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Diffstat (limited to 'src/sound/RingBuffer.h')
| -rw-r--r-- | src/sound/RingBuffer.h | 572 |
1 files changed, 572 insertions, 0 deletions
diff --git a/src/sound/RingBuffer.h b/src/sound/RingBuffer.h new file mode 100644 index 0000000..0cc5dc6 --- /dev/null +++ b/src/sound/RingBuffer.h @@ -0,0 +1,572 @@ +// -*- c-basic-offset: 4 -*- + +/* + Rosegarden + A sequencer and musical notation editor. + + This program is Copyright 2000-2008 + Guillaume Laurent <glaurent@telegraph-road.org>, + Chris Cannam <cannam@all-day-breakfast.com>, + Richard Bown <bownie@bownie.com> + + The moral right of the authors to claim authorship of this work + has been asserted. + + 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. +*/ + +#ifndef _RINGBUFFER_H_ +#define _RINGBUFFER_H_ + +#include <sys/types.h> +#include <sys/mman.h> + +#include "Scavenger.h" + +//#define DEBUG_RINGBUFFER 1 +//#define DEBUG_RINGBUFFER_CREATE_DESTROY 1 + +#ifdef DEBUG_RINGBUFFER +#define DEBUG_RINGBUFFER_CREATE_DESTROY 1 +#endif + +#ifdef DEBUG_RINGBUFFER_CREATE_DESTROY +#include <iostream> +static int __extant_ringbuffers = 0; +#endif + +namespace Rosegarden { + +/** + * 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(); + + /** + * Unlock the ring buffer from physical memory. Returns true for + * success. + */ + bool munlock(); + + /** + * 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 peek(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_CREATE_DESTROY + std::cerr << "RingBuffer<T," << N << ">[" << this << "]::RingBuffer(" << n << ") [now have " << (++__extant_ringbuffers) << "]" << 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_CREATE_DESTROY + std::cerr << "RingBuffer<T," << N << ">[" << this << "]::~RingBuffer [now have " << (--__extant_ringbuffers) << "]" << 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_CREATE_DESTROY + 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> +bool +RingBuffer<T, N>::munlock() +{ + if (::munlock((void *)m_buffer, m_size * sizeof(T))) return false; + m_mlocked = false; + 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>::peek(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_ |