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lzw and flate filters: use common predict logic

--- a/f_flate.c

+++ b/f_flate.c

@@ -3,70 +3,8 @@

 #include <flate.h>

 #include "pdf.h"

-typedef struct FlateParms FlateParms;

-struct FlateParms {

-	int predictor;

-	int columns;

-};

-

-static uchar 

-paeth(uchar a, uchar b, uchar c)

-{

-	int p, pa, pb, pc;

-

-	p = a + b - c;

-	pa = abs(p - a);

-	pb = abs(p - b);

-	pc = abs(p - c);

-

-	if(pa <= pb && pa <= pc)

-		return a;

-	return pb <= pc ? b : c;

-}

-

 static int

-pngunpredict(int pred, uchar *buf, uchar *up, int len)

-{

-	int i;

-

-	switch(pred){

-	case 0: /* None */

-		break;

-

-	case 1: /* Sub */

-		for(i = 1; i < len; ++i)

-			buf[i] += buf[i-1];

-		break;

-

-	case 2: /* Up */

-		for(i = 0; i < len; ++i)

-			buf[i] += up[i];

-		break;

-

-	case 3: /* Average */

-		buf[0] += up[0]/2;

-		for(i = 1; i < len; ++i)

-			buf[i] += (buf[i-1]+up[i])/2;

-		break;

-

-	case 4: /* Paeth */

-		buf[0] += paeth(0, up[0], 0);

-		for(i = 0; i < len; ++i)

-			buf[i] += paeth(buf[i-1], up[i], up[i-1]);

-		break;

-

-	/* FIXME 5 optimum??? */

-

-	default:

-		werrstr("unsupported predictor %d", pred);

-		return -1;

-	}

-

-	return 0;

-}

-

-static int

 bw(void *aux, void *d, int n)

 {

 	return bufput(aux, d, n);

@@ -83,12 +21,8 @@

 static int

 flreadall(void *aux, Buffer *bi, Buffer *bo)

 {

-	int r, i, rows, n;

-	FlateParms *fp;

-	uchar *x, *y, *zero;

+	int r;

-	fp = aux;

-

 	do{

 		r = inflatezlib(bo, bw, bi, bget);

 	}while(r == FlateOk && !bufeof(bi));

@@ -97,66 +31,13 @@

 		werrstr("%s", flateerr(r));

 		return -1;

 	}

-	r = 0;

-	/* 7.4.4.4 LZW and Flate predictor functions */

-	if(fp->predictor >= 10 && fp->columns > 0){

-		n = fp->columns + 1;

-		rows = bo->sz/n;

-		x = bo->b;

-		y = bo->b;

-		zero = mallocz(fp->columns, 1);

-		for(i = r = 0; i < rows && r == 0; i++, x += n, y += n)

-			r = pngunpredict(x[0], x+1, i < 1 ? zero : y+1-n, fp->columns);

-		free(zero);

-

-		x = bo->b;

-		y = bo->b+1;

-		for(i = 0; i < rows; i++, x += fp->columns, y += n)

-			memmove(x, y, fp->columns);

-		bo->sz -= rows;

-	}

-

-	return r;

+	return unpredict(aux, bo);

 }

-static int

-flopen(Filter *f, Object *o)

-{

-	Object *parms;

-	FlateParms *fp;

-	int predictor, columns;

-

-	parms = dictget(o, "DecodeParms");

-	predictor = dictint(parms, "Predictor");

-	columns = dictint(parms, "Columns");

-	if((predictor >= 2 && predictor < 10) || predictor >= 15){

-		werrstr("unsupported flate predictor %d", predictor);

-		return -1;

-	}

-	if(predictor >= 10 && predictor <= 15 && columns < 1){

-		werrstr("invalid columns %d for predictor %d", columns, predictor);

-		return -1;

-	}

-

-	if((fp = malloc(sizeof(FlateParms))) == nil)

-		return -1;

-	fp->predictor = predictor;

-	fp->columns = columns;

-	f->aux = fp;

-

-	return 0;

-}

-

-static void

-flclose(Filter *f)

-{

-	free(f->aux);

-}

-

 Filter filterFlate = {

 	.name = "FlateDecode",

 	.readall = flreadall,

-	.open = flopen,

-	.close = flclose,

+	.open = flopenpredict,

+	.close = flclosepredict,

 };

--- a/f_lzw.c

+++ b/f_lzw.c

@@ -121,8 +121,6 @@

 	uchar *in;

 	Tb tb;

-	USED(aux);

-

 	memset(&tb, 0, sizeof(tb));

 	in = bufdata(bi, &insz);

 	width = 9;

@@ -155,10 +153,12 @@

 	tbfree(&tb);

 	bi->off = bi->sz;

-	return 0;

+	return unpredict(aux, bo);

 }

 Filter filterLZW = {

 	.name = "LZWDecode",

 	.readall = flreadall,

+	.open = flopenpredict,

+	.close = flclosepredict,

 };

--- a/mkfile

+++ b/mkfile

@@ -7,12 +7,12 @@

 	buffer.$O\

 	dict.$O\

 	eval.$O\

-	f_dct.$O\

 	f_ascii85.$O\

 	f_asciihex.$O\

 	f_ccittfax.$O\

 	f_crypt.$O\

 	f_dct.$O\

+	f_dct.$O\

 	f_flate.$O\

 	f_jbig2.$O\

 	f_jpx.$O\

@@ -25,6 +25,7 @@

 	object.$O\

 	pdf.$O\

 	pdffs.$O\

+	predict.$O\

 	stream.$O\

 	string.$O\

 	xref.$O\

--- a/pdf.h

+++ b/pdf.h

@@ -15,6 +15,8 @@

 typedef struct KeyValue KeyValue;

 typedef struct Object Object;

 typedef struct Pdf Pdf;

+typedef struct PredictParms PredictParms;

+#pragma incomplete PredictParms;

 typedef struct Stream Stream;

 typedef struct Xref Xref;

@@ -185,6 +187,11 @@

 Filter *filteropen(char *name, Object *o);

 int filterrun(Filter *f, Buffer *bi, Buffer *bo);

 void filterclose(Filter *f);

+

+/* 7.4.4.4 LZW and Flate predictor functions */

+int unpredict(PredictParms *pp, Buffer *bo);

+int flopenpredict(Filter *f, Object *o);

+void flclosepredict(Filter *f);

 void bufinit(Buffer *b, uchar *d, int sz);

 void buffree(Buffer *b);

--- /dev/null

+++ b/predict.c

@@ -1,0 +1,128 @@

+#include <u.h>

+#include <libc.h>

+#include "pdf.h"

+

+struct PredictParms {

+	int predictor;

+	int columns;

+};

+

+static uchar 

+paeth(uchar a, uchar b, uchar c)

+{

+	int p, pa, pb, pc;

+

+	p = a + b - c;

+	pa = abs(p - a);

+	pb = abs(p - b);

+	pc = abs(p - c);

+

+	if(pa <= pb && pa <= pc)

+		return a;

+	return pb <= pc ? b : c;

+}

+

+static int

+pngunpredict(int pred, uchar *buf, uchar *up, int len)

+{

+	int i;

+

+	switch(pred){

+	case 0: /* None */

+		break;

+

+	case 1: /* Sub */

+		for(i = 1; i < len; ++i)

+			buf[i] += buf[i-1];

+		break;

+

+	case 2: /* Up */

+		for(i = 0; i < len; ++i)

+			buf[i] += up[i];

+		break;

+

+	case 3: /* Average */

+		buf[0] += up[0]/2;

+		for(i = 1; i < len; ++i)

+			buf[i] += (buf[i-1]+up[i])/2;

+		break;

+

+	case 4: /* Paeth */

+		buf[0] += paeth(0, up[0], 0);

+		for(i = 0; i < len; ++i)

+			buf[i] += paeth(buf[i-1], up[i], up[i-1]);

+		break;

+

+	/* FIXME 5 optimum??? */

+

+	default:

+		werrstr("unsupported predictor %d", pred);

+		return -1;

+	}

+

+	return 0;

+}

+

+int

+unpredict(PredictParms *pp, Buffer *bo)

+{

+	uchar *x, *y, *zero;

+	int i, r, rows, n;

+

+	if(pp->predictor < 10 || pp->columns < 1)

+		return 0;

+

+	n = pp->columns + 1;

+	rows = bo->sz/n;

+	x = bo->b;

+	y = bo->b;

+	zero = mallocz(pp->columns, 1);

+	for(i = r = 0; i < rows && r == 0; i++, x += n, y += n)

+		r = pngunpredict(x[0], x+1, i < 1 ? zero : y+1-n, pp->columns);

+	free(zero);

+

+	if(r != 0)

+		return r;

+

+	x = bo->b;

+	y = bo->b+1;

+	for(i = 0; i < rows; i++, x += pp->columns, y += n)

+		memmove(x, y, pp->columns);

+	bo->sz -= rows;

+

+	return r;

+}

+

+int

+flopenpredict(Filter *f, Object *o)

+{

+	Object *parms;

+	PredictParms *pp;

+	int predictor, columns;

+

+	parms = dictget(o, "DecodeParms");

+	predictor = dictint(parms, "Predictor");

+	columns = dictint(parms, "Columns");

+	if((predictor >= 2 && predictor < 10) || predictor >= 15){

+		werrstr("unsupported flate predictor %d", predictor);

+		return -1;

+	}

+	if(predictor >= 10 && predictor <= 15 && columns < 1){

+		werrstr("invalid columns %d for predictor %d", columns, predictor);

+		return -1;

+	}

+

+	if((pp = malloc(sizeof(*pp))) == nil)

+		return -1;

+	pp->predictor = predictor;

+	pp->columns = columns;

+	f->aux = pp;

+

+	return 0;

+}

+

+void

+flclosepredict(Filter *f)

+{

+	free(f->aux);

+}