf(stderr, "saving state .....\n");
        startWatch(&watch);
    }

    int64_t now = mstime();

    int parts = STATE_BLOBS;
    int stride = 1;

    threadpool_t *pool = threadpool_create(imax(1, Modes.num_procs), 4);
    task_group_t *group = allocate_task_group(parts + 1);
    threadpool_task_t *tasks = group->tasks;
    task_info_t *infos = group->infos;

    // assign tasks
    int taskCount = 0;
    {
        threadpool_task_t *task = &tasks[taskCount];
        task->function = writeInternalMiscTask;
        task->argument = NULL;
        taskCount++;
    }

    for (int i = 0; i < parts; i++) {
        threadpool_task_t *task = &tasks[taskCount];
        task_info_t *range = &infos[taskCount];

        range->now = now;
        range->from = i * stride;
        range->to = imin(STATE_BLOBS, range->from + stride);

        //fprintf(stderr, "from %d to %d\n", range->from, range->to);

        task->function = save_blobs;
        task->argument = range;

        taskCount++;
    }

    // run tasks
    threadpool_run(pool, tasks, taskCount);

    threadpool_destroy(pool);
    destroy_task_group(group);


    if (Modes.state_dir) {
        double elapsed = stopWatch(&watch) / 1000.0;
        fprintf(stderr, " .......... done, saved %llu aircraft in %.3f seconds!\n", (unsigned long long) Modes.total_aircraft_count, elapsed);
    }
}


void readInternalState() {
    int retval = mkdir(Modes.state_dir, 0755);
    if (retval != 0 && errno != EEXIST) {
        fprintf(stderr, "Unable to create state directory (%s): %s\n", Modes.state_dir, strerror(errno));
        return;
    }
    if (retval == 0) {
        fprintf(stderr, "%s: state directory didn't exist, created it, possible reasons: "
                "first start with state enabled / directory not backed by persistent storage\n",
                Modes.state_dir);
        fprintf(stderr, "loading state ..... FAILED!\n");
        return;
    }

    fprintf(stderr, "loading state .....\n");
    struct timespec watch;
    startWatch(&watch);

    int64_t now = mstime();

    int parts = STATE_BLOBS;
    int stride = 1;

    threadpool_t *pool = threadpool_create(imax(1, Modes.num_procs), 4);
    task_group_t *group = allocate_task_group(parts + 1);
    threadpool_task_t *tasks = group->tasks;
    task_info_t *infos = group->infos;

    // assign tasks
    int taskCount = 0;
    {
        threadpool_task_t *task = &tasks[taskCount];
        task->function = readInternalMiscTask;
        task->argument = NULL;
        taskCount++;
    }

    int k = STATE_BLOBS - 1;
    for (int i = 0; i < parts; i++) {
        threadpool_task_t *task = &tasks[taskCount];
        task_info_t *range = &infos[taskCount];

        range->now = now;
        range->from = k * stride;
        range->to = imin(STATE_BLOBS, (k + 1) * stride);
        k--;

        //fprintf(stderr, "from %d to %d\n", range->from, range->to);

        task->function = load_blobs;
        task->argument = range;

        taskCount++;
    }

    // run tasks
    threadpool_run(pool, tasks, taskCount);

    threadpool_destroy(pool);
    destroy_task_group(group);

    int64_t aircraftCount = 0; // includes quite old aircraft, just for checking hash table fill
    for (int j = 0; j < AIRCRAFT_BUCKETS; j++) {
        for (struct aircraft *a = Modes.aircraft[j]; a; a = a->next) {
            aircraftCount++;
        }
    }
    Modes.total_aircraft_count = aircraftCount;

    double elapsed = stopWatch(&watch) / 1000.0;
    fprintf(stderr, " .......... done, loaded %llu aircraft in %.3f seconds!\n", (unsigned long long) aircraftCount, elapsed);
    fprintf(stderr, "aircraft table fill: %0.1f\n", aircraftCount / (double) AIRCRAFT_BUCKETS );
}

void unlinkPerm(struct aircraft *a) {
    if (!Modes.globe_history_dir) {
        return;
    }

    int64_t now = mstime();

    a->trace_perm_last_timestamp = 0;

    // fiftyfive_ago changes day 55 min after midnight: stop writing the previous days traces
    // fiftysix_ago changes day 56 min after midnight: allow webserver to read the previous days traces (see checkNewDay function)
    // this is in seconds, not milliseconds
    time_t fiftyfive_time = now / 1000 - 55 * 60;

    struct tm fiftyfive;
    gmtime_r(&fiftyfive_time, &fiftyfive);

    // we just use the day of the struct tm in the next lines
    fiftyfive.tm_sec = 0;
    fiftyfive.tm_min = 0;
    fiftyfive.tm_hour = 0;

    char tstring[100];
    strftime (tstring, 100, TDATE_FORMAT, &fiftyfive);

    char filename[PATH_MAX];

    snprintf(filename, PATH_MAX, "%s/%s/traces/%02x/trace_full_%s%06x.json", Modes.globe_history_dir, tstring, a->addr % 256, (a->addr & MODES_NON_ICAO_ADDRESS) ? "~" : "", a->addr & 0xFFFFFF);
    filename[PATH_MAX - 101] = 0;

    unlink(filename);

}

void traceDelete() {
    struct hexInterval* entry = Modes.deleteTrace;

    if (!entry) {
        return;
    }

    threadpool_buffer_t passbuffer = { 0 };

    while (entry) {
        struct hexInterval* curr = entry;
        struct aircraft *a = aircraftGet(curr->hex);
        if (!a) {
            fprintf(stderr, "Deleting trace points, aircraft not found: %06x\n", curr->hex);
            goto next;
        }

        traceUnlink(a);
        unlinkPerm(a);

        if (a->trace_len == 0) {
            fprintf(stderr, "Deleting trace points, aircraft has no trace: %06x\n", curr->hex);
            goto next;
        }


        traceUsePosBuffered(a);


        traceBuffer tb = reassembleTrace(a, -1, -1, &passbuffer);
        fourState *trace = tb.trace;
        int trace_len = tb.len;

        int old_len = trace_len;

        int start = 0;
        int end = trace_len + SFOUR; // point well past the end if not found

        int64_t from = curr->from * 1000;
        int64_t to = curr->to * 1000;

        for (int i = 0; i < trace_len; i += SFOUR) {
            int64_t timestamp = getState(trace, i)->timestamp;
            if (timestamp <= from) {
                start = i;
            }
            if (timestamp > to) {
                end = i;
                break;
            }
        }

        // align to fourState, delete whole fourState tuple if stuff we want to delete is contained
        start = start / SFOUR; // round down
        end = getFourStates(end);

        // end points past the last point to be deleted
        if (end >= getFourStates(trace_len)) {
            trace_len = imax(0, (start - 1) * SFOUR);
        } else if (end - start > 0) {
            memmove(trace + start, trace + end, (getFourStates(trace_len) - end) * sizeof(fourState));
            trace_len -= (end - start) * SFOUR;
        }


        setTrace(a, trace, trace_len, &passbuffer);

        int64_t now = mstime();
        a->trace_next_perm = now;
        scheduleMemBothWrite(a, now);
        traceMaintenance(a, now, &passbuffer);

        // write immediately:
        a->trace_write |= WRECENT;
        a->trace_write |= WPERM;
        a->trace_write |= WMEM;

        fprintf(stderr, "Deleted %06x from %lld to %lld trace_len %ld -> %ld\n", curr->hex, (long long) curr->from, (long long) curr->to, (long) old_len, (long) trace_len);

next:
        entry = entry->next;
        sfree(curr);
    }
    Modes.deleteTrace = NULL;
    free_threadpool_buffer(&passbuffer);
}

/*
void *load_state(void *arg) {
    int64_t now = mstime();
    char pathbuf[PATH_MAX];
    //struct stat fileinfo = {0};
    //fstat(fd, &fileinfo);
    //off_t len = fileinfo.st_size;
    int thread_number = *((int *) arg);
    srandom(get_seed());
    for (int i = 0; i < 256; i++) {
        if (i % Modes.io_threads != thread_number)
            continue;
        snprintf(pathbuf, PATH_MAX, "%s/%02x", Modes.state_dir, i);

        DIR *dp;
        struct dirent *ep;

        dp = opendir (pathbuf);
        if (dp == NULL)
            continue;

        while ((ep = readdir (dp))) {
            if (strlen(ep->d_name) < 6)
                continue;
            snprintf(pathbuf, PATH_MAX, "%s/%02x/%s", Modes.state_dir, i, ep->d_name);

            int fd = open(pathbuf, O_RDONLY);
            if (fd == -1)
                continue;

            struct char_buffer cb = readWholeFile(fd, pathbuf);
            if (!cb.buffer)
                continue;
            char *p = cb.buffer;
            char *end = p + cb.len;

            load_aircraft(&p, end, now);

            free(cb.buffer);
            close(fd);
            // old internal state format, no longer needed
            unlink(pathbuf);
        }

        closedir (dp);
    }
    return NULL;
}
*/