ref: 41e27b2d10c6a60c49931332e8677438736a1e36
dir: /os/boot/libflate/crc.c/
#include "lib9.h" #include <flate.h> ulong* mkcrctab(ulong poly) { ulong *crctab; ulong crc; int i, j; crctab = malloc(256 * sizeof(ulong)); if(crctab == nil) return nil; for(i = 0; i < 256; i++){ crc = i; for(j = 0; j < 8; j++){ if(crc & 1) crc = (crc >> 1) ^ poly; else crc >>= 1; } crctab[i] = crc; } return crctab; } ulong blockcrc(ulong *crctab, ulong crc, void *vbuf, int n) { uchar *buf, *ebuf; crc ^= 0xffffffff; buf = vbuf; ebuf = buf + n; while(buf < ebuf) crc = crctab[(crc & 0xff) ^ *buf++] ^ (crc >> 8); return crc ^ 0xffffffff; }