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decoder.h

/*  aKode: Decoder abstract-type

    Copyright (C) 2004 Allan Sandfeld Jensen <kde@carewolf.com>

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library 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
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LIB.  If not, write to
    the Free Software Foundation, Inc., 51 Franklin Steet, Fifth Floor,
    Boston, MA 02110-1301, USA.
*/

#ifndef _AKODE_DECODER_H
#define _AKODE_DECODER_H

#include "pluginhandler.h"
#include "akode_export.h"

namespace aKode {

class AudioConfiguration;
class File;
class AudioFrame;

//! A generic interface for all decoders

/*!
 * The Decoder works by decoding one audio-frame at a time. It is up to
 * the decoder itself to decide how large a frame is.
 */
00039 class AKODE_EXPORT Decoder {
public:
    virtual ~Decoder() {};
    /*!
     * Reads one frame from the decoder.
     * It is advisable to reuse the the same frame for every readFrame()-call,
     * as the frame size is likely to be constant in the same file,
     * which saves re-allocations.
     *
     * If readFrame returns false, it can be one of three things:
     * 1. End-of-File (check eof()).
     * 2. Fatal error (check error()).
     * 3. Recoverable error (call readFrame again)
     */
    virtual bool readFrame(AudioFrame*) = 0;
    /*!
     * Returns the length of the file/stream in milliseconds.
     * Returns -1 if the length is unknown.
     */
    virtual long length() = 0;
    /*!
     * Returns the current position in file/stream in milliseconds.
     * Returns -1 if the position is unknown.
     */
    virtual long position() = 0;
    /*!
     * Attempts a seek to \a pos milliseconds into the file/stream.
     * Returns true if succesfull.
     */
    virtual bool seek(long pos) = 0;
    /*!
     * Returns true if the decoder is seekable
     */
    virtual bool seekable() = 0;
    /*!
     * Returns true if the decoder has reached the end-of-file/stream
     */
    virtual bool eof() = 0;
    /*!
     * Returns true if the decoder has encountered a non-recoverable error
     */
    virtual bool error() = 0;
    /*!
     * Returns the configuration of the decoded stream.
     * Returns 0 if unknown.
     */
    virtual const AudioConfiguration* audioConfiguration() = 0;
};

/*!
 * Parent class for decoder plugins
 */
00091 class DecoderPlugin {
public:
    /*!
     * Asks the plugin to open a Decoder, returns 0 if the
     * plugin could not.
     */
00097     virtual Decoder* openDecoder(File *) { return 0; };
    /*!
     * Old version version of openDecoder.
     * \deprecated
     */
00102     Decoder* openFrameDecoder(File *src) { return openDecoder(src); };
};

/*!
 * Handler for decoder-plugins.
 */
00108 class AKODE_EXPORT DecoderPluginHandler : public PluginHandler, public DecoderPlugin {
public:
    static list<string> listDecoderPlugins();

    DecoderPluginHandler() : decoder_plugin(0) {};
    DecoderPluginHandler(const string name);
    /*!
     * Open a Decoder for the File \a src. Returns 0 if unsuccesfull
     */
    Decoder* openDecoder(File *src);
    /*!
     * Old version version of openDecoder.
     * \deprecated
     */
00122     Decoder* openFrameDecoder(File *src) { return openDecoder(src); };
    /*!
     * Loads a decoder-plugin named \a name (xiph, mpc, mpeg..)
     */
    virtual bool load(const string name);
    virtual void unload();
00128     bool isLoaded() { return decoder_plugin != 0; };
protected:
    DecoderPlugin* decoder_plugin;
};

} // namespace

#endif

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