tag_ape: move code to ape.c

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

3 files changed, 174 insertions, 93 deletions

diff --git a/src/ape.c b/src/ape.c
new file mode 100644
index 000000000..5fca98e28
--- /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;
+}
diff --git a/src/ape.h b/src/ape.h
new file mode 100644
index 000000000..754b9bb2d
--- /dev/null
+++ b/src/ape.h
@@ -0,0 +1,42 @@
+/*
+ * 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.
+ */
+
+#ifndef MPD_APE_H
+#define MPD_APE_H
+
+#include "check.h"
+
+#include <stdbool.h>
+#include <stddef.h>
+
+typedef bool (*tag_ape_callback_t)(unsigned long flags, const char *key,
+				   const char *value, size_t value_length,
+				   void *ctx);
+
+/**
+ * Scans the APE tag values from a file.
+ *
+ * @param path_fs the path of the file in filesystem encoding
+ * @return false if the file could not be opened or if no APE tag is
+ * present
+ */
+bool
+tag_ape_scan(const char *path_fs, tag_ape_callback_t callback, void *ctx);
+
+#endif
diff --git a/src/tag_ape.c b/src/tag_ape.c
index 4841b3138..82e36d7a4 100644
--- a/src/tag_ape.c
+++ b/src/tag_ape.c
@@ -21,11 +21,7 @@
 #include "tag_ape.h"
 #include "tag.h"
 #include "tag_table.h"
-
-#include <glib.h>
-
-#include <assert.h>
-#include <stdio.h>
+#include "ape.h"
 
 static const char *const ape_tag_names[TAG_NUM_OF_ITEM_TYPES] = {
 	[TAG_ALBUM_ARTIST] = "album artist",
@@ -61,96 +57,26 @@ tag_ape_import_item(struct tag *tag, unsigned long flags,
 	return tag;
 }
 
-struct tag *
-tag_ape_load(const char *file)
-{
-	struct tag *ret = NULL;
-	FILE *fp;
-	int tagCount;
-	char *buffer = NULL;
-	char *p;
-	size_t tagLen;
-	size_t size;
-	unsigned long flags;
-	char *key;
-
-	struct {
-		unsigned char id[8];
-		uint32_t version;
-		uint32_t length;
-		uint32_t tagCount;
-		unsigned char flags[4];
-		unsigned char reserved[8];
-	} footer;
-
-	fp = fopen(file, "rb");
-	if (!fp)
-		return NULL;
-
-	/* determine if file has an apeV2 tag */
-	if (fseek(fp, 0, SEEK_END))
-		goto fail;
-	size = (size_t)ftell(fp);
-	if (fseek(fp, size - sizeof(footer), SEEK_SET))
-		goto fail;
-	if (fread(&footer, 1, sizeof(footer), fp) != sizeof(footer))
-		goto fail;
-	if (memcmp(footer.id, "APETAGEX", sizeof(footer.id)) != 0)
-		goto fail;
-	if (GUINT32_FROM_LE(footer.version) != 2000)
-		goto fail;
-
-	/* find beginning of ape tag */
-	tagLen = GUINT32_FROM_LE(footer.length);
-	if (tagLen <= sizeof(footer) + 10)
-		goto fail;
-	if (tagLen > 1024 * 1024)
-		/* refuse to load more than one megabyte of tag data */
-		goto fail;
-	if (fseek(fp, size - tagLen, SEEK_SET))
-		goto fail;
-
-	/* read tag into buffer */
-	tagLen -= sizeof(footer);
-	assert(tagLen > 10);
-
-	buffer = g_malloc(tagLen);
-	if (fread(buffer, 1, tagLen, fp) != tagLen)
-		goto fail;
-
-	/* read tags */
-	tagCount = GUINT32_FROM_LE(footer.tagCount);
-	p = buffer;
-	while (tagCount-- && tagLen > 10) {
-		size = GUINT32_FROM_LE(*(const uint32_t *)p);
-		p += 4;
-		tagLen -= 4;
-		flags = GUINT32_FROM_LE(*(const uint32_t *)p);
-		p += 4;
-		tagLen -= 4;
-
-		/* get the key */
-		key = p;
-		while (tagLen > size && *p != '\0') {
-			p++;
-			tagLen--;
-		}
-		p++;
-		tagLen--;
+struct tag_ape_ctx {
+	struct tag *tag;
+};
 
-		/* get the value */
-		if (tagLen < size)
-			goto fail;
+static bool
+tag_ape_callback(unsigned long flags, const char *key,
+		 const char *value, size_t value_length, void *_ctx)
+{
+	struct tag_ape_ctx *ctx = _ctx;
 
-		ret = tag_ape_import_item(ret, flags, key, p, size);
+	ctx->tag = tag_ape_import_item(ctx->tag, flags, key,
+				       value, value_length);
+	return true;
+}
 
-		p += size;
-		tagLen -= size;
-	}
+struct tag *
+tag_ape_load(const char *file)
+{
+	struct tag_ape_ctx ctx = { .tag = NULL };
 
-fail:
-	if (fp)
-		fclose(fp);
-	g_free(buffer);
-	return ret;
+	tag_ape_scan(file, tag_ape_callback, &ctx);
+	return ctx.tag;
 }