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authorMatt A. Tobin <email@mattatobin.com>2019-11-03 14:14:26 -0500
committerMatt A. Tobin <email@mattatobin.com>2019-11-03 14:14:26 -0500
commit1960d6e08a949ceed50e6a18240d40a7ecee879c (patch)
tree580b06d4df15ff5f8a9c3f20468bf2160ac666e5 /media/libcubeb/src/cubeb_ringbuffer.h
parent732fe36241032a1793e09209ccc06cb720225b9e (diff)
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Revert "Issue #1267 - Part 1: Update libcubeb to a1200c34."
This reverts commit d162ecbaffe845c9707da5d2f6cab11f343ef00e.
Diffstat (limited to 'media/libcubeb/src/cubeb_ringbuffer.h')
-rw-r--r--media/libcubeb/src/cubeb_ringbuffer.h495
1 files changed, 0 insertions, 495 deletions
diff --git a/media/libcubeb/src/cubeb_ringbuffer.h b/media/libcubeb/src/cubeb_ringbuffer.h
deleted file mode 100644
index b6696e886..000000000
--- a/media/libcubeb/src/cubeb_ringbuffer.h
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@@ -1,495 +0,0 @@
-/*
- * Copyright © 2016 Mozilla Foundation
- *
- * This program is made available under an ISC-style license. See the
- * accompanying file LICENSE for details.
- */
-
-#ifndef CUBEB_RING_BUFFER_H
-#define CUBEB_RING_BUFFER_H
-
-#include "cubeb_utils.h"
-#include <algorithm>
-#include <atomic>
-#include <cstdint>
-#include <memory>
-#include <thread>
-
-/**
- * Single producer single consumer lock-free and wait-free ring buffer.
- *
- * This data structure allows producing data from one thread, and consuming it on
- * another thread, safely and without explicit synchronization. If used on two
- * threads, this data structure uses atomics for thread safety. It is possible
- * to disable the use of atomics at compile time and only use this data
- * structure on one thread.
- *
- * The role for the producer and the consumer must be constant, i.e., the
- * producer should always be on one thread and the consumer should always be on
- * another thread.
- *
- * Some words about the inner workings of this class:
- * - Capacity is fixed. Only one allocation is performed, in the constructor.
- * When reading and writing, the return value of the method allows checking if
- * the ring buffer is empty or full.
- * - We always keep the read index at least one element ahead of the write
- * index, so we can distinguish between an empty and a full ring buffer: an
- * empty ring buffer is when the write index is at the same position as the
- * read index. A full buffer is when the write index is exactly one position
- * before the read index.
- * - We synchronize updates to the read index after having read the data, and
- * the write index after having written the data. This means that the each
- * thread can only touch a portion of the buffer that is not touched by the
- * other thread.
- * - Callers are expected to provide buffers. When writing to the queue,
- * elements are copied into the internal storage from the buffer passed in.
- * When reading from the queue, the user is expected to provide a buffer.
- * Because this is a ring buffer, data might not be contiguous in memory,
- * providing an external buffer to copy into is an easy way to have linear
- * data for further processing.
- */
-template <typename T>
-class ring_buffer_base
-{
-public:
- /**
- * Constructor for a ring buffer.
- *
- * This performs an allocation, but is the only allocation that will happen
- * for the life time of a `ring_buffer_base`.
- *
- * @param capacity The maximum number of element this ring buffer will hold.
- */
- ring_buffer_base(int capacity)
- /* One more element to distinguish from empty and full buffer. */
- : capacity_(capacity + 1)
- {
- assert(storage_capacity() <
- std::numeric_limits<int>::max() / 2 &&
- "buffer too large for the type of index used.");
- assert(capacity_ > 0);
-
- data_.reset(new T[storage_capacity()]);
- /* If this queue is using atomics, initializing those members as the last
- * action in the constructor acts as a full barrier, and allow capacity() to
- * be thread-safe. */
- write_index_ = 0;
- read_index_ = 0;
- }
- /**
- * Push `count` zero or default constructed elements in the array.
- *
- * Only safely called on the producer thread.
- *
- * @param count The number of elements to enqueue.
- * @return The number of element enqueued.
- */
- int enqueue_default(int count)
- {
- return enqueue(nullptr, count);
- }
- /**
- * @brief Put an element in the queue
- *
- * Only safely called on the producer thread.
- *
- * @param element The element to put in the queue.
- *
- * @return 1 if the element was inserted, 0 otherwise.
- */
- int enqueue(T& element)
- {
- return enqueue(&element, 1);
- }
- /**
- * Push `count` elements in the ring buffer.
- *
- * Only safely called on the producer thread.
- *
- * @param elements a pointer to a buffer containing at least `count` elements.
- * If `elements` is nullptr, zero or default constructed elements are enqueued.
- * @param count The number of elements to read from `elements`
- * @return The number of elements successfully coped from `elements` and inserted
- * into the ring buffer.
- */
- int enqueue(T * elements, int count)
- {
-#ifndef NDEBUG
- assert_correct_thread(producer_id);
-#endif
-
- int rd_idx = read_index_.load(std::memory_order::memory_order_relaxed);
- int wr_idx = write_index_.load(std::memory_order::memory_order_relaxed);
-
- if (full_internal(rd_idx, wr_idx)) {
- return 0;
- }
-
- int to_write =
- std::min(available_write_internal(rd_idx, wr_idx), count);
-
- /* First part, from the write index to the end of the array. */
- int first_part = std::min(storage_capacity() - wr_idx,
- to_write);
- /* Second part, from the beginning of the array */
- int second_part = to_write - first_part;
-
- if (elements) {
- Copy(data_.get() + wr_idx, elements, first_part);
- Copy(data_.get(), elements + first_part, second_part);
- } else {
- ConstructDefault(data_.get() + wr_idx, first_part);
- ConstructDefault(data_.get(), second_part);
- }
-
- write_index_.store(increment_index(wr_idx, to_write), std::memory_order::memory_order_release);
-
- return to_write;
- }
- /**
- * Retrieve at most `count` elements from the ring buffer, and copy them to
- * `elements`, if non-null.
- *
- * Only safely called on the consumer side.
- *
- * @param elements A pointer to a buffer with space for at least `count`
- * elements. If `elements` is `nullptr`, `count` element will be discarded.
- * @param count The maximum number of elements to dequeue.
- * @return The number of elements written to `elements`.
- */
- int dequeue(T * elements, int count)
- {
-#ifndef NDEBUG
- assert_correct_thread(consumer_id);
-#endif
-
- int wr_idx = write_index_.load(std::memory_order::memory_order_acquire);
- int rd_idx = read_index_.load(std::memory_order::memory_order_relaxed);
-
- if (empty_internal(rd_idx, wr_idx)) {
- return 0;
- }
-
- int to_read =
- std::min(available_read_internal(rd_idx, wr_idx), count);
-
- int first_part = std::min(storage_capacity() - rd_idx, to_read);
- int second_part = to_read - first_part;
-
- if (elements) {
- Copy(elements, data_.get() + rd_idx, first_part);
- Copy(elements + first_part, data_.get(), second_part);
- }
-
- read_index_.store(increment_index(rd_idx, to_read), std::memory_order::memory_order_relaxed);
-
- return to_read;
- }
- /**
- * Get the number of available element for consuming.
- *
- * Only safely called on the consumer thread.
- *
- * @return The number of available elements for reading.
- */
- int available_read() const
- {
-#ifndef NDEBUG
- assert_correct_thread(consumer_id);
-#endif
- return available_read_internal(read_index_.load(std::memory_order::memory_order_relaxed),
- write_index_.load(std::memory_order::memory_order_relaxed));
- }
- /**
- * Get the number of available elements for consuming.
- *
- * Only safely called on the producer thread.
- *
- * @return The number of empty slots in the buffer, available for writing.
- */
- int available_write() const
- {
-#ifndef NDEBUG
- assert_correct_thread(producer_id);
-#endif
- return available_write_internal(read_index_.load(std::memory_order::memory_order_relaxed),
- write_index_.load(std::memory_order::memory_order_relaxed));
- }
- /**
- * Get the total capacity, for this ring buffer.
- *
- * Can be called safely on any thread.
- *
- * @return The maximum capacity of this ring buffer.
- */
- int capacity() const
- {
- return storage_capacity() - 1;
- }
- /**
- * Reset the consumer and producer thread identifier, in case the thread are
- * being changed. This has to be externally synchronized. This is no-op when
- * asserts are disabled.
- */
- void reset_thread_ids()
- {
-#ifndef NDEBUG
- consumer_id = producer_id = std::thread::id();
-#endif
- }
-private:
- /** Return true if the ring buffer is empty.
- *
- * @param read_index the read index to consider
- * @param write_index the write index to consider
- * @return true if the ring buffer is empty, false otherwise.
- **/
- bool empty_internal(int read_index,
- int write_index) const
- {
- return write_index == read_index;
- }
- /** Return true if the ring buffer is full.
- *
- * This happens if the write index is exactly one element behind the read
- * index.
- *
- * @param read_index the read index to consider
- * @param write_index the write index to consider
- * @return true if the ring buffer is full, false otherwise.
- **/
- bool full_internal(int read_index,
- int write_index) const
- {
- return (write_index + 1) % storage_capacity() == read_index;
- }
- /**
- * Return the size of the storage. It is one more than the number of elements
- * that can be stored in the buffer.
- *
- * @return the number of elements that can be stored in the buffer.
- */
- int storage_capacity() const
- {
- return capacity_;
- }
- /**
- * Returns the number of elements available for reading.
- *
- * @return the number of available elements for reading.
- */
- int
- available_read_internal(int read_index,
- int write_index) const
- {
- if (write_index >= read_index) {
- return write_index - read_index;
- } else {
- return write_index + storage_capacity() - read_index;
- }
- }
- /**
- * Returns the number of empty elements, available for writing.
- *
- * @return the number of elements that can be written into the array.
- */
- int
- available_write_internal(int read_index,
- int write_index) const
- {
- /* We substract one element here to always keep at least one sample
- * free in the buffer, to distinguish between full and empty array. */
- int rv = read_index - write_index - 1;
- if (write_index >= read_index) {
- rv += storage_capacity();
- }
- return rv;
- }
- /**
- * Increments an index, wrapping it around the storage.
- *
- * @param index a reference to the index to increment.
- * @param increment the number by which `index` is incremented.
- * @return the new index.
- */
- int
- increment_index(int index, int increment) const
- {
- assert(increment >= 0);
- return (index + increment) % storage_capacity();
- }
- /**
- * @brief This allows checking that enqueue (resp. dequeue) are always called
- * by the right thread.
- *
- * @param id the id of the thread that has called the calling method first.
- */
-#ifndef NDEBUG
- static void assert_correct_thread(std::thread::id& id)
- {
- if (id == std::thread::id()) {
- id = std::this_thread::get_id();
- return;
- }
- assert(id == std::this_thread::get_id());
- }
-#endif
- /** Index at which the oldest element is at, in samples. */
- std::atomic<int> read_index_;
- /** Index at which to write new elements. `write_index` is always at
- * least one element ahead of `read_index_`. */
- std::atomic<int> write_index_;
- /** Maximum number of elements that can be stored in the ring buffer. */
- const int capacity_;
- /** Data storage */
- std::unique_ptr<T[]> data_;
-#ifndef NDEBUG
- /** The id of the only thread that is allowed to read from the queue. */
- mutable std::thread::id consumer_id;
- /** The id of the only thread that is allowed to write from the queue. */
- mutable std::thread::id producer_id;
-#endif
-};
-
-/**
- * Adapter for `ring_buffer_base` that exposes an interface in frames.
- */
-template <typename T>
-class audio_ring_buffer_base
-{
-public:
- /**
- * @brief Constructor.
- *
- * @param channel_count Number of channels.
- * @param capacity_in_frames The capacity in frames.
- */
- audio_ring_buffer_base(int channel_count, int capacity_in_frames)
- : channel_count(channel_count)
- , ring_buffer(frames_to_samples(capacity_in_frames))
- {
- assert(channel_count > 0);
- }
- /**
- * @brief Enqueue silence.
- *
- * Only safely called on the producer thread.
- *
- * @param frame_count The number of frames of silence to enqueue.
- * @return The number of frames of silence actually written to the queue.
- */
- int enqueue_default(int frame_count)
- {
- return samples_to_frames(ring_buffer.enqueue(nullptr, frames_to_samples(frame_count)));
- }
- /**
- * @brief Enqueue `frames_count` frames of audio.
- *
- * Only safely called from the producer thread.
- *
- * @param [in] frames If non-null, the frames to enqueue.
- * Otherwise, silent frames are enqueued.
- * @param frame_count The number of frames to enqueue.
- *
- * @return The number of frames enqueued
- */
-
- int enqueue(T * frames, int frame_count)
- {
- return samples_to_frames(ring_buffer.enqueue(frames, frames_to_samples(frame_count)));
- }
-
- /**
- * @brief Removes `frame_count` frames from the buffer, and
- * write them to `frames` if it is non-null.
- *
- * Only safely called on the consumer thread.
- *
- * @param frames If non-null, the frames are copied to `frames`.
- * Otherwise, they are dropped.
- * @param frame_count The number of frames to remove.
- *
- * @return The number of frames actually dequeud.
- */
- int dequeue(T * frames, int frame_count)
- {
- return samples_to_frames(ring_buffer.dequeue(frames, frames_to_samples(frame_count)));
- }
- /**
- * Get the number of available frames of audio for consuming.
- *
- * Only safely called on the consumer thread.
- *
- * @return The number of available frames of audio for reading.
- */
- int available_read() const
- {
- return samples_to_frames(ring_buffer.available_read());
- }
- /**
- * Get the number of available frames of audio for consuming.
- *
- * Only safely called on the producer thread.
- *
- * @return The number of empty slots in the buffer, available for writing.
- */
- int available_write() const
- {
- return samples_to_frames(ring_buffer.available_write());
- }
- /**
- * Get the total capacity, for this ring buffer.
- *
- * Can be called safely on any thread.
- *
- * @return The maximum capacity of this ring buffer.
- */
- int capacity() const
- {
- return samples_to_frames(ring_buffer.capacity());
- }
-private:
- /**
- * @brief Frames to samples conversion.
- *
- * @param frames The number of frames.
- *
- * @return A number of samples.
- */
- int frames_to_samples(int frames) const
- {
- return frames * channel_count;
- }
- /**
- * @brief Samples to frames conversion.
- *
- * @param samples The number of samples.
- *
- * @return A number of frames.
- */
- int samples_to_frames(int samples) const
- {
- return samples / channel_count;
- }
- /** Number of channels of audio that will stream through this ring buffer. */
- int channel_count;
- /** The underlying ring buffer that is used to store the data. */
- ring_buffer_base<T> ring_buffer;
-};
-
-/**
- * Lock-free instantiation of the `ring_buffer_base` type. This is safe to use
- * from two threads, one producer, one consumer (that never change role),
- * without explicit synchronization.
- */
-template<typename T>
-using lock_free_queue = ring_buffer_base<T>;
-/**
- * Lock-free instantiation of the `audio_ring_buffer` type. This is safe to use
- * from two threads, one producer, one consumer (that never change role),
- * without explicit synchronization.
- */
-template<typename T>
-using lock_free_audio_ring_buffer = audio_ring_buffer_base<T>;
-
-#endif // CUBEB_RING_BUFFER_H