48 lines
921 B
C
48 lines
921 B
C
#include <inttypes.h>
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#include <stdio.h>
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#include <string.h>
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uint32_t
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rc_crc32(uint32_t crc, const char *buf, size_t len)
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{
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static uint32_t table[256];
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static int have_table = 0;
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uint32_t rem;
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uint8_t octet;
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int i, j;
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const char *p, *q;
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/* This check is not thread safe; there is no mutex. */
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if (have_table == 0) {
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/* Calculate CRC table. */
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for (i = 0; i < 256; i++) {
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rem = i; /* remainder from polynomial division */
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for (j = 0; j < 8; j++) {
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if (rem & 1) {
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rem >>= 1;
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rem ^= 0xedb88320;
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} else
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rem >>= 1;
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}
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table[i] = rem;
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}
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have_table = 1;
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}
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crc = ~crc;
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q = buf + len;
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for (p = buf; p < q; p++) {
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octet = *p; /* Cast to unsigned octet. */
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crc = (crc >> 8) ^ table[(crc & 0xff) ^ octet];
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}
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return ~crc;
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}
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int
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main()
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{
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const char *s = "The quick brown fox jumps over the lazy dog";
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printf("%" PRIX32 "\n", rc_crc32(0, s, strlen(s)));
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return 0;
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}
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