decoder/flac: support FLAC files inside archives

Implement the "scan_stream" method that can read tags from any
input_stream object.  This requires a FLAC__IOCallbacks implementation
based on the input_stream API.

1 files changed, 114 insertions, 0 deletions

diff --git a/src/decoder/FLACIOHandle.cxx b/src/decoder/FLACIOHandle.cxx
new file mode 100644
index 000000000..08ec36e48
--- /dev/null
+++ b/src/decoder/FLACIOHandle.cxx
@@ -0,0 +1,114 @@
+/*
+ * Copyright (C) 2003-2012 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "FLACIOHandle.hxx"
+#include "io_error.h"
+#include "gcc.h"
+
+#include <errno.h>
+
+static size_t
+FLACIORead(void *ptr, size_t size, size_t nmemb, FLAC__IOHandle handle)
+{
+	input_stream *is = (input_stream *)handle;
+
+	uint8_t *const p0 = (uint8_t *)ptr, *p = p0,
+		*const end = p0 + size * nmemb;
+
+	/* libFLAC is very picky about short reads, and expects the IO
+	   callback to fill the whole buffer (undocumented!) */
+
+	GError *error = nullptr;
+	while (p < end) {
+		size_t nbytes = input_stream_lock_read(is, p, end - p, &error);
+		if (nbytes == 0) {
+			if (error == nullptr)
+				/* end of file */
+				break;
+
+			if (error->domain == errno_quark())
+				errno = error->code;
+			else
+				/* just some random non-zero
+				   errno value */
+				errno = EINVAL;
+			g_error_free(error);
+			return 0;
+		}
+
+		p += nbytes;
+	}
+
+	/* libFLAC expects a clean errno after returning from the IO
+	   callbacks (undocumented!) */
+	errno = 0;
+	return (p - p0) / size;
+}
+
+static int
+FLACIOSeek(FLAC__IOHandle handle, FLAC__int64 offset, int whence)
+{
+	input_stream *is = (input_stream *)handle;
+
+	return input_stream_lock_seek(is, offset, whence, nullptr) ? 0 : -1;
+}
+
+static FLAC__int64
+FLACIOTell(FLAC__IOHandle handle)
+{
+	input_stream *is = (input_stream *)handle;
+
+	return is->offset;
+}
+
+static int
+FLACIOEof(FLAC__IOHandle handle)
+{
+	input_stream *is = (input_stream *)handle;
+
+	return input_stream_lock_eof(is);
+}
+
+static int
+FLACIOClose(gcc_unused FLAC__IOHandle handle)
+{
+	/* no-op because the libFLAC caller is repsonsible for closing
+	   the #input_stream */
+
+	return 0;
+}
+
+const FLAC__IOCallbacks flac_io_callbacks = {
+	FLACIORead,
+	nullptr,
+	nullptr,
+	nullptr,
+	FLACIOEof,
+	FLACIOClose,
+};
+
+const FLAC__IOCallbacks flac_io_callbacks_seekable = {
+	FLACIORead,
+	nullptr,
+	FLACIOSeek,
+	FLACIOTell,
+	FLACIOEof,
+	FLACIOClose,
+};