Adds a parseblink method to turn a blinker code into a numeric displa…

…y. (#516)

* Adds a parseblink method to turn a blinker code into a numeric display.

* Clarify the bit order.

src/utils/Blinker.cxx

@@ -0,0 +1,96 @@
+/** \copyright
+ * Copyright (c) 2021, Balazs Racz
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are  permitted provided that the following conditions are met:
+ *
+ *  - Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ *  - Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ * \file Blinker.cxx
+ *
+ * Implementations of blinker routines
+ *
+ * @author Balazs Racz
+ * @date 27 Feb 2021
+ */
+
+#include "utils/blinker.h"
+
+extern "C"
+{
+
+unsigned parseblink(uint32_t pattern)
+{
+    unsigned ret = 0;
+    if (!pattern)
+    {
+        return ret;
+    }
+    // Finds the top bit.
+    uint32_t tb = 1U << 31;
+    while ((tb & pattern) == 0)
+    {
+        tb >>= 1;
+    }
+    unsigned nibble_shift = 1;
+    unsigned last_len = 1;
+    unsigned curr_len = 1;
+    pattern &= ~tb;
+    while (true)
+    {
+        if (curr_len)
+        {
+            if (pattern & 1)
+            {
+                curr_len++;
+            }
+            else
+            {
+                // end of lit period
+                if (last_len != curr_len)
+                {
+                    // new blink length
+                    nibble_shift <<= 4;
+                    last_len = curr_len;
+                }
+                ret += nibble_shift;
+                curr_len = 0;
+            }
+        }
+        else
+        {
+            // we are in unlit
+            if (pattern & 1)
+            {
+                // start of a new lit period.
+                curr_len = 1;
+            }
+        }
+        if (!pattern)
+        {
+            break;
+        }
+        pattern >>= 1;
+    }
+    return ret;
+}
+
+}

src/utils/Blinker.cxxtest

@@ -0,0 +1,14 @@
+#include "utils/blinker.h"
+
+#include "utils/test_main.hxx"
+
+TEST(BlinkerTest, parse_test)
+{
+    EXPECT_EQ(0u, parseblink(0));
+    EXPECT_EQ(0x33u, parseblink(BLINK_DIE_ABORT));
+    EXPECT_EQ(0x213u, parseblink(BLINK_DIE_HARDFAULT));
+    EXPECT_EQ(0x123u, parseblink(BLINK_DIE_OUTOFMEM));
+    EXPECT_EQ(0x313u, parseblink(BLINK_DIE_NMI));
+    EXPECT_EQ(0x223u, parseblink(BLINK_DIE_ASSERT));
+    EXPECT_EQ(0x133u, parseblink(BLINK_DIE_WATCHDOG));
+};

src/utils/blinker.h

@@ -90,6 +90,14 @@ extern uint32_t blinker_pattern;
 /** Sets a blinking pattern and never returns. */
 extern void diewith(uint32_t);
 
+/** Turns a blinker pattern into an error code in BCD.
+ * @param pattern a blinker pattern from the above examples.
+ * @return a nonnegative integer with each 4-bit nibble representing the number
+ * of repeats in the block of blinks, in LSB-first order. So a blink 3-1-2 will
+ * be represented as 0x213.
+ */
+extern unsigned parseblink(uint32_t pattern);
+
 #ifdef __cplusplus
 }
 #endif  // cplusplus

src/utils/sources

@@ -5,6 +5,7 @@ CSRCS += errno_exit.c \
 
 CXXSRCS += \
 	   Base64.cxx \
+	   Blinker.cxx \
 	   CanIf.cxx \
 	   Crc.cxx \
 	   StringPrintf.cxx \