Click here to Skip to main content
Click here to Skip to main content
Add your own
alternative version

CHM Reader for Pocket PC 2003

, 29 Feb 2004
Allows the reading of CHM files on a Pocket PC2003.
chmreaderexe.zip
chmreadersource.zip
PocketPC
CHM Reader
CHMLib
AUTHORS
ChmLib.dsp
ChmLib.dsw
COPYING
enumdir_chmLib.dsp
enum_chmLib.dsp
extract_chmLib.dsp
INSTALL
Makefile
NEWS
README
test_chmLib.dsp
res
CHM Reader.ico
Cmdbar.bmp
icon1.ico
CHM Reader.vcl
CHM Reader.ico
CHM Reader.vcp
CHM Reader.vcw
CHM Reader.vcb
CHM Reader.vcc
CHM Reader.vco
chm_readerexe-pc2002.zip
ARMRel
CHM Reader.exe
/* $Id: lzx.c,v 1.5 2002/10/09 01:16:33 jedwin Exp $ */
/***************************************************************************
 *                        lzx.c - LZX decompression routines               *
 *                           -------------------                           *
 *                                                                         *
 *  maintainer: Jed Wing <jedwin@ugcs.caltech.edu>                         *
 *  source:     modified lzx.c from cabextract v0.5                        *
 *  notes:      This file was taken from cabextract v0.5, which was,       *
 *              itself, a modified version of the lzx decompression code   *
 *              from unlzx.                                                *
 *                                                                         *
 *  platforms:  In its current incarnation, this file has been tested on   *
 *              two different Linux platforms (one, redhat-based, with a   *
 *              2.1.2 glibc and gcc 2.95.x, and the other, Debian, with    *
 *              2.2.4 glibc and both gcc 2.95.4 and gcc 3.0.2).  Both were *
 *              Intel x86 compatible machines.                             *
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.  Note that an exemption to this   *
 *   license has been granted by Stuart Caie for the purposes of           *
 *   distribution with chmlib.  This does not, to the best of my           *
 *   knowledge, constitute a change in the license of this (the LZX) code  *
 *   in general.                                                           *
 *                                                                         *
 ***************************************************************************/

#include "lzx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifdef __GNUC__
#define memcpy __builtin_memcpy
#endif

/* sized types */
typedef unsigned char  UBYTE; /* 8 bits exactly    */
typedef unsigned short UWORD; /* 16 bits (or more) */
typedef unsigned int   ULONG; /* 32 bits (or more) */
typedef   signed int    LONG; /* 32 bits (or more) */

/* some constants defined by the LZX specification */
#define LZX_MIN_MATCH                (2)
#define LZX_MAX_MATCH                (257)
#define LZX_NUM_CHARS                (256)
#define LZX_BLOCKTYPE_INVALID        (0)   /* also blocktypes 4-7 invalid */
#define LZX_BLOCKTYPE_VERBATIM       (1)
#define LZX_BLOCKTYPE_ALIGNED        (2)
#define LZX_BLOCKTYPE_UNCOMPRESSED   (3)
#define LZX_PRETREE_NUM_ELEMENTS     (20)
#define LZX_ALIGNED_NUM_ELEMENTS     (8)   /* aligned offset tree #elements */
#define LZX_NUM_PRIMARY_LENGTHS      (7)   /* this one missing from spec! */
#define LZX_NUM_SECONDARY_LENGTHS    (249) /* length tree #elements */

/* LZX huffman defines: tweak tablebits as desired */
#define LZX_PRETREE_MAXSYMBOLS  (LZX_PRETREE_NUM_ELEMENTS)
#define LZX_PRETREE_TABLEBITS   (6)
#define LZX_MAINTREE_MAXSYMBOLS (LZX_NUM_CHARS + 50*8)
#define LZX_MAINTREE_TABLEBITS  (12)
#define LZX_LENGTH_MAXSYMBOLS   (LZX_NUM_SECONDARY_LENGTHS+1)
#define LZX_LENGTH_TABLEBITS    (12)
#define LZX_ALIGNED_MAXSYMBOLS  (LZX_ALIGNED_NUM_ELEMENTS)
#define LZX_ALIGNED_TABLEBITS   (7)

#define LZX_LENTABLE_SAFETY (64) /* we allow length table decoding overruns */

#define LZX_DECLARE_TABLE(tbl) \
  UWORD tbl##_table[(1<<LZX_##tbl##_TABLEBITS) + (LZX_##tbl##_MAXSYMBOLS<<1)];\
  UBYTE tbl##_len  [LZX_##tbl##_MAXSYMBOLS + LZX_LENTABLE_SAFETY]

struct LZXstate
{
    UBYTE *window;         /* the actual decoding window              */
    ULONG window_size;     /* window size (32Kb through 2Mb)          */
    ULONG actual_size;     /* window size when it was first allocated */
    ULONG window_posn;     /* current offset within the window        */
    ULONG R0, R1, R2;      /* for the LRU offset system               */
    UWORD main_elements;   /* number of main tree elements            */
    int   header_read;     /* have we started decoding at all yet?    */
    UWORD block_type;      /* type of this block                      */
    ULONG block_length;    /* uncompressed length of this block       */
    ULONG block_remaining; /* uncompressed bytes still left to decode */
    ULONG frames_read;     /* the number of CFDATA blocks processed   */
    LONG  intel_filesize;  /* magic header value used for transform   */
    LONG  intel_curpos;    /* current offset in transform space       */
    int   intel_started;   /* have we seen any translatable data yet? */

    LZX_DECLARE_TABLE(PRETREE);
    LZX_DECLARE_TABLE(MAINTREE);
    LZX_DECLARE_TABLE(LENGTH);
    LZX_DECLARE_TABLE(ALIGNED);
};

/* LZX decruncher */

/* Microsoft's LZX document and their implementation of the
 * com.ms.util.cab Java package do not concur.
 *
 * In the LZX document, there is a table showing the correlation between
 * window size and the number of position slots. It states that the 1MB
 * window = 40 slots and the 2MB window = 42 slots. In the implementation,
 * 1MB = 42 slots, 2MB = 50 slots. The actual calculation is 'find the
 * first slot whose position base is equal to or more than the required
 * window size'. This would explain why other tables in the document refer
 * to 50 slots rather than 42.
 *
 * The constant NUM_PRIMARY_LENGTHS used in the decompression pseudocode
 * is not defined in the specification.
 *
 * The LZX document does not state the uncompressed block has an
 * uncompressed length field. Where does this length field come from, so
 * we can know how large the block is? The implementation has it as the 24
 * bits following after the 3 blocktype bits, before the alignment
 * padding.
 *
 * The LZX document states that aligned offset blocks have their aligned
 * offset huffman tree AFTER the main and length trees. The implementation
 * suggests that the aligned offset tree is BEFORE the main and length
 * trees.
 *
 * The LZX document decoding algorithm states that, in an aligned offset
 * block, if an extra_bits value is 1, 2 or 3, then that number of bits
 * should be read and the result added to the match offset. This is
 * correct for 1 and 2, but not 3, where just a huffman symbol (using the
 * aligned tree) should be read.
 *
 * Regarding the E8 preprocessing, the LZX document states 'No translation
 * may be performed on the last 6 bytes of the input block'. This is
 * correct.  However, the pseudocode provided checks for the *E8 leader*
 * up to the last 6 bytes. If the leader appears between -10 and -7 bytes
 * from the end, this would cause the next four bytes to be modified, at
 * least one of which would be in the last 6 bytes, which is not allowed
 * according to the spec.
 *
 * The specification states that the huffman trees must always contain at
 * least one element. However, many CAB files contain blocks where the
 * length tree is completely empty (because there are no matches), and
 * this is expected to succeed.
 */


/* LZX uses what it calls 'position slots' to represent match offsets.
 * What this means is that a small 'position slot' number and a small
 * offset from that slot are encoded instead of one large offset for
 * every match.
 * - position_base is an index to the position slot bases
 * - extra_bits states how many bits of offset-from-base data is needed.
 */
static const UBYTE extra_bits[51] = {
     0,  0,  0,  0,  1,  1,  2,  2,  3,  3,  4,  4,  5,  5,  6,  6,
     7,  7,  8,  8,  9,  9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 14,
    15, 15, 16, 16, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17,
    17, 17, 17
};

static const ULONG position_base[51] = {
          0,       1,       2,      3,      4,      6,      8,     12,     16,     24,     32,       48,      64,      96,     128,     192,
        256,     384,     512,    768,   1024,   1536,   2048,   3072,   4096,   6144,   8192,    12288,   16384,   24576,   32768,   49152,
      65536,   98304,  131072, 196608, 262144, 393216, 524288, 655360, 786432, 917504, 1048576, 1179648, 1310720, 1441792, 1572864, 1703936,
    1835008, 1966080, 2097152
};

struct LZXstate *LZXinit(int window)
{
    struct LZXstate *pState=NULL;
    ULONG wndsize = 1 << window;
    int i, posn_slots;

    /* LZX supports window sizes of 2^15 (32Kb) through 2^21 (2Mb) */
    /* if a previously allocated window is big enough, keep it     */
    if (window < 15 || window > 21) return NULL;

    /* allocate state and associated window */
    pState = (struct LZXstate *)malloc(sizeof(struct LZXstate));
    if (!(pState->window = (UBYTE *)malloc(wndsize)))
    {
        free(pState);
        return NULL;
    }
    pState->actual_size = wndsize;
    pState->window_size = wndsize;

    /* calculate required position slots */
    if (window == 20) posn_slots = 42;
    else if (window == 21) posn_slots = 50;
    else posn_slots = window << 1;

    /** alternatively **/
    /* posn_slots=i=0; while (i < wndsize) i += 1 << extra_bits[posn_slots++]; */

    /* initialize other state */
    pState->R0  =  pState->R1  = pState->R2 = 1;
    pState->main_elements   = LZX_NUM_CHARS + (posn_slots << 3);
    pState->header_read     = 0;
    pState->frames_read     = 0;
    pState->block_remaining = 0;
    pState->block_type      = LZX_BLOCKTYPE_INVALID;
    pState->intel_curpos    = 0;
    pState->intel_started   = 0;
    pState->window_posn     = 0;

    /* initialise tables to 0 (because deltas will be applied to them) */
    for (i = 0; i < LZX_MAINTREE_MAXSYMBOLS; i++) pState->MAINTREE_len[i] = 0;
    for (i = 0; i < LZX_LENGTH_MAXSYMBOLS; i++)   pState->LENGTH_len[i]   = 0;

    return pState;
}

void LZXteardown(struct LZXstate *pState)
{
    if (pState)
    {
        if (pState->window)
            free(pState->window);
        free(pState);
    }
}

int LZXreset(struct LZXstate *pState)
{
    int i;

    pState->R0  =  pState->R1  = pState->R2 = 1;
    pState->header_read     = 0;
    pState->frames_read     = 0;
    pState->block_remaining = 0;
    pState->block_type      = LZX_BLOCKTYPE_INVALID;
    pState->intel_curpos    = 0;
    pState->intel_started   = 0;
    pState->window_posn     = 0;

    for (i = 0; i < LZX_MAINTREE_MAXSYMBOLS + LZX_LENTABLE_SAFETY; i++) pState->MAINTREE_len[i] = 0;
    for (i = 0; i < LZX_LENGTH_MAXSYMBOLS + LZX_LENTABLE_SAFETY; i++)   pState->LENGTH_len[i]   = 0;

    return DECR_OK;
};


/* Bitstream reading macros:
 *
 * INIT_BITSTREAM    should be used first to set up the system
 * READ_BITS(var,n)  takes N bits from the buffer and puts them in var
 *
 * ENSURE_BITS(n)    ensures there are at least N bits in the bit buffer
 * PEEK_BITS(n)      extracts (without removing) N bits from the bit buffer
 * REMOVE_BITS(n)    removes N bits from the bit buffer
 *
 * These bit access routines work by using the area beyond the MSB and the
 * LSB as a free source of zeroes. This avoids having to mask any bits.
 * So we have to know the bit width of the bitbuffer variable. This is
 * sizeof(ULONG) * 8, also defined as ULONG_BITS
 */

/* number of bits in ULONG. Note: This must be at multiple of 16, and at
 * least 32 for the bitbuffer code to work (ie, it must be able to ensure
 * up to 17 bits - that's adding 16 bits when there's one bit left, or
 * adding 32 bits when there are no bits left. The code should work fine
 * for machines where ULONG >= 32 bits.
 */
#define ULONG_BITS (sizeof(ULONG)<<3)

#define INIT_BITSTREAM do { bitsleft = 0; bitbuf = 0; } while (0)

#define ENSURE_BITS(n)							\
  while (bitsleft < (n)) {						\
    bitbuf |= ((inpos[1]<<8)|inpos[0]) << (ULONG_BITS-16 - bitsleft);	\
    bitsleft += 16; inpos+=2;						\
  }

#define PEEK_BITS(n)   (bitbuf >> (ULONG_BITS - (n)))
#define REMOVE_BITS(n) ((bitbuf <<= (n)), (bitsleft -= (n)))

#define READ_BITS(v,n) do {						\
  ENSURE_BITS(n);							\
  (v) = PEEK_BITS(n);							\
  REMOVE_BITS(n);							\
} while (0)


/* Huffman macros */

#define TABLEBITS(tbl)   (LZX_##tbl##_TABLEBITS)
#define MAXSYMBOLS(tbl)  (LZX_##tbl##_MAXSYMBOLS)
#define SYMTABLE(tbl)    (pState->tbl##_table)
#define LENTABLE(tbl)    (pState->tbl##_len)

/* BUILD_TABLE(tablename) builds a huffman lookup table from code lengths.
 * In reality, it just calls make_decode_table() with the appropriate
 * values - they're all fixed by some #defines anyway, so there's no point
 * writing each call out in full by hand.
 */
#define BUILD_TABLE(tbl)						\
  if (make_decode_table(						\
    MAXSYMBOLS(tbl), TABLEBITS(tbl), LENTABLE(tbl), SYMTABLE(tbl)	\
  )) { return DECR_ILLEGALDATA; }


/* READ_HUFFSYM(tablename, var) decodes one huffman symbol from the
 * bitstream using the stated table and puts it in var.
 */
#define READ_HUFFSYM(tbl,var) do {					\
  ENSURE_BITS(16);							\
  hufftbl = SYMTABLE(tbl);						\
  if ((i = hufftbl[PEEK_BITS(TABLEBITS(tbl))]) >= MAXSYMBOLS(tbl)) {	\
    j = 1 << (ULONG_BITS - TABLEBITS(tbl));				\
    do {								\
      j >>= 1; i <<= 1; i |= (bitbuf & j) ? 1 : 0;			\
      if (!j) { return DECR_ILLEGALDATA; }	                        \
    } while ((i = hufftbl[i]) >= MAXSYMBOLS(tbl));			\
  }									\
  j = LENTABLE(tbl)[(var) = i];						\
  REMOVE_BITS(j);							\
} while (0)


/* READ_LENGTHS(tablename, first, last) reads in code lengths for symbols
 * first to last in the given table. The code lengths are stored in their
 * own special LZX way.
 */
#define READ_LENGTHS(tbl,first,last) do { \
  lb.bb = bitbuf; lb.bl = bitsleft; lb.ip = inpos; \
  if (lzx_read_lens(pState, LENTABLE(tbl),(first),(last),&lb)) { \
    return DECR_ILLEGALDATA; \
  } \
  bitbuf = lb.bb; bitsleft = lb.bl; inpos = lb.ip; \
} while (0)


/* make_decode_table(nsyms, nbits, length[], table[])
 *
 * This function was coded by David Tritscher. It builds a fast huffman
 * decoding table out of just a canonical huffman code lengths table.
 *
 * nsyms  = total number of symbols in this huffman tree.
 * nbits  = any symbols with a code length of nbits or less can be decoded
 *          in one lookup of the table.
 * length = A table to get code lengths from [0 to syms-1]
 * table  = The table to fill up with decoded symbols and pointers.
 *
 * Returns 0 for OK or 1 for error
 */

static int make_decode_table(ULONG nsyms, ULONG nbits, UBYTE *length, UWORD *table) {
    register UWORD sym;
    register ULONG leaf;
    register UBYTE bit_num = 1;
    ULONG fill;
    ULONG pos         = 0; /* the current position in the decode table */
    ULONG table_mask  = 1 << nbits;
    ULONG bit_mask    = table_mask >> 1; /* don't do 0 length codes */
    ULONG next_symbol = bit_mask; /* base of allocation for long codes */

    /* fill entries for codes short enough for a direct mapping */
    while (bit_num <= nbits) {
        for (sym = 0; sym < nsyms; sym++) {
            if (length[sym] == bit_num) {
                leaf = pos;

                if((pos += bit_mask) > table_mask) return 1; /* table overrun */

                /* fill all possible lookups of this symbol with the symbol itself */
                fill = bit_mask;
                while (fill-- > 0) table[leaf++] = sym;
            }
        }
        bit_mask >>= 1;
        bit_num++;
    }

    /* if there are any codes longer than nbits */
    if (pos != table_mask) {
        /* clear the remainder of the table */
        for (sym = pos; sym < table_mask; sym++) table[sym] = 0;

        /* give ourselves room for codes to grow by up to 16 more bits */
        pos <<= 16;
        table_mask <<= 16;
        bit_mask = 1 << 15;

        while (bit_num <= 16) {
            for (sym = 0; sym < nsyms; sym++) {
                if (length[sym] == bit_num) {
                    leaf = pos >> 16;
                    for (fill = 0; fill < bit_num - nbits; fill++) {
                        /* if this path hasn't been taken yet, 'allocate' two entries */
                        if (table[leaf] == 0) {
                            table[(next_symbol << 1)] = 0;
                            table[(next_symbol << 1) + 1] = 0;
                            table[leaf] = next_symbol++;
                        }
                        /* follow the path and select either left or right for next bit */
                        leaf = table[leaf] << 1;
                        if ((pos >> (15-fill)) & 1) leaf++;
                    }
                    table[leaf] = sym;

                    if ((pos += bit_mask) > table_mask) return 1; /* table overflow */
                }
            }
            bit_mask >>= 1;
            bit_num++;
        }
    }

    /* full table? */
    if (pos == table_mask) return 0;

    /* either erroneous table, or all elements are 0 - let's find out. */
    for (sym = 0; sym < nsyms; sym++) if (length[sym]) return 1;
    return 0;
}

struct lzx_bits {
  ULONG bb;
  int bl;
  UBYTE *ip;
};

static int lzx_read_lens(struct LZXstate *pState, UBYTE *lens, ULONG first, ULONG last, struct lzx_bits *lb) {
    ULONG i,j, x,y;
    int z;

    register ULONG bitbuf = lb->bb;
    register int bitsleft = lb->bl;
    UBYTE *inpos = lb->ip;
    UWORD *hufftbl;

    for (x = 0; x < 20; x++) {
        READ_BITS(y, 4);
        LENTABLE(PRETREE)[x] = y;
    }
    BUILD_TABLE(PRETREE);

    for (x = first; x < last; ) {
        READ_HUFFSYM(PRETREE, z);
        if (z == 17) {
            READ_BITS(y, 4); y += 4;
            while (y--) lens[x++] = 0;
        }
        else if (z == 18) {
            READ_BITS(y, 5); y += 20;
            while (y--) lens[x++] = 0;
        }
        else if (z == 19) {
            READ_BITS(y, 1); y += 4;
            READ_HUFFSYM(PRETREE, z);
            z = lens[x] - z; if (z < 0) z += 17;
            while (y--) lens[x++] = z;
        }
        else {
            z = lens[x] - z; if (z < 0) z += 17;
            lens[x++] = z;
        }
    }

    lb->bb = bitbuf;
    lb->bl = bitsleft;
    lb->ip = inpos;
    return 0;
}

int LZXdecompress(struct LZXstate *pState, unsigned char *inpos, unsigned char *outpos, int inlen, int outlen) {
    UBYTE *endinp = inpos + inlen;
    UBYTE *window = pState->window;
    UBYTE *runsrc, *rundest;
    UWORD *hufftbl; /* used in READ_HUFFSYM macro as chosen decoding table */

    ULONG window_posn = pState->window_posn;
    ULONG window_size = pState->window_size;
    ULONG R0 = pState->R0;
    ULONG R1 = pState->R1;
    ULONG R2 = pState->R2;

    register ULONG bitbuf;
    register int bitsleft;
    ULONG match_offset, i,j,k; /* ijk used in READ_HUFFSYM macro */
    struct lzx_bits lb; /* used in READ_LENGTHS macro */

    int togo = outlen, this_run, main_element, aligned_bits;
    int match_length, length_footer, extra, verbatim_bits;

    INIT_BITSTREAM;

    /* read header if necessary */
    if (!pState->header_read) {
        i = j = 0;
        READ_BITS(k, 1); if (k) { READ_BITS(i,16); READ_BITS(j,16); }
        pState->intel_filesize = (i << 16) | j; /* or 0 if not encoded */
        pState->header_read = 1;
    }

    /* main decoding loop */
    while (togo > 0) {
        /* last block finished, new block expected */
        if (pState->block_remaining == 0) {
            if (pState->block_type == LZX_BLOCKTYPE_UNCOMPRESSED) {
                if (pState->block_length & 1) inpos++; /* realign bitstream to word */
                INIT_BITSTREAM;
            }

            READ_BITS(pState->block_type, 3);
            READ_BITS(i, 16);
            READ_BITS(j, 8);
            pState->block_remaining = pState->block_length = (i << 8) | j;

            switch (pState->block_type) {
                case LZX_BLOCKTYPE_ALIGNED:
                    for (i = 0; i < 8; i++) { READ_BITS(j, 3); LENTABLE(ALIGNED)[i] = j; }
                    BUILD_TABLE(ALIGNED);
                    /* rest of aligned header is same as verbatim */

                case LZX_BLOCKTYPE_VERBATIM:
                    READ_LENGTHS(MAINTREE, 0, 256);
                    READ_LENGTHS(MAINTREE, 256, pState->main_elements);
                    BUILD_TABLE(MAINTREE);
                    if (LENTABLE(MAINTREE)[0xE8] != 0) pState->intel_started = 1;

                    READ_LENGTHS(LENGTH, 0, LZX_NUM_SECONDARY_LENGTHS);
                    BUILD_TABLE(LENGTH);
                    break;

                case LZX_BLOCKTYPE_UNCOMPRESSED:
                    pState->intel_started = 1; /* because we can't assume otherwise */
                    ENSURE_BITS(16); /* get up to 16 pad bits into the buffer */
                    if (bitsleft > 16) inpos -= 2; /* and align the bitstream! */
                    R0 = inpos[0]|(inpos[1]<<8)|(inpos[2]<<16)|(inpos[3]<<24);inpos+=4;
                    R1 = inpos[0]|(inpos[1]<<8)|(inpos[2]<<16)|(inpos[3]<<24);inpos+=4;
                    R2 = inpos[0]|(inpos[1]<<8)|(inpos[2]<<16)|(inpos[3]<<24);inpos+=4;
                    break;

                default:
                    return DECR_ILLEGALDATA;
            }
        }

        /* buffer exhaustion check */
        if (inpos > endinp) {
            /* it's possible to have a file where the next run is less than
             * 16 bits in size. In this case, the READ_HUFFSYM() macro used
             * in building the tables will exhaust the buffer, so we should
             * allow for this, but not allow those accidentally read bits to
             * be used (so we check that there are at least 16 bits
             * remaining - in this boundary case they aren't really part of
             * the compressed data)
             */
            if (inpos > (endinp+2) || bitsleft < 16) return DECR_ILLEGALDATA;
        }

        while ((this_run = pState->block_remaining) > 0 && togo > 0) {
            if (this_run > togo) this_run = togo;
            togo -= this_run;
            pState->block_remaining -= this_run;

            /* apply 2^x-1 mask */
            window_posn &= window_size - 1;
            /* runs can't straddle the window wraparound */
            if ((window_posn + this_run) > window_size)
                return DECR_DATAFORMAT;

            switch (pState->block_type) {

                case LZX_BLOCKTYPE_VERBATIM:
                    while (this_run > 0) {
                        READ_HUFFSYM(MAINTREE, main_element);

                        if (main_element < LZX_NUM_CHARS) {
                            /* literal: 0 to LZX_NUM_CHARS-1 */
                            window[window_posn++] = main_element;
                            this_run--;
                        }
                        else {
                            /* match: LZX_NUM_CHARS + ((slot<<3) | length_header (3 bits)) */
                            main_element -= LZX_NUM_CHARS;

                            match_length = main_element & LZX_NUM_PRIMARY_LENGTHS;
                            if (match_length == LZX_NUM_PRIMARY_LENGTHS) {
                                READ_HUFFSYM(LENGTH, length_footer);
                                match_length += length_footer;
                            }
                            match_length += LZX_MIN_MATCH;

                            match_offset = main_element >> 3;

                            if (match_offset > 2) {
                                /* not repeated offset */
                                if (match_offset != 3) {
                                    extra = extra_bits[match_offset];
                                    READ_BITS(verbatim_bits, extra);
                                    match_offset = position_base[match_offset] - 2 + verbatim_bits;
                                }
                                else {
                                    match_offset = 1;
                                }

                                /* update repeated offset LRU queue */
                                R2 = R1; R1 = R0; R0 = match_offset;
                            }
                            else if (match_offset == 0) {
                                match_offset = R0;
                            }
                            else if (match_offset == 1) {
                                match_offset = R1;
                                R1 = R0; R0 = match_offset;
                            }
                            else /* match_offset == 2 */ {
                                match_offset = R2;
                                R2 = R0; R0 = match_offset;
                            }

                            rundest = window + window_posn;
                            runsrc  = rundest - match_offset;
                            window_posn += match_length;
                            this_run -= match_length;

                            /* copy any wrapped around source data */
                            while ((runsrc < window) && (match_length-- > 0)) {
                                *rundest++ = *(runsrc + window_size); runsrc++;
                            }
                            /* copy match data - no worries about destination wraps */
                            while (match_length-- > 0) *rundest++ = *runsrc++;

                        }
                    }
                    break;

                case LZX_BLOCKTYPE_ALIGNED:
                    while (this_run > 0) {
                        READ_HUFFSYM(MAINTREE, main_element);

                        if (main_element < LZX_NUM_CHARS) {
                            /* literal: 0 to LZX_NUM_CHARS-1 */
                            window[window_posn++] = main_element;
                            this_run--;
                        }
                        else {
                            /* match: LZX_NUM_CHARS + ((slot<<3) | length_header (3 bits)) */
                            main_element -= LZX_NUM_CHARS;

                            match_length = main_element & LZX_NUM_PRIMARY_LENGTHS;
                            if (match_length == LZX_NUM_PRIMARY_LENGTHS) {
                                READ_HUFFSYM(LENGTH, length_footer);
                                match_length += length_footer;
                            }
                            match_length += LZX_MIN_MATCH;

                            match_offset = main_element >> 3;

                            if (match_offset > 2) {
                                /* not repeated offset */
                                extra = extra_bits[match_offset];
                                match_offset = position_base[match_offset] - 2;
                                if (extra > 3) {
                                    /* verbatim and aligned bits */
                                    extra -= 3;
                                    READ_BITS(verbatim_bits, extra);
                                    match_offset += (verbatim_bits << 3);
                                    READ_HUFFSYM(ALIGNED, aligned_bits);
                                    match_offset += aligned_bits;
                                }
                                else if (extra == 3) {
                                    /* aligned bits only */
                                    READ_HUFFSYM(ALIGNED, aligned_bits);
                                    match_offset += aligned_bits;
                                }
                                else if (extra > 0) { /* extra==1, extra==2 */
                                    /* verbatim bits only */
                                    READ_BITS(verbatim_bits, extra);
                                    match_offset += verbatim_bits;
                                }
                                else /* extra == 0 */ {
                                    /* ??? */
                                    match_offset = 1;
                                }

                                /* update repeated offset LRU queue */
                                R2 = R1; R1 = R0; R0 = match_offset;
                            }
                            else if (match_offset == 0) {
                                match_offset = R0;
                            }
                            else if (match_offset == 1) {
                                match_offset = R1;
                                R1 = R0; R0 = match_offset;
                            }
                            else /* match_offset == 2 */ {
                                match_offset = R2;
                                R2 = R0; R0 = match_offset;
                            }

                            rundest = window + window_posn;
                            runsrc  = rundest - match_offset;
                            window_posn += match_length;
                            this_run -= match_length;

                            /* copy any wrapped around source data */
                            while ((runsrc < window) && (match_length-- > 0)) {
                                *rundest++ = *(runsrc + window_size); runsrc++;
                            }
                            /* copy match data - no worries about destination wraps */
                            while (match_length-- > 0) *rundest++ = *runsrc++;

                        }
                    }
                    break;

                case LZX_BLOCKTYPE_UNCOMPRESSED:
                    if ((inpos + this_run) > endinp) return DECR_ILLEGALDATA;
                    memcpy(window + window_posn, inpos, (size_t) this_run);
                    inpos += this_run; window_posn += this_run;
                    break;

                default:
                    return DECR_ILLEGALDATA; /* might as well */
            }

        }
    }

    if (togo != 0) return DECR_ILLEGALDATA;
    memcpy(outpos, window + ((!window_posn) ? window_size : window_posn) - outlen, (size_t) outlen);

    pState->window_posn = window_posn;
    pState->R0 = R0;
    pState->R1 = R1;
    pState->R2 = R2;

    /* intel E8 decoding */
    if ((pState->frames_read++ < 32768) && pState->intel_filesize != 0) {
        if (outlen <= 6 || !pState->intel_started) {
            pState->intel_curpos += outlen;
        }
        else {
            UBYTE *data    = outpos;
            UBYTE *dataend = data + outlen - 10;
            LONG curpos    = pState->intel_curpos;
            LONG filesize  = pState->intel_filesize;
            LONG abs_off, rel_off;

            pState->intel_curpos = curpos + outlen;

            while (data < dataend) {
                if (*data++ != 0xE8) { curpos++; continue; }
                abs_off = data[0] | (data[1]<<8) | (data[2]<<16) | (data[3]<<24);
                if ((abs_off >= -curpos) && (abs_off < filesize)) {
                    rel_off = (abs_off >= 0) ? abs_off - curpos : abs_off + filesize;
                    data[0] = (UBYTE) rel_off;
                    data[1] = (UBYTE) (rel_off >> 8);
                    data[2] = (UBYTE) (rel_off >> 16);
                    data[3] = (UBYTE) (rel_off >> 24);
                }
                data += 4;
                curpos += 5;
            }
        }
    }
    return DECR_OK;
}

#ifdef LZX_CHM_TESTDRIVER
int main(int c, char **v)
{
    FILE *fin, *fout;
    struct LZXstate state;
    UBYTE ibuf[16384];
    UBYTE obuf[32768];
    int ilen, olen;
    int status;
    int i;
    int count=0;
    int w = atoi(v[1]);
    LZXinit(&state, w);
    fout = fopen(v[2], "wb");
    for (i=3; i<c; i++)
    {
        fin = fopen(v[i], "rb");
        ilen = fread(ibuf, 1, 16384, fin);
        status = LZXdecompress(&state, ibuf, obuf, ilen, 32768);
        switch (status)
        {
            case DECR_OK:
                printf("ok\n");
                fwrite(obuf, 1, 32768, fout);
                break;
            case DECR_DATAFORMAT:
                printf("bad format\n");
                break;
            case DECR_ILLEGALDATA:
                printf("illegal data\n");
                break;
            case DECR_NOMEMORY:
                printf("no memory\n");
                break;
            default:
                break;
        }
        fclose(fin);
        if (++count == 2)
        {
            count = 0;
            LZXreset(&state);
        }
    }
    fclose(fout);
}
#endif

By viewing downloads associated with this article you agree to the Terms of Service and the article's licence.

If a file you wish to view isn't highlighted, and is a text file (not binary), please let us know and we'll add colourisation support for it.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Share

About the Author

Peter Tewkesbury
Software Developer (Senior)
United Kingdom United Kingdom
Hi, I am a developer working in Cheshire, England. I started programming on a Vic-20 back in the 80's with only 5K of ram), and I have not looked back since. I have developed software using Visual C/C++, C#/.NET, MFC, ATL & ASP.NET, SQL Server, Crystal Reports, DevExpress .NET Components, WinForms, SQL Server client side reporting.
 
My favourite language is C# on .NET V3.5 and I am always trying to learn new stuff like LINQ.

| Advertise | Privacy | Mobile
Web03 | 2.8.140826.1 | Last Updated 1 Mar 2004
Article Copyright 2004 by Peter Tewkesbury
Everything else Copyright © CodeProject, 1999-2014
Terms of Service
Layout: fixed | fluid