allow setting an explicit timestamp when generating a uuidv7

docs/uuid.md

@@ -52,6 +52,18 @@ select uuid7();
 -- 018ff383-94fd-70fa-8da6-339180b8e15d
 ```
 
+The timestamp used for creating the UUID can be specified explicitly by passing the number of seconds since 1 January 1970.
+
+```sql
+select uuid7(0);
+-- 00000000-0000-7558-a13b-e7014913d8ad
+```
+
+```sql
+select uuid7(1700000000);
+-- 018bcfe5-6800-7b8a-8a96-e315717d31bb
+```
+
 ### uuid7_timestamp_ms
 
 ```text

src/uuid/extension.c

@@ -14,6 +14,7 @@
  *
  *     uuid4()                  - generate a version 4 UUID as a string
  *     uuid7()                  - generate a version 7 UUID as a string
+ *     uuid7(X)                 - generate a version 7 UUID as a string using X seconds since the unix epoch as the timestamp
  *     uuid_str(X)              - convert a UUID X into a well-formed UUID string
  *     uuid_blob(X)             - convert a UUID X into a 16-byte blob
  *     uuid7_timestamp_ms(X)    - extract unix timestamp in miliseconds
@@ -190,7 +191,12 @@ static void uuid_v7_generate(sqlite3_context* context, int argc, sqlite3_value**
     (void)argv;
 
     struct timespec ts;
-    timespec_get(&ts, TIME_UTC);
+    if (argc == 1 && sqlite3_value_type(argv[0])==SQLITE_INTEGER) {
+      sqlite3_int64 seconds = sqlite3_value_int64(argv[0]);
+      ts.tv_sec = seconds;
+    } else {
+      timespec_get(&ts, TIME_UTC);
+    }
     unsigned long long timestampMs = ts.tv_sec * 1000ULL + ts.tv_nsec / 1000000;
 
     sqlite3_randomness(16, aBlob);
@@ -266,7 +272,7 @@ int uuid_init(sqlite3* db) {
     sqlite3_create_function(db, "uuid4", 0, flags, 0, uuid_v4_generate, 0, 0);
     sqlite3_create_function(db, "gen_random_uuid", 0, flags, 0, uuid_v4_generate, 0, 0);
 #ifndef SQLEAN_OMIT_UUID7
-    sqlite3_create_function(db, "uuid7", 0, flags, 0, uuid_v7_generate, 0, 0);
+    sqlite3_create_function(db, "uuid7", -1, flags, 0, uuid_v7_generate, 0, 0);
     sqlite3_create_function(db, "uuid7_timestamp_ms", 1, det_flags, 0, uuid_v7_extract_timestamp_ms,
                             0, 0);
 #endif

test/uuid.sql

@@ -30,6 +30,7 @@ select '3_07', uuid_blob(null) is null;
 
 -- uuid7
 select '4_01', uuid7() like '________-____-7___-____-____________';
+select '4_02', uuid7(0) like '00000000-0000-7___-____-____________';
 
 -- uuid7_timestamp_ms
 select '5_01', uuid7_timestamp_ms('018ff38a-a5c9-712d-bc80-0550b3ad41a2') = 1717777901001;