decoder/DecoderPlugin: container_scan() returns forward_list<string>

NEWS

@@ -21,9 +21,11 @@ ver 0.20 (not yet released)
   - ffmpeg: support ReplayGain and MixRamp
   - ffmpeg: support stream tags
   - gme: add option "accuracy"
+  - gme: faster scanning
   - mad: reduce memory usage while scanning tags
   - mpcdec: read the bit rate
   - pcm: support audio/L16 (RFC 2586) and audio/x-mpd-float
+  - sidplay: faster scanning
 * playlist
   - cue: don't skip pregap
   - embcue: fix last track

src/db/update/Container.cxx

@@ -96,10 +96,14 @@ UpdateWalk::UpdateContainerFile(Directory &directory,
 		return false;
 	}
 
-	AllocatedString<> vtrack = nullptr;
-	unsigned int tnum = 0;
+	const auto v = plugin.container_scan(pathname);
+	if (v.empty()) {
+		editor.LockDeleteDirectory(contdir);
+		return false;
+	}
+
 	TagBuilder tag_builder;
-	while ((vtrack = plugin.container_scan(pathname, ++tnum)) != nullptr) {
+	for (const auto &vtrack : v) {
 		Song *song = Song::NewFile(vtrack.c_str(), *contdir);
 
 		// shouldn't be necessary but it's there..
@@ -126,9 +130,5 @@ UpdateWalk::UpdateContainerFile(Directory &directory,
 			      directory.GetPath(), vtrack.c_str());
 	}
 
-	if (tnum == 1) {
-		editor.LockDeleteDirectory(contdir);
-		return false;
-	} else
-		return true;
+	return true;
 }

src/decoder/DecoderPlugin.hxx

@@ -22,11 +22,13 @@
 
 #include "Compiler.h"
 
+#include <forward_list>
+#include <string>
+
 struct ConfigBlock;
 class InputStream;
 struct TagHandler;
 class Path;
-template<typename T> class AllocatedString;
 class DecoderClient;
 
 struct DecoderPlugin {
@@ -85,14 +87,13 @@ struct DecoderPlugin {
 	/**
 	 * @brief Return a "virtual" filename for subtracks in
 	 * container formats like flac
-	 * @param const char* pathname full pathname for the file on fs
-	 * @param const unsigned int tnum track number
+	 * @param path_fs full pathname for the file on fs
 	 *
-	 * @return nullptr if there are no multiple files
-	 * a filename for every single track according to tnum (param 2)
+	 * @return an empty list if there are no multiple files
+	 * a filename for every single track;
 	 * do not include full pathname here, just the "virtual" file
 	 */
-	AllocatedString<char> (*container_scan)(Path path_fs, unsigned tnum);
+	std::forward_list<std::string> (*container_scan)(Path path_fs);
 
 	/* last element in these arrays must always be a nullptr: */
 	const char *const*suffixes;

src/decoder/plugins/GmeDecoderPlugin.cxx

@@ -27,16 +27,16 @@
 #include "fs/AllocatedPath.hxx"
 #include "util/ScopeExit.hxx"
 #include "util/FormatString.hxx"
-#include "util/AllocatedString.hxx"
 #include "util/UriUtil.hxx"
 #include "util/Domain.hxx"
 #include "Log.hxx"
 
+#include <gme/gme.h>
+
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h>
-
-#include <gme/gme.h>
+#include <stdio.h>
 
 #define SUBTUNE_PREFIX "tune_"
 
@@ -103,29 +103,36 @@ ParseContainerPath(Path path_fs)
 	return { path_fs.GetDirectoryName(), track - 1 };
 }
 
-static AllocatedString<>
-gme_container_scan(Path path_fs, const unsigned int tnum)
+static std::forward_list<std::string>
+gme_container_scan(Path path_fs)
 {
+	std::forward_list<std::string> list;
+
 	Music_Emu *emu;
 	const char *gme_err = gme_open_file(path_fs.c_str(), &emu,
 					    GME_SAMPLE_RATE);
 	if (gme_err != nullptr) {
 		LogWarning(gme_domain, gme_err);
-		return nullptr;
+		return list;
 	}
 
 	const unsigned num_songs = gme_track_count(emu);
 	gme_delete(emu);
 	/* if it only contains a single tune, don't treat as container */
 	if (num_songs < 2)
-		return nullptr;
+		return list;
 
 	const char *subtune_suffix = uri_get_suffix(path_fs.c_str());
-	if (tnum <= num_songs){
-		return FormatString(SUBTUNE_PREFIX "%03u.%s",
-				    tnum, subtune_suffix);
-	} else
-		return nullptr;
+
+	auto tail = list.before_begin();
+	for (unsigned i = 1; i < num_songs; ++i) {
+		char track_name[64];
+		snprintf(track_name, sizeof(track_name),
+			 "%03u.%s", i, subtune_suffix);
+		tail = list.emplace_after(tail, track_name);
+	}
+
+	return list;
 }
 
 static void

src/decoder/plugins/SidplayDecoderPlugin.cxx

@@ -25,14 +25,11 @@
 #include "fs/AllocatedPath.hxx"
 #include "util/Macros.hxx"
 #include "util/FormatString.hxx"
-#include "util/AllocatedString.hxx"
 #include "util/Domain.hxx"
 #include "system/ByteOrder.hxx"
 #include "system/FatalError.hxx"
 #include "Log.hxx"
 
-#include <string.h>
-
 #ifdef HAVE_SIDPLAYFP
 #include <sidplayfp/sidplayfp.h>
 #include <sidplayfp/SidInfo.h>
@@ -49,6 +46,9 @@
 #include <sidplay/utils/SidDatabase.h>
 #endif
 
+#include <string.h>
+#include <stdio.h>
+
 #define SUBTUNE_PREFIX "tune_"
 
 static constexpr Domain sidplay_domain("sidplay");
@@ -476,12 +476,14 @@ sidplay_scan_file(Path path_fs,
 	return true;
 }
 
-static AllocatedString<>
-sidplay_container_scan(Path path_fs, const unsigned int tnum)
+static std::forward_list<std::string>
+sidplay_container_scan(Path path_fs)
 {
+	std::forward_list<std::string> list;
+
 	SidTune tune(path_fs.c_str(), nullptr, true);
 	if (!tune.getStatus())
-		return nullptr;
+		return list;
 
 #ifdef HAVE_SIDPLAYFP
 	const SidTuneInfo &info = *tune.getInfo();
@@ -494,14 +496,18 @@ sidplay_container_scan(Path path_fs, const unsigned int tnum)
 	/* Don't treat sids containing a single tune
 		as containers */
 	if(!all_files_are_containers && n_tracks < 2)
-		return nullptr;
+		return list;
+
+	auto tail = list.before_begin();
+	for (unsigned i = 1; i < n_tracks; ++i) {
+		char track_name[32];
+		/* Construct container/tune path names, eg.
+		   Delta.sid/tune_001.sid */
+		sprintf(track_name, SUBTUNE_PREFIX "%03u.sid", i);
+		tail = list.emplace_after(tail, track_name);
+	}
 
-	/* Construct container/tune path names, eg.
-		Delta.sid/tune_001.sid */
-	if (tnum <= n_tracks) {
-		return FormatString(SUBTUNE_PREFIX "%03u.sid", tnum);
-	} else
-		return nullptr;
+	return list;
 }
 
 static const char *const sidplay_suffixes[] = {