From 91689c5ef8174cc65e1f3ce31f9869778b2af671 Mon Sep 17 00:00:00 2001
From: Nick Bowler <nbowler@draconx.ca>
Date: Tue, 9 Feb 2010 00:27:30 -0500
Subject: [PATCH] liblbx: Add support for "chunked" images.

It appears that the frame count fields aren't actually two 16-bit
fields, but rather four 8-bit fields.  The images in monster.lbx
appear to have "chunks" of animation and what was previously thought to
be the most significant byte of the lead-in now seems to be the length
of a "chunk".

These images are much like any other, except that the first frame of
every chunk is drawn on a clean slate.  Examples are found in
monster.lbx.
---
 src/image.c       | 21 +++++++++++++--------
 src/image.h       |  7 +++----
 src/lbximg.c      |  1 +
 tests/regress.zsh |  9 +++++++++
 4 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/src/image.c b/src/image.c
index 21f5a8e..5f3a6e3 100644
--- a/src/image.c
+++ b/src/image.c
@@ -43,7 +43,7 @@
 struct lbx_image {
 	unsigned short width, height;
 	unsigned short wtf, flags;
-	unsigned short frames, leadin;
+	unsigned char  frames, wtf2, leadin, chunk;
 	unsigned short palstart, palcount;
 
 	const struct lbx_file_ops *fops;
@@ -75,8 +75,10 @@ static struct lbx_image *lbximg_init(unsigned char hdr[static HDR_LEN])
 		.width  = unpack_16_le(hdr+0),
 		.height = unpack_16_le(hdr+2),
 		.wtf    = unpack_16_le(hdr+4),
-		.frames = unpack_16_le(hdr+6),
-		.leadin = unpack_16_le(hdr+8),
+		.frames = hdr[6],
+		.wtf2   = hdr[7],
+		.leadin = hdr[8],
+		.chunk  = hdr[9],
 		.flags  = unpack_16_le(hdr+10),
 
 		.currentframe = -1,
@@ -109,11 +111,12 @@ struct lbx_image *lbximg_open(void *f, const struct lbx_file_ops *fops,
 	/*
 	 * DEBUG ONLY.  These assertions exist to catch otherwise valid image
 	 * files which differ from what I believe to be true of all LBX images.
-	 * If we never find any exceptions, we can replace the assertions with
-	 * assumptions.
+	 * When we can decode every image, then these assertions should be
+	 * replaced with constraints.
 	 */
-	_lbx_assert(img->wtf == 0); /* version? */
-	_lbx_assert(img->frames > img->leadin); /* cmbtshp.lbx breaks this. */
+	_lbx_assert(img->wtf  == 0); /* version? */
+	_lbx_assert(img->wtf2 == 0); /* very likely is simply reserved. */
+	_lbx_assert(img->frames > img->leadin);
 	_lbx_assert(!(img->flags & ~FLAG_ALL));
 
 	/* Read all offsets.  Should be merged with identical code in lbx.c */
@@ -315,7 +318,8 @@ unsigned char **lbximg_getframe(struct lbx_image *img, int frame)
 	if (img->flags & FLAG_RAW)
 		return read_raw_frame(img, frame);
 
-	if (img->flags & FLAG_OVERWRITE) {
+	if ((img->flags & FLAG_OVERWRITE)
+	     || (img->chunk && !(frame % img->chunk))) {
 		/* Clear the slate. */
 		img->currentframe = -1;
 		memset(img->framedata[0], 0, img->width * img->height);
@@ -435,6 +439,7 @@ void lbximg_getinfo(struct lbx_image *img, struct lbx_imginfo *info)
 		.width      = img->width,
 		.height     = img->height,
 		.nframes    = img->frames,
+		.chunk      = img->chunk,
 		.palettesz  = (img->flags & FLAG_PALETTE) ? img->palcount : 0,
 	};
 
diff --git a/src/image.h b/src/image.h
index 2f427d1..9bd41eb 100644
--- a/src/image.h
+++ b/src/image.h
@@ -14,10 +14,9 @@ struct lbx_colour {
 };
 
 struct lbx_imginfo {
-	unsigned int width, height;
-	unsigned int nframes, loopstart;
-	int palettesz;
-	int looping;
+	unsigned short width, height;
+	unsigned char  nframes, loopstart, chunk;
+	int palettesz, looping;
 };
 
 LBX_IMG *lbximg_open(void *f, const struct lbx_file_ops *fops,
diff --git a/src/lbximg.c b/src/lbximg.c
index 67d8635..933e1e0 100644
--- a/src/lbximg.c
+++ b/src/lbximg.c
@@ -468,6 +468,7 @@ int main(int argc, char **argv)
 		printf("%s is %ux%u LBX image, %u frame(s)%s%s\n",
 		       name, info.width, info.height, info.nframes,
 		       info.palettesz ? ", embedded palette" : "",
+		       info.chunk     ? ", chunked" : "",
 		       info.looping   ? ", loops" : "");
 	}
 
diff --git a/tests/regress.zsh b/tests/regress.zsh
index 0131fbd..041e83f 100755
--- a/tests/regress.zsh
+++ b/tests/regress.zsh
@@ -82,6 +82,15 @@ echo "starbg.lbx.009: single frame, raw data:"
 $LBXIMG -df starbg.lbx.009 -p fonts.lbx.005
 compare 0 cfc5d92b6503951c4962498c7dcfea31
 
+# Monsters
+$LBXTOOL -xf $DATADIR/monster.lbx monster.lbx.{007,014}
+
+echo "monster.lbx.007: multi frame, chunked:"
+$LBXIMG -df monster.lbx.007 -p fonts.lbx.004 -O monster.lbx.014 0 5 19
+compare  0 59399c8d2d74116ff4b330a2cc1f3cc2
+compare  5 6947e108f7c8d2d2d626c67af3fdb7e2
+compare 19 03d86257527f0d7a91c2cde57059e734
+
 # Clean up
 if [[ $FAILED -eq 0 ]]; then
 	echo "All tests completed successfully."
-- 
2.43.0