]> git.saurik.com Git - wxWidgets.git/blobdiff - src/tiff/tif_lzw.c
[ 1509599 ] 'Split pickers page in widgets sample' with more icons and rebaking.
[wxWidgets.git] / src / tiff / tif_lzw.c
index e41314a6a371cf54dcacfbbf0cfaa0472267b0e8..9909ee43aa67e518cbd6c8452f8929ffa7b38d3a 100644 (file)
@@ -4,23 +4,23 @@
  * Copyright (c) 1988-1997 Sam Leffler
  * Copyright (c) 1991-1997 Silicon Graphics, Inc.
  *
- * Permission to use, copy, modify, distribute, and sell this software and
+ * 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.
- *
+ * 
+ * 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
+ * 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.
  */
 
@@ -105,6 +105,11 @@ typedef    struct {
 #define        lzw_nextdata    base.nextdata
 #define        lzw_nextbits    base.nextbits
 
+/*
+ * Encoding-specific state.
+ */
+typedef uint16 hcode_t;                        /* codes fit in 16 bits */
+
 /*
  * Decoding-specific state.
  */
@@ -115,10 +120,12 @@ typedef struct code_ent {
        u_char  firstchar;              /* first token of string */
 } code_t;
 
-typedef        int (LINKAGEMODE *decodeFunc)(TIFF*, tidata_t, tsize_t, tsample_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
@@ -130,38 +137,15 @@ typedef struct {
        code_t* dec_free_entp;          /* next free entry */
        code_t* dec_maxcodep;           /* max available entry */
        code_t* dec_codetab;            /* kept separate for small machines */
-} LZWDecodeState;
-
-/*
- * Encoding-specific state.
- */
-typedef uint16 hcode_t;                        /* codes fit in 16 bits */
-typedef struct {
-       long    hash;
-       hcode_t code;
-} hash_t;
-
-typedef struct {
-       LZWBaseState base;
-       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 */
-} LZWEncodeState;
+} LZWCodecState;
 
 #define        LZWState(tif)           ((LZWBaseState*) (tif)->tif_data)
-#define        DecoderState(tif)       ((LZWDecodeState*) LZWState(tif))
-#define        EncoderState(tif)       ((LZWEncodeState*) LZWState(tif))
+#define        DecoderState(tif)       ((LZWCodecState*) LZWState(tif))
 
-static int LINKAGEMODE LZWDecode(TIFF*, tidata_t, tsize_t, tsample_t);
+static int LZWDecode(TIFF*, tidata_t, tsize_t, tsample_t);
 #ifdef LZW_COMPAT
-static int LINKAGEMODE LZWDecodeCompat(TIFF*, tidata_t, tsize_t, tsample_t);
+static int LZWDecodeCompat(TIFF*, tidata_t, tsize_t, tsample_t);
 #endif
-static void cl_hash(LZWEncodeState*);
 
 /*
  * LZW Decoder.
@@ -190,11 +174,12 @@ static    void cl_hash(LZWEncodeState*);
 static int
 LZWSetupDecode(TIFF* tif)
 {
-       LZWDecodeState* sp = DecoderState(tif);
-       static const char module[] = " LZWSetupDecode";
+       LZWCodecState* sp = DecoderState(tif);
+       static const char module[] = "LZWSetupDecode";
        int code;
 
        assert(sp != NULL);
+
        if (sp->dec_codetab == NULL) {
                sp->dec_codetab = (code_t*)_TIFFmalloc(CSIZE*sizeof (code_t));
                if (sp->dec_codetab == NULL) {
@@ -204,12 +189,13 @@ LZWSetupDecode(TIFF* tif)
                /*
                 * Pre-load the table.
                 */
-               for (code = 255; code >= 0; code--) {
-                       sp->dec_codetab[code].value = code;
-                       sp->dec_codetab[code].firstchar = code;
-                       sp->dec_codetab[code].length = 1;
-                       sp->dec_codetab[code].next = NULL;
-               }
+                code = 255;
+                do {
+                    sp->dec_codetab[code].value = (u_char) code;
+                    sp->dec_codetab[code].firstchar = (u_char) code;
+                    sp->dec_codetab[code].length = 1;
+                    sp->dec_codetab[code].next = NULL;
+                } while (code--);
        }
        return (1);
 }
@@ -220,7 +206,7 @@ LZWSetupDecode(TIFF* tif)
 static int
 LZWPreDecode(TIFF* tif, tsample_t s)
 {
-       LZWDecodeState *sp = DecoderState(tif);
+       LZWCodecState *sp = DecoderState(tif);
 
        (void) s;
        assert(sp != NULL);
@@ -311,7 +297,7 @@ codeLoop(TIFF* tif)
 static int
 LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
 {
-       LZWDecodeState *sp = DecoderState(tif);
+       LZWCodecState *sp = DecoderState(tif);
        char *op = (char*) op0;
        long occ = (long) occ0;
        char *tp;
@@ -361,7 +347,7 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
                        --tp;
                        t = codep->value;
                        codep = codep->next;
-                       *tp = t;
+                       *tp = (char) t;
                } while (--residue && codep);
                sp->dec_restart = 0;
        }
@@ -387,7 +373,7 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
                        NextCode(tif, sp, bp, code, GetNextCode);
                        if (code == CODE_EOI)
                                break;
-                       *op++ = code, occ--;
+                       *op++ = (char)code, occ--;
                        oldcodep = sp->dec_codetab + code;
                        continue;
                }
@@ -396,8 +382,22 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
                /*
                 * Add the new entry to the code table.
                 */
-               assert(&sp->dec_codetab[0] <= free_entp && free_entp < &sp->dec_codetab[CSIZE]);
+               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) ?
@@ -414,6 +414,13 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
                         * 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,
@@ -444,7 +451,7 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
                                --tp;
                                t = codep->value;
                                codep = codep->next;
-                               *tp = t;
+                               *tp = (char) t;
                        } while (codep && tp > op);
                        if (codep) {
                            codeLoop(tif);
@@ -452,7 +459,7 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
                        }
                        op += len, occ -= len;
                } else
-                       *op++ = code, occ--;
+                       *op++ = (char)code, occ--;
        }
 
        tif->tif_rawcp = (tidata_t) bp;
@@ -489,10 +496,10 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
        nextbits -= nbits;                                      \
 }
 
-static int LINKAGEMODE
+static int
 LZWDecodeCompat(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
 {
-       LZWDecodeState *sp = DecoderState(tif);
+       LZWCodecState *sp = DecoderState(tif);
        char *op = (char*) op0;
        long occ = (long) occ0;
        char *tp;
@@ -562,7 +569,7 @@ LZWDecodeCompat(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
                        NextCode(tif, sp, bp, code, GetNextCodeCompat);
                        if (code == CODE_EOI)
                                break;
-                       *op++ = code, occ--;
+                       *op++ = (char) code, occ--;
                        oldcodep = sp->dec_codetab + code;
                        continue;
                }
@@ -571,8 +578,22 @@ LZWDecodeCompat(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
                /*
                 * Add the new entry to the code table.
                 */
-               assert(&sp->dec_codetab[0] <= free_entp && free_entp < &sp->dec_codetab[CSIZE]);
+               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) ?
@@ -589,6 +610,13 @@ LZWDecodeCompat(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
                         * 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,
@@ -614,11 +642,11 @@ LZWDecodeCompat(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
                                *--tp = codep->value;
                        } while( (codep = codep->next) != NULL);
                } else
-                       *op++ = code, occ--;
+                       *op++ = (char) code, occ--;
        }
 
        tif->tif_rawcp = (tidata_t) bp;
-       sp->lzw_nbits = nbits;
+       sp->lzw_nbits = (u_short) nbits;
        sp->lzw_nextdata = nextdata;
        sp->lzw_nextbits = nextbits;
        sp->dec_nbitsmask = nbitsmask;
@@ -636,355 +664,59 @@ LZWDecodeCompat(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
 }
 #endif /* LZW_COMPAT */
 
-/*
- * LZW Encoding.
- */
-
-static int
-LZWSetupEncode(TIFF* tif)
-{
-       LZWEncodeState* 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)
-{
-       LZWEncodeState *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++ = (u_char)(nextdata >> (nextbits-8));             \
-       nextbits -= 8;                                          \
-       if (nextbits >= 8) {                                    \
-               *op++ = (u_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 LINKAGEMODE
-LZWEncode(TIFF* tif, tidata_t bp, tsize_t cc, tsample_t s)
-{
-       register LZWEncodeState *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 LZWEncodeState *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++ = (u_char)(nextdata << (8-nextbits));
-       tif->tif_rawcc = (tsize_t)(op - tif->tif_rawdata);
-       return (1);
-}
-
-/*
- * Reset encoding hash table.
- */
 static void
-cl_hash(LZWEncodeState* sp)
+LZWCleanup(TIFF* tif)
 {
-       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;
+    if (tif->tif_data) {
+        if (DecoderState(tif)->dec_codetab)
+            _TIFFfree(DecoderState(tif)->dec_codetab);
+        _TIFFfree(tif->tif_data);
+        tif->tif_data = NULL;
+    }
 }
 
-static void
-LZWCleanup(TIFF* tif)
+static int
+LZWSetupEncode(TIFF* tif)
 {
-       if (tif->tif_data) {
-               if (tif->tif_mode == O_RDONLY) {
-                       if (DecoderState(tif)->dec_codetab)
-                               _TIFFfree(DecoderState(tif)->dec_codetab);
-               } else {
-                       if (EncoderState(tif)->enc_hashtab)
-                               _TIFFfree(EncoderState(tif)->enc_hashtab);
-               }
-               _TIFFfree(tif->tif_data);
-               tif->tif_data = NULL;
-       }
+    TIFFError(tif->tif_name,
+              "LZW compression is not available to due to Unisys patent enforcement");
+    return (0);
 }
 
 int
 TIFFInitLZW(TIFF* tif, int scheme)
 {
        assert(scheme == COMPRESSION_LZW);
+
        /*
         * Allocate state block so tag methods have storage to record values.
         */
-       if (tif->tif_mode == O_RDONLY) {
-               tif->tif_data = (tidata_t) _TIFFmalloc(sizeof (LZWDecodeState));
-               if (tif->tif_data == NULL)
-                       goto bad;
-               DecoderState(tif)->dec_codetab = NULL;
-               DecoderState(tif)->dec_decode = NULL;
-       } else {
-               tif->tif_data = (tidata_t) _TIFFmalloc(sizeof (LZWEncodeState));
-               if (tif->tif_data == NULL)
-                       goto bad;
-               EncoderState(tif)->enc_hashtab = NULL;
-       }
+       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;
+
        /*
         * Install codec methods.
         */
+       tif->tif_setupencode = LZWSetupEncode;
        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);