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//
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//  lzssdec.h
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//  img4tool
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//
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//  Code borrowed from: http://newosxbook.com/src.jl?tree=listings&file=joker.c
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//  Coded by Jonathan Levin (a.k.a @Morpheus______), http://newosxbook.com
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#include "lzssdec.h"
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#include <string.h>
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#include <stdlib.h>
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/**************************************************************
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 LZSS.C -- A Data Compression Program
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 ***************************************************************
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 4/6/1989 Haruhiko Okumura
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 Use, distribute, and modify this program freely.
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 Please send me your improved versions.
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 PC-VAN      SCIENCE
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 NIFTY-Serve PAF01022
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 CompuServe  74050,1022
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 **************************************************************/
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/*
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 *  lzss.c - Package for decompressing lzss compressed objects
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 *
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 *  Copyright (c) 2003 Apple Computer, Inc.
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 *
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 *  DRI: Josh de Cesare
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 */
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#define N         4096  /* size of ring buffer - must be power of 2 */
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#define F         18    /* upper limit for match_length */
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#define THRESHOLD 2     /* encode string into position and length
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if match_length is greater than this */
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#define NIL       N     /* index for root of binary search trees */
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int decompress_lzss(u_int8_t *dst, u_int8_t *src, u_int32_t srclen){
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    /* ring buffer of size N, with extra F-1 bytes to aid string comparison */
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    u_int8_t text_buf[N + F - 1];
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    u_int8_t *dststart = dst;
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    u_int8_t *srcend = src + srclen;
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    int  i, j, k, r, c;
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    unsigned int flags;
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    dst = dststart;
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    srcend = src + srclen;
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    for (i = 0; i < N - F; i++)
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        text_buf[i] = ' ';
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    r = N - F;
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    flags = 0;
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    for ( ; ; ) {
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        if (((flags >>= 1) & 0x100) == 0) {
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            if (src < srcend) c = *src++; else break;
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            flags = c | 0xFF00;  /* uses higher byte cleverly */
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        }   /* to count eight */
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        if (flags & 1) {
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            if (src < srcend) c = *src++; else break;
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            *dst++ = c;
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            text_buf[r++] = c;
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            r &= (N - 1);
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        } else {
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            if (src < srcend) i = *src++; else break;
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            if (src < srcend) j = *src++; else break;
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            i |= ((j & 0xF0) << 4);
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            j  =  (j & 0x0F) + THRESHOLD;
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            for (k = 0; k <= j; k++) {
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                c = text_buf[(i + k) & (N - 1)];
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                *dst++ = c;
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                text_buf[r++] = c;
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                r &= (N - 1);
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            }
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        }
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    }
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    return (int)(dst - dststart);
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}
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struct compHeader {
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    char        sig[8] ; // "complzss"
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    uint32_t    unknown; // Likely CRC32. But who cares, anyway?
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    uint32_t    uncompressedSize;
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    uint32_t    compressedSize;
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    uint32_t    unknown1; // 1
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};
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char *tryLZSS(char *compressed, size_t *filesize){
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    struct compHeader *compHeader = (struct compHeader*)compressed;
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    if (!compHeader) return NULL;
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    int sig[2] = { 0xfeedfacf, 0x0100000c };
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    char *decomp = malloc (ntohl(compHeader->uncompressedSize));
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    char *feed = memmem(compressed+64, 1024, sig, sizeof(sig));
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    if (!feed)
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        return NULL;
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    feed--;
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    int rc = decompress_lzss((void*)decomp, (void*)feed, ntohl(compHeader->compressedSize));
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    if (rc != ntohl(compHeader->uncompressedSize)) {
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        return NULL;
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    }
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    *filesize = rc;
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    return (decomp);
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} // compLZSS
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