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Code Issues Packages Projects Releases 2 Wiki Activity

LJ CRC class code cleanup

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dennis.sheirer
2014-12-05 13:11:33 +00:00
parent 412f1ac9f7
commit 974487b740
1 changed files with 14 additions and 16 deletions
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30
src/crc/CRCLJ.java
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@@ -52,11 +52,11 @@ public class CRCLJ
private static int[] CHECKSUMS = new int[] private static int[] CHECKSUMS = new int[]
{ {
0x26EA, //Function 0 (MSB) 0x26EA, //Function 0 (LSB)
0x1375, //Function 1 0x1375, //Function 1
0xBE0B, //Function 2 0xBE0B, //Function 2
0xE8B4, //Function 3 (LSB) 0xE8B4, //Function 3 (MSB)
0x745A, //Address 0 (MSB) 0x745A, //Address 0 (LSB)
0x3A2D, //Address 1 0x3A2D, //Address 1
0xAAA7, //Address 2 0xAAA7, //Address 2
0xE2E2, //Address 3 0xE2E2, //Address 3
@@ -83,7 +83,7 @@ public class CRCLJ
0xCABD, //Address 24 0xCABD, //Address 24
0xD2EF, //Address 25 0xD2EF, //Address 25
0xDEC6, //Address 26 0xDEC6, //Address 26
0x6F63, //Address 27 0x6F63, //Address 27 (MSB)
//Single bit errors in the CRC Checksum //Single bit errors in the CRC Checksum
0x8000, //CRC 0 0x8000, //CRC 0
@@ -105,25 +105,24 @@ public class CRCLJ
}; };
/** /**
* Determines if message bits 16 - 47 pass the LJ CRC checksum * Determines if FUNCTION AND ADDRESS bits pass the LJ CRC checksum
* contained in bits 48 - 63, using a lookup table of CRC checksum values * using a lookup table of CRC checksum values derived from the CRC-16 value
* derived from the CRC-16 value
*/ */
public static CRC checkAndCorrect( BitSetBuffer msg ) public static CRC checkAndCorrect( BitSetBuffer message )
{ {
int calculated = 0; //Starting value int calculated = 0; //Starting value
/* Iterate the set bits and XOR running checksum with lookup value */ /* Iterate the set bits and XOR running checksum with lookup value */
for (int i = msg.nextSetBit( MESSAGE_START ); for (int i = message.nextSetBit( MESSAGE_START );
i >= MESSAGE_START && i < CRC_START; i >= MESSAGE_START && i < CRC_START;
i = msg.nextSetBit( i+1 ) ) i = message.nextSetBit( i+1 ) )
{ {
calculated ^= CHECKSUMS[ i - MESSAGE_START ]; calculated ^= CHECKSUMS[ i - MESSAGE_START ];
} }
int checksum = getChecksum( msg ); int checksum = getChecksum( message );
if( calculated == getChecksum( msg ) ) if( calculated == checksum )
{ {
return CRC.PASSED; return CRC.PASSED;
} }
@@ -135,7 +134,7 @@ public class CRCLJ
{ {
for( int error: errors ) for( int error: errors )
{ {
msg.flip( MESSAGE_START + error ); message.flip( MESSAGE_START + error );
} }
return CRC.CORRECTED; return CRC.CORRECTED;
@@ -146,7 +145,7 @@ public class CRCLJ
} }
/** /**
* Returns the integer value of the 15 bit crc checksum * Returns the integer value of the 16 bit crc checksum
*/ */
public static int getChecksum( BitSet msg ) public static int getChecksum( BitSet msg )
{ {
@@ -164,8 +163,7 @@ public class CRCLJ
} }
/** /**
* Returns the bit position of any bit checksums that match the checksum * Identifies 1 or 2 bit error positions that match the checksum error value.
* error pattern.
*/ */
public static int[] findBitErrors( int checksumError ) public static int[] findBitErrors( int checksumError )
{ {