TagStream: add TagBuilder overload with ScanGenericTags() fallback

This commit adds support for APE/ID3 tags from NFS/SMB files.

See http://bugs.musicpd.org/view.php?id=4270

NEWS

@@ -14,6 +14,7 @@ ver 0.20 (not yet released)
   - id3: remove the "id3v1_encoding" setting; by definition, all ID3v1 tags
     are ISO-Latin-1
   - ape: support APE replay gain on remote files
+  - read ID3 tags from NFS/SMB
 * decoder
   - improved error logging
   - report I/O errors to clients

src/SongUpdate.cxx

@@ -92,8 +92,7 @@ Song::UpdateFile(Storage &storage)
 	if (path_fs.IsNull()) {
 		const auto absolute_uri =
 			storage.MapUTF8(relative_uri.c_str());
-		if (!tag_stream_scan(absolute_uri.c_str(),
-				     full_tag_handler, &tag_builder))
+		if (!tag_stream_scan(absolute_uri.c_str(), tag_builder))
 			return false;
 	} else {
 		if (!tag_file_scan(path_fs, tag_builder))
@@ -165,8 +164,7 @@ DetachedSong::Update()
 		return LoadFile(path_fs);
 	} else if (IsRemote()) {
 		TagBuilder tag_builder;
-		if (!tag_stream_scan(uri.c_str(), full_tag_handler,
-				     &tag_builder))
+		if (!tag_stream_scan(uri.c_str(), tag_builder))
 			return false;
 
 		mtime = 0;

src/TagStream.cxx

@@ -19,6 +19,9 @@
 
 #include "config.h"
 #include "TagStream.hxx"
+#include "tag/Generic.hxx"
+#include "tag/TagHandler.hxx"
+#include "tag/TagBuilder.hxx"
 #include "util/UriUtil.hxx"
 #include "util/Error.hxx"
 #include "decoder/DecoderList.hxx"
@@ -72,3 +75,28 @@ tag_stream_scan(const char *uri, const TagHandler &handler, void *ctx)
 					 IgnoreError());
 	return is && tag_stream_scan(*is, handler, ctx);
 }
+
+bool
+tag_stream_scan(InputStream &is, TagBuilder &builder)
+{
+	assert(is.IsReady());
+
+	if (!tag_stream_scan(is, full_tag_handler, &builder))
+		return false;
+
+	if (builder.IsEmpty())
+		ScanGenericTags(is, full_tag_handler, &builder);
+
+	return true;
+}
+
+bool
+tag_stream_scan(const char *uri, TagBuilder &builder)
+{
+	Mutex mutex;
+	Cond cond;
+
+	auto is = InputStream::OpenReady(uri, mutex, cond,
+					 IgnoreError());
+	return is && tag_stream_scan(*is, builder);
+}

src/TagStream.hxx

@@ -24,6 +24,7 @@
 
 class InputStream;
 struct TagHandler;
+class TagBuilder;
 
 /**
  * Scan the tags of an #InputStream.  Invokes matching decoder
@@ -38,4 +39,18 @@ tag_stream_scan(InputStream &is, const TagHandler &handler, void *ctx);
 bool
 tag_stream_scan(const char *uri, const TagHandler &handler, void *ctx);
 
+/**
+ * Scan the tags of an #InputStream.  Invokes matching decoder
+ * plugins, and falls back to generic scanners (APE and ID3) if no
+ * tags were found (but the file was recognized).
+ *
+ * @return true if the file was recognized (even if no metadata was
+ * found)
+ */
+bool
+tag_stream_scan(InputStream &is, TagBuilder &builder);
+
+bool
+tag_stream_scan(const char *uri, TagBuilder &builder);
+
 #endif