zlib.c

/* exported to allow conversion of error code to string for compress() and
 * uncompress()
 */
#ifndef MY_ZCALLOC /* Any system without a special alloc function */

#ifndef STDC
extern voidp    malloc OF((uInt size));
extern voidp    calloc OF((uInt items, uInt size));
extern void     free   OF((voidpf ptr));
#endif

voidpf zcalloc (opaque, items, size)
	voidpf opaque;
	unsigned items;
	unsigned size;
{
	if (opaque)
		items += size - size; /* make compiler happy */
	return sizeof(uInt) > 2 ? (voidpf)malloc(items * size) :
		(voidpf)calloc(items, size);
}

void  zcfree (opaque, ptr, nb)
	voidpf opaque;
	voidpf ptr;
	unsigned nb;
{
	free(ptr);
	if (opaque)
		return; /* make compiler happy */
}

#endif /* MY_ZCALLOC */
/*+++++*/
/* adler32.c -- compute the Adler-32 checksum of a data stream
 * Copyright (C) 1995-2004 Mark Adler
 * For conditions of distribution and use, see copyright notice in zlib.h
 */

/* @(#) $Id$ */

#define BASE 65521UL    /* 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)  {adler += (buf)[i]; sum2 += adler;}
#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);

/* use NO_DIVIDE if your processor does not do division in hardware */
#ifdef NO_DIVIDE
#define MOD(a) \
	do { \
		if (a >= (BASE << 16)) \
			a -= (BASE << 16); \
		if (a >= (BASE << 15)) \
			a -= (BASE << 15); \
		if (a >= (BASE << 14)) \
			a -= (BASE << 14); \
		if (a >= (BASE << 13)) \
			a -= (BASE << 13); \
		if (a >= (BASE << 12)) \
			a -= (BASE << 12); \
		if (a >= (BASE << 11)) \
			a -= (BASE << 11); \
		if (a >= (BASE << 10)) \
			a -= (BASE << 10); \
		if (a >= (BASE << 9)) \
			a -= (BASE << 9); \
		if (a >= (BASE << 8)) \
			a -= (BASE << 8); \
		if (a >= (BASE << 7)) \
			a -= (BASE << 7); \
		if (a >= (BASE << 6)) \
			a -= (BASE << 6); \
		if (a >= (BASE << 5)) \
			a -= (BASE << 5); \
		if (a >= (BASE << 4)) \
			a -= (BASE << 4); \
		if (a >= (BASE << 3)) \
			a -= (BASE << 3); \
		if (a >= (BASE << 2)) \
			a -= (BASE << 2); \
		if (a >= (BASE << 1)) \
			a -= (BASE << 1); \
		if (a >= BASE) \
			a -= BASE; \
	} while (0)
#define MOD4(a) \
	do { \
		if (a >= (BASE << 4)) \
			a -= (BASE << 4); \
		if (a >= (BASE << 3)) \
			a -= (BASE << 3); \
		if (a >= (BASE << 2)) \
			a -= (BASE << 2); \
		if (a >= (BASE << 1)) \
			a -= (BASE << 1); \
		if (a >= BASE) \
			a -= BASE; \
	} while (0)
#else
#define MOD(a) a %= BASE
#define MOD4(a) a %= BASE
#endif

/* ========================================================================= */
uLong ZEXPORT adler32(adler, buf, len)
    uLong adler;
    const Bytef *buf;
    uInt len;
{
    unsigned long sum2;
    unsigned n;

    /* split Adler-32 into component sums */
    sum2 = (adler >> 16) & 0xffff;
    adler &= 0xffff;

    /* in case user likes doing a byte at a time, keep it fast */
    if (len == 1) {
        adler += buf[0];
        if (adler >= BASE)
            adler -= BASE;
        sum2 += adler;
        if (sum2 >= BASE)
            sum2 -= BASE;
        return adler | (sum2 << 16);
    }

    /* initial Adler-32 value (deferred check for len == 1 speed) */
    if (buf == Z_NULL)
        return 1L;

    /* in case short lengths are provided, keep it somewhat fast */
    if (len < 16) {
        while (len--) {
            adler += *buf++;
            sum2 += adler;
        }
        if (adler >= BASE)
            adler -= BASE;
        MOD4(sum2);             /* only added so many BASE's */
        return adler | (sum2 << 16);
    }

    /* do length NMAX blocks -- requires just one modulo operation */
    while (len >= NMAX) {
        len -= NMAX;
        n = NMAX / 16;          /* NMAX is divisible by 16 */
        do {
            DO16(buf);          /* 16 sums unrolled */
            buf += 16;
        } while (--n);
        MOD(adler);
        MOD(sum2);
    }

    /* do remaining bytes (less than NMAX, still just one modulo) */
    if (len) {                  /* avoid modulos if none remaining */
        while (len >= 16) {
            len -= 16;
            DO16(buf);
            buf += 16;
        }
        while (len--) {
            adler += *buf++;
            sum2 += adler;
        }
        MOD(adler);
        MOD(sum2);
    }

    /* return recombined sums */
    return adler | (sum2 << 16);
}