From 0ae0a344200291ae958fcb3c9c3ece9c5b604f6e Mon Sep 17 00:00:00 2001
From: Nick Bowler <draconx@gmail.com>
Date: Mon, 31 Dec 2007 05:24:40 -0500
Subject: [PATCH] Update handling of embedded palette data in image files.

The pal (formerly wtf2) value indicates the presence of a palette: 0x1000 if
present; 0 otherwise.  Then, immediately following the offsets comes the
palette header: 2 bytes always zero, 2 bytes for the number of entries.
Entries are sequential starting from zero.

This makes the logo images work.
---
 src/image.c | 59 +++++++++++++++++++++++++++++++++--------------------
 1 file changed, 37 insertions(+), 22 deletions(-)

diff --git a/src/image.c b/src/image.c
index c1ad351..4f1a2bd 100644
--- a/src/image.c
+++ b/src/image.c
@@ -14,8 +14,9 @@
 
 struct lbx_image {
 	uint16_t width, height;
-	uint16_t wtf1, wtf2;
+	uint16_t wtf1;
 	uint16_t offs, frames;
+	uint16_t pal;
 
 	FILE *f;
 	long foff;
@@ -36,19 +37,20 @@ struct lbx_image *lbximg_fopen(FILE *f)
 	if (fread(&tmp.wtf1,   sizeof tmp.wtf1,    1, f) != 1) goto readerr;
 	if (fread(&tmp.offs,   sizeof tmp.offs,    1, f) != 1) goto readerr;
 	if (fread(&tmp.frames, sizeof tmp.frames,  1, f) != 1) goto readerr;
-	if (fread(&tmp.wtf2,   sizeof tmp.wtf2,    1, f) != 1) goto readerr;
+	if (fread(&tmp.pal,    sizeof tmp.pal,     1, f) != 1) goto readerr;
 
 	tmp.width  = letohs(tmp.width);  tmp.foff += sizeof tmp.width;
 	tmp.height = letohs(tmp.height); tmp.foff += sizeof tmp.height;
 	tmp.wtf1   = letohs(tmp.wtf1);   tmp.foff += sizeof tmp.wtf1;
 	tmp.offs   = letohs(tmp.offs);   tmp.foff += sizeof tmp.offs;
 	tmp.frames = letohs(tmp.frames); tmp.foff += sizeof tmp.frames;
-	tmp.wtf2   = letohs(tmp.wtf2);   tmp.foff += sizeof tmp.wtf2;
+	tmp.pal    = letohs(tmp.pal);    tmp.foff += sizeof tmp.pal;
 
 	/* For some reason, the format seems to need this. */
 	tmp.offs++;
 	tmp.frames++;
 
+	/* Format constraints. */
 	if (tmp.offs <= tmp.frames) {
 		lbx_errno = LBX_EFORMAT;
 		return NULL;
@@ -62,6 +64,7 @@ struct lbx_image *lbximg_fopen(FILE *f)
 	 */
 	_lbx_assert(tmp.wtf1 == 0);
 	_lbx_assert(tmp.offs == tmp.frames + 1);
+	_lbx_assert(tmp.pal  == 0 || tmp.pal == 0x1000);
 
 	new = malloc(sizeof *new + tmp.offs * sizeof *new->offsets);
 	if (!new) {
@@ -260,18 +263,38 @@ int lbximg_loadpalette(FILE *f, struct lbx_colour palette[static 256])
 int
 lbximg_getpalette(struct lbx_image *img, struct lbx_colour palette[static 256])
 {
-	int index = 0;
+	size_t hdrlen = 6*(sizeof img->pal)+(img->offs)*(sizeof *img->offsets);
+	unsigned int i;
 	size_t rc;
-	size_t hdrlen = 6*(sizeof img->width)
-	                + (img->offs)*(sizeof *img->offsets);
-	
-	uint8_t entry[4];
+
+	uint16_t zero, count;
+	uint8_t  entry[4];
+
+	/* Do nothing if the image doesn't have embedded palette data. */
+	if (img->pal == 0)
+		return 0;
 
 	/* Palette data is located right after the header. */
 	if (_lbx_fseek(img->f, &img->foff, hdrlen) == -1)
 		return -1;
 	
-	while (img->foff + sizeof entry <= img->offsets[0]) {
+	/* Palette header */
+	if (fread(&zero,  sizeof zero,  1, img->f) != 1) goto readerr;
+	if (fread(&count, sizeof count, 1, img->f) != 1) goto readerr;
+	zero  = letohs(zero);  img->foff += sizeof zero;
+	count = letohs(count); img->foff += sizeof count;
+
+	if (zero != 0 || count > 256) {
+		lbx_errno = LBX_EFORMAT;
+		return -1;
+	}
+
+	if (hdrlen + 2*(sizeof zero) + count*(sizeof entry) > img->offsets[0]) {
+		lbx_errno = LBX_EFORMAT;
+		return -1;
+	}
+
+	for (i = 0; i < count; i++) {
 		rc = fread(entry, 1, sizeof entry, img->f);
 		img->foff += rc;
 
@@ -279,17 +302,12 @@ lbximg_getpalette(struct lbx_image *img, struct lbx_colour palette[static 256])
 			goto readerr;
 		}
 
-		if (entry[0] == 0) {
-			index++;
-			if (index >= 256) {
-				lbx_errno = LBX_EFORMAT;
-				return -1;
-			}
-		} else {
-			index = entry[0];
+		if (entry[0] != 0) {
+			lbx_errno = LBX_EFORMAT;
+			return -1;
 		}
 
-		palette[index] = (struct lbx_colour){
+		palette[i] = (struct lbx_colour){
 			.red   = entry[1] << 2,
 			.green = entry[2] << 2,
 			.blue  = entry[3] << 2,
@@ -298,10 +316,7 @@ lbximg_getpalette(struct lbx_image *img, struct lbx_colour palette[static 256])
 
 	return 0;
 readerr:
-	if (feof(img->f))
-		lbx_errno = LBX_EEOF;
-	else
-		lbx_errno = -errno;
+	lbx_errno = feof(img->f) ? LBX_EEOF : -errno;
 	return -1;
 }
 
-- 
2.43.2