TagBuilder: new class for constructing Tag objects

Makefile.am

@@ -424,6 +424,7 @@ TAG_LIBS = \
 libtag_a_SOURCES =\
 	src/tag/TagType.h \
 	src/tag/Tag.cxx src/tag/Tag.hxx \
+	src/tag/TagBuilder.cxx src/tag/TagBuilder.hxx \
 	src/tag/TagItem.hxx \
 	src/tag/TagHandler.cxx src/tag/TagHandler.hxx \
 	src/tag/TagSettings.c src/tag/TagSettings.h \

src/tag/TagBuilder.cxx

+/*
+ * Copyright (C) 2003-2013 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 "TagBuilder.hxx"
+#include "TagSettings.h"
+#include "TagPool.hxx"
+#include "TagString.hxx"
+#include "Tag.hxx"
+
+#include <glib.h>
+
+#include <assert.h>
+#include <string.h>
+
+void
+TagBuilder::Clear()
+{
+	time = -1;
+	has_playlist = false;
+
+	tag_pool_lock.lock();
+	for (auto i : items)
+		tag_pool_put_item(i);
+	tag_pool_lock.unlock();
+
+	items.clear();
+}
+
+Tag *
+TagBuilder::Commit()
+{
+	Tag *tag = new Tag();
+	tag->time = time;
+	tag->has_playlist = has_playlist;
+
+	/* move all TagItem pointers to the new Tag object without
+	   touching the TagPool reference counters; the
+	   vector::clear() call is important to detach them from this
+	   object */
+	const unsigned n_items = items.size();
+	tag->num_items = n_items;
+	tag->items = g_new(TagItem *, n_items);
+	std::copy_n(items.begin(), n_items, tag->items);
+	items.clear();
+
+	/* now ensure that this object is fresh (will not delete any
+	   items because we've already moved them out) */
+	Clear();
+
+	return tag;
+}
+
+inline void
+TagBuilder::AddItemInternal(tag_type type, const char *value, size_t length)
+{
+	assert(value != nullptr);
+	assert(length > 0);
+
+	char *p = FixTagString(value, length);
+	if (p != nullptr) {
+		value = p;
+		length = strlen(value);
+	}
+
+	tag_pool_lock.lock();
+	auto i = tag_pool_get_item(type, value, length);
+	tag_pool_lock.unlock();
+
+	g_free(p);
+
+	items.push_back(i);
+}
+
+void
+TagBuilder::AddItem(tag_type type, const char *value, size_t length)
+{
+	assert(value != nullptr);
+
+	if (length == 0 || ignore_tag_items[type])
+		return;
+
+	AddItemInternal(type, value, length);
+}
+
+void
+TagBuilder::AddItem(tag_type type, const char *value)
+{
+	assert(value != nullptr);
+
+	AddItem(type, value, strlen(value));
+}

src/tag/TagBuilder.hxx

+/*
+ * Copyright (C) 2003-2013 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_TAG_BUILDER_HXX
+#define MPD_TAG_BUILDER_HXX
+
+#include "TagType.h"
+#include "gcc.h"
+
+#include <vector>
+
+#include <stddef.h>
+
+struct TagItem;
+struct Tag;
+
+/**
+ * A class that constructs #Tag objects.
+ */
+class TagBuilder {
+	/**
+	 * The duration of the song (in seconds).  A value of zero
+	 * means that the length is unknown.  If the duration is
+	 * really between zero and one second, you should round up to
+	 * 1.
+	 */
+	int time;
+
+	/**
+	 * Does this file have an embedded playlist (e.g. embedded CUE
+	 * sheet)?
+	 */
+	bool has_playlist;
+
+	/** an array of tag items */
+	std::vector<TagItem *> items;
+
+public:
+	/**
+	 * Create an empty tag.
+	 */
+	TagBuilder()
+		:time(-1), has_playlist(false) {}
+
+	~TagBuilder() {
+		Clear();
+	}
+
+	TagBuilder(const TagBuilder &other) = delete;
+	TagBuilder &operator=(const TagBuilder &other) = delete;
+
+	/**
+	 * Returns true if the object contains any information.
+	 */
+	gcc_pure
+	bool IsDefined() const {
+		return time >= 0 || has_playlist || !items.empty();
+	}
+
+	void Clear();
+
+	/**
+	 * Create a new #Tag instance from data in this object.  The
+	 * returned object is owned by the caller.  This object is
+	 * empty afterwards.
+	 */
+	Tag *Commit();
+
+	void SetTime(int _time) {
+		time = _time;
+	}
+
+	void SetHasPlaylist(bool _has_playlist) {
+		has_playlist = _has_playlist;
+	}
+
+	void Reserve(unsigned n) {
+		items.reserve(n);
+	}
+
+	/**
+	 * Appends a new tag item.
+	 *
+	 * @param type the type of the new tag item
+	 * @param value the value of the tag item (not null-terminated)
+	 * @param len the length of #value
+	 */
+	gcc_nonnull_all
+	void AddItem(tag_type type, const char *value, size_t length);
+
+	/**
+	 * Appends a new tag item.
+	 *
+	 * @param type the type of the new tag item
+	 * @param value the value of the tag item (null-terminated)
+	 */
+	gcc_nonnull_all
+	void AddItem(tag_type type, const char *value);
+
+private:
+	gcc_nonnull_all
+	void AddItemInternal(tag_type type, const char *value, size_t length);
+};
+
+#endif