#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