/* $Id: tif_lzw.c,v 1.4 2005/11/19 16:02:59 malaterre 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*, tidata_t, tsize_t, tsample_t);

typedef struct {
  LZWBaseState base;

  /* Decoding specific data */
  long  dec_nbitsmask;    /* lzw_nbits 1 bits, right adjusted */
  long  dec_restart;    /* restart count */
#ifdef LZW_CHECKEOS
  long  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 */
  tidata_t 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*, tidata_t, tsize_t, tsample_t);
#ifdef LZW_COMPAT
static  int LZWDecodeCompat(TIFF*, tidata_t, tsize_t, tsample_t);
#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 < nbits) {        \
    TIFFWarning(_tif->tif_name,        \
        "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
LZWSetupDecode(TIFF* tif)
{
  LZWCodecState* sp = DecoderState(tif);
  static const char module[] = " LZWSetupDecode";
  int code;

        if( sp == NULL )
        {
            /*
             * Allocate state block so tag methods have storage to record 
             * values.
             */
            tif->tif_data = (tidata_t) _TIFFmalloc(sizeof(LZWCodecState));
            if (tif->tif_data == NULL)
            {
                TIFFError("LZWPreDecode", "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) {
      TIFFError(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--);
  }
  return (1);
}

/*
 * Setup state for decoding a strip.
 */
static int
LZWPreDecode(TIFF* tif, tsample_t s)
{
  LZWCodecState *sp = DecoderState(tif);

  (void) s;
  assert(sp != NULL);
  /*
   * Check for old bit-reversed codes.
   */
  if (tif->tif_rawdata[0] == 0 && (tif->tif_rawdata[1] & 0x1)) {
#ifdef LZW_COMPAT
    if (!sp->dec_decode) {
      TIFFWarning(tif->tif_name,
          "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) {
      TIFFError(tif->tif_name,
          "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 = 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)
{
  TIFFError(tif->tif_name,
      "LZWDecode: Bogus encoding, loop in the code table; scanline %d",
      tif->tif_row);
}

static int
LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
{
  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);
  /*
   * 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;
      nbits = BITS_MIN;
      nbitsmask = MAXCODE(BITS_MIN);
      maxcodep = sp->dec_codetab + nbitsmask-1;
      NextCode(tif, sp, bp, code, GetNextCode);
      if (code == CODE_EOI)
        break;
      *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]) {
      TIFFError(tif->tif_name,
      "LZWDecode: 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]) {
      TIFFError(tif->tif_name,
      "LZWDecode: 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) {
          TIFFError(tif->tif_name,
              "LZWDecode: 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 = occ;
          tp = op + occ;
          do  {
            *--tp = codep->value;
            codep = codep->next;
          }  while (--occ && codep);
          if (codep)
            codeLoop(tif);
        }
        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);
          break;
      }
      op += len, occ -= len;
    } else
      *op++ = (char)code, occ--;
  }

  tif->tif_rawcp = (tidata_t) 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) {
    TIFFError(tif->tif_name,
    "LZWDecode: Not enough data at scanline %d (short %d bytes)",
        tif->tif_row, occ);
    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, tidata_t op0, tsize_t occ0, tsample_t s)
{
  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);
  /*
   * 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;
      nbits = BITS_MIN;
      nbitsmask = MAXCODE(BITS_MIN);
      maxcodep = sp->dec_codetab + nbitsmask;
      NextCode(tif, sp, bp, code, GetNextCodeCompat);
      if (code == CODE_EOI)
        break;
      *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]) {
      TIFFError(tif->tif_name,
      "LZWDecodeCompat: 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]) {
      TIFFError(tif->tif_name,
      "LZWDecodeCompat: 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) {
          TIFFError(tif->tif_name,
              "LZWDecodeCompat: 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;
      }
      op += codep->length, occ -= codep->length;
      tp = op;
      do {
        *--tp = codep->value;
      } while( (codep = codep->next) != NULL);
    } else
      *op++ = code, occ--;
  }

  tif->tif_rawcp = (tidata_t) 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) {
    TIFFError(tif->tif_name,
      "LZWDecodeCompat: Not enough data at scanline %d (short %d bytes)",
        tif->tif_row, occ);
    return (0);
  }
  return (1);
}
#endif /* LZW_COMPAT */

/*
 * LZW Encoding.
 */

static int
LZWSetupEncode(TIFF* tif)
{
  LZWCodecState* sp = EncoderState(tif);
  static const char module[] = "LZWSetupEncode";

  assert(sp != NULL);
  sp->enc_hashtab = (hash_t*) _TIFFmalloc(HSIZE*sizeof (hash_t));
  if (sp->enc_hashtab == NULL) {
    TIFFError(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, tsample_t s)
{
  LZWCodecState *sp = EncoderState(tif);

  (void) s;
  assert(sp != NULL);
  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, tidata_t bp, tsize_t cc, tsample_t 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;
  tidata_t op, limit;

  (void) s;
  if (sp == NULL)
    return (0);
  /*
   * 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 = (tsize_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;
      }
    }
  hit:
    ;
  }

  /*
   * Restore global state.
   */
  sp->enc_incount = incount;
  sp->enc_outcount = outcount;
  sp->enc_checkpoint = checkpoint;
  sp->enc_oldcode = ent;
  sp->lzw_nextdata = nextdata;
  sp->lzw_nextbits = nextbits;
  sp->lzw_free_ent = free_ent;
  sp->lzw_maxcode = maxcode;
  sp->lzw_nbits = nbits;
  tif->tif_rawcp = op;
  return (1);
}

/*
 * Finish off an encoded strip by flushing the last
 * string and tacking on an End Of Information code.
 */
static int
LZWPostEncode(TIFF* tif)
{
  register LZWCodecState *sp = EncoderState(tif);
  tidata_t op = tif->tif_rawcp;
  long nextbits = sp->lzw_nextbits;
  long nextdata = sp->lzw_nextdata;
  long outcount = sp->enc_outcount;
  int nbits = sp->lzw_nbits;

  if (op > sp->enc_rawlimit) {
    tif->tif_rawcc = (tsize_t)(op - tif->tif_rawdata);
    TIFFFlushData1(tif);
    op = tif->tif_rawdata;
  }
  if (sp->enc_oldcode != (hcode_t) -1) {
    PutNextCode(op, sp->enc_oldcode);
    sp->enc_oldcode = (hcode_t) -1;
  }
  PutNextCode(op, CODE_EOI);
  if (nextbits > 0) 
    *op++ = (unsigned char)(nextdata << (8-nextbits));
  tif->tif_rawcc = (tsize_t)(op - tif->tif_rawdata);
  return (1);
}

/*
 * Reset encoding hash table.
 */
static void
cl_hash(LZWCodecState* sp)
{
  register hash_t *hp = &sp->enc_hashtab[HSIZE-1];
  register long i = HSIZE-8;

   do {
    i -= 8;
    hp[-7].hash = -1;
    hp[-6].hash = -1;
    hp[-5].hash = -1;
    hp[-4].hash = -1;
    hp[-3].hash = -1;
    hp[-2].hash = -1;
    hp[-1].hash = -1;
    hp[ 0].hash = -1;
    hp -= 8;
  } while (i >= 0);
      for (i += 8; i > 0; i--, hp--)
    hp->hash = -1;
}

static void
LZWCleanup(TIFF* tif)
{
  if (tif->tif_data) {
    if (DecoderState(tif)->dec_codetab)
      _TIFFfree(DecoderState(tif)->dec_codetab);

    if (EncoderState(tif)->enc_hashtab)
      _TIFFfree(EncoderState(tif)->enc_hashtab);

    _TIFFfree(tif->tif_data);
    tif->tif_data = NULL;
  }
}

int
TIFFInitLZW(TIFF* tif, int scheme)
{
  assert(scheme == COMPRESSION_LZW);
  /*
   * Allocate state block so tag methods have storage to record values.
   */
  tif->tif_data = (tidata_t) _TIFFmalloc(sizeof (LZWCodecState));
  if (tif->tif_data == NULL)
    goto bad;
  DecoderState(tif)->dec_codetab = NULL;
  DecoderState(tif)->dec_decode = NULL;
  EncoderState(tif)->enc_hashtab = NULL;
        LZWState(tif)->rw_mode = tif->tif_mode;

  /*
   * Install codec methods.
   */
  tif->tif_setupdecode = LZWSetupDecode;
  tif->tif_predecode = LZWPreDecode;
  tif->tif_decoderow = LZWDecode;
  tif->tif_decodestrip = LZWDecode;
  tif->tif_decodetile = LZWDecode;
  tif->tif_setupencode = LZWSetupEncode;
  tif->tif_preencode = LZWPreEncode;
  tif->tif_postencode = LZWPostEncode;
  tif->tif_encoderow = LZWEncode;
  tif->tif_encodestrip = LZWEncode;
  tif->tif_encodetile = LZWEncode;
  tif->tif_cleanup = LZWCleanup;
  /*
   * Setup predictor setup.
   */
  (void) TIFFPredictorInit(tif);
  return (1);
bad:
  TIFFError("TIFFInitLZW", "No space for LZW state block");
  return (0);
}

/*
 * Copyright (c) 1985, 1986 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * James A. Woods, derived from original work by Spencer Thomas
 * and Joseph Orost.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
#endif /* LZW_SUPPORT */

