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diff --git a/src/MusicPipe.hxx b/src/MusicPipe.hxx
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+++ b/src/MusicPipe.hxx
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+/*
+ * Copyright (C) 2003-2011 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_PIPE_H
+#define MPD_PIPE_H
+
+#include "thread/Mutex.hxx"
+#include "gcc.h"
+
+#ifndef NDEBUG
+#include "AudioFormat.hxx"
+#endif
+
+#include <assert.h>
+
+struct music_chunk;
+class MusicBuffer;
+
+/**
+ * A queue of #music_chunk objects.  One party appends chunks at the
+ * tail, and the other consumes them from the head.
+ */
+class MusicPipe {
+	/** the first chunk */
+	music_chunk *head;
+
+	/** a pointer to the tail of the chunk */
+	music_chunk **tail_r;
+
+	/** the current number of chunks */
+	unsigned size;
+
+	/** a mutex which protects #head and #tail_r */
+	mutable Mutex mutex;
+
+#ifndef NDEBUG
+	AudioFormat audio_format;
+#endif
+
+public:
+	/**
+	 * Creates a new #MusicPipe object.  It is empty.
+	 */
+	MusicPipe()
+		:head(nullptr), tail_r(&head), size(0) {
+#ifndef NDEBUG
+		audio_format.Clear();
+#endif
+	}
+
+	/**
+	 * Frees the object.  It must be empty now.
+	 */
+	~MusicPipe() {
+		assert(head == nullptr);
+		assert(tail_r == &head);
+	}
+
+#ifndef NDEBUG
+	/**
+	 * Checks if the audio format if the chunk is equal to the specified
+	 * audio_format.
+	 */
+	gcc_pure
+	bool CheckFormat(AudioFormat other) const {
+		return !audio_format.IsDefined() ||
+			audio_format == other;
+	}
+
+	/**
+	 * Checks if the specified chunk is enqueued in the music pipe.
+	 */
+	gcc_pure
+	bool Contains(const music_chunk *chunk) const;
+#endif
+
+	/**
+	 * Returns the first #music_chunk from the pipe.  Returns
+	 * nullptr if the pipe is empty.
+	 */
+	gcc_pure
+	const music_chunk *Peek() const {
+		return head;
+	}
+
+	/**
+	 * Removes the first chunk from the head, and returns it.
+	 */
+	music_chunk *Shift();
+
+	/**
+	 * Clears the whole pipe and returns the chunks to the buffer.
+	 *
+	 * @param buffer the buffer object to return the chunks to
+	 */
+	void Clear(MusicBuffer &buffer);
+
+	/**
+	 * Pushes a chunk to the tail of the pipe.
+	 */
+	void Push(music_chunk *chunk);
+
+	/**
+	 * Returns the number of chunks currently in this pipe.
+	 */
+	gcc_pure
+	unsigned GetSize() const {
+		return size;
+	}
+
+	gcc_pure
+	bool IsEmpty() const {
+		return GetSize() == 0;
+	}
+};
+
+#endif