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Changed NID error detection and correction (edac) to using Berlekemp Massey 63-bit block decoder for the BCH(63,16,11) code so that we can correct up to 11 bit errors in a NID (versus previous 2).

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dennis.sheirer
2015-01-04 15:29:34 +00:00
parent bb27d5cb42
commit 84261a4be9
7 changed files with 145 additions and 74 deletions
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68
src/edac/CRCP25.java
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@@ -29,33 +29,6 @@ public class CRCP25
{
private final static Logger mLog = LoggerFactory.getLogger( CRCP25.class );
private static final int NID_MESSAGE_START = 0;
private static final int NID_CRC_START = 16;
private static final int NID_CRC_END = 48;
/**
* Network ID and Data Unit ID checksums
*/
private static long[] NID_DUID_CHECKSUMS = new long[]
{
0xCD930BDD3B2Al, 0xAB5A8E33A6BEl, 0x983E4CC4E874l, 0x4C1F2662743Al,
0xEB9C98EC0136l, 0xB85D47AB3BB0l, 0x5C2EA3D59DD8l, 0x2E1751EACEECl,
0x170BA8F56776l, 0xC616DFA78890l, 0x630B6FD3C448l, 0x3185B7E9E224l,
0x18C2DBF4F112l, 0xC1F2662743A2l, 0xAD6A38CE9AFBl, 0x9B2617BA7657l,
0x800000000000l, 0x400000000000l, 0x200000000000l, 0x100000000000l,
0x080000000000l, 0x040000000000l, 0x020000000000l, 0x010000000000l,
0x008000000000l, 0x004000000000l, 0x002000000000l, 0x001000000000l,
0x000800000000l, 0x000400000000l, 0x000200000000l, 0x000100000000l,
0x000080000000l, 0x000040000000l, 0x000020000000l, 0x000010000000l,
0x000008000000l, 0x000004000000l, 0x000002000000l, 0x000001000000l,
0x000000800000l, 0x000000400000l, 0x000000200000l, 0x000000100000l,
0x000000080000l, 0x000000040000l, 0x000000020000l, 0x000000010000l,
0x000000008000l, 0x000000004000l, 0x000000002000l, 0x000000001000l,
0x000000000800l, 0x000000000400l, 0x000000000200l, 0x000000000100l,
0x000000000080l, 0x000000000040l, 0x000000000020l, 0x000000000010l,
0x000000000008l, 0x000000000004l, 0x000000000002l, 0x000000000001l
};
/**
* CRC-CCITT 16-bit checksums for a message length of 80 bits plus 16
* additional checksums representing CRC checksum bit errors
@@ -222,47 +195,6 @@ public class CRCP25
0x20000000l, 0x40000000l, 0x80000000l
};
/**
* Performs CRC check and corrects single-bit errors against the message.
* @param message - bitsetbuffer containing a message of at least 64 bits.
* @return - results of CRC check and/or correction attempt
*/
public static CRC correctNID( BitSetBuffer message )
{
long calculated = 0; //Starting value
/* Iterate the set bits and XOR running checksum with lookup value */
for (int i = message.nextSetBit( NID_MESSAGE_START );
i >= NID_MESSAGE_START && i < NID_CRC_START;
i = message.nextSetBit( i+1 ) )
{
calculated ^= NID_DUID_CHECKSUMS[ i - NID_MESSAGE_START ];
}
long checksum = getLongChecksum( message, NID_CRC_START, NID_CRC_END );
if( calculated == checksum )
{
return CRC.PASSED;
}
else
{
int errorLocation = getBitError( calculated ^ checksum,
NID_DUID_CHECKSUMS );
if( errorLocation >= 0 )
{
message.flip( errorLocation + NID_MESSAGE_START );
return CRC.CORRECTED;
}
}
return CRC.FAILED_CRC;
}
/**
* Performs error detection and single-bit error correction against the
* data blocks of a PDU1 message.