view base/RingBuffer.h @ 1752:6d09d68165a4 by-id

Further review of ById: make IDs only available when adding a model to the ById store, not by querying the item directly. This means any id encountered in the wild must have been added to the store at some point (even if later released), which simplifies reasoning about lifecycles

/* -*- 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 SV_RINGBUFFER_H
#define SV_RINGBUFFER_H

#include <sys/types.h>

#include "system/System.h"

#include <bqvec/Barrier.h>

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

//#define DEBUG_RINGBUFFER 1

#ifdef DEBUG_RINGBUFFER
#include <iostream>
#endif

/**
 * RingBuffer implements a lock-free ring buffer for one writer and N
 * readers, that is to be used to store a sample type T.
 *
 * For efficiency, RingBuffer frequently initialises samples by
 * writing zeroes into their memory space, so T should normally be a
 * simple type that can safely be set to zero using memset.
 */

template <typename T, int N = 1>
class RingBuffer
{
public:
    /**
     * Create a ring buffer with room to write n samples.
     *
     * Note that the internal storage size will actually be n+1
     * samples, as one element is unavailable for administrative
     * reasons.  Since the ring buffer performs best if its size is a
     * power of two, this means n should ideally be some power of two
     * minus one.
     */
    RingBuffer(int n);

    virtual ~RingBuffer();

    /**
     * Return the total capacity of the ring buffer in samples.
     * (This is the argument n passed to the constructor.)
     */
    int getSize() const;

    /**
     * Return a new ring buffer (allocated with "new" -- caller must
     * delete when no longer needed) of the given size, containing the
     * same data as this one as perceived by reader 0 of this buffer.
     * If another thread reads from or writes to this buffer during
     * the call, the contents of the new buffer may be incomplete or
     * inconsistent.  If this buffer's data will not fit in the new
     * size, the contents are undefined.
     */
    RingBuffer<T, N> *resized(int newSize) const;

    /**
     * Lock the ring buffer into physical memory.  Returns true
     * for success.
     */
    bool mlock();

    /**
     * Reset read and write pointers, thus emptying the buffer.
     * Should be called from the write thread.
     */
    void reset();

    /**
     * Return the amount of data available for reading by reader R, in
     * samples.
     */
    int getReadSpace(int R = 0) const;

    /**
     * Return the amount of space available for writing, in samples.
     */
    int getWriteSpace() const;

    /**
     * Read n samples from the buffer, for reader R.  If fewer than n
     * are available, the remainder will be zeroed out.  Returns the
     * number of samples actually read.
     */
    int read(T *destination, int n, int R = 0);

    /**
     * Read n samples from the buffer, for reader R, adding them to
     * the destination.  If fewer than n are available, the remainder
     * will be left alone.  Returns the number of samples actually
     * read.
     */
    int readAdding(T *destination, int n, int R = 0);

    /**
     * Read one sample from the buffer, for reader R.  If no sample is
     * available, this will silently return zero.  Calling this
     * repeatedly is obviously slower than calling read once, but it
     * may be good enough if you don't want to allocate a buffer to
     * read into.
     */
    T readOne(int R = 0);

    /**
     * Read n samples from the buffer, if available, for reader R,
     * without advancing the read pointer -- i.e. a subsequent read()
     * or skip() will be necessary to empty the buffer.  If fewer than
     * n are available, the remainder will be zeroed out.  Returns the
     * number of samples actually read.
     */
    int peek(T *destination, int n, int R = 0) const;

    /**
     * Read one sample from the buffer, if available, without
     * advancing the read pointer -- i.e. a subsequent read() or
     * skip() will be necessary to empty the buffer.  Returns zero if
     * no sample was available.
     */
    T peekOne(int R = 0) const;

    /**
     * Pretend to read n samples from the buffer, for reader R,
     * without actually returning them (i.e. discard the next n
     * samples).  Returns the number of samples actually available for
     * discarding.
     */
    int skip(int n, int R = 0);

    /**
     * Write n samples to the buffer.  If insufficient space is
     * available, not all samples may actually be written.  Returns
     * the number of samples actually written.
     */
    int write(const T *source, int n);

    /**
     * Write n zero-value samples to the buffer.  If insufficient
     * space is available, not all zeros may actually be written.
     * Returns the number of zeroes actually written.
     */
    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));
    }

    BQ_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];
        }
    }

    BQ_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]];
    BQ_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));
    }

    BQ_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));
    }
    
    BQ_MBARRIER();
    m_writer = (m_writer + n) % m_size;
    return n;
}

#endif // _RINGBUFFER_H_