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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*/
#include "tomcrypt.h"
/**
@file adler32.c
Adler-32 checksum algorithm
Written and placed in the public domain by Wei Dai
Adapted for libtomcrypt by Steffen Jaeckel
*/
#ifdef LTC_ADLER32
static const unsigned long _adler32_base = 65521;
void adler32_init(adler32_state *ctx)
{
LTC_ARGCHKVD(ctx != NULL);
ctx->s[0] = 1;
ctx->s[1] = 0;
}
void adler32_update(adler32_state *ctx, const unsigned char *input, unsigned long length)
{
unsigned long s1, s2;
LTC_ARGCHKVD(ctx != NULL);
LTC_ARGCHKVD(input != NULL);
s1 = ctx->s[0];
s2 = ctx->s[1];
if (length % 8 != 0) {
do {
s1 += *input++;
s2 += s1;
length--;
} while (length % 8 != 0);
if (s1 >= _adler32_base)
s1 -= _adler32_base;
s2 %= _adler32_base;
}
while (length > 0) {
s1 += input[0];
s2 += s1;
s1 += input[1];
s2 += s1;
s1 += input[2];
s2 += s1;
s1 += input[3];
s2 += s1;
s1 += input[4];
s2 += s1;
s1 += input[5];
s2 += s1;
s1 += input[6];
s2 += s1;
s1 += input[7];
s2 += s1;
length -= 8;
input += 8;
if (s1 >= _adler32_base)
s1 -= _adler32_base;
s2 %= _adler32_base;
}
LTC_ARGCHKVD(s1 < _adler32_base);
LTC_ARGCHKVD(s2 < _adler32_base);
ctx->s[0] = (unsigned short)s1;
ctx->s[1] = (unsigned short)s2;
}
void adler32_finish(adler32_state *ctx, void *hash, unsigned long size)
{
unsigned char* h;
LTC_ARGCHKVD(ctx != NULL);
LTC_ARGCHKVD(hash != NULL);
h = hash;
switch (size) {
default:
h[3] = ctx->s[0] & 0x0ff;
/* FALLTHROUGH */
case 3:
h[2] = (ctx->s[0] >> 8) & 0x0ff;
/* FALLTHROUGH */
case 2:
h[1] = ctx->s[1] & 0x0ff;
/* FALLTHROUGH */
case 1:
h[0] = (ctx->s[1] >> 8) & 0x0ff;
/* FALLTHROUGH */
case 0:
;
}
}
int adler32_test(void)
{
#ifndef LTC_TEST
return CRYPT_NOP;
#else
const void* in = "libtomcrypt";
const unsigned char adler32[] = { 0x1b, 0xe8, 0x04, 0xba };
unsigned char out[4];
adler32_state ctx;
adler32_init(&ctx);
adler32_update(&ctx, in, strlen(in));
adler32_finish(&ctx, out, 4);
if (compare_testvector(adler32, 4, out, 4, "adler32", 0)) {
return CRYPT_FAIL_TESTVECTOR;
}
return CRYPT_OK;
#endif
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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