tag_ape: move code to ape.c

Generic library for scanning APE tags.  Eliminated one "goto"!

1 files changed, 113 insertions, 0 deletions

diff --git a/src/ape.c b/src/ape.c
new file mode 100644
index 00000000..5fca98e2
--- /dev/null
+++ b/src/ape.c
@@ -0,0 +1,113 @@
+/*
+ * Copyright (C) 2003-2010 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "ape.h"
+
+#include <glib.h>
+
+#include <stdint.h>
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+struct ape_footer {
+	unsigned char id[8];
+	uint32_t version;
+	uint32_t length;
+	uint32_t count;
+	unsigned char flags[4];
+	unsigned char reserved[8];
+};
+
+static bool
+ape_scan_internal(FILE *fp, tag_ape_callback_t callback, void *ctx)
+{
+	/* determine if file has an apeV2 tag */
+	struct ape_footer footer;
+	if (fseek(fp, -(long)sizeof(footer), SEEK_END) ||
+	    fread(&footer, 1, sizeof(footer), fp) != sizeof(footer) ||
+	    memcmp(footer.id, "APETAGEX", sizeof(footer.id)) != 0 ||
+	    GUINT32_FROM_LE(footer.version) != 2000)
+		return false;
+
+	/* find beginning of ape tag */
+	size_t remaining = GUINT32_FROM_LE(footer.length);
+	if (remaining <= sizeof(footer) + 10 ||
+	    /* refuse to load more than one megabyte of tag data */
+	    remaining > 1024 * 1024 ||
+	    fseek(fp, -(long)remaining, SEEK_END))
+		return false;
+
+	/* read tag into buffer */
+	remaining -= sizeof(footer);
+	assert(remaining > 10);
+
+	char *buffer = g_malloc(remaining);
+	if (fread(buffer, 1, remaining, fp) != remaining)
+		return false;
+
+	/* read tags */
+	unsigned n = GUINT32_FROM_LE(footer.count);
+	const char *p = buffer;
+	while (n-- && remaining > 10) {
+		size_t size = GUINT32_FROM_LE(*(const uint32_t *)p);
+		p += 4;
+		remaining -= 4;
+		unsigned long flags = GUINT32_FROM_LE(*(const uint32_t *)p);
+		p += 4;
+		remaining -= 4;
+
+		/* get the key */
+		const char *key = p;
+		while (remaining > size && *p != '\0') {
+			p++;
+			remaining--;
+		}
+		p++;
+		remaining--;
+
+		/* get the value */
+		if (remaining < size)
+			break;
+
+		if (!callback(flags, key, p, size, ctx))
+			break;
+
+		p += size;
+		remaining -= size;
+	}
+
+	g_free(buffer);
+	return true;
+}
+
+bool
+tag_ape_scan(const char *path_fs, tag_ape_callback_t callback, void *ctx)
+{
+	FILE *fp;
+
+	fp = fopen(path_fs, "rb");
+	if (fp == NULL)
+		return false;
+
+	bool success = ape_scan_internal(fp, callback, ctx);
+	fclose(fp);
+	return success;
+}