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audiostream.h

/* ScummVM - Scumm Interpreter
 * Copyright (C) 2001-2005 The ScummVM project
 *
 * 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.
 *
 * $Header: /cvsroot/scummvm/scummvm/sound/audiostream.h,v 1.49.2.1 2005/10/18 02:11:26 sev Exp $
 *
 */

#ifndef AUDIOSTREAM_H
#define AUDIOSTREAM_H

#include "common/stdafx.h"
#include "common/util.h"
#include "common/scummsys.h"


/**
 * Generic input stream for the resampling code.
 */
00033 class AudioStream {
public:
      virtual ~AudioStream() {}

      /**
       * Fill the given buffer with up to numSamples samples.
       * Returns the actual number of samples read, or -1 if
       * a critical error occured (note: you *must* check if
       * this value is less than what you requested, this can
       * happen when the stream is fully used up).
       *
       * Data has to be in native endianess, 16 bit per sample, signed.
       * For stereo stream, buffer will be filled with interleaved
       * left and right channel samples, starting with a left sample.
       * Furthermore, the samples in the left and right are summed up.
       * So if you request 4 samples from a stereo stream, you will get
       * a total of two left channel and two right channel samples.
       */
      virtual int readBuffer(int16 *buffer, const int numSamples) = 0;

      /** Is this a stereo stream? */
      virtual bool isStereo() const = 0;

      /**
       * End of data reached? If this returns true, it means that at this
       * time there is no data available in the stream. However there may be
       * more data in the future.
       * This is used by e.g. a rate converter to decide whether to keep on
       * converting data or stop.
       */
      virtual bool endOfData() const = 0;

      /**
       * End of stream reached? If this returns true, it means that all data
       * in this stream is used up and no additional data will appear in it
       * in the future.
       * This is used by the mixer to decide whether a given stream shall be
       * removed from the list of active streams (and thus be destroyed).
       * By default this maps to endOfData()
       */
00073       virtual bool endOfStream() const { return endOfData(); }

      /** Sample rate of the stream. */
      virtual int getRate() const = 0;

      /**
       * Tries to load a file by trying all available formats.
       * In case of an error, the file handle will be closed, but deleting
       * it is still the responsibilty of the caller.
       * @param filename      a filename without an extension
       * @return  an Audiostream ready to use in case of success;
       *                NULL in case of an error (e.g. invalid/nonexisting file)
       */
      static AudioStream* openStreamFile(const char *filename);
};

/**
 * A simple AudioStream which represents a 'silent' stream,
 * containing the specified number of zero samples.
 */
00093 class ZeroInputStream : public AudioStream {
private:
      int _len;
public:
      ZeroInputStream(uint len) : _len(len) { }
00098       int readBuffer(int16 *buffer, const int numSamples) {
            int samples = MIN(_len, numSamples);
            memset(buffer, 0, samples * 2);
            _len -= samples;
            return samples;
      }
00104       bool isStereo() const { return false; }
      bool eos() const { return _len <= 0; }

00107       int getRate() const { return -1; }
};

AudioStream *makeLinearInputStream(int rate, byte flags, const byte *ptr, uint32 len, uint loopOffset, uint loopLen);


// This used to be an inline template function, but
// buggy template function handling in MSVC6 forced
// us to go with the macro approach. So far this is
// the only template function that MSVC6 seemed to
// compile incorrectly. Knock on wood.
#define READSAMPLE(is16Bit, isUnsigned, ptr) \
      ((is16Bit ? READ_BE_UINT16(ptr) : (*ptr << 8)) ^ (isUnsigned ? 0x8000 : 0))

#define READ_ENDIAN_SAMPLE(is16Bit, isUnsigned, ptr, isLE) \
      ((is16Bit ? (isLE ? READ_LE_UINT16(ptr) : READ_BE_UINT16(ptr)) : (*ptr << 8)) ^ (isUnsigned ? 0x8000 : 0))


#endif

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