Mercurial > hg > svcore
view base/RingBuffer.h @ 6:44bbf5793d84
* Rework handling of layer properties in file I/O -- we now get the individual
layers to load and save them rather than doing it via generic property lists
in the base class, so as to ensure we read and write meaningful values rather
than generic int values requiring conversion.
author | Chris Cannam |
---|---|
date | Thu, 19 Jan 2006 12:54:38 +0000 |
parents | d86891498eef |
children | 2fb933f88604 |
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/* -*- 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, 2005-2006 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_