tag/Handler: pass StringView to OnTag() and OnPair()

Eliminates a number of allocations, because callers don't need to copy
the strings to a newly allocated buffer only to null-terminate them.
And most callers don't need to have a null-terminated string.

src/TagPrint.cxx

@@ -21,6 +21,7 @@
 #include "tag/Tag.hxx"
 #include "tag/Settings.hxx"
 #include "client/Response.hxx"
+#include "util/StringView.hxx"
 
 void
 tag_print_types(Response &r) noexcept
@@ -31,6 +32,13 @@ tag_print_types(Response &r) noexcept
 			r.Format("tagtype: %s\n", tag_item_names[i]);
 }
 
+void
+tag_print(Response &r, TagType type, StringView value) noexcept
+{
+	r.Format("%s: %.*s\n", tag_item_names[type],
+		 int(value.size), value.data);
+}
+
 void
 tag_print(Response &r, TagType type, const char *value) noexcept
 {

src/TagPrint.hxx

@@ -25,11 +25,15 @@
 enum TagType : uint8_t;
 
 struct Tag;
+struct StringView;
 class Response;
 
 void
 tag_print_types(Response &response) noexcept;
 
+void
+tag_print(Response &response, TagType type, StringView value) noexcept;
+
 void
 tag_print(Response &response, TagType type, const char *value) noexcept;
 

src/command/FileCommands.cxx

@@ -27,6 +27,7 @@
 #include "client/Client.hxx"
 #include "client/Response.hxx"
 #include "util/CharUtil.hxx"
+#include "util/StringView.hxx"
 #include "util/UriUtil.hxx"
 #include "tag/Handler.hxx"
 #include "tag/Generic.hxx"
@@ -110,13 +111,12 @@ handle_listfiles_local(Response &r, Path path_fs)
 
 gcc_pure
 static bool
-IsValidName(const char *p) noexcept
+IsValidName(const StringView s) noexcept
 {
-	if (!IsAlphaASCII(*p))
+	if (s.empty() || !IsAlphaASCII(s.front()))
 		return false;
 
-	while (*++p) {
+	for (const char ch : s) {
-		const char ch = *p;
 		if (!IsAlphaASCII(ch) && ch != '_' && ch != '-')
 			return false;
 	}
@@ -126,11 +126,9 @@ IsValidName(const char *p) noexcept
 
 gcc_pure
 static bool
-IsValidValue(const char *p) noexcept
+IsValidValue(const StringView s) noexcept
 {
-	while (*p) {
+	for (const char ch : s) {
-		const char ch = *p++;
-
 		if ((unsigned char)ch < 0x20)
 			return false;
 	}
@@ -145,9 +143,11 @@ public:
 	explicit PrintCommentHandler(Response &_response) noexcept
 		:NullTagHandler(WANT_PAIR), response(_response) {}
 
-	void OnPair(const char *key, const char *value) noexcept override {
+	void OnPair(StringView key, StringView value) noexcept override {
 		if (IsValidName(key) && IsValidValue(value))
-			response.Format("%s: %s\n", key, value);
+			response.Format("%.*s: %.*s\n",
+					int(key.size), key.data,
+					int(value.size), value.data);
 	}
 };
 

src/command/OtherCommands.cxx

@@ -38,6 +38,7 @@
 #include "time/ChronoUtil.hxx"
 #include "util/UriUtil.hxx"
 #include "util/StringAPI.hxx"
+#include "util/StringView.hxx"
 #include "fs/AllocatedPath.hxx"
 #include "Stats.hxx"
 #include "PlaylistFile.hxx"
@@ -147,7 +148,7 @@ public:
 	explicit PrintTagHandler(Response &_response) noexcept
 		:NullTagHandler(WANT_TAG), response(_response) {}
 
-	void OnTag(TagType type, const char *value) noexcept override {
+	void OnTag(TagType type, StringView value) noexcept override {
 		if (response.GetClient().tag_mask.Test(type))
 			tag_print(response, type, value);
 	}

src/decoder/plugins/AdPlugDecoderPlugin.cxx

@@ -24,6 +24,7 @@
 #include "fs/Path.hxx"
 #include "util/Domain.hxx"
 #include "util/Macros.hxx"
+#include "util/StringView.hxx"
 #include "Log.hxx"
 
 #include <adplug/adplug.h>
@@ -85,7 +86,7 @@ adplug_scan_tag(TagType type, const std::string &value,
 		TagHandler &handler) noexcept
 {
 	if (!value.empty())
-		handler.OnTag(type, value.c_str());
+		handler.OnTag(type, {value.data(), value.size()});
 }
 
 static bool

src/decoder/plugins/DsdiffDecoderPlugin.cxx

@@ -33,6 +33,7 @@
 #include "CheckAudioFormat.hxx"
 #include "util/bit_reverse.h"
 #include "util/ByteOrder.hxx"
+#include "util/StringView.hxx"
 #include "tag/Handler.hxx"
 #include "DsdLib.hxx"
 #include "Log.hxx"
@@ -205,15 +206,14 @@ dsdiff_handle_native_tag(DecoderClient *client, InputStream &is,
 	if (length == 0 || length > MAX_LENGTH)
 		return;
 
-	char string[MAX_LENGTH + 1];
+	char string[MAX_LENGTH];
 	char *label;
 	label = string;
 
 	if (!decoder_read_full(client, is, label, (size_t)length))
 		return;
 
-	string[length] = '\0';
+	handler.OnTag(type, {label, length});
-	handler.OnTag(type, label);
 	return;
 }
 

src/decoder/plugins/FfmpegMetaData.cxx

@@ -24,6 +24,7 @@
 #include "tag/Table.hxx"
 #include "tag/Handler.hxx"
 #include "tag/Id3MusicBrainz.hxx"
+#include "util/StringView.hxx"
 
 extern "C" {
 #include <libavutil/dict.h>

src/decoder/plugins/GmeDecoderPlugin.cxx

@@ -29,6 +29,7 @@
 #include "fs/FileSystem.hxx"
 #include "util/ScopeExit.hxx"
 #include "util/StringFormat.hxx"
+#include "util/StringView.hxx"
 #include "util/UriUtil.hxx"
 #include "util/Domain.hxx"
 #include "Log.hxx"
@@ -220,7 +221,7 @@ ScanGmeInfo(const gme_info_t &info, unsigned song_num, int track_count,
 		handler.OnDuration(SongTime::FromMS(info.play_length));
 
 	if (track_count > 1)
-		handler.OnTag(TAG_TRACK, StringFormat<16>("%u", song_num + 1));
+		handler.OnTag(TAG_TRACK, StringFormat<16>("%u", song_num + 1).c_str());
 
 	if (info.song != nullptr) {
 		if (track_count > 1) {
@@ -229,7 +230,7 @@ ScanGmeInfo(const gme_info_t &info, unsigned song_num, int track_count,
 				StringFormat<1024>("%s (%u/%d)",
 						   info.song, song_num + 1,
 						   track_count);
-			handler.OnTag(TAG_TITLE, tag_title);
+			handler.OnTag(TAG_TITLE, tag_title.c_str());
 		} else
 			handler.OnTag(TAG_TITLE, info.song);
 	}

src/decoder/plugins/MikmodDecoderPlugin.cxx

@@ -24,6 +24,7 @@
 #include "fs/Path.hxx"
 #include "util/Domain.hxx"
 #include "util/RuntimeError.hxx"
+#include "util/StringView.hxx"
 #include "Log.hxx"
 
 #include <mikmod.h>

src/decoder/plugins/ModplugDecoderPlugin.cxx

@@ -24,6 +24,7 @@
 #include "util/WritableBuffer.hxx"
 #include "util/Domain.hxx"
 #include "util/RuntimeError.hxx"
+#include "util/StringView.hxx"
 #include "Log.hxx"
 
 #include <libmodplug/modplug.h>

src/decoder/plugins/SidplayDecoderPlugin.cxx

@@ -31,6 +31,7 @@
 #endif
 #include "util/Macros.hxx"
 #include "util/StringFormat.hxx"
+#include "util/StringView.hxx"
 #include "util/Domain.hxx"
 #include "util/ByteOrder.hxx"
 #include "Log.hxx"
@@ -460,7 +461,7 @@ ScanSidTuneInfo(const SidTuneInfo &info, unsigned track, unsigned n_tracks,
 		const auto tag_title =
 			StringFormat<1024>("%s (%u/%u)",
 					   title, track, n_tracks);
-		handler.OnTag(TAG_TITLE, tag_title);
+		handler.OnTag(TAG_TITLE, tag_title.c_str());
 	} else
 		handler.OnTag(TAG_TITLE, title);
 
@@ -475,7 +476,7 @@ ScanSidTuneInfo(const SidTuneInfo &info, unsigned track, unsigned n_tracks,
 		handler.OnTag(TAG_DATE, date);
 
 	/* track */
-	handler.OnTag(TAG_TRACK, StringFormat<16>("%u", track));
+	handler.OnTag(TAG_TRACK, StringFormat<16>("%u", track).c_str());
 }
 
 static bool

src/decoder/plugins/SndfileDecoderPlugin.cxx

@@ -24,6 +24,7 @@
 #include "tag/Handler.hxx"
 #include "util/Domain.hxx"
 #include "util/ScopeExit.hxx"
+#include "util/StringView.hxx"
 #include "Log.hxx"
 
 #include <exception>

src/lib/xiph/FlacStreamMetadata.cxx

@@ -30,7 +30,7 @@
 #include "tag/ReplayGain.hxx"
 #include "tag/MixRamp.hxx"
 #include "ReplayGainInfo.hxx"
-#include "util/DivideString.hxx"
+#include "util/StringView.hxx"
 
 #include <assert.h>
 
@@ -98,10 +98,10 @@ flac_scan_comment(const FLAC__StreamMetadata_VorbisComment_Entry *entry,
 		  TagHandler &handler) noexcept
 {
 	if (handler.WantPair()) {
-		const char *comment = (const char *)entry->entry;
+		const StringView comment((const char *)entry->entry);
-		const DivideString split(comment, '=');
+		const auto split = StringView(comment).Split('=');
-		if (split.IsDefined() && !split.empty())
+		if (!split.first.empty() && !split.second.IsNull())
-			handler.OnPair(split.GetFirst(), split.GetSecond());
+			handler.OnPair(split.first, split.second);
 	}
 
 	for (const struct tag_table *i = xiph_tags; i->name != nullptr; ++i)

src/lib/xiph/VorbisComments.cxx

@@ -26,7 +26,7 @@
 #include "tag/VorbisComment.hxx"
 #include "tag/ReplayGain.hxx"
 #include "ReplayGainInfo.hxx"
-#include "util/DivideString.hxx"
+#include "util/StringView.hxx"
 
 bool
 vorbis_comments_to_replay_gain(ReplayGainInfo &rgi, char **comments) noexcept
@@ -69,9 +69,9 @@ static void
 vorbis_scan_comment(const char *comment, TagHandler &handler) noexcept
 {
 	if (handler.WantPair()) {
-		const DivideString split(comment, '=');
+		const auto split = StringView(comment).Split('=');
-		if (split.IsDefined() && !split.empty())
+		if (!split.first.empty() && !split.second.IsNull())
-			handler.OnPair(split.GetFirst(), split.GetSecond());
+			handler.OnPair(split.first, split.second);
 	}
 
 	for (const struct tag_table *i = xiph_tags; i->name != nullptr; ++i)

src/playlist/plugins/EmbeddedCuePlaylistPlugin.cxx

@@ -33,7 +33,7 @@
 #include "TagFile.hxx"
 #include "fs/Traits.hxx"
 #include "fs/AllocatedPath.hxx"
-#include "util/ASCII.hxx"
+#include "util/StringView.hxx"
 
 #include <memory>
 
@@ -70,15 +70,14 @@ public:
 
 	ExtractCuesheetTagHandler() noexcept:NullTagHandler(WANT_PAIR) {}
 
-	void OnPair(const char *key, const char *value) noexcept override;
+	void OnPair(StringView key, StringView value) noexcept override;
 };
 
 void
-ExtractCuesheetTagHandler::OnPair(const char *name, const char *value) noexcept
+ExtractCuesheetTagHandler::OnPair(StringView name, StringView value) noexcept
 {
-	if (cuesheet.empty() &&
+	if (cuesheet.empty() && name.EqualsIgnoreCase("cuesheet"))
-	    StringEqualsCaseASCII(name, "cuesheet"))
+		cuesheet = {value.data, value.size};
-		cuesheet = value;
 }
 
 static std::unique_ptr<SongEnumerator>

src/tag/Handler.cxx

@@ -1,5 +1,5 @@
 /*
- * Copyright 2003-2018 The Music Player Daemon Project
+ * Copyright 2003-2019 The Music Player Daemon Project
  * http://www.musicpd.org
  *
  * This program is free software; you can redistribute it and/or modify
@@ -21,9 +21,20 @@
 #include "Builder.hxx"
 #include "AudioFormat.hxx"
 #include "util/ASCII.hxx"
-#include "util/StringFormat.hxx"
+#include "util/CharUtil.hxx"
+#include "util/StringView.hxx"
 
-#include <stdlib.h>
+#include <algorithm>
+
+void
+NullTagHandler::OnTag(TagType, StringView) noexcept
+{
+}
+
+void
+NullTagHandler::OnPair(StringView, StringView) noexcept
+{
+}
 
 void
 NullTagHandler::OnAudioFormat(gcc_unused AudioFormat af) noexcept
@@ -36,23 +47,35 @@ AddTagHandler::OnDuration(SongTime duration) noexcept
 	tag.SetDuration(duration);
 }
 
+/**
+ * Skip leading zeroes and a non-decimal suffix.
+ */
+static StringView
+NormalizeDecimal(StringView s)
+{
+	auto start = std::find_if(s.begin(), s.end(),
+				  [](char ch){ return ch != '0'; });
+	auto end = std::find_if(start, s.end(),
+				[](char ch){ return !IsDigitASCII(ch); });
+	return {start, end};
+}
+
 void
-AddTagHandler::OnTag(TagType type, const char *value) noexcept
+AddTagHandler::OnTag(TagType type, StringView value) noexcept
 {
 	if (type == TAG_TRACK || type == TAG_DISC) {
 		/* filter out this extra data and leading zeroes */
-		char *end;
+
-		unsigned n = strtoul(value, &end, 10);
+		value = NormalizeDecimal(value);
-		if (value != end)
+	}
-			tag.AddItem(type, StringFormat<21>("%u", n));
+
-	} else
 	tag.AddItem(type, value);
 }
 
 void
-FullTagHandler::OnPair(const char *name, gcc_unused const char *value) noexcept
+FullTagHandler::OnPair(StringView name, StringView) noexcept
 {
-	if (StringEqualsCaseASCII(name, "cuesheet"))
+	if (name.EqualsIgnoreCase("cuesheet"))
 		tag.SetHasPlaylist(true);
 }
 

src/tag/Handler.hxx

@@ -1,5 +1,5 @@
 /*
- * Copyright 2003-2018 The Music Player Daemon Project
+ * Copyright 2003-2019 The Music Player Daemon Project
  * http://www.musicpd.org
  *
  * This program is free software; you can redistribute it and/or modify
@@ -24,6 +24,7 @@
 #include "Chrono.hxx"
 #include "util/Compiler.h"
 
+struct StringView;
 struct AudioFormat;
 class TagBuilder;
 
@@ -74,13 +75,13 @@ public:
 	 * @param the value of the tag; the pointer will become
 	 * invalid after returning
 	 */
-	virtual void OnTag(TagType type, const char *value) noexcept = 0;
+	virtual void OnTag(TagType type, StringView value) noexcept = 0;
 
 	/**
 	 * A name-value pair has been read.  It is the codec specific
 	 * representation of tags.
 	 */
-	virtual void OnPair(const char *key, const char *value) noexcept = 0;
+	virtual void OnPair(StringView key, StringView value) noexcept = 0;
 
 	/**
 	 * Declare the audio format of a song.
@@ -106,10 +107,8 @@ public:
 		:TagHandler(_want_mask) {}
 
 	void OnDuration(gcc_unused SongTime duration) noexcept override {}
-	void OnTag(gcc_unused TagType type,
+	void OnTag(TagType type, StringView value) noexcept override;
-		   gcc_unused const char *value) noexcept override {}
+	void OnPair(StringView key, StringView value) noexcept override;
-	void OnPair(gcc_unused const char *key,
-		    gcc_unused const char *value) noexcept override {}
 	void OnAudioFormat(AudioFormat af) noexcept override;
 };
 
@@ -130,7 +129,7 @@ public:
 		:AddTagHandler(0, _builder) {}
 
 	void OnDuration(SongTime duration) noexcept override;
-	void OnTag(TagType type, const char *value) noexcept override;
+	void OnTag(TagType type, StringView value) noexcept override;
 };
 
 /**
@@ -154,7 +153,7 @@ public:
 				AudioFormat *_audio_format=nullptr) noexcept
 		:FullTagHandler(0, _builder, _audio_format) {}
 
-	void OnPair(const char *key, const char *value) noexcept override;
+	void OnPair(StringView key, StringView value) noexcept override;
 	void OnAudioFormat(AudioFormat af) noexcept override;
 };
 

src/tag/Id3Scan.cxx

@@ -27,6 +27,7 @@
 #include "util/Alloc.hxx"
 #include "util/ScopeExit.hxx"
 #include "util/StringStrip.hxx"
+#include "util/StringView.hxx"
 #include "Log.hxx"
 
 #include <id3tag.h>

test/read_tags.cxx

@@ -30,6 +30,7 @@
 #include "AudioFormat.hxx"
 #include "util/ScopeExit.hxx"
 #include "util/StringBuffer.hxx"
+#include "util/StringView.hxx"
 #include "util/PrintException.hxx"
 
 #include <stdexcept>
@@ -58,13 +59,16 @@ public:
 		printf("duration=%f\n", duration.ToDoubleS());
 	}
 
-	void OnTag(TagType type, const char *value) noexcept override {
+	void OnTag(TagType type, StringView value) noexcept override {
-		printf("[%s]=%s\n", tag_item_names[type], value);
+		printf("[%s]=%.*s\n", tag_item_names[type],
+		       int(value.size), value.data);
 		empty = false;
 	}
 
-	void OnPair(const char *key, const char *value) noexcept override {
+	void OnPair(StringView key, StringView value) noexcept override {
-		printf("\"%s\"=%s\n", key, value);
+		printf("\"%.*s\"=%.*s\n",
+		       int(key.size), key.data,
+		       int(value.size), value.data);
 	}
 
 	void OnAudioFormat(AudioFormat af) noexcept override {