/* $Id: tif_lzw.c,v 1.57 2017-07-11 10:54:29 erouault 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 */

	unsigned 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 = (unsigned char)code;

			sp->dec_codetab[code].firstchar = (unsigned char)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 );

	    if( sp->dec_codetab == NULL )

		return (0);

        }

	/*

	 * Check for old bit-reversed codes.

	 */

	if (tif->tif_rawcc >= 2 &&

	    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 = 0;

#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, nbitsmask;

        unsigned long nextdata;

	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 = (char)t;

		} while (--residue && codep);

		sp->dec_restart = 0;

	}

	bp = (unsigned char *)tif->tif_rawcp;

#ifdef LZW_CHECKEOS

	sp->dec_bitsleft = (((uint64)tif->tif_rawcc) << 3);

#endif

	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) {

			do {

				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);

			} while (code == CODE_CLEAR);	/* consecutive CODE_CLEAR codes */

			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 = (char)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_rawcc -= (tmsize_t)( (uint8*) bp - tif->tif_rawcp );

	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;

#ifdef LZW_CHECKEOS

	sp->dec_bitsleft = (((uint64)tif->tif_rawcc) << 3);

#endif

	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) {

			do {

				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);

			} while (code == CODE_CLEAR);	/* consecutive CODE_CLEAR codes */

			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;

		}

		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++ = (char)code;

			occ--;

		}

	}

	tif->tif_rawcc -= (tmsize_t)( (uint8*) bp - tif->tif_rawcp );

	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);

}

#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;			\

}

/* Explicit 0xff masking to make icc -check=conversions happy */

#define	PutNextCode(op, c) {					\

	nextdata = (nextdata << nbits) | c;			\

	nextbits += nbits;					\

	*op++ = (unsigned char)((nextdata >> (nextbits-8))&0xff);		\

	nextbits -= 8;						\

	if (nextbits >= 8) {					\

		*op++ = (unsigned char)((nextdata >> (nextbits-8))&0xff);	\

		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.