ref: 82edb2aff5e7f0f00e5c921e591274591f338635
parent: ea97e8d0c797fa5dedb99ecec11605915e672802
author: sur <sur>
date: Fri Jul 7 08:20:51 EDT 2006
Table-lookup CRC implemented
--- a/libfaac/bitstream.c
+++ b/libfaac/bitstream.c
@@ -24,7 +24,7 @@
Copyright (c) 1997.
**********************************************************************/
/*
- * $Id: bitstream.c,v 1.31 2005/02/02 16:48:01 sur Exp $
+ * $Id: bitstream.c,v 1.32 2006/07/07 12:20:51 sur Exp $
*/
#include <stdio.h>
@@ -1350,21 +1350,140 @@
return coderInfo->iLenReordSpData;
}
-static void calc_CRC(BitStream *bitStream, int len)
+/*
+ CRC8 x^8 + x^4 + x^3 + x^2 + 1
+*/
+static const unsigned char _crctable[256] =
{- int i;
- unsigned char r = 255; /* Initialize to all ones */
+ 0x00, 0x1D, 0x3A, 0x27, 0x74, 0x69, 0x4E, 0x53,
+ 0xE8, 0xF5, 0xD2, 0xCF, 0x9C, 0x81, 0xA6, 0xBB,
+ 0xCD, 0xD0, 0xF7, 0xEA, 0xB9, 0xA4, 0x83, 0x9E,
+ 0x25, 0x38, 0x1F, 0x02, 0x51, 0x4C, 0x6B, 0x76,
+ 0x87, 0x9A, 0xBD, 0xA0, 0xF3, 0xEE, 0xC9, 0xD4,
+ 0x6F, 0x72, 0x55, 0x48, 0x1B, 0x06, 0x21, 0x3C,
+ 0x4A, 0x57, 0x70, 0x6D, 0x3E, 0x23, 0x04, 0x19,
+ 0xA2, 0xBF, 0x98, 0x85, 0xD6, 0xCB, 0xEC, 0xF1,
+ 0x13, 0x0E, 0x29, 0x34, 0x67, 0x7A, 0x5D, 0x40,
+ 0xFB, 0xE6, 0xC1, 0xDC, 0x8F, 0x92, 0xB5, 0xA8,
+ 0xDE, 0xC3, 0xE4, 0xF9, 0xAA, 0xB7, 0x90, 0x8D,
+ 0x36, 0x2B, 0x0C, 0x11, 0x42, 0x5F, 0x78, 0x65,
+ 0x94, 0x89, 0xAE, 0xB3, 0xE0, 0xFD, 0xDA, 0xC7,
+ 0x7C, 0x61, 0x46, 0x5B, 0x08, 0x15, 0x32, 0x2F,
+ 0x59, 0x44, 0x63, 0x7E, 0x2D, 0x30, 0x17, 0x0A,
+ 0xB1, 0xAC, 0x8B, 0x96, 0xC5, 0xD8, 0xFF, 0xE2,
+ 0x26, 0x3B, 0x1C, 0x01, 0x52, 0x4F, 0x68, 0x75,
+ 0xCE, 0xD3, 0xF4, 0xE9, 0xBA, 0xA7, 0x80, 0x9D,
+ 0xEB, 0xF6, 0xD1, 0xCC, 0x9F, 0x82, 0xA5, 0xB8,
+ 0x03, 0x1E, 0x39, 0x24, 0x77, 0x6A, 0x4D, 0x50,
+ 0xA1, 0xBC, 0x9B, 0x86, 0xD5, 0xC8, 0xEF, 0xF2,
+ 0x49, 0x54, 0x73, 0x6E, 0x3D, 0x20, 0x07, 0x1A,
+ 0x6C, 0x71, 0x56, 0x4B, 0x18, 0x05, 0x22, 0x3F,
+ 0x84, 0x99, 0xBE, 0xA3, 0xF0, 0xED, 0xCA, 0xD7,
+ 0x35, 0x28, 0x0F, 0x12, 0x41, 0x5C, 0x7B, 0x66,
+ 0xDD, 0xC0, 0xE7, 0xFA, 0xA9, 0xB4, 0x93, 0x8E,
+ 0xF8, 0xE5, 0xC2, 0xDF, 0x8C, 0x91, 0xB6, 0xAB,
+ 0x10, 0x0D, 0x2A, 0x37, 0x64, 0x79, 0x5E, 0x43,
+ 0xB2, 0xAF, 0x88, 0x95, 0xC6, 0xDB, 0xFC, 0xE1,
+ 0x5A, 0x47, 0x60, 0x7D, 0x2E, 0x33, 0x14, 0x09,
+ 0x7F, 0x62, 0x45, 0x58, 0x0B, 0x16, 0x31, 0x2C,
+ 0x97, 0x8A, 0xAD, 0xB0, 0xE3, 0xFE, 0xD9, 0xC4
+};
+static void calc_CRC(BitStream *bitStream, int len)
+{+ //int i;
+ //unsigned char r = ~0; /* Initialize to all ones */
+ unsigned char crc = ~0; /* Initialize to all ones */
+
/* CRC polynome used x^8 + x^4 + x^3 + x^2 +1 */
-#define GPOLY 0435
- for (i = 8; i < len + 8; i++) {- r = ( (r << 1) ^ (( (
- ( bitStream->data[i / 8] >> (7 - (i % 8)) )
- & 1) ^ ((r >> 7) & 1)) * GPOLY )) & 0xFF;
+ unsigned int cb = len / 8;
+ unsigned int taillen = len & 0x7;
+ unsigned char* pb = &bitStream->data[1];
+ //compatible, but slower unsigned char b = ( bitStream->data[cb + 1] ) >> ( 8 - taillen );
+ unsigned char b = bitStream->data[cb + 1];
+
+//#define GPOLY 0435
+//
+// for (i = 8; i < len + 8; i++) {+// r = ( (r << 1) ^ (( (
+// ( bitStream->data[i / 8] >> (7 - (i % 8)) )
+// & 1) ^ ((r >> 7) & 1)) * GPOLY )) & 0xFF;
+// }
+
+#define GP 0x1d
+
+//fprintf( stderr, "\nfaac:" );
+
+ while ( cb-- )
+ {+//fprintf( stderr, " %02X", *pb );
+ crc = _crctable[ crc ^ *pb++ ];
}
+
+ //compatible, but slower switch ( taillen )
+ //{+ //case 7:
+ // crc = ( ( crc << 1 ) ^ ( ( ( ( b >> 6 ) & 1 ) ^ ( ( crc >> 7 ) & 1 ) ) * GP ) ) & 0xFF;
+ // // goto next case
+ //case 6:
+ // crc = ( ( crc << 1 ) ^ ( ( ( ( b >> 5 ) & 1 ) ^ ( ( crc >> 7 ) & 1 ) ) * GP ) ) & 0xFF;
+ // // goto next case
+ //case 5:
+ // crc = ( ( crc << 1 ) ^ ( ( ( ( b >> 4 ) & 1 ) ^ ( ( crc >> 7 ) & 1 ) ) * GP ) ) & 0xFF;
+ // // goto next case
+ //case 4:
+ // crc = ( ( crc << 1 ) ^ ( ( ( ( b >> 3 ) & 1 ) ^ ( ( crc >> 7 ) & 1 ) ) * GP ) ) & 0xFF;
+ // // goto next case
+ //case 3:
+ // crc = ( ( crc << 1 ) ^ ( ( ( ( b >> 2 ) & 1 ) ^ ( ( crc >> 7 ) & 1 ) ) * GP ) ) & 0xFF;
+ // // goto next case
+ //case 2:
+ // crc = ( ( crc << 1 ) ^ ( ( ( ( b >> 1 ) & 1 ) ^ ( ( crc >> 7 ) & 1 ) ) * GP ) ) & 0xFF;
+ // // goto next case
+ //case 1:
+ // crc = ( ( crc << 1 ) ^ ( ( ( b & 1 ) ^ ( ( crc >> 7 ) & 1 ) ) * GP ) ) & 0xFF;
+ // break;
+ //}
+//fprintf( stderr, " %02X", ( b >> ( 8 - taillen ) ) << 7 );
+ switch ( taillen )
+ {+ case 7:
+ crc = ( ( crc << 1 ) ^ ( ( (signed char)( b ^ crc ) >> 7 ) & GP ) ) & 0xFF;
+ b <<= 1;
+ // goto next case
+ case 6:
+ crc = ( ( crc << 1 ) ^ ( ( (signed char)( b ^ crc ) >> 7 ) & GP ) ) & 0xFF;
+ b <<= 1;
+ // goto next case
+ case 5:
+ crc = ( ( crc << 1 ) ^ ( ( (signed char)( b ^ crc ) >> 7 ) & GP ) ) & 0xFF;
+ b <<= 1;
+ // goto next case
+ case 4:
+ crc = ( ( crc << 1 ) ^ ( ( (signed char)( b ^ crc ) >> 7 ) & GP ) ) & 0xFF;
+ b <<= 1;
+ // goto next case
+ case 3:
+ crc = ( ( crc << 1 ) ^ ( ( (signed char)( b ^ crc ) >> 7 ) & GP ) ) & 0xFF;
+ b <<= 1;
+ // goto next case
+ case 2:
+ crc = ( ( crc << 1 ) ^ ( ( (signed char)( b ^ crc ) >> 7 ) & GP ) ) & 0xFF;
+ b <<= 1;
+ // goto next case
+ case 1:
+ crc = ( ( crc << 1 ) ^ ( ( (signed char)( b ^ crc ) >> 7 ) & GP ) ) & 0xFF;
+ break;
+ }
+ //if ( crc != r )
+ //{+ // fprintf( stderr, "%08X != %08X\n", crc, r );
+ //}
+//fprintf( stderr, " (%5d bits), CRC is %02X\n", len, ~crc & 0xFF );
+
/* CRC is stored inverted, per definition at first byte in stream */
- bitStream->data[0] = ~r;
+ bitStream->data[0] = ~crc;
}
#endif