LZW compression code is merged back from the separate package.

libtiff/tif_lzw.c

@@ -1,4 +1,4 @@
-/* $Header: /cvs/maptools/cvsroot/libtiff/libtiff/tif_lzw.c,v 1.20 2003-11-03 14:45:38 dron Exp $ */
+/* $Id: tif_lzw.c,v 1.21 2004-07-24 19:01:15 dron Exp $ */
 
 /*
  * Copyright (c) 1988-1997 Sam Leffler
@@ -97,6 +97,8 @@ typedef	struct {
 	u_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
@@ -109,6 +111,10 @@ typedef	struct {
  * Encoding-specific state.
  */
 typedef uint16 hcode_t;			/* codes fit in 16 bits */
+typedef struct {
+	long	hash;
+	hcode_t	code;
+} hash_t;
 
 /*
  * Decoding-specific state.
@@ -137,15 +143,27 @@ 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 */
+
+	/* 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.
@@ -178,6 +196,30 @@ LZWSetupDecode(TIFF* 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) {
@@ -191,8 +233,8 @@ LZWSetupDecode(TIFF* tif)
 		 */
                 code = 255;
                 do {
-                    sp->dec_codetab[code].value = (u_char) code;
+                    sp->dec_codetab[code].value = code;
-                    sp->dec_codetab[code].firstchar = (u_char) code;
+                    sp->dec_codetab[code].firstchar = code;
                     sp->dec_codetab[code].length = 1;
                     sp->dec_codetab[code].next = NULL;
                 } while (code--);
@@ -347,7 +389,7 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
 			--tp;
 			t = codep->value;
 			codep = codep->next;
-			*tp = (char) t;
+			*tp = t;
 		} while (--residue && codep);
 		sp->dec_restart = 0;
 	}
@@ -373,7 +415,7 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
 			NextCode(tif, sp, bp, code, GetNextCode);
 			if (code == CODE_EOI)
 				break;
-			*op++ = (char)code, occ--;
+			*op++ = code, occ--;
 			oldcodep = sp->dec_codetab + code;
 			continue;
 		}
@@ -451,7 +493,7 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
 				--tp;
 				t = codep->value;
 				codep = codep->next;
-				*tp = (char) t;
+				*tp = t;
 			} while (codep && tp > op);
 			if (codep) {
 			    codeLoop(tif);
@@ -459,7 +501,7 @@ LZWDecode(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
 			}
 			op += len, occ -= len;
 		} else
-			*op++ = (char)code, occ--;
+			*op++ = code, occ--;
 	}
 
 	tif->tif_rawcp = (tidata_t) bp;
@@ -569,7 +611,7 @@ LZWDecodeCompat(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
 			NextCode(tif, sp, bp, code, GetNextCodeCompat);
 			if (code == CODE_EOI)
 				break;
-			*op++ = (char) code, occ--;
+			*op++ = code, occ--;
 			oldcodep = sp->dec_codetab + code;
 			continue;
 		}
@@ -642,11 +684,11 @@ LZWDecodeCompat(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
 				*--tp = codep->value;
 			} while( (codep = codep->next) != NULL);
 		} else
-			*op++ = (char) code, occ--;
+			*op++ = code, occ--;
 	}
 
 	tif->tif_rawcp = (tidata_t) bp;
-	sp->lzw_nbits = (u_short) nbits;
+	sp->lzw_nbits = nbits;
 	sp->lzw_nextdata = nextdata;
 	sp->lzw_nextbits = nextbits;
 	sp->dec_nbitsmask = nbitsmask;
@@ -664,7 +706,299 @@ LZWDecodeCompat(TIFF* tif, tidata_t op0, tsize_t occ0, tsample_t s)
 }
 #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++ = (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
+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++ = (u_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)
@@ -672,24 +1006,19 @@ 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;
 	}
 }
 
-static int
-LZWSetupEncode(TIFF* tif)
-{
-    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.
 	 */
@@ -698,25 +1027,29 @@ TIFFInitLZW(TIFF* tif, int scheme)
 		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_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);