From f076a6cccee804712f049d72c4fa12627992e200 Mon Sep 17 00:00:00 2001
From: Sergey Kvachonok <ravenexp@gmail.com>
Date: Wed, 11 Aug 2010 18:41:52 +0300
Subject: [PATCH] Add MGD to PNG extraction filter.

---
 fjfix.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 106 insertions(+), 6 deletions(-)

diff --git a/fjfix.c b/fjfix.c
index 2cab963..d831530 100644
--- a/fjfix.c
+++ b/fjfix.c
@@ -202,6 +202,15 @@ unsigned fjentry_size(fjentry_t s)
 	return s->fjfile->tab[s->tabind].data_size;
 }
 
+int fjentry_seek(fjentry_t s, unsigned seekpos)
+{
+	if (seekpos > s->fjfile->tab[s->tabind].data_size)
+		return -1;
+
+	s->seekpos = seekpos;
+	return 0;
+}
+
 unsigned fjentry_read(fjentry_t s, void* buf, unsigned size)
 {
 	struct fjtabent* te = &s->fjfile->tab[s->tabind];
@@ -435,6 +444,8 @@ static int entry_extract(fjentry_t s, const char* fname)
 	       fjentry_name(s), fname, fjentry_size(s));
 	fflush(stdout);
 
+	fjentry_seek(s, 0);
+
 	size_t n, sz = 0;
 	char buf[COPYBUF_SZ];
 	while ((n = fjentry_read(s, buf, sizeof(buf))) > 0) {
@@ -459,7 +470,83 @@ err:
 	return -1;
 }
 
-static int extract(fjfile_t fjf, const char* destdir)
+#define MGDHDR_SZ 0x60
+#define MGD_MAGIC "MGD "
+
+struct mgdhdr
+{
+	char magic[4];
+	char padding[MGDHDR_SZ - 8];
+	unsigned png_size;
+};
+
+#define PNG_MAGIC "\x89PNG\r\n\x1A\n"
+
+static int filter_mgd_test(fjentry_t s)
+{
+	struct mgdhdr hdr;
+	unsigned sz;
+
+	sz = fjentry_read(s, &hdr, sizeof(hdr));
+	if (sz != sizeof(hdr))
+		return 0;
+
+	if (strncmp(hdr.magic, MGD_MAGIC, sizeof(hdr.magic)))
+		return 0;
+
+	char magic[sizeof(PNG_MAGIC) - 1];
+	sz = fjentry_read(s, magic, sizeof(magic));
+	if (strncmp(magic, PNG_MAGIC, sizeof(magic)))
+		return 0;
+
+	return 1;
+}
+
+static int entry_mgd_extract(fjentry_t s, const char* fname)
+{
+	FILE* f = fopen(fname, "wb");
+	if (!f)
+		goto err;
+
+	struct mgdhdr hdr;
+	fjentry_seek(s, 0);
+	fjentry_read(s, &hdr, sizeof(hdr));
+
+	printf("PNG extracting '%s' to '%s', size %d bytes\n",
+	       fjentry_name(s), fname, hdr.png_size);
+	fflush(stdout);
+
+	size_t n, sz = 0;
+	char buf[COPYBUF_SZ];
+	while ((n = fjentry_read(s, buf, sizeof(buf))) > 0) {
+		if (sz + n > hdr.png_size)
+			n = hdr.png_size - sz;
+		if (!n)
+			break;
+		if (fwrite(buf, n, 1, f) != 1)
+			goto err;
+		sz += n;
+	}
+
+	fclose(f);
+
+	if (sz != hdr.png_size) {
+		fprintf(stderr, "PNG extract truncated file '%s': %d of %d bytes written\n",
+			fjentry_name(s), sz, fjentry_size(s));
+		return -1;
+	}
+
+	return 0;
+err:
+	if (f)
+		fclose(f);
+	fprintf(stderr, "Can't extract PNG to file '%s': %s\n", fname, strerror(errno));
+	return -1;
+}
+
+enum {EX_FILTER_MGD = 0x1};
+
+static int extract(fjfile_t fjf, const char* destdir, unsigned filters)
 {
 	char fname[PATH_MAX];
 	char* ddir = format_destdir(fjfile_name(fjf), destdir);
@@ -471,8 +558,16 @@ static int extract(fjfile_t fjf, const char* destdir)
 
 	fjentry_t ent;
 	for (ent = fjfile_first_entry(fjf); ent; ent = fjentry_next(ent)) {
-		sprintf(fname, "%s/%s", ddir, fjentry_name(ent));
-		entry_extract(ent, fname);
+		if ((filters & EX_FILTER_MGD) && filter_mgd_test(ent)) {
+			int l = sprintf(fname, "%s/%s.png", ddir, fjentry_name(ent));
+			char* ext = fname + l - (sizeof(".mgd.png") - 1);
+			if (ext > fname && !strcasecmp(ext, ".mgd.png"))
+				strcpy(ext, ".png");
+			entry_mgd_extract(ent, fname);
+		} else {
+			sprintf(fname, "%s/%s", ddir, fjentry_name(ent));
+			entry_extract(ent, fname);
+		}
 	}
 
 	free(ddir);
@@ -494,6 +589,7 @@ static const char* usage =
 	"    -t - test entry index, do not fix it. Enabled by default.\n"
 	"    -x - extract entries as files to DESTDIR or FILE.d if DESDIR not specified.\n"
 	"    -v - verbose. Print additional data which might be useful for problem analysis and reporting.\n"
+	"    -G - additionally extract PNG files embedded in MGD container entries. Must be used with -x.\n"
 	"Version " VERSION " built " __DATE__ "\n";
 
 enum {
@@ -505,12 +601,16 @@ enum {
 int main(int argc, char* argv[0])
 {
 	int opt;
-	int options = OPT_TEST | OPT_BACKUP;
+	unsigned options = OPT_TEST | OPT_BACKUP;
+	unsigned ext_filters = 0;
 	int needfix = 0;
 	char* fname;
 
-	while ((opt = getopt(argc, argv, "blvtfhx")) != -1) {
+	while ((opt = getopt(argc, argv, "Gblvtfhx")) != -1) {
 		switch (opt) {
+		case 'G':
+			ext_filters |= EX_FILTER_MGD;
+			break;
 		case 'b':
 			options &= ~OPT_BACKUP;
 			break;
@@ -570,7 +670,7 @@ int main(int argc, char* argv[0])
 		if (optind + 1 < argc)
 			destdir = argv[optind + 1];
 
-		extract(fjf, destdir);
+		extract(fjf, destdir, ext_filters);
 	}
 
 	if (options & (OPT_TEST | OPT_FIX)) {
-- 
2.11.4.GIT