Tag: add class const_iterator and methods begin(), end()

Enables using range-based "for".

12 files changed, 88 insertions, 45 deletions

diff --git a/src/SongFilter.cxx b/src/SongFilter.cxx
index 0640ae19e..7a8e6fd12 100644
--- a/src/SongFilter.cxx
+++ b/src/SongFilter.cxx
@@ -92,10 +92,10 @@ SongFilter::Item::Match(const Tag &_tag) const
 	bool visited_types[TAG_NUM_OF_ITEM_TYPES];
 	std::fill_n(visited_types, size_t(TAG_NUM_OF_ITEM_TYPES), false);
 
-	for (unsigned i = 0; i < _tag.num_items; i++) {
-		visited_types[_tag.items[i]->type] = true;
+	for (const auto &i : _tag) {
+		visited_types[i.type] = true;
 
-		if (Match(*_tag.items[i]))
+		if (Match(i))
 			return true;
 	}
 
@@ -112,12 +112,10 @@ SongFilter::Item::Match(const Tag &_tag) const
 		if (tag == TAG_ALBUM_ARTIST && visited_types[TAG_ARTIST]) {
 			/* if we're looking for "album artist", but
 			   only "artist" exists, use that */
-			for (unsigned i = 0; i < _tag.num_items; i++) {
-				const TagItem &item = *_tag.items[i];
+			for (const auto &item : _tag)
 				if (item.type == TAG_ARTIST &&
 				    StringMatch(item.value))
 					return true;
-			}
 		}
 	}
 
diff --git a/src/TagPrint.cxx b/src/TagPrint.cxx
index 228b5fd90..297bf45e3 100644
--- a/src/TagPrint.cxx
+++ b/src/TagPrint.cxx
@@ -47,9 +47,7 @@ void tag_print(Client &client, const Tag &tag)
 	if (tag.time >= 0)
 		client_printf(client, SONG_TIME "%i\n", tag.time);
 
-	for (unsigned i = 0; i < tag.num_items; i++) {
+	for (const auto &i : tag)
 		client_printf(client, "%s: %s\n",
-			      tag_item_names[tag.items[i]->type],
-			      tag.items[i]->value);
-	}
+			      tag_item_names[i.type], i.value);
 }
diff --git a/src/TagSave.cxx b/src/TagSave.cxx
index 3a291e115..7666287af 100644
--- a/src/TagSave.cxx
+++ b/src/TagSave.cxx
@@ -32,8 +32,7 @@ tag_save(FILE *file, const Tag &tag)
 	if (tag.has_playlist)
 		fprintf(file, "Playlist: yes\n");
 
-	for (unsigned i = 0; i < tag.num_items; i++)
+	for (const auto &i : tag)
 		fprintf(file, "%s: %s\n",
-			tag_item_names[tag.items[i]->type],
-			tag.items[i]->value);
+			tag_item_names[i.type], i.value);
 }
diff --git a/src/db/Count.cxx b/src/db/Count.cxx
index ec3eacd1f..4fd53a73b 100644
--- a/src/db/Count.cxx
+++ b/src/db/Count.cxx
@@ -73,9 +73,7 @@ static bool
 CollectGroupCounts(TagCountMap &map, TagType group, const Tag &tag)
 {
 	bool found = false;
-	for (unsigned i = 0; i < tag.num_items; ++i) {
-		const TagItem &item = *tag.items[i];
-
+	for (const auto &item : tag) {
 		if (item.type == group) {
 			auto r = map.insert(std::make_pair(item.value,
 							   SearchStats()));
diff --git a/src/db/DatabasePrint.cxx b/src/db/DatabasePrint.cxx
index f6663311e..498aedf97 100644
--- a/src/db/DatabasePrint.cxx
+++ b/src/db/DatabasePrint.cxx
@@ -184,12 +184,10 @@ PrintUniqueTag(Client &client, TagType tag_type,
 	assert(value != nullptr);
 	client_printf(client, "%s: %s\n", tag_item_names[tag_type], value);
 
-	for (unsigned i = 0, n = tag.num_items; i < n; i++) {
-		const TagItem &item = *tag.items[i];
+	for (const auto &item : tag)
 		if (item.type != tag_type)
 			client_printf(client, "%s: %s\n",
 				      tag_item_names[item.type], item.value);
-	}
 
 	return true;
 }
diff --git a/src/db/Helpers.cxx b/src/db/Helpers.cxx
index b849e73e8..089b2b17d 100644
--- a/src/db/Helpers.cxx
+++ b/src/db/Helpers.cxx
@@ -43,9 +43,7 @@ StatsVisitTag(DatabaseStats &stats, StringSet &artists, StringSet &albums,
 	if (tag.time > 0)
 		stats.total_duration += tag.time;
 
-	for (unsigned i = 0; i < tag.num_items; ++i) {
-		const TagItem &item = *tag.items[i];
-
+	for (const auto &item : tag) {
 		switch (item.type) {
 		case TAG_ARTIST:
 #if defined(__clang__) || GCC_CHECK_VERSION(4,8)
diff --git a/src/encoder/plugins/VorbisEncoderPlugin.cxx b/src/encoder/plugins/VorbisEncoderPlugin.cxx
index 7fdb3066f..ecc784a47 100644
--- a/src/encoder/plugins/VorbisEncoderPlugin.cxx
+++ b/src/encoder/plugins/VorbisEncoderPlugin.cxx
@@ -272,8 +272,7 @@ vorbis_encoder_pre_tag(Encoder *_encoder, gcc_unused Error &error)
 static void
 copy_tag_to_vorbis_comment(vorbis_comment *vc, const Tag *tag)
 {
-	for (unsigned i = 0; i < tag->num_items; i++) {
-		const TagItem &item = *tag->items[i];
+	for (const auto &item : *tag) {
 		char *name = g_ascii_strup(tag_item_names[item.type], -1);
 		vorbis_comment_add_tag(vc, name, item.value);
 		g_free(name);
diff --git a/src/output/plugins/RoarOutputPlugin.cxx b/src/output/plugins/RoarOutputPlugin.cxx
index ac4dd8a4e..ae6bdf1b1 100644
--- a/src/output/plugins/RoarOutputPlugin.cxx
+++ b/src/output/plugins/RoarOutputPlugin.cxx
@@ -374,20 +374,22 @@ RoarOutput::SendTag(const Tag &tag)
 	vals[0].key = const_cast<char *>("LENGTH");
 	vals[0].value = timebuf;
 
-	for (unsigned i = 0; i < tag.num_items && cnt < 32; i++)
-	{
+	for (const auto &item : tag) {
+		if (cnt >= 32)
+			break;
+
 		bool is_uuid = false;
-		const char *key = roar_tag_convert(tag.items[i]->type,
+		const char *key = roar_tag_convert(item.type,
 						   &is_uuid);
 		if (key != nullptr) {
 			vals[cnt].key = const_cast<char *>(key);
 
 			if (is_uuid) {
 				snprintf(uuid_buf[cnt], sizeof(uuid_buf[0]), "{UUID}%s",
-					 tag.items[i]->value);
+					 item.value);
 				vals[cnt].value = uuid_buf[cnt];
 			} else {
-				vals[cnt].value = tag.items[i]->value;
+				vals[cnt].value = const_cast<char *>(item.value);
 			}
 
 			cnt++;
diff --git a/src/output/plugins/ShoutOutputPlugin.cxx b/src/output/plugins/ShoutOutputPlugin.cxx
index a16c8fecd..0341e1cf7 100644
--- a/src/output/plugins/ShoutOutputPlugin.cxx
+++ b/src/output/plugins/ShoutOutputPlugin.cxx
@@ -470,13 +470,13 @@ shout_tag_to_metadata(const Tag *tag, char *dest, size_t size)
 	artist[0] = 0;
 	title[0] = 0;
 
-	for (unsigned i = 0; i < tag->num_items; i++) {
-		switch (tag->items[i]->type) {
+	for (const auto &item : *tag) {
+		switch (item.type) {
 		case TAG_ARTIST:
-			strncpy(artist, tag->items[i]->value, size);
+			strncpy(artist, item.value, size);
 			break;
 		case TAG_TITLE:
-			strncpy(title, tag->items[i]->value, size);
+			strncpy(title, item.value, size);
 			break;
 
 		default:
diff --git a/src/tag/Set.cxx b/src/tag/Set.cxx
index 59f66bf84..47a8423bf 100644
--- a/src/tag/Set.cxx
+++ b/src/tag/Set.cxx
@@ -30,10 +30,10 @@ CopyTagItem(TagBuilder &dest, TagType dest_type,
 	    const Tag &src, TagType src_type)
 {
 	bool found = false;
-	const unsigned n = src.num_items;
-	for (unsigned i = 0; i < n; ++i) {
-		if (src.items[i]->type == src_type) {
-			dest.AddItem(dest_type, src.items[i]->value);
+
+	for (const auto &item : src) {
+		if (item.type == src_type) {
+			dest.AddItem(dest_type, item.value);
 			found = true;
 		}
 	}
@@ -87,11 +87,10 @@ TagSet::CheckUnique(TagType dest_type,
 		    uint32_t group_mask)
 {
 	bool found = false;
-	for (unsigned i = 0; i < tag.num_items; ++i) {
-		if (tag.items[i]->type == src_type) {
-			InsertUnique(tag, dest_type,
-					tag.items[i]->value,
-					group_mask);
+
+	for (const auto &item : tag) {
+		if (item.type == src_type) {
+			InsertUnique(tag, dest_type, item.value, group_mask);
 			found = true;
 		}
 	}
diff --git a/src/tag/Tag.cxx b/src/tag/Tag.cxx
index 448f3b26a..1b338ae8d 100644
--- a/src/tag/Tag.cxx
+++ b/src/tag/Tag.cxx
@@ -118,9 +118,9 @@ Tag::GetValue(TagType type) const
 {
 	assert(type < TAG_NUM_OF_ITEM_TYPES);
 
-	for (unsigned i = 0; i < num_items; i++)
-		if (items[i]->type == type)
-			return items[i]->value;
+	for (const auto &item : *this)
+		if (item.type == type)
+			return item.value;
 
 	return nullptr;
 }
diff --git a/src/tag/Tag.hxx b/src/tag/Tag.hxx
index 5d3aaad0c..74221417f 100644
--- a/src/tag/Tag.hxx
+++ b/src/tag/Tag.hxx
@@ -25,6 +25,7 @@
 #include "Compiler.h"
 
 #include <algorithm>
+#include <iterator>
 
 #include <stddef.h>
 
@@ -136,6 +137,59 @@ struct Tag {
 	 */
 	gcc_pure
 	bool HasType(TagType type) const;
+
+	class const_iterator {
+		friend struct Tag;
+		const TagItem *const*cursor;
+
+		constexpr const_iterator(const TagItem *const*_cursor)
+			:cursor(_cursor) {}
+
+	public:
+		constexpr const TagItem &operator*() const {
+			return **cursor;
+		}
+
+		constexpr const TagItem *operator->() const {
+			return *cursor;
+		}
+
+		const_iterator &operator++() {
+			++cursor;
+			return *this;
+		}
+
+		const_iterator operator++(int) {
+			auto result = cursor++;
+			return const_iterator{result};
+		}
+
+		const_iterator &operator--() {
+			--cursor;
+			return *this;
+		}
+
+		const_iterator operator--(int) {
+			auto result = cursor--;
+			return const_iterator{result};
+		}
+
+		constexpr bool operator==(const_iterator other) const {
+			return cursor == other.cursor;
+		}
+
+		constexpr bool operator!=(const_iterator other) const {
+			return cursor != other.cursor;
+		}
+	};
+
+	const_iterator begin() const {
+		return const_iterator{items};
+	}
+
+	const_iterator end() const {
+		return const_iterator{items + num_items};
+	}
 };
 
 /**