comparison base/RingBuffer.h @ 0:da6937383da8

initial import

+/* -*- c-basic-offset: 4 -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    A waveform viewer and audio annotation editor.
+    Chris Cannam, Queen Mary University of London, 2005
+    
+    This is experimental software.  Not for distribution.
+*/
+
+/*
+   This is a modified version of a source file from the 
+   Rosegarden MIDI and audio sequencer and notation editor.
+   This file copyright 2000-2005 Chris Cannam.
+*/
+
+#ifndef _RINGBUFFER_H_
+#define _RINGBUFFER_H_
+
+#include <sys/types.h>
+
+#include "System.h"
+#include "Scavenger.h"
+
+//#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(size_t n);
+
+    virtual ~RingBuffer();
+
+    /**
+     * Return the total capacity of the ring buffer in samples.
+     * (This is the argument n passed to the constructor.)
+     */
+    size_t getSize() const;
+
+    /**
+     * Resize the ring buffer.  This also empties it.  Actually swaps
+     * in a new, larger buffer; the old buffer is scavenged after a
+     * seemly delay.  Should be called from the write thread.
+     */
+    void resize(size_t newSize);
+
+    /**
+     * 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.
+     */
+    size_t getReadSpace(int R = 0) const;
+
+    /**
+     * Return the amount of space available for writing, in samples.
+     */
+    size_t 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.
+     */
+    size_t read(T *destination, size_t 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.
+     */
+    size_t readAdding(T *destination, size_t 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.
+     */
+    size_t peek(T *destination, size_t 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.
+     */
+    size_t skip(size_t 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.
+     */
+    size_t write(const T *source, size_t 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.
+     */
+    size_t zero(size_t n);
+
+protected:
+    T               *m_buffer;
+    volatile size_t  m_writer;
+    volatile size_t  m_readers[N];
+    size_t           m_size;
+    bool             m_mlocked;
+
+    static Scavenger<ScavengerArrayWrapper<T> > m_scavenger;
+
+private:
+    RingBuffer(const RingBuffer &); // not provided
+    RingBuffer &operator=(const RingBuffer &); // not provided
+};
+
+template <typename T, int N>
+Scavenger<ScavengerArrayWrapper<T> > RingBuffer<T, N>::m_scavenger;
+
+template <typename T, int N>
+RingBuffer<T, N>::RingBuffer(size_t n) :
+    m_buffer(new T[n + 1]),
+    m_writer(0),
+    m_size(n + 1),
+    m_mlocked(false)
+{
+#ifdef DEBUG_RINGBUFFER
+    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::RingBuffer(" << n << ")" << std::endl;
+#endif
+
+    for (int i = 0; i < N; ++i) m_readers[i] = 0;
+
+    m_scavenger.scavenge();
+}
+
+template <typename T, int N>
+RingBuffer<T, N>::~RingBuffer()
+{
+#ifdef DEBUG_RINGBUFFER
+    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::~RingBuffer" << std::endl;
+#endif
+
+    if (m_mlocked) {
+	MUNLOCK((void *)m_buffer, m_size * sizeof(T));
+    }
+    delete[] m_buffer;
+
+    m_scavenger.scavenge();
+}
+
+template <typename T, int N>
+size_t
+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>
+void
+RingBuffer<T, N>::resize(size_t newSize)
+{
+#ifdef DEBUG_RINGBUFFER
+    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::resize(" << newSize << ")" << std::endl;
+#endif
+
+    m_scavenger.scavenge();
+
+    if (m_mlocked) {
+	MUNLOCK((void *)m_buffer, m_size * sizeof(T));
+    }
+
+    m_scavenger.claim(new ScavengerArrayWrapper<T>(m_buffer));
+
+    reset();
+    m_buffer = new T[newSize + 1];
+    m_size = newSize + 1;
+
+    if (m_mlocked) {
+	if (MLOCK((void *)m_buffer, m_size * sizeof(T))) {
+	    m_mlocked = false;
+	}
+    }
+}
+
+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>
+size_t
+RingBuffer<T, N>::getReadSpace(int R) const
+{
+    size_t writer = m_writer;
+    size_t reader = m_readers[R];
+    size_t 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>
+size_t
+RingBuffer<T, N>::getWriteSpace() const
+{
+    size_t space = 0;
+    for (int i = 0; i < N; ++i) {
+	size_t here = (m_readers[i] + m_size - m_writer - 1) % m_size;
+	if (i == 0 || here < space) space = here;
+    }
+
+#ifdef DEBUG_RINGBUFFER
+    size_t 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>
+size_t
+RingBuffer<T, N>::read(T *destination, size_t n, int R)
+{
+#ifdef DEBUG_RINGBUFFER
+    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::read(dest, " << n << ", " << R << ")" << std::endl;
+#endif
+
+    size_t 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;
+
+    size_t 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));
+    }
+
+    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>
+size_t
+RingBuffer<T, N>::readAdding(T *destination, size_t n, int R)
+{
+#ifdef DEBUG_RINGBUFFER
+    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::readAdding(dest, " << n << ", " << R << ")" << std::endl;
+#endif
+
+    size_t 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;
+
+    size_t here = m_size - m_readers[R];
+
+    if (here >= n) {
+	for (size_t i = 0; i < n; ++i) {
+	    destination[i] += (m_buffer + m_readers[R])[i];
+	}
+    } else {
+	for (size_t i = 0; i < here; ++i) {
+	    destination[i] += (m_buffer + m_readers[R])[i];
+	}
+	for (size_t i = 0; i < (n - here); ++i) {
+	    destination[i + here] += m_buffer[i];
+	}
+    }
+
+    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]];
+    if (++m_readers[R] == m_size) m_readers[R] = 0;
+    return value;
+}
+
+template <typename T, int N>
+size_t
+RingBuffer<T, N>::peek(T *destination, size_t n, int R) const
+{
+#ifdef DEBUG_RINGBUFFER
+    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::peek(dest, " << n << ", " << R << ")" << std::endl;
+#endif
+
+    size_t 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;
+
+    size_t 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>
+size_t
+RingBuffer<T, N>::skip(size_t n, int R)
+{
+#ifdef DEBUG_RINGBUFFER
+    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::skip(" << n << ", " << R << ")" << std::endl;
+#endif
+
+    size_t 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>
+size_t
+RingBuffer<T, N>::write(const T *source, size_t n)
+{
+#ifdef DEBUG_RINGBUFFER
+    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::write(" << n << ")" << std::endl;
+#endif
+
+    size_t 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;
+
+    size_t 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));
+    }
+
+    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>
+size_t
+RingBuffer<T, N>::zero(size_t n)
+{
+#ifdef DEBUG_RINGBUFFER
+    std::cerr << "RingBuffer<T," << N << ">[" << this << "]::zero(" << n << ")" << std::endl;
+#endif
+
+    size_t 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;
+
+    size_t 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));
+    }
+
+    m_writer = (m_writer + n) % m_size;
+    return n;
+}
+
+#endif // _RINGBUFFER_H_