src/zlib/adler32.c

/* adler32.c -- compute the Adler-32 checksum of a data stream
 * Copyright (C) 1995-1998 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

/* @(#) $Id$ */

#include "../zlib/zlib.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,i)  {s1 += buf[i]; s2 += s1;}
#define DO2(buf,i)  DO1(buf,i); DO1(buf,i+1);
#define DO4(buf,i)  DO2(buf,i); DO2(buf,i+2);
#define DO8(buf,i)  DO4(buf,i); DO4(buf,i+4);
#define DO16(buf)   DO8(buf,0); DO8(buf,8);

/* ========================================================================= */
uLong ZEXPORT adler32(adler, buf, len)
    uLong adler;
    const Bytef *buf;
    uInt len;
{
    unsigned long s1 = adler & 0xffff;
    unsigned long s2 = (adler >> 16) & 0xffff;
    int k;

    if (buf == Z_NULL) return 1L;

    while (len > 0) {
        k = len < NMAX ? len : NMAX;
        len -= k;
        while (k >= 16) {
            DO16(buf);
	    buf += 16;
            k -= 16;
        }
        if (k != 0) do {
            s1 += *buf++;
	    s2 += s1;
        } while (--k);
        s1 %= BASE;
        s2 %= BASE;
    }
    return (s2 << 16) | s1;
}
Commit	Line	Data
	1	/* adler32.c -- compute the Adler-32 checksum of a data stream
	2	* Copyright (C) 1995-1998 Mark Adler
	3	* For conditions of distribution and use, see copyright notice in zlib.h
	4	*/
	5
	6	/* @(#) $Id$ */
	7
	8	#include "../zlib/zlib.h"
	9
	10	#define BASE 65521L /* largest prime smaller than 65536 */
	11	#define NMAX 5552
	12	/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
	13
	14	#define DO1(buf,i) {s1 += buf[i]; s2 += s1;}
	15	#define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
	16	#define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
	17	#define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
	18	#define DO16(buf) DO8(buf,0); DO8(buf,8);
	19
	20	/* ========================================================================= */
	21	uLong ZEXPORT adler32(adler, buf, len)
	22	uLong adler;
	23	const Bytef *buf;
	24	uInt len;
	25	{
	26	unsigned long s1 = adler & 0xffff;
	27	unsigned long s2 = (adler >> 16) & 0xffff;
	28	int k;
	29
	30	if (buf == Z_NULL) return 1L;
	31
	32	while (len > 0) {
	33	k = len < NMAX ? len : NMAX;
	34	len -= k;
	35	while (k >= 16) {
	36	DO16(buf);
	37	buf += 16;
	38	k -= 16;
	39	}
	40	if (k != 0) do {
	41	s1 += *buf++;
	42	s2 += s1;
	43	} while (--k);
	44	s1 %= BASE;
	45	s2 %= BASE;
	46	}
	47	return (s2 << 16) \| s1;
	48	}