lzx.c File Reference

#include "lzx.h"
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "windef.h"
#include "winbase.h"

Include dependency graph for lzx.c:

Go to the source code of this file.

Classes
struct	LZXstate
struct	lzx_bits

Macros
#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 */
#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)
#define	ULONG_BITS   (sizeof(ULONG)<<3)
#define	INIT_BITSTREAM   do { bitsleft = 0; bitbuf = 0; } while (0)
#define	ENSURE_BITS(n)
#define	PEEK_BITS(n)   (bitbuf >> (ULONG_BITS - (n)))
#define	REMOVE_BITS(n)   ((bitbuf <<= (n)), (bitsleft -= (n)))
#define	READ_BITS(v, n)
#define	TABLEBITS(tbl)   (LZX_##tbl##_TABLEBITS)
#define	MAXSYMBOLS(tbl)   (LZX_##tbl##_MAXSYMBOLS)
#define	SYMTABLE(tbl)   (pState->tbl##_table)
#define	LENTABLE(tbl)   (pState->tbl##_len)
#define	BUILD_TABLE(tbl)
#define	READ_HUFFSYM(tbl, var)
#define	READ_LENGTHS(tbl, first, last)

Typedefs
typedef unsigned char	UBYTE
typedef unsigned short	UWORD

Functions
struct LZXstate *	LZXinit (int window)
void	LZXteardown (struct LZXstate *pState)
int	LZXreset (struct LZXstate *pState)
static int	make_decode_table (ULONG nsyms, ULONG nbits, UBYTE *length, UWORD *table)
static int	lzx_read_lens (struct LZXstate *pState, UBYTE *lens, ULONG first, ULONG last, struct lzx_bits *lb)
int	LZXdecompress (struct LZXstate *pState, unsigned char *inpos, unsigned char *outpos, int inlen, int outlen)

Variables
static const UBYTE	extra_bits [51]
static const ULONG	position_base [51]

Macro Definition Documentation

BUILD_TABLE

#define BUILD_TABLE

(

tbl

)

Value:

  if (make_decode_table(                        \
    MAXSYMBOLS(tbl), TABLEBITS(tbl), LENTABLE(tbl), SYMTABLE(tbl)   \
  )) { return DECR_ILLEGALDATA; }

Definition at line 300 of file lzx.c.

ENSURE_BITS

#define ENSURE_BITS

(

n

)

Value:

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

Definition at line 272 of file lzx.c.

INIT_BITSTREAM

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

Definition at line 270 of file lzx.c.

LENTABLE

#define LENTABLE

(

tbl

)

(pState->tbl##_len)

Definition at line 293 of file lzx.c.

LZX_ALIGNED_MAXSYMBOLS

#define LZX_ALIGNED_MAXSYMBOLS   (LZX_ALIGNED_NUM_ELEMENTS)

Definition at line 71 of file lzx.c.

LZX_ALIGNED_NUM_ELEMENTS

#define LZX_ALIGNED_NUM_ELEMENTS   (8) /* aligned offset tree #elements */

Definition at line 60 of file lzx.c.

LZX_ALIGNED_TABLEBITS

#define LZX_ALIGNED_TABLEBITS   (7)

Definition at line 72 of file lzx.c.

LZX_BLOCKTYPE_ALIGNED

#define LZX_BLOCKTYPE_ALIGNED   (2)

Definition at line 57 of file lzx.c.

LZX_BLOCKTYPE_INVALID

#define LZX_BLOCKTYPE_INVALID   (0) /* also blocktypes 4-7 invalid */

Definition at line 55 of file lzx.c.

LZX_BLOCKTYPE_UNCOMPRESSED

#define LZX_BLOCKTYPE_UNCOMPRESSED   (3)

Definition at line 58 of file lzx.c.

LZX_BLOCKTYPE_VERBATIM

#define LZX_BLOCKTYPE_VERBATIM   (1)

Definition at line 56 of file lzx.c.

LZX_DECLARE_TABLE

#define LZX_DECLARE_TABLE

(

tbl

)

Value:

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

Definition at line 76 of file lzx.c.

LZX_LENGTH_MAXSYMBOLS

#define LZX_LENGTH_MAXSYMBOLS   (LZX_NUM_SECONDARY_LENGTHS+1)

Definition at line 69 of file lzx.c.

LZX_LENGTH_TABLEBITS

#define LZX_LENGTH_TABLEBITS   (12)

Definition at line 70 of file lzx.c.

LZX_LENTABLE_SAFETY

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

Definition at line 74 of file lzx.c.

LZX_MAINTREE_MAXSYMBOLS

#define LZX_MAINTREE_MAXSYMBOLS   (LZX_NUM_CHARS + 50*8)

Definition at line 67 of file lzx.c.

LZX_MAINTREE_TABLEBITS

#define LZX_MAINTREE_TABLEBITS   (12)

Definition at line 68 of file lzx.c.

LZX_MAX_MATCH

#define LZX_MAX_MATCH   (257)

Definition at line 53 of file lzx.c.

LZX_MIN_MATCH

#define LZX_MIN_MATCH   (2)

Definition at line 52 of file lzx.c.

LZX_NUM_CHARS

#define LZX_NUM_CHARS   (256)

Definition at line 54 of file lzx.c.

LZX_NUM_PRIMARY_LENGTHS

#define LZX_NUM_PRIMARY_LENGTHS   (7) /* this one missing from spec! */

Definition at line 61 of file lzx.c.

LZX_NUM_SECONDARY_LENGTHS

#define LZX_NUM_SECONDARY_LENGTHS   (249) /* length tree #elements */

Definition at line 62 of file lzx.c.

LZX_PRETREE_MAXSYMBOLS

#define LZX_PRETREE_MAXSYMBOLS   (LZX_PRETREE_NUM_ELEMENTS)

Definition at line 65 of file lzx.c.

LZX_PRETREE_NUM_ELEMENTS

#define LZX_PRETREE_NUM_ELEMENTS   (20)

Definition at line 59 of file lzx.c.

LZX_PRETREE_TABLEBITS

#define LZX_PRETREE_TABLEBITS   (6)

Definition at line 66 of file lzx.c.

MAXSYMBOLS

#define MAXSYMBOLS

(

tbl

)

(LZX_##tbl##_MAXSYMBOLS)

Definition at line 291 of file lzx.c.

PEEK_BITS

#define PEEK_BITS

(

n

)

(bitbuf >> (ULONG_BITS - (n)))

Definition at line 278 of file lzx.c.

READ_BITS

#define READ_BITS	(		v,
			n
	)

Value:

  do {                      \
  ENSURE_BITS(n);                           \
  (v) = PEEK_BITS(n);                           \
  REMOVE_BITS(n);                           \
} while (0)

Definition at line 281 of file lzx.c.

READ_HUFFSYM

#define READ_HUFFSYM	(		tbl,
			var
	)

Value:

  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)

Definition at line 309 of file lzx.c.

READ_LENGTHS

#define READ_LENGTHS	(		tbl,
			first,
			last
	)

Value:

  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)

Definition at line 328 of file lzx.c.

REMOVE_BITS

#define REMOVE_BITS

(

n

)

((bitbuf <<= (n)), (bitsleft -= (n)))

Definition at line 279 of file lzx.c.

SYMTABLE

#define SYMTABLE

(

tbl

)

(pState->tbl##_table)

Definition at line 292 of file lzx.c.

TABLEBITS

#define TABLEBITS

(

tbl

)

(LZX_##tbl##_TABLEBITS)

Definition at line 290 of file lzx.c.

ULONG_BITS

#define ULONG_BITS   (sizeof(ULONG)<<3)

Definition at line 268 of file lzx.c.

Typedef Documentation

UBYTE

typedef unsigned char UBYTE

Definition at line 48 of file lzx.c.

UWORD

typedef unsigned short UWORD

Definition at line 49 of file lzx.c.

Function Documentation

lzx_read_lens()

static int lzx_read_lens ( struct LZXstate *  pState, UBYTE *  lens, ULONG  first, ULONG  last, struct lzx_bits *  lb  )

static

Definition at line 427 of file lzx.c.

                                                                                                             {
    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;
}

LZXdecompress()

int LZXdecompress	(	struct LZXstate *	pState,
		unsigned char *	inpos,
		unsigned char *	outpos,
		int	inlen,
		int	outlen
	)

Definition at line 470 of file lzx.c.

                                                                                                               {
    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;
    int copy_length;
 
    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;
                            this_run -= match_length;
 
                            /* copy any wrapped around source data */
                            if (window_posn >= match_offset) {
                                /* no wrap */
                                 runsrc = rundest - match_offset;
                            } else {
                                runsrc = rundest + (window_size - match_offset);
                                copy_length = match_offset - window_posn;
                                if (copy_length < match_length) {
                                     match_length -= copy_length;
                                     window_posn += copy_length;
                                     while (copy_length-- > 0) *rundest++ = *runsrc++;
                                     runsrc = window;
                                }
                            }
                            window_posn += match_length;
 
                            /* 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;
                            this_run -= match_length;
 
                            /* copy any wrapped around source data */
                            if (window_posn >= match_offset) {
                                /* no wrap */
                                 runsrc = rundest - match_offset;
                            } else {
                                runsrc = rundest + (window_size - match_offset);
                                copy_length = match_offset - window_posn;
                                if (copy_length < match_length) {
                                     match_length -= copy_length;
                                     window_posn += copy_length;
                                     while (copy_length-- > 0) *rundest++ = *runsrc++;
                                     runsrc = window;
                                }
                            }
                            window_posn += match_length;
 
                            /* 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;
}

LZXinit()

struct LZXstate * LZXinit

(

int

window

)

alternatively

Definition at line 172 of file lzx.c.

{
    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 = HeapAlloc(GetProcessHeap(), 0, sizeof(struct LZXstate));
    if (!(pState->window = HeapAlloc(GetProcessHeap(), 0, wndsize)))
    {
        HeapFree(GetProcessHeap(), 0, 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;
 
    /* 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;
}

LZXreset()

int LZXreset

(

struct LZXstate *

pState

)

Definition at line 227 of file lzx.c.

{
    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;
}

LZXteardown()

void LZXteardown

(

struct LZXstate *

pState

)

Definition at line 218 of file lzx.c.

{
    if (pState)
    {
        HeapFree(GetProcessHeap(), 0, pState->window);
        HeapFree(GetProcessHeap(), 0, pState);
    }
}

make_decode_table()

static int make_decode_table ( ULONG  nsyms, ULONG  nbits, UBYTE *  length, UWORD *  table  )

static

Definition at line 351 of file lzx.c.

                                                                                    {
    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;
}

Variable Documentation

extra_bits

const UBYTE extra_bits[51]

static

Initial value:

= {
     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
}

Definition at line 158 of file lzx.c.

position_base

const ULONG position_base[51]

static

Initial value:

= {
          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
}

Definition at line 165 of file lzx.c.