AUD_ReverseReader.cpp

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/*
 * $Id: AUD_ReverseReader.cpp 35141 2011-02-25 10:21:56Z jesterking $
 *
 * ***** 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_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, sample_t* & buffer)
{
        // first correct the length
        if(m_position + length > m_length)
                length = m_length - m_position;

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

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

        // resize buffer if needed
        if(m_buffer.getSize() < length * samplesize)
                m_buffer.resize(length * samplesize);

        buffer = m_buffer.getBuffer();

        sample_t* buf;
        int len = length;

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

        // set null if reader didn't give enough data
        if(len < length)
        {
                memset(buffer, 0, (length - len) * samplesize);
                buffer += (length - len) * specs.channels;
        }

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

        m_position += length;

        buffer = m_buffer.getBuffer();
}