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#ifdef IMG3_SUPPORT
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#define BASE 65521L /* largest prime smaller than 65536 */
#define NMAX 5000
// NMAX (was 5521) 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);
uint32_t lzadler32(uint8_t *buf, int32_t len)
{
unsigned long s1 = 1; // adler & 0xffff;
unsigned long s2 = 0; // (adler >> 16) & 0xffff;
int k;
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;
}
/**************************************************************
LZSS.C -- A Data Compression Program
***************************************************************
4/6/1989 Haruhiko Okumura
Use, distribute, and modify this program freely.
Please send me your improved versions.
PC-VAN SCIENCE
NIFTY-Serve PAF01022
CompuServe 74050,1022
**************************************************************/
#define N 4096 /* size of ring buffer - must be power of 2 */
#define F 18 /* upper limit for match_length */
#define THRESHOLD 2 /* encode string into position and length
if match_length is greater than this */
int
decompress_lzss(uint8_t *dst, uint8_t *src, uint32_t srclen)
{
/* ring buffer of size N, with extra F-1 bytes to aid string comparison */
uint8_t text_buf[N + F - 1];
uint8_t *dststart = dst;
uint8_t *srcend = src + srclen;
int i, j, k, r, c;
unsigned int flags;
dst = dststart;
srcend = src + srclen;
memset(text_buf, ' ', N - F);
r = N - F;
flags = 0;
for ( ; ; ) {
if (((flags >>= 1) & 0x100) == 0) {
if (src < srcend) c = *src++; else break;
flags = c | 0xFF00; /* uses higher byte cleverly */
} /* to count eight */
if (flags & 1) {
if (src < srcend) c = *src++; else break;
*dst++ = c;
text_buf[r++] = c;
r &= (N - 1);
} else {
if (src < srcend) i = *src++; else break;
if (src < srcend) j = *src++; else break;
i |= ((j & 0xF0) << 4);
j = (j & 0x0F) + THRESHOLD;
for (k = 0; k <= j; k++) {
c = text_buf[(i + k) & (N - 1)];
*dst++ = c;
text_buf[r++] = c;
r &= (N - 1);
}
}
}
return dst - dststart;
}
#endif
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