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edac: correct Golay(24,12) words that are not at the start of the message (#2631)

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Golay24.checkAndCorrect indexed the word from bit 0 (getInt(0, 22), xor(12, ...),
flip(index)) and took the parity over the whole message, so it was only right for a
message that is exactly one 24-bit word. P25 TDULC words 2-12 and the DMR voice
superframe words at 24 and 48 were "corrected" in the wrong bits. Decode any other
word in a 24-bit copy and write it back.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
This commit is contained in:
Steve Pinkham
2026-11-13 01:29:50 -05:00
committed by GitHub
parent a53f6e9d99
commit 7fcf035337
2 changed files with 108 additions and 0 deletions
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23
src/main/java/io/github/dsheirer/edac/Golay24.java
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@@ -68,6 +68,29 @@ public class Golay24
*/
public static int checkAndCorrect(CorrectedBinaryMessage message, int startIndex)
{
//The correction below indexes the word from bit 0 and takes the parity over the whole message, so it is only
//correct for a message that is exactly the 24-bit word. Decode any other word in a 24-bit copy.
if(startIndex != 0 || message.size() != 24)
{
CorrectedBinaryMessage word = new CorrectedBinaryMessage(24);
int original = message.getInt(startIndex, startIndex + 23);
word.load(0, 24, original);
int result = checkAndCorrectWord(word);
int corrected = word.getInt(0, 23);
message.load(startIndex, 24, corrected);
message.incrementCorrectedBitCount(Integer.bitCount(original ^ corrected));
return result;
}
return checkAndCorrectWord(message);
}
/**
* Error detection and correction of a message that is exactly one 24-bit word.
*/
private static int checkAndCorrectWord(CorrectedBinaryMessage message)
{
int startIndex = 0;
boolean parityError = message.cardinality() % 2 != 0;
int syndrome = getSyndrome(message, startIndex);