AUD_ReverseReader.cpp

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/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * Copyright 2009-2011 Jörg Hermann Müller
 *
 * This file is part of AudaSpace.
 *
 * Audaspace 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.
 *
 * AudaSpace 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 Audaspace; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#include "AUD_ReverseReader.h"

#include <cstring>

static const char* props_error = "AUD_ReverseReader: The reader has to be "
                                 "seekable and a finite length.";

AUD_ReverseReader::AUD_ReverseReader(AUD_Reference<AUD_IReader> reader) :
        AUD_EffectReader(reader),
        m_length(reader->getLength()),
        m_position(0)
{
    if(m_length < 0 || !reader->isSeekable())
        AUD_THROW(AUD_ERROR_PROPS, props_error);
}

void AUD_ReverseReader::seek(int position)
{
    m_position = position;
}

int AUD_ReverseReader::getLength() const
{
    return m_length;
}

int AUD_ReverseReader::getPosition() const
{
    return m_position;
}

void AUD_ReverseReader::read(int& length, bool& eos, sample_t* buffer)
{
    // first correct the length
    if(m_position + length > m_length)
        length = m_length - m_position;

    if(length <= 0)
    {
        length = 0;
        eos = true;
        return;
    }

    const AUD_Specs specs = getSpecs();
    const int samplesize = AUD_SAMPLE_SIZE(specs);

    sample_t temp[AUD_CHANNEL_MAX];

    int len = length;

    // read from reader
    m_reader->seek(m_length - m_position - len);
    m_reader->read(len, eos, buffer);

    // set null if reader didn't give enough data
    if(len < length)
        memset(buffer, 0, (length - len) * samplesize);

    // copy the samples reverted
    for(int i = 0; i < length / 2; i++)
    {
        memcpy(temp,
               buffer + (len - 1 - i) * specs.channels,
               samplesize);
        memcpy(buffer + (len - 1 - i) * specs.channels,
               buffer + i * specs.channels,
               samplesize);
        memcpy(buffer + i * specs.channels,
               temp,
               samplesize);
    }

    m_position += length;
    eos = false;
}