fs/io/PeekReader: new utility class

1 files changed, 52 insertions, 0 deletions

diff --git a/src/fs/io/PeekReader.hxx b/src/fs/io/PeekReader.hxx
new file mode 100644
index 000000000..27e7ff7c1
--- /dev/null
+++ b/src/fs/io/PeekReader.hxx
@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2003-2014 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.
+ */
+
+#ifndef MPD_PEEK_READER_HXX
+#define MPD_PEEK_READER_HXX
+
+#include "check.h"
+#include "Reader.hxx"
+
+#include <stdint.h>
+
+class AutoGunzipReader;
+
+/**
+ * A filter that allows the caller to peek the first few bytes without
+ * consuming them.  The first call must be Peek(), and the following
+ * Read() will deliver the same bytes again.
+ */
+class PeekReader final : public Reader {
+	Reader &next;
+
+	size_t buffer_size, buffer_position;
+
+	uint8_t buffer[64];
+
+public:
+	PeekReader(Reader &_next)
+		:next(_next), buffer_size(0), buffer_position(0) {}
+
+	const void *Peek(size_t size, Error &error);
+
+	/* virtual methods from class Reader */
+	virtual size_t Read(void *data, size_t size, Error &error) override;
+};
+
+#endif