| 名称 | 多项式 | 初始值 | 异或值 | Bit反转 |
|---|---|---|---|---|
| CRC-32 | 0x04C11DB7 | 0xFFFFFFFF | 0xFFFFFFFF | LSB First |
| CRC-32/B | 0x04C11DB7 | 0xFFFFFFFF | 0xFFFFFFFF | MSB First |
| CRC-32/C | 0x1EDC6F41 | 0xFFFFFFFF | 0xFFFFFFFF | LSB First |
| CRC-32/D | 0xA833982B | 0xFFFFFFFF | 0xFFFFFFFF | LSB First |
| CRC-32/MPEG-2 | 0x04C11DB7 | 0xFFFFFFFF | 0x00000000 | MSB First |
| CRC-32/POSIX | 0x04C11DB7 | 0x00000000 | 0xFFFFFFFF | MSB First |
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public class CRC32Utils { /** * CRC-32 * * @param source * @param offset * @param length * @return */ public static long CRC32(byte[] source, int offset, int length) { long wCRCin = 0xFFFFFFFFL; // Long.reverse(0x04C11DB7L) >>> 32 long wCPoly = 0xEDB88320L; for (int i = offset, cnt = offset + length; i < cnt; i++) { wCRCin ^= ((long) source[i] & 0x000000FFL); for (int j = 0; j < 8; j++) { if ((wCRCin & 0x00000001L) != 0) { wCRCin >>= 1; wCRCin ^= wCPoly; } else { wCRCin >>= 1; } } } return wCRCin ^= 0xFFFFFFFFL; } /** * CRC-32/B * * @param source * @param offset * @param length * @return */ public static long CRC32_B(byte[] source, int offset, int length) { long wCRCin = 0xFFFFFFFFL; long wCPoly = 0x04C11DB7L; for (int i = offset, cnt = offset + length; i < cnt; i++) { for (int j = 0; j < 8; j++) { boolean bit = ((source[i] >> (7 - j) & 1) == 1); boolean c31 = ((wCRCin >> 31 & 1) == 1); wCRCin <<= 1; if (c31 ^ bit) { wCRCin ^= wCPoly; } } } wCRCin &= 0xFFFFFFFFL; return wCRCin ^= 0xFFFFFFFFL; } /** * CRC-32/C * * @param source * @param offset * @param length * @return */ public static long CRC32_C(byte[] source, int offset, int length) { long wCRCin = 0xFFFFFFFFL; // Long.reverse(0x1EDC6F41L) >>> 32 long wCPoly = 0x82F63B78L; for (int i = offset, cnt = offset + length; i < cnt; i++) { wCRCin ^= ((long) source[i] & 0x000000FFL); for (int j = 0; j < 8; j++) { if ((wCRCin & 0x00000001L) != 0) { wCRCin >>= 1; wCRCin ^= wCPoly; } else { wCRCin >>= 1; } } } return wCRCin ^= 0xFFFFFFFFL; } /** * CRC-32/D * * @param source * @param offset * @param length * @return */ public static long CRC32_D(byte[] source, int offset, int length) { long wCRCin = 0xFFFFFFFFL; // Long.reverse(0xA833982BL) >>> 32 long wCPoly = 0xD419CC15L; for (int i = offset, cnt = offset + length; i < cnt; i++) { wCRCin ^= ((long) source[i] & 0x000000FFL); for (int j = 0; j < 8; j++) { if ((wCRCin & 0x00000001L) != 0) { wCRCin >>= 1; wCRCin ^= wCPoly; } else { wCRCin >>= 1; } } } return wCRCin ^= 0xFFFFFFFFL; } /** * CRC-32/MPEG-2 * * @param source * @param offset * @param length * @return */ public static long CRC32_MPEG_2(byte[] source, int offset, int length) { long wCRCin = 0xFFFFFFFFL; long wCPoly = 0x04C11DB7L; for (int i = offset, cnt = offset + length; i < cnt; i++) { for (int j = 0; j < 8; j++) { boolean bit = ((source[i] >> (7 - j) & 1) == 1); boolean c31 = ((wCRCin >> 31 & 1) == 1); wCRCin <<= 1; if (c31 ^ bit) { wCRCin ^= wCPoly; } } } wCRCin &= 0xFFFFFFFFL; return wCRCin ^= 0x00000000L; } /** * CRC-32/POSIX * * @param source * @param offset * @param length * @return */ public static long CRC32_POSIX(byte[] source, int offset, int length) { long wCRCin = 0x00000000L; long wCPoly = 0x04C11DB7L; for (int i = offset, cnt = offset + length; i < cnt; i++) { for (int j = 0; j < 8; j++) { boolean bit = ((source[i] >> (7 - j) & 1) == 1); boolean c31 = ((wCRCin >> 31 & 1) == 1); wCRCin <<= 1; if (c31 ^ bit) { wCRCin ^= wCPoly; } } } wCRCin &= 0xFFFFFFFFL; return wCRCin ^= 0xFFFFFFFFL; } } |
