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tif_lzw.c
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/* $Id: tif_lzw.c,v 1.45 2011-04-02 20:54:09 bfriesen Exp $ */
/*
* Copyright (c) 1988-1997 Sam Leffler
* Copyright (c) 1991-1997 Silicon Graphics, Inc.
*
* Permission to use, copy, modify, distribute, and sell this software and
* its documentation for any purpose is hereby granted without fee, provided
* that (i) the above copyright notices and this permission notice appear in
* all copies of the software and related documentation, and (ii) the names of
* Sam Leffler and Silicon Graphics may not be used in any advertising or
* publicity relating to the software without the specific, prior written
* permission of Sam Leffler and Silicon Graphics.
*
* THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
* EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
* WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
*
* IN NO EVENT SHALL SAM LEFFLER OR SILICON GRAPHICS BE LIABLE FOR
* ANY SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND,
* OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
* WHETHER OR NOT ADVISED OF THE POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF
* LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
* OF THIS SOFTWARE.
*/
#include "tiffiop.h"
#ifdef LZW_SUPPORT
/*
* TIFF Library.
* Rev 5.0 Lempel-Ziv & Welch Compression Support
*
* This code is derived from the compress program whose code is
* derived from software contributed to Berkeley by James A. Woods,
* derived from original work by Spencer Thomas and Joseph Orost.
*
* The original Berkeley copyright notice appears below in its entirety.
*/
#include "tif_predict.h"
#include <stdio.h>
/*
* NB: The 5.0 spec describes a different algorithm than Aldus
* implements. Specifically, Aldus does code length transitions
* one code earlier than should be done (for real LZW).
* Earlier versions of this library implemented the correct
* LZW algorithm, but emitted codes in a bit order opposite
* to the TIFF spec. Thus, to maintain compatibility w/ Aldus
* we interpret MSB-LSB ordered codes to be images written w/
* old versions of this library, but otherwise adhere to the
* Aldus "off by one" algorithm.
*
* Future revisions to the TIFF spec are expected to "clarify this issue".
*/
#define LZW_COMPAT /* include backwards compatibility code */
/*
* Each strip of data is supposed to be terminated by a CODE_EOI.
* If the following #define is included, the decoder will also
* check for end-of-strip w/o seeing this code. This makes the
* library more robust, but also slower.
*/
#define LZW_CHECKEOS /* include checks for strips w/o EOI code */
#define MAXCODE(n) ((1L<<(n))-1)
/*
* The TIFF spec specifies that encoded bit
* strings range from 9 to 12 bits.
*/
#define BITS_MIN 9 /* start with 9 bits */
#define BITS_MAX 12 /* max of 12 bit strings */
/* predefined codes */
#define CODE_CLEAR 256 /* code to clear string table */
#define CODE_EOI 257 /* end-of-information code */
#define CODE_FIRST 258 /* first free code entry */
#define CODE_MAX MAXCODE(BITS_MAX)
#define HSIZE 9001L /* 91% occupancy */
#define HSHIFT (13-8)
#ifdef LZW_COMPAT
/* NB: +1024 is for compatibility with old files */
#define CSIZE (MAXCODE(BITS_MAX)+1024L)
#else
#define CSIZE (MAXCODE(BITS_MAX)+1L)
#endif
/*
* State block for each open TIFF file using LZW
* compression/decompression. Note that the predictor
* state block must be first in this data structure.
*/
typedef struct {
TIFFPredictorState predict; /* predictor super class */
unsigned short nbits; /* # of bits/code */
unsigned short maxcode; /* maximum code for lzw_nbits */
unsigned short free_ent; /* next free entry in hash table */
long nextdata; /* next bits of i/o */
long nextbits; /* # of valid bits in lzw_nextdata */
int rw_mode; /* preserve rw_mode from init */
} LZWBaseState;
#define lzw_nbits base.nbits
#define lzw_maxcode base.maxcode
#define lzw_free_ent base.free_ent
#define lzw_nextdata base.nextdata
#define lzw_nextbits base.nextbits
/*
* Encoding-specific state.
*/
typedef uint16 hcode_t; /* codes fit in 16 bits */
typedef struct {
long hash;
hcode_t code;
} hash_t;
/*
* Decoding-specific state.
*/
typedef struct code_ent {
struct code_ent *next;
unsigned short length; /* string len, including this token */
unsigned char value; /* data value */
unsigned char firstchar; /* first token of string */
} code_t;
typedef int (*decodeFunc)(TIFF*, uint8*, tmsize_t, uint16);
typedef struct {
LZWBaseState base;
/* Decoding specific data */
long dec_nbitsmask; /* lzw_nbits 1 bits, right adjusted */
long dec_restart; /* restart count */
#ifdef LZW_CHECKEOS
uint64 dec_bitsleft; /* available bits in raw data */
#endif
decodeFunc dec_decode; /* regular or backwards compatible */
code_t* dec_codep; /* current recognized code */
code_t* dec_oldcodep; /* previously recognized code */
code_t* dec_free_entp; /* next free entry */
code_t* dec_maxcodep; /* max available entry */
code_t* dec_codetab; /* kept separate for small machines */
/* Encoding specific data */
int enc_oldcode; /* last code encountered */
long enc_checkpoint; /* point at which to clear table */
#define CHECK_GAP 10000 /* enc_ratio check interval */
long enc_ratio; /* current compression ratio */
long enc_incount; /* (input) data bytes encoded */
long enc_outcount; /* encoded (output) bytes */
uint8* enc_rawlimit; /* bound on tif_rawdata buffer */
hash_t* enc_hashtab; /* kept separate for small machines */
} LZWCodecState;
#define LZWState(tif) ((LZWBaseState*) (tif)->tif_data)
#define DecoderState(tif) ((LZWCodecState*) LZWState(tif))
#define EncoderState(tif) ((LZWCodecState*) LZWState(tif))
static int LZWDecode(TIFF* tif, uint8* op0, tmsize_t occ0, uint16 s);
#ifdef LZW_COMPAT
static int LZWDecodeCompat(TIFF* tif, uint8* op0, tmsize_t occ0, uint16 s);
#endif
static void cl_hash(LZWCodecState*);
/*
* LZW Decoder.
*/
#ifdef LZW_CHECKEOS
/*
* This check shouldn't be necessary because each
* strip is suppose to be terminated with CODE_EOI.
*/
#define NextCode(_tif, _sp, _bp, _code, _get) { \
if ((_sp)->dec_bitsleft < (uint64)nbits) { \
TIFFWarningExt(_tif->tif_clientdata, module, \
"LZWDecode: Strip %d not terminated with EOI code", \
_tif->tif_curstrip); \
_code = CODE_EOI; \
} else { \
_get(_sp,_bp,_code); \
(_sp)->dec_bitsleft -= nbits; \
} \
}
#else
#define NextCode(tif, sp, bp, code, get) get(sp, bp, code)
#endif
static int
LZWFixupTags(TIFF* tif)
{
(void) tif;
return (1);
}
static int
LZWSetupDecode(TIFF* tif)
{
static const char module[] = "LZWSetupDecode";
LZWCodecState* sp = DecoderState(tif);
int code;
if( sp == NULL )
{
/*
* Allocate state block so tag methods have storage to record
* values.
*/
tif->tif_data = (uint8*) _TIFFmalloc(sizeof(LZWCodecState));
if (tif->tif_data == NULL)
{
TIFFErrorExt(tif->tif_clientdata, module, "No space for LZW state block");
return (0);
}
DecoderState(tif)->dec_codetab = NULL;
DecoderState(tif)->dec_decode = NULL;
/*
* Setup predictor setup.
*/
(void) TIFFPredictorInit(tif);
sp = DecoderState(tif);
}
assert(sp != NULL);
if (sp->dec_codetab == NULL) {
sp->dec_codetab = (code_t*)_TIFFmalloc(CSIZE*sizeof (code_t));
if (sp->dec_codetab == NULL) {
TIFFErrorExt(tif->tif_clientdata, module,
"No space for LZW code table");
return (0);
}
/*
* Pre-load the table.
*/
code = 255;
do {
sp->dec_codetab[code].value = code;
sp->dec_codetab[code].firstchar = code;
sp->dec_codetab[code].length = 1;
sp->dec_codetab[code].next = NULL;
} while (code--);
/*
* Zero-out the unused entries
*/
_TIFFmemset(&sp->dec_codetab[CODE_CLEAR], 0,
(CODE_FIRST - CODE_CLEAR) * sizeof (code_t));
}
return (1);
}
/*
* Setup state for decoding a strip.
*/
static int
LZWPreDecode(TIFF* tif, uint16 s)
{
static const char module[] = "LZWPreDecode";
LZWCodecState *sp = DecoderState(tif);
(void) s;
assert(sp != NULL);
if( sp->dec_codetab == NULL )
{
tif->tif_setupdecode( tif );
}
/*
* Check for old bit-reversed codes.
*/
if (tif->tif_rawdata[0] == 0 && (tif->tif_rawdata[1] & 0x1)) {
#ifdef LZW_COMPAT
if (!sp->dec_decode) {
TIFFWarningExt(tif->tif_clientdata, module,
"Old-style LZW codes, convert file");
/*
* Override default decoding methods with
* ones that deal with the old coding.
* Otherwise the predictor versions set
* above will call the compatibility routines
* through the dec_decode method.
*/
tif->tif_decoderow = LZWDecodeCompat;
tif->tif_decodestrip = LZWDecodeCompat;
tif->tif_decodetile = LZWDecodeCompat;
/*
* If doing horizontal differencing, must
* re-setup the predictor logic since we
* switched the basic decoder methods...
*/
(*tif->tif_setupdecode)(tif);
sp->dec_decode = LZWDecodeCompat;
}
sp->lzw_maxcode = MAXCODE(BITS_MIN);
#else /* !LZW_COMPAT */
if (!sp->dec_decode) {
TIFFErrorExt(tif->tif_clientdata, module,
"Old-style LZW codes not supported");
sp->dec_decode = LZWDecode;
}
return (0);
#endif/* !LZW_COMPAT */
} else {
sp->lzw_maxcode = MAXCODE(BITS_MIN)-1;
sp->dec_decode = LZWDecode;
}
sp->lzw_nbits = BITS_MIN;
sp->lzw_nextbits = 0;
sp->lzw_nextdata = 0;
sp->dec_restart = 0;
sp->dec_nbitsmask = MAXCODE(BITS_MIN);
#ifdef LZW_CHECKEOS
sp->dec_bitsleft = ((uint64)tif->tif_rawcc) << 3;
#endif
sp->dec_free_entp = sp->dec_codetab + CODE_FIRST;
/*
* Zero entries that are not yet filled in. We do
* this to guard against bogus input data that causes
* us to index into undefined entries. If you can
* come up with a way to safely bounds-check input codes
* while decoding then you can remove this operation.
*/
_TIFFmemset(sp->dec_free_entp, 0, (CSIZE-CODE_FIRST)*sizeof (code_t));
sp->dec_oldcodep = &sp->dec_codetab[-1];
sp->dec_maxcodep = &sp->dec_codetab[sp->dec_nbitsmask-1];
return (1);
}
/*
* Decode a "hunk of data".
*/
#define GetNextCode(sp, bp, code) { \
nextdata = (nextdata<<8) | *(bp)++; \
nextbits += 8; \
if (nextbits < nbits) { \
nextdata = (nextdata<<8) | *(bp)++; \
nextbits += 8; \
} \
code = (hcode_t)((nextdata >> (nextbits-nbits)) & nbitsmask); \
nextbits -= nbits; \
}
static void
codeLoop(TIFF* tif, const char* module)
{
TIFFErrorExt(tif->tif_clientdata, module,
"Bogus encoding, loop in the code table; scanline %d",
tif->tif_row);
}
static int
LZWDecode(TIFF* tif, uint8* op0, tmsize_t occ0, uint16 s)
{
static const char module[] = "LZWDecode";
LZWCodecState *sp = DecoderState(tif);
char *op = (char*) op0;
long occ = (long) occ0;
char *tp;
unsigned char *bp;
hcode_t code;
int len;
long nbits, nextbits, nextdata, nbitsmask;
code_t *codep, *free_entp, *maxcodep, *oldcodep;
(void) s;
assert(sp != NULL);
assert(sp->dec_codetab != NULL);
/*
Fail if value does not fit in long.
*/
if ((tmsize_t) occ != occ0)
return (0);
/*
* Restart interrupted output operation.
*/
if (sp->dec_restart) {
long residue;
codep = sp->dec_codep;
residue = codep->length - sp->dec_restart;
if (residue > occ) {
/*
* Residue from previous decode is sufficient
* to satisfy decode request. Skip to the
* start of the decoded string, place decoded
* values in the output buffer, and return.
*/
sp->dec_restart += occ;
do {
codep = codep->next;
} while (--residue > occ && codep);
if (codep) {
tp = op + occ;
do {
*--tp = codep->value;
codep = codep->next;
} while (--occ && codep);
}
return (1);
}
/*
* Residue satisfies only part of the decode request.
*/
op += residue, occ -= residue;
tp = op;
do {
int t;
--tp;
t = codep->value;
codep = codep->next;
*tp = t;
} while (--residue && codep);
sp->dec_restart = 0;
}
bp = (unsigned char *)tif->tif_rawcp;
nbits = sp->lzw_nbits;
nextdata = sp->lzw_nextdata;
nextbits = sp->lzw_nextbits;
nbitsmask = sp->dec_nbitsmask;
oldcodep = sp->dec_oldcodep;
free_entp = sp->dec_free_entp;
maxcodep = sp->dec_maxcodep;
while (occ > 0) {
NextCode(tif, sp, bp, code, GetNextCode);
if (code == CODE_EOI)
break;
if (code == CODE_CLEAR) {
free_entp = sp->dec_codetab + CODE_FIRST;
_TIFFmemset(free_entp, 0,
(CSIZE - CODE_FIRST) * sizeof (code_t));
nbits = BITS_MIN;
nbitsmask = MAXCODE(BITS_MIN);
maxcodep = sp->dec_codetab + nbitsmask-1;
NextCode(tif, sp, bp, code, GetNextCode);
if (code == CODE_EOI)
break;
if (code >= CODE_CLEAR) {
TIFFErrorExt(tif->tif_clientdata, tif->tif_name,
"LZWDecode: Corrupted LZW table at scanline %d",
tif->tif_row);
return (0);
}
*op++ = (char)code, occ--;
oldcodep = sp->dec_codetab + code;
continue;
}
codep = sp->dec_codetab + code;
/*
* Add the new entry to the code table.
*/
if (free_entp < &sp->dec_codetab[0] ||
free_entp >= &sp->dec_codetab[CSIZE]) {
TIFFErrorExt(tif->tif_clientdata, module,
"Corrupted LZW table at scanline %d",
tif->tif_row);
return (0);
}
free_entp->next = oldcodep;
if (free_entp->next < &sp->dec_codetab[0] ||
free_entp->next >= &sp->dec_codetab[CSIZE]) {
TIFFErrorExt(tif->tif_clientdata, module,
"Corrupted LZW table at scanline %d",
tif->tif_row);
return (0);
}
free_entp->firstchar = free_entp->next->firstchar;
free_entp->length = free_entp->next->length+1;
free_entp->value = (codep < free_entp) ?
codep->firstchar : free_entp->firstchar;
if (++free_entp > maxcodep) {
if (++nbits > BITS_MAX) /* should not happen */
nbits = BITS_MAX;
nbitsmask = MAXCODE(nbits);
maxcodep = sp->dec_codetab + nbitsmask-1;
}
oldcodep = codep;
if (code >= 256) {
/*
* Code maps to a string, copy string
* value to output (written in reverse).
*/
if(codep->length == 0) {
TIFFErrorExt(tif->tif_clientdata, module,
"Wrong length of decoded string: "
"data probably corrupted at scanline %d",
tif->tif_row);
return (0);
}
if (codep->length > occ) {
/*
* String is too long for decode buffer,
* locate portion that will fit, copy to
* the decode buffer, and setup restart
* logic for the next decoding call.
*/
sp->dec_codep = codep;
do {
codep = codep->next;
} while (codep && codep->length > occ);
if (codep) {
sp->dec_restart = (long)occ;
tp = op + occ;
do {
*--tp = codep->value;
codep = codep->next;
} while (--occ && codep);
if (codep)
codeLoop(tif, module);
}
break;
}
len = codep->length;
tp = op + len;
do {
int t;
--tp;
t = codep->value;
codep = codep->next;
*tp = t;
} while (codep && tp > op);
if (codep) {
codeLoop(tif, module);
break;
}
assert(occ >= len);
op += len, occ -= len;
} else
*op++ = (char)code, occ--;
}
tif->tif_rawcp = (uint8*) bp;
sp->lzw_nbits = (unsigned short) nbits;
sp->lzw_nextdata = nextdata;
sp->lzw_nextbits = nextbits;
sp->dec_nbitsmask = nbitsmask;
sp->dec_oldcodep = oldcodep;
sp->dec_free_entp = free_entp;
sp->dec_maxcodep = maxcodep;
if (occ > 0) {
#if defined(__WIN32__) && (defined(_MSC_VER) || defined(__MINGW32__))
TIFFErrorExt(tif->tif_clientdata, module,
"Not enough data at scanline %d (short %I64d bytes)",
tif->tif_row, (unsigned __int64) occ);
#else
TIFFErrorExt(tif->tif_clientdata, module,
"Not enough data at scanline %d (short %llu bytes)",
tif->tif_row, (unsigned long long) occ);
#endif
return (0);
}
return (1);
}
#ifdef LZW_COMPAT
/*
* Decode a "hunk of data" for old images.
*/
#define GetNextCodeCompat(sp, bp, code) { \
nextdata |= (unsigned long) *(bp)++ << nextbits; \
nextbits += 8; \
if (nextbits < nbits) { \
nextdata |= (unsigned long) *(bp)++ << nextbits;\
nextbits += 8; \
} \
code = (hcode_t)(nextdata & nbitsmask); \
nextdata >>= nbits; \
nextbits -= nbits; \
}
static int
LZWDecodeCompat(TIFF* tif, uint8* op0, tmsize_t occ0, uint16 s)
{
static const char module[] = "LZWDecodeCompat";
LZWCodecState *sp = DecoderState(tif);
char *op = (char*) op0;
long occ = (long) occ0;
char *tp;
unsigned char *bp;
int code, nbits;
long nextbits, nextdata, nbitsmask;
code_t *codep, *free_entp, *maxcodep, *oldcodep;
(void) s;
assert(sp != NULL);
/*
Fail if value does not fit in long.
*/
if ((tmsize_t) occ != occ0)
return (0);
/*
* Restart interrupted output operation.
*/
if (sp->dec_restart) {
long residue;
codep = sp->dec_codep;
residue = codep->length - sp->dec_restart;
if (residue > occ) {
/*
* Residue from previous decode is sufficient
* to satisfy decode request. Skip to the
* start of the decoded string, place decoded
* values in the output buffer, and return.
*/
sp->dec_restart += occ;
do {
codep = codep->next;
} while (--residue > occ);
tp = op + occ;
do {
*--tp = codep->value;
codep = codep->next;
} while (--occ);
return (1);
}
/*
* Residue satisfies only part of the decode request.
*/
op += residue, occ -= residue;
tp = op;
do {
*--tp = codep->value;
codep = codep->next;
} while (--residue);
sp->dec_restart = 0;
}
bp = (unsigned char *)tif->tif_rawcp;
nbits = sp->lzw_nbits;
nextdata = sp->lzw_nextdata;
nextbits = sp->lzw_nextbits;
nbitsmask = sp->dec_nbitsmask;
oldcodep = sp->dec_oldcodep;
free_entp = sp->dec_free_entp;
maxcodep = sp->dec_maxcodep;
while (occ > 0) {
NextCode(tif, sp, bp, code, GetNextCodeCompat);
if (code == CODE_EOI)
break;
if (code == CODE_CLEAR) {
free_entp = sp->dec_codetab + CODE_FIRST;
_TIFFmemset(free_entp, 0,
(CSIZE - CODE_FIRST) * sizeof (code_t));
nbits = BITS_MIN;
nbitsmask = MAXCODE(BITS_MIN);
maxcodep = sp->dec_codetab + nbitsmask;
NextCode(tif, sp, bp, code, GetNextCodeCompat);
if (code == CODE_EOI)
break;
if (code >= CODE_CLEAR) {
TIFFErrorExt(tif->tif_clientdata, tif->tif_name,
"LZWDecode: Corrupted LZW table at scanline %d",
tif->tif_row);
return (0);
}
*op++ = code, occ--;
oldcodep = sp->dec_codetab + code;
continue;
}
codep = sp->dec_codetab + code;
/*
* Add the new entry to the code table.
*/
if (free_entp < &sp->dec_codetab[0] ||
free_entp >= &sp->dec_codetab[CSIZE]) {
TIFFErrorExt(tif->tif_clientdata, module,
"Corrupted LZW table at scanline %d", tif->tif_row);
return (0);
}
free_entp->next = oldcodep;
if (free_entp->next < &sp->dec_codetab[0] ||
free_entp->next >= &sp->dec_codetab[CSIZE]) {
TIFFErrorExt(tif->tif_clientdata, module,
"Corrupted LZW table at scanline %d", tif->tif_row);
return (0);
}
free_entp->firstchar = free_entp->next->firstchar;
free_entp->length = free_entp->next->length+1;
free_entp->value = (codep < free_entp) ?
codep->firstchar : free_entp->firstchar;
if (++free_entp > maxcodep) {
if (++nbits > BITS_MAX) /* should not happen */
nbits = BITS_MAX;
nbitsmask = MAXCODE(nbits);
maxcodep = sp->dec_codetab + nbitsmask;
}
oldcodep = codep;
if (code >= 256) {
/*
* Code maps to a string, copy string
* value to output (written in reverse).
*/
if(codep->length == 0) {
TIFFErrorExt(tif->tif_clientdata, module,
"Wrong length of decoded "
"string: data probably corrupted at scanline %d",
tif->tif_row);
return (0);
}
if (codep->length > occ) {
/*
* String is too long for decode buffer,
* locate portion that will fit, copy to
* the decode buffer, and setup restart
* logic for the next decoding call.
*/
sp->dec_codep = codep;
do {
codep = codep->next;
} while (codep->length > occ);
sp->dec_restart = occ;
tp = op + occ;
do {
*--tp = codep->value;
codep = codep->next;
} while (--occ);
break;
}
assert(occ >= codep->length);
op += codep->length, occ -= codep->length;
tp = op;
do {
*--tp = codep->value;
} while( (codep = codep->next) != NULL );
} else
*op++ = code, occ--;
}
tif->tif_rawcp = (uint8*) bp;
sp->lzw_nbits = nbits;
sp->lzw_nextdata = nextdata;
sp->lzw_nextbits = nextbits;
sp->dec_nbitsmask = nbitsmask;
sp->dec_oldcodep = oldcodep;
sp->dec_free_entp = free_entp;
sp->dec_maxcodep = maxcodep;
if (occ > 0) {
#if defined(__WIN32__) && (defined(_MSC_VER) || defined(__MINGW32__))
TIFFErrorExt(tif->tif_clientdata, module,
"Not enough data at scanline %d (short %I64d bytes)",
tif->tif_row, (unsigned __int64) occ);
#else
TIFFErrorExt(tif->tif_clientdata, module,
"Not enough data at scanline %d (short %llu bytes)",
tif->tif_row, (unsigned long long) occ);
#endif
return (0);
}
return (1);
}
#endif /* LZW_COMPAT */
/*
* LZW Encoding.
*/
static int
LZWSetupEncode(TIFF* tif)
{
static const char module[] = "LZWSetupEncode";
LZWCodecState* sp = EncoderState(tif);
assert(sp != NULL);
sp->enc_hashtab = (hash_t*) _TIFFmalloc(HSIZE*sizeof (hash_t));
if (sp->enc_hashtab == NULL) {
TIFFErrorExt(tif->tif_clientdata, module,
"No space for LZW hash table");
return (0);
}
return (1);
}
/*
* Reset encoding state at the start of a strip.
*/
static int
LZWPreEncode(TIFF* tif, uint16 s)
{
LZWCodecState *sp = EncoderState(tif);
(void) s;
assert(sp != NULL);
if( sp->enc_hashtab == NULL )
{
tif->tif_setupencode( tif );
}
sp->lzw_nbits = BITS_MIN;
sp->lzw_maxcode = MAXCODE(BITS_MIN);
sp->lzw_free_ent = CODE_FIRST;
sp->lzw_nextbits = 0;
sp->lzw_nextdata = 0;
sp->enc_checkpoint = CHECK_GAP;
sp->enc_ratio = 0;
sp->enc_incount = 0;
sp->enc_outcount = 0;
/*
* The 4 here insures there is space for 2 max-sized
* codes in LZWEncode and LZWPostDecode.
*/
sp->enc_rawlimit = tif->tif_rawdata + tif->tif_rawdatasize-1 - 4;
cl_hash(sp); /* clear hash table */
sp->enc_oldcode = (hcode_t) -1; /* generates CODE_CLEAR in LZWEncode */
return (1);
}
#define CALCRATIO(sp, rat) { \
if (incount > 0x007fffff) { /* NB: shift will overflow */\
rat = outcount >> 8; \
rat = (rat == 0 ? 0x7fffffff : incount/rat); \
} else \
rat = (incount<<8) / outcount; \
}
#define PutNextCode(op, c) { \
nextdata = (nextdata << nbits) | c; \
nextbits += nbits; \
*op++ = (unsigned char)(nextdata >> (nextbits-8)); \
nextbits -= 8; \
if (nextbits >= 8) { \
*op++ = (unsigned char)(nextdata >> (nextbits-8)); \
nextbits -= 8; \
} \
outcount += nbits; \
}
/*
* Encode a chunk of pixels.
*
* Uses an open addressing double hashing (no chaining) on the
* prefix code/next character combination. We do a variant of
* Knuth's algorithm D (vol. 3, sec. 6.4) along with G. Knott's
* relatively-prime secondary probe. Here, the modular division
* first probe is gives way to a faster exclusive-or manipulation.
* Also do block compression with an adaptive reset, whereby the
* code table is cleared when the compression ratio decreases,
* but after the table fills. The variable-length output codes
* are re-sized at this point, and a CODE_CLEAR is generated
* for the decoder.
*/
static int
LZWEncode(TIFF* tif, uint8* bp, tmsize_t cc, uint16 s)
{
register LZWCodecState *sp = EncoderState(tif);
register long fcode;
register hash_t *hp;
register int h, c;
hcode_t ent;
long disp;
long incount, outcount, checkpoint;
long nextdata, nextbits;
int free_ent, maxcode, nbits;
uint8* op;
uint8* limit;
(void) s;
if (sp == NULL)
return (0);
assert(sp->enc_hashtab != NULL);
/*
* Load local state.
*/
incount = sp->enc_incount;
outcount = sp->enc_outcount;
checkpoint = sp->enc_checkpoint;
nextdata = sp->lzw_nextdata;
nextbits = sp->lzw_nextbits;
free_ent = sp->lzw_free_ent;
maxcode = sp->lzw_maxcode;
nbits = sp->lzw_nbits;
op = tif->tif_rawcp;
limit = sp->enc_rawlimit;
ent = sp->enc_oldcode;
if (ent == (hcode_t) -1 && cc > 0) {
/*
* NB: This is safe because it can only happen
* at the start of a strip where we know there
* is space in the data buffer.
*/
PutNextCode(op, CODE_CLEAR);
ent = *bp++; cc--; incount++;
}
while (cc > 0) {
c = *bp++; cc--; incount++;
fcode = ((long)c << BITS_MAX) + ent;
h = (c << HSHIFT) ^ ent; /* xor hashing */
#ifdef _WINDOWS
/*
* Check hash index for an overflow.
*/
if (h >= HSIZE)
h -= HSIZE;
#endif
hp = &sp->enc_hashtab[h];
if (hp->hash == fcode) {
ent = hp->code;
continue;
}
if (hp->hash >= 0) {
/*
* Primary hash failed, check secondary hash.
*/
disp = HSIZE - h;
if (h == 0)
disp = 1;
do {
/*
* Avoid pointer arithmetic 'cuz of
* wraparound problems with segments.
*/
if ((h -= disp) < 0)
h += HSIZE;
hp = &sp->enc_hashtab[h];
if (hp->hash == fcode) {
ent = hp->code;
goto hit;
}
} while (hp->hash >= 0);
}
/*
* New entry, emit code and add to table.
*/
/*
* Verify there is space in the buffer for the code
* and any potential Clear code that might be emitted
* below. The value of limit is setup so that there
* are at least 4 bytes free--room for 2 codes.
*/
if (op > limit) {
tif->tif_rawcc = (tmsize_t)(op - tif->tif_rawdata);
TIFFFlushData1(tif);
op = tif->tif_rawdata;
}
PutNextCode(op, ent);
ent = c;
hp->code = free_ent++;
hp->hash = fcode;
if (free_ent == CODE_MAX-1) {
/* table is full, emit clear code and reset */
cl_hash(sp);
sp->enc_ratio = 0;
incount = 0;
outcount = 0;
free_ent = CODE_FIRST;
PutNextCode(op, CODE_CLEAR);
nbits = BITS_MIN;
maxcode = MAXCODE(BITS_MIN);
} else {
/*
* If the next entry is going to be too big for
* the code size, then increase it, if possible.
*/
if (free_ent > maxcode) {
nbits++;
assert(nbits <= BITS_MAX);
maxcode = (int) MAXCODE(nbits);
} else if (incount >= checkpoint) {
long rat;
/*
* Check compression ratio and, if things seem
* to be slipping, clear the hash table and
* reset state. The compression ratio is a
* 24+8-bit fractional number.
*/
checkpoint = incount+CHECK_GAP;
CALCRATIO(sp, rat);
if (rat <= sp->enc_ratio) {
cl_hash(sp);
sp->enc_ratio = 0;
incount = 0;
outcount = 0;
free_ent = CODE_FIRST;
PutNextCode(op, CODE_CLEAR);
nbits = BITS_MIN;
maxcode = MAXCODE(BITS_MIN);
} else
sp->enc_ratio = rat;
}
}