input/Open: use OpenLocalInputStream()

Make the "open" method of plugins "file" and "archive" dummy methods
that always fail.  Instead, let InputStream::Open() hard-code access
to these two plugins by using OpenLocalInputStream().  This allows
simplifyin the algorithm for falling back to probing archive plugins.

src/decoder/DecoderThread.cxx

@@ -115,9 +115,7 @@ decoder_input_stream_open(DecoderControl &dc, Path path)
 
 	InputStream *is = OpenLocalInputStream(path, dc.mutex, dc.cond, error);
 	if (is == nullptr) {
-		if (error.IsDefined())
+		LogError(error);
-			LogError(error);
-
 		return nullptr;
 	}
 

src/input/LocalOpen.cxx

@@ -31,6 +31,10 @@
 
 #include <assert.h>
 
+#ifdef ENABLE_ARCHIVE
+#include <errno.h>
+#endif
+
 InputStream *
 OpenLocalInputStream(Path path, Mutex &mutex, Cond &cond, Error &error)
 {
@@ -38,8 +42,15 @@ OpenLocalInputStream(Path path, Mutex &mutex, Cond &cond, Error &error)
 
 	InputStream *is = OpenFileInputStream(path, mutex, cond, error);
 #ifdef ENABLE_ARCHIVE
-	if (is == nullptr && !error.IsDefined())
+	if (is == nullptr && error.IsDomain(errno_domain) &&
-		is = OpenArchiveInputStream(path, mutex, cond, error);
+	    error.GetCode() == ENOTDIR) {
+		/* ENOTDIR means this may be a path inside an archive
+		   file */
+		Error error2;
+		is = OpenArchiveInputStream(path, mutex, cond, error2);
+		if (is == nullptr && error2.IsDefined())
+			error = std::move(error2);
+	}
 #endif
 
 	assert(is == nullptr || is->IsReady());

src/input/Open.cxx

@@ -21,7 +21,10 @@
 #include "InputStream.hxx"
 #include "Registry.hxx"
 #include "InputPlugin.hxx"
+#include "LocalOpen.hxx"
 #include "plugins/RewindInputPlugin.hxx"
+#include "fs/Traits.hxx"
+#include "fs/Path.hxx"
 #include "util/Error.hxx"
 #include "util/Domain.hxx"
 
@@ -32,6 +35,11 @@ InputStream::Open(const char *url,
 		  Mutex &mutex, Cond &cond,
 		  Error &error)
 {
+	if (PathTraitsFS::IsAbsolute(url))
+		/* TODO: the parameter is UTF-8, not filesystem charset */
+		return OpenLocalInputStream(Path::FromFS(url),
+					    mutex, cond, error);
+
 	input_plugins_for_each_enabled(plugin) {
 		InputStream *is;
 

src/input/plugins/ArchiveInputPlugin.cxx

@@ -71,25 +71,14 @@ OpenArchiveInputStream(Path path, Mutex &mutex, Cond &cond, Error &error)
 	return is;
 }
 
-/**
- * select correct archive plugin to handle the input stream
- * may allow stacking of archive plugins. for example for handling
- * tar.gz a gzip handler opens file (through inputfile stream)
- * then it opens a tar handler and sets gzip inputstream as
- * parent_stream so tar plugin fetches file data from gzip
- * plugin and gzip fetches file from disk
- */
 static InputStream *
-input_archive_open(const char *pathname,
+input_archive_open(gcc_unused const char *filename,
-		   Mutex &mutex, Cond &cond,
+		gcc_unused Mutex &mutex, gcc_unused Cond &cond,
-		   Error &error)
+		gcc_unused Error &error)
 {
-	if (!PathTraitsFS::IsAbsolute(pathname))
+	/* dummy method; use OpenArchiveInputStream() instead */
-		return nullptr;
 
-	/* TODO: the parameter is UTF-8, not filesystem charset */
+	return nullptr;
-	return OpenArchiveInputStream(Path::FromFS(pathname),
-				      mutex, cond, error);
 }
 
 const InputPlugin input_plugin_archive = {

src/input/plugins/FileInputPlugin.cxx

@@ -68,9 +68,8 @@ OpenFileInputStream(Path path,
 {
 	const int fd = OpenFile(path, O_RDONLY|O_BINARY, 0);
 	if (fd < 0) {
-		if (errno != ENOTDIR)
+		error.FormatErrno("Failed to open \"%s\"",
-			error.FormatErrno("Failed to open \"%s\"",
+				  path.c_str());
-					  path.c_str());
 		return nullptr;
 	}
 
@@ -96,17 +95,13 @@ OpenFileInputStream(Path path,
 }
 
 static InputStream *
-input_file_open(const char *filename,
+input_file_open(gcc_unused const char *filename,
-		Mutex &mutex, Cond &cond,
+		gcc_unused Mutex &mutex, gcc_unused Cond &cond,
-		Error &error)
+		gcc_unused Error &error)
 {
-	if (!PathTraitsFS::IsAbsolute(filename))
+	/* dummy method; use OpenFileInputStream() instead */
-		return nullptr;
 
-	/* TODO: the parameter is UTF-8, not filesystem charset */
+	return nullptr;
-	const Path path = Path::FromFS(filename);
-
-	return OpenFileInputStream(path, mutex, cond, error);
 }
 
 bool