PeerStreamer

/* adler32.c -- compute the Adler-32 checksum of a data stream

 * Copyright (C) 1995 Mark Adler

 * For conditions of distribution and use, see copyright notice in zlib.h

 */

#include "common.h"

#include "adler32.h"

#define BASE 65521L /* largest prime smaller than 65536 */

#define NMAX 5552

/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */

#define DO1(buf)  {s1 += *buf++; s2 += s1;}

#define DO2(buf)  DO1(buf); DO1(buf);

#define DO4(buf)  DO2(buf); DO2(buf);

#define DO8(buf)  DO4(buf); DO4(buf);

#define DO16(buf) DO8(buf); DO8(buf);

unsigned long av_adler32_update(unsigned long adler, const uint8_t *buf, unsigned int len)

{

    unsigned long s1 = adler & 0xffff;

    unsigned long s2 = (adler >> 16) & 0xffff;

    int k;

    if (buf == NULL) return 1L;

    while (len > 0) {

        k = FFMIN(len, NMAX);

        len -= k;

#ifndef CONFIG_SMALL

        while (k >= 16) {

            DO16(buf);

            k -= 16;

        }

#endif

        while(k--) {

            DO1(buf);

        }

        s1 %= BASE;

        s2 %= BASE;

    }

    return (s2 << 16) | s1;

}