зеркало из https://github.com/mozilla/gecko-dev.git
85 строки
2.8 KiB
C
85 строки
2.8 KiB
C
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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim:set ts=2 sw=2 sts=2 et cindent: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this file,
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* You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef MEMORY_BLOCK_CACHE_H_
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#define MEMORY_BLOCK_CACHE_H_
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#include "MediaBlockCacheBase.h"
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#include "mozilla/Mutex.h"
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namespace mozilla {
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// Manages block management for the media cache. Data comes in over the network
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// via callbacks on the main thread, however we don't want to write the
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// incoming data to the media cache on the main thread, as this could block
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// causing UI jank.
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//
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// So MediaBlockCacheBase provides an abstraction for a temporary memory buffer
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// as an array of blocks, which supports a block move operation, and
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// allows synchronous reading and writing from any thread.
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//
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// Writes and cache block moves (which require reading) may be deferred to
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// their own non-main thread. This object also ensures that data which has
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// been scheduled to be written, but hasn't actually *been* written, is read
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// as if it had, i.e. pending writes are cached in readable memory until
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// they're flushed to file.
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//
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// To improve efficiency, writes can only be done at block granularity,
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// whereas reads can be done with byte granularity.
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class MemoryBlockCache : public MediaBlockCacheBase
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{
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public:
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explicit MemoryBlockCache(int64_t aContentLength);
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protected:
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virtual ~MemoryBlockCache();
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public:
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// Allocate initial buffer.
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virtual nsresult Init() override;
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// Empty buffer.
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virtual void Close() override;
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// Can be called on any thread.
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virtual nsresult WriteBlock(uint32_t aBlockIndex,
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Span<const uint8_t> aData1,
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Span<const uint8_t> aData2) override;
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// Synchronously reads data from buffer.
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virtual nsresult Read(int64_t aOffset,
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uint8_t* aData,
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int32_t aLength,
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int32_t* aBytes) override;
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// Moves a block. Can be called on any thread.
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virtual nsresult MoveBlock(int32_t aSourceBlockIndex,
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int32_t aDestBlockIndex) override;
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private:
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static size_t BlockIndexToOffset(uint32_t aBlockIndex)
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{
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return static_cast<size_t>(aBlockIndex) * BLOCK_SIZE;
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}
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// Ensure the buffer has at least a multiple of BLOCK_SIZE that can contain
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// aContentLength bytes. Buffer size can only grow.
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// Returns false if allocation failed.
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bool EnsureBufferCanContain(size_t aContentLength);
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// Initial content length.
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const size_t mInitialContentLength;
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// Mutex which controls access to all members below.
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Mutex mMutex;
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nsTArray<uint8_t> mBuffer;
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};
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} // End namespace mozilla.
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#endif /* MEMORY_BLOCK_CACHE_H_ */
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