123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172 |
- #include <u.h>
- #include <libc.h>
- #include <flate.h>
- enum
- {
- ADLERITERS = 5552, /* max iters before can overflow 32 bits */
- ADLERBASE = 65521 /* largest prime smaller than 65536 */
- };
- ulong
- adler32(ulong adler, void *vbuf, int n)
- {
- ulong s1, s2;
- uchar *buf, *ebuf;
- int m;
- buf = vbuf;
- s1 = adler & 0xffff;
- s2 = (adler >> 16) & 0xffff;
- for(; n >= 16; n -= m){
- m = n;
- if(m > ADLERITERS)
- m = ADLERITERS;
- m &= ~15;
- for(ebuf = buf + m; buf < ebuf; buf += 16){
- s1 += buf[0];
- s2 += s1;
- s1 += buf[1];
- s2 += s1;
- s1 += buf[2];
- s2 += s1;
- s1 += buf[3];
- s2 += s1;
- s1 += buf[4];
- s2 += s1;
- s1 += buf[5];
- s2 += s1;
- s1 += buf[6];
- s2 += s1;
- s1 += buf[7];
- s2 += s1;
- s1 += buf[8];
- s2 += s1;
- s1 += buf[9];
- s2 += s1;
- s1 += buf[10];
- s2 += s1;
- s1 += buf[11];
- s2 += s1;
- s1 += buf[12];
- s2 += s1;
- s1 += buf[13];
- s2 += s1;
- s1 += buf[14];
- s2 += s1;
- s1 += buf[15];
- s2 += s1;
- }
- s1 %= ADLERBASE;
- s2 %= ADLERBASE;
- }
- if(n){
- for(ebuf = buf + n; buf < ebuf; buf++){
- s1 += buf[0];
- s2 += s1;
- }
- s1 %= ADLERBASE;
- s2 %= ADLERBASE;
- }
- return (s2 << 16) + s1;
- }
|