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- /* Simple public domain implementation of the standard CRC32 checksum.
- * Outputs the checksum for each file given as a command line argument.
- * Invalid file names and files that cause errors are silently skipped.
- * The program reads from stdin if it is called with no arguments. */
- #include <stdio.h>
- #include <stdint.h>
- #include <stdlib.h>
- static uint32_t crc32_for_byte(uint32_t r) {
- for(int j = 0; j < 8; ++j)
- r = (r & 1? 0: (uint32_t)0xEDB88320L) ^ r >> 1;
- return r ^ (uint32_t)0xFF000000L;
- }
- void crc32(const void *data, uint32_t n_bytes, uint32_t* crc) {
- static uint32_t table[0x100];
- if(!*table)
- for(uint32_t i = 0; i < 0x100; ++i)
- table[i] = crc32_for_byte(i);
- for(uint32_t i = 0; i < n_bytes; ++i)
- *crc = table[(uint8_t)*crc ^ ((uint8_t*)data)[i]] ^ *crc >> 8;
- }
- uint32_t crc32_buf(const void *buf, uint32_t n_bytes) {
- uint32_t crc = 0;
- crc32(buf, n_bytes, &crc);
- return crc;
- }
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