Mercurial > hg > svcore
view base/RingBuffer.h @ 536:beb51f558e9c
* Change QMutex in Editable DTDM to a read/write lock
author | Chris Cannam |
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date | Mon, 26 Jan 2009 15:18:32 +0000 |
parents | 9eb7ef610d7f |
children | 2d551c765d51 |
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/* -*- 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 "Scavenger.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(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_