RingBuffer.h

Go to the documentation of this file.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    
    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.  See the file
    COPYING included with this distribution for more information.
*/

/*
   This is a modified version of a source file from the 
   Rosegarden MIDI and audio sequencer and notation editor.
   This file copyright 2000-2006 Chris Cannam.
*/

#ifndef _RINGBUFFER_H_
#define _RINGBUFFER_H_

#include <sys/types.h>

#include "system/System.h"

#include <cstring> // memcpy, memset &c

//#define DEBUG_RINGBUFFER 1

#ifdef DEBUG_RINGBUFFER
#include <iostream>
#endif

template <typename T, int N = 1>
class RingBuffer
{
public:
    RingBuffer(int n);

    virtual ~RingBuffer();

    int getSize() const;

    RingBuffer<T, N> *resized(int newSize) const;

    bool mlock();

    void reset();

    int getReadSpace(int R = 0) const;

    int getWriteSpace() const;

    int read(T *destination, int n, int R = 0);

    int readAdding(T *destination, int n, int R = 0);

    T readOne(int R = 0);

    int peek(T *destination, int n, int R = 0) const;

    T peekOne(int R = 0) const;

    int skip(int n, int R = 0);

    int write(const T *source, int n);

    int zero(int n);

protected:
    T   *m_buffer;
    bool m_mlocked;
    int  m_writer;
    int *m_readers;
    int  m_size;
    int  m_spare;

private:
    RingBuffer(const RingBuffer &); // not provided
    RingBuffer &operator=(const RingBuffer &); // not provided
};

template <typename T, int N>
RingBuffer<T, N>::RingBuffer(int n) :
    m_buffer(new T[n + 1]),
    m_mlocked(false),
    m_writer(0),
    m_readers(new int[N]),
    m_size(n + 1)
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::RingBuffer(" << n << ")" << std::endl;
#endif
/*
    std::cerr << "note: sizeof(RingBuffer<T,N> = " << sizeof(RingBuffer<T,N>) << ")" << std::endl;

    std::cerr << "this = " << this << std::endl;
    std::cerr << "&m_buffer = " << &m_buffer << std::endl;
    std::cerr << "&m_mlocked = " << &m_mlocked << std::endl;
    std::cerr << "&m_writer = " << &m_writer << std::endl;
    std::cerr << "&m_readers = " << &m_readers << std::endl;
    std::cerr << "&m_size = " << &m_size << std::endl;
*/
    
    for (int i = 0; i < N; ++i) m_readers[i] = 0;
}

template <typename T, int N>
RingBuffer<T, N>::~RingBuffer()
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::~RingBuffer" << std::endl;
#endif

    delete[] m_readers;

    if (m_mlocked) {
        MUNLOCK((void *)m_buffer, m_size * sizeof(T));
    }
    delete[] m_buffer;
}

template <typename T, int N>
int
RingBuffer<T, N>::getSize() const
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::getSize(): " << m_size-1 << std::endl;
#endif

    return m_size - 1;
}

template <typename T, int N>
RingBuffer<T, N> *
RingBuffer<T, N>::resized(int newSize) const
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::resized(" << newSize << ")" << std::endl;
#endif

    RingBuffer<T, N> *newBuffer = new RingBuffer<T, N>(newSize);

    int w = m_writer;
    int r = m_readers[0];

    while (r != w) {
        T value = m_buffer[r];
        newBuffer->write(&value, 1);
        if (++r == m_size) r = 0;
    }

    return newBuffer;
}

template <typename T, int N>
bool
RingBuffer<T, N>::mlock()
{
    if (MLOCK((void *)m_buffer, m_size * sizeof(T))) return false;
    m_mlocked = true;
    return true;
}

template <typename T, int N>
void
RingBuffer<T, N>::reset()
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::reset" << std::endl;
#endif

    m_writer = 0;
    for (int i = 0; i < N; ++i) m_readers[i] = 0;
}

template <typename T, int N>
int
RingBuffer<T, N>::getReadSpace(int R) const
{
    int writer = m_writer;
    int reader = m_readers[R];
    int space = 0;

    if (writer > reader) space = writer - reader;
    else space = ((writer + m_size) - reader) % m_size;

#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::getReadSpace(" << R << "): " << space << std::endl;
#endif

    return space;
}

template <typename T, int N>
int
RingBuffer<T, N>::getWriteSpace() const
{
    int space = 0;
    for (int i = 0; i < N; ++i) {
        int here = (m_readers[i] + m_size - m_writer - 1) % m_size;
        if (i == 0 || here < space) space = here;
    }

#ifdef DEBUG_RINGBUFFER
    int rs(getReadSpace()), rp(m_readers[0]);

    std::cerr << "RingBuffer: write space " << space << ", read space "
              << rs << ", total " << (space + rs) << ", m_size " << m_size << std::endl;
    std::cerr << "RingBuffer: reader " << rp << ", writer " << m_writer << std::endl;
#endif

#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::getWriteSpace(): " << space << std::endl;
#endif

    return space;
}

template <typename T, int N>
int
RingBuffer<T, N>::read(T *destination, int n, int R)
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::read(dest, " << n << ", " << R << ")" << std::endl;
#endif

    int available = getReadSpace(R);
    if (n > available) {
#ifdef DEBUG_RINGBUFFER
        std::cerr << "WARNING: Only " << available << " samples available"
                  << std::endl;
#endif
        memset(destination + available, 0, (n - available) * sizeof(T));
        n = available;
    }
    if (n == 0) return n;

    int here = m_size - m_readers[R];
    if (here >= n) {
        memcpy(destination, m_buffer + m_readers[R], n * sizeof(T));
    } else {
        memcpy(destination, m_buffer + m_readers[R], here * sizeof(T));
        memcpy(destination + here, m_buffer, (n - here) * sizeof(T));
    }

    MBARRIER();
    m_readers[R] = (m_readers[R] + n) % m_size;

#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::read: read " << n << ", reader now " << m_readers[R] << std::endl;
#endif

    return n;
}

template <typename T, int N>
int
RingBuffer<T, N>::readAdding(T *destination, int n, int R)
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::readAdding(dest, " << n << ", " << R << ")" << std::endl;
#endif

    int available = getReadSpace(R);
    if (n > available) {
#ifdef DEBUG_RINGBUFFER
        std::cerr << "WARNING: Only " << available << " samples available"
                  << std::endl;
#endif
        n = available;
    }
    if (n == 0) return n;

    int here = m_size - m_readers[R];

    if (here >= n) {
        for (int i = 0; i < n; ++i) {
            destination[i] += (m_buffer + m_readers[R])[i];
        }
    } else {
        for (int i = 0; i < here; ++i) {
            destination[i] += (m_buffer + m_readers[R])[i];
        }
        for (int i = 0; i < (n - here); ++i) {
            destination[i + here] += m_buffer[i];
        }
    }

    MBARRIER();
    m_readers[R] = (m_readers[R] + n) % m_size;
    return n;
}

template <typename T, int N>
T
RingBuffer<T, N>::readOne(int R)
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::readOne(" << R << ")" << std::endl;
#endif

    if (m_writer == m_readers[R]) {
#ifdef DEBUG_RINGBUFFER
        std::cerr << "WARNING: No sample available"
                  << std::endl;
#endif
        T t;
        memset(&t, 0, sizeof(T));
        return t;
    }
    T value = m_buffer[m_readers[R]];
    MBARRIER();
    if (++m_readers[R] == m_size) m_readers[R] = 0;
    return value;
}

template <typename T, int N>
int
RingBuffer<T, N>::peek(T *destination, int n, int R) const
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::peek(dest, " << n << ", " << R << ")" << std::endl;
#endif

    int available = getReadSpace(R);
    if (n > available) {
#ifdef DEBUG_RINGBUFFER
        std::cerr << "WARNING: Only " << available << " samples available"
                  << std::endl;
#endif
        memset(destination + available, 0, (n - available) * sizeof(T));
        n = available;
    }
    if (n == 0) return n;

    int here = m_size - m_readers[R];
    if (here >= n) {
        memcpy(destination, m_buffer + m_readers[R], n * sizeof(T));
    } else {
        memcpy(destination, m_buffer + m_readers[R], here * sizeof(T));
        memcpy(destination + here, m_buffer, (n - here) * sizeof(T));
    }

#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::peek: read " << n << std::endl;
#endif

    return n;
}

template <typename T, int N>
T
RingBuffer<T, N>::peekOne(int R) const
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::peek(" << R << ")" << std::endl;
#endif

    if (m_writer == m_readers[R]) {
#ifdef DEBUG_RINGBUFFER
        std::cerr << "WARNING: No sample available"
                  << std::endl;
#endif
        T t;
        memset(&t, 0, sizeof(T));
        return t;
    }
    T value = m_buffer[m_readers[R]];
    return value;
}

template <typename T, int N>
int
RingBuffer<T, N>::skip(int n, int R)
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::skip(" << n << ", " << R << ")" << std::endl;
#endif

    int available = getReadSpace(R);
    if (n > available) {
#ifdef DEBUG_RINGBUFFER
        std::cerr << "WARNING: Only " << available << " samples available"
                  << std::endl;
#endif
        n = available;
    }
    if (n == 0) return n;
    m_readers[R] = (m_readers[R] + n) % m_size;
    return n;
}

template <typename T, int N>
int
RingBuffer<T, N>::write(const T *source, int n)
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::write(" << n << ")" << std::endl;
#endif

    int available = getWriteSpace();
    if (n > available) {
#ifdef DEBUG_RINGBUFFER
        std::cerr << "WARNING: Only room for " << available << " samples"
                  << std::endl;
#endif
        n = available;
    }
    if (n == 0) return n;

    int here = m_size - m_writer;
    if (here >= n) {
        memcpy(m_buffer + m_writer, source, n * sizeof(T));
    } else {
        memcpy(m_buffer + m_writer, source, here * sizeof(T));
        memcpy(m_buffer, source + here, (n - here) * sizeof(T));
    }

    MBARRIER();
    m_writer = (m_writer + n) % m_size;

#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::write: wrote " << n << ", writer now " << m_writer << std::endl;
#endif

    return n;
}

template <typename T, int N>
int
RingBuffer<T, N>::zero(int n)
{
#ifdef DEBUG_RINGBUFFER
    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::zero(" << n << ")" << std::endl;
#endif

    int available = getWriteSpace();
    if (n > available) {
#ifdef DEBUG_RINGBUFFER
        std::cerr << "WARNING: Only room for " << available << " samples"
                  << std::endl;
#endif
        n = available;
    }
    if (n == 0) return n;

    int here = m_size - m_writer;
    if (here >= n) {
        memset(m_buffer + m_writer, 0, n * sizeof(T));
    } else {
        memset(m_buffer + m_writer, 0, here * sizeof(T));
        memset(m_buffer, 0, (n - here) * sizeof(T));
    }
    
    MBARRIER();
    m_writer = (m_writer + n) % m_size;
    return n;
}

#endif // _RINGBUFFER_H_