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#define _GNU_SOURCE /* for error() */
#include <errno.h> /* for errno */
#include <error.h> /* for error() */
#include <stdint.h> /* for uint{n}_t */
#include <stdio.h> /* for printf() */
#include <unistd.h> /* for read() */
void nut_crc32_init(uint32_t *crc) {
/* "Starting value is zero." */
*crc = 0;
}
void nut_crc32_write(uint32_t *crc, uint8_t *dat, size_t len) {
/* "Generator polynomial is 0x104C11DB7." */
static const uint32_t table[16] = {
0x00000000, 0x04C11DB7, 0x09823B6E, 0x0D4326D9,
0x130476DC, 0x17C56B6B, 0x1A864DB2, 0x1E475005,
0x2608EDB8, 0x22C9F00F, 0x2F8AD6D6, 0x2B4BCB61,
0x350C9B64, 0x31CD86D3, 0x3C8EA00A, 0x384FBDBD,
};
while (len--) {
*crc ^= *dat++ << 24;
*crc = (*crc<<4) ^ table[*crc>>28];
*crc = (*crc<<4) ^ table[*crc>>28];
}
}
int main() {
uint32_t crc;
uint8_t buf[128];
nut_crc32_init(&crc);
size_t tot = 0;
for (;;) {
ssize_t n = read(0, buf, sizeof(buf));
if (n <= 0)
break;
nut_crc32_write(&crc, buf, n);
tot += n;
}
printf("crc32 = 0x%08x ; size = %zu\n", crc, tot);
if (errno)
error(1, errno, "read");
return 0;
}
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