| // Copyright (c) 2015 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef NET_QUIC_STREAM_SEQUENCER_BUFFER_H_ |
| #define NET_QUIC_STREAM_SEQUENCER_BUFFER_H_ |
| |
| // StreamSequencerBuffer implements QuicStreamSequencerBufferInterface. |
| // It is a circular stream buffer with random write and |
| // in-sequence read. It consists of a vector of pointers pointing |
| // to memory blocks created as needed and a list of Gaps to indicate |
| // the missing data between the data already written into the buffer. |
| // - Data are written in with offset indicating where it should be in the |
| // stream, and the buffer grown as needed (up to the maximum buffer capacity), |
| // without expensive copying (extra blocks are allocated). |
| // - Data can be read from the buffer if there is no gap before it, |
| // and the buffer shrinks as the data are consumed. |
| // - An upper limit on the number of blocks in the buffer provides an upper |
| // bound on memory use. |
| // |
| // This class is thread-unsafe. |
| // |
| // StreamSequencerBuffer maintains a concept of the readable region, which |
| // contains all written data that has not been read. |
| // It promises stability of the underlying memory addresses in the readable |
| // region, so pointers into it can be maintained, and the offset of a pointer |
| // from the start of the read region can be calculated. |
| // |
| // Expected Use: |
| // StreamSequencerBuffer buffer(2.5 * 8 * 1024); |
| // std::string source(1024, 'a'); |
| // base::StringPiece std::string_piece(source.data(), source.size()); |
| // size_t written = 0; |
| // buffer.OnStreamData(800, std::string_piece, GetEpollClockNow(), &written); |
| // source = std::string{800, 'b'}; |
| // base::StringPiece std::string_piece1(source.data(), 800); |
| // // Try to write to [1, 801), but should fail due to overlapping, |
| // // res should be QUIC_INVALID_STREAM_DATA |
| // auto res = buffer.OnStreamData(1, std::string_piece1, &written)); |
| // // write to [0, 800), res should be QUIC_NO_ERROR |
| // auto res = buffer.OnStreamData(0, std::string_piece1, GetEpollClockNow(), |
| // &written); |
| // |
| // // Read into a iovec array with total capacity of 120 bytes. |
| // char dest[120]; |
| // iovec iovecs[3]{iovec{dest, 40}, iovec{dest + 40, 40}, |
| // iovec{dest + 80, 40}}; |
| // size_t read = buffer.Readv(iovecs, 3); |
| // |
| // // Get single readable region with timestamp. |
| // QuicTime t; |
| // iovec iov; |
| // buffer.GetReadableRegion(iov, &t); |
| // |
| // // Get readable regions from [256, 1024) and consume some of it. |
| // iovec iovs[2]; |
| // int iov_count = buffer.GetReadableRegions(iovs, 2); |
| // // Consume some bytes in iovs, returning number of bytes having been |
| // consumed. |
| // size_t consumed = consume_iovs(iovs, iov_count); |
| // buffer.MarkConsumed(consumed); |
| |
| #include <stddef.h> |
| |
| #include <functional> |
| #include <list> |
| #include <memory> |
| |
| #include "base/macros.h" |
| #include "net/quic/quic_protocol.h" |
| #include "net/quic/quic_stream_sequencer_buffer_interface.h" |
| |
| namespace net { |
| |
| namespace test { |
| class StreamSequencerBufferPeer; |
| } // namespace test |
| |
| class NET_EXPORT_PRIVATE StreamSequencerBuffer |
| : public QuicStreamSequencerBufferInterface { |
| public: |
| // A Gap indicates a missing chunk of bytes between |
| // [begin_offset, end_offset) in the stream |
| struct Gap { |
| Gap(QuicStreamOffset begin_offset, QuicStreamOffset end_offset); |
| QuicStreamOffset begin_offset; |
| QuicStreamOffset end_offset; |
| }; |
| |
| // A FrameInfo stores the length of a frame and the time it arrived. |
| struct NET_EXPORT_PRIVATE FrameInfo { |
| FrameInfo(); |
| FrameInfo(size_t length, QuicTime timestamp); |
| |
| size_t length; |
| QuicTime timestamp; |
| }; |
| |
| // Size of blocks used by this buffer. |
| // Choose 8K to make block large enough to hold multiple frames, each of |
| // which could be up to 1.5 KB. |
| static const size_t kBlockSizeBytes = 8 * 1024; // 8KB |
| |
| // The basic storage block used by this buffer. |
| struct BufferBlock { |
| char buffer[kBlockSizeBytes]; |
| }; |
| |
| explicit StreamSequencerBuffer(size_t max_capacity_bytes); |
| |
| ~StreamSequencerBuffer() override; |
| |
| // QuicStreamSequencerBufferInterface implementation. |
| void Clear() override; |
| bool Empty() const override; |
| QuicErrorCode OnStreamData(QuicStreamOffset offset, |
| base::StringPiece data, |
| QuicTime timestamp, |
| size_t* bytes_buffered) override; |
| size_t Readv(const struct iovec* dest_iov, size_t dest_count) override; |
| int GetReadableRegions(struct iovec* iov, int iov_len) const override; |
| bool GetReadableRegion(iovec* iov, QuicTime* timestamp) const override; |
| bool MarkConsumed(size_t bytes_buffered) override; |
| size_t FlushBufferedFrames() override; |
| bool HasBytesToRead() const override; |
| QuicStreamOffset BytesConsumed() const override; |
| size_t BytesBuffered() const override; |
| |
| private: |
| friend class test::StreamSequencerBufferPeer; |
| |
| // Dispose the given buffer block. |
| // After calling this method, blocks_[index] is set to nullptr |
| // in order to indicate that no memory set is allocated for that block. |
| void RetireBlock(size_t index); |
| |
| // Should only be called after the indexed block is read till the end of the |
| // block or a gap has been reached. |
| // If the block at |block_index| contains no buffered data, then the block is |
| // retired. |
| void RetireBlockIfEmpty(size_t block_index); |
| |
| // Called within OnStreamData() to update the gap OnStreamData() writes into |
| // (remove, split or change begin/end offset). |
| void UpdateGapList(std::list<Gap>::iterator gap_with_new_data_written, |
| QuicStreamOffset start_offset, |
| size_t bytes_written); |
| |
| // Calculate the capacity of block at specified index. |
| // Return value should be either kBlockSizeBytes for non-trailing blocks and |
| // max_buffer_capacity % kBlockSizeBytes for trailing block. |
| size_t GetBlockCapacity(size_t index) const; |
| |
| // Does not check if offset is within reasonable range. |
| size_t GetBlockIndex(QuicStreamOffset offset) const; |
| |
| // Given an offset in the stream, return the offset from the beginning of the |
| // block which contains this data. |
| size_t GetInBlockOffset(QuicStreamOffset offset) const; |
| |
| // Get offset relative to index 0 in logical 1st block to start next read. |
| size_t ReadOffset() const; |
| |
| // Get the index of the logical 1st block to start next read. |
| size_t NextBlockToRead() const; |
| |
| // Returns number of bytes available to be read out. |
| size_t ReadableBytes() const; |
| |
| // Called after Readv() and MarkConsumed() to keep frame_arrival_time_map_ |
| // up to date. |
| // |offset| is the byte next read should start from. All frames before it |
| // should be removed from the map. |
| void UpdateFrameArrivalMap(QuicStreamOffset offset); |
| |
| // The maximum total capacity of this buffer in byte, as constructed. |
| const size_t max_buffer_capacity_bytes_; |
| |
| // How many blocks this buffer would need when it reaches full capacity. |
| const size_t blocks_count_; |
| |
| // Number of bytes read out of buffer. |
| QuicStreamOffset total_bytes_read_; |
| |
| // Contains Gaps which represents currently missing data. |
| std::list<Gap> gaps_; |
| |
| // An ordered, variable-length list of blocks, with the length limited |
| // such that the number of blocks never exceeds blocks_count_. |
| // Each list entry can hold up to kBlockSizeBytes bytes. |
| std::vector<BufferBlock*> blocks_; |
| |
| // Number of bytes in buffer. |
| size_t num_bytes_buffered_; |
| |
| // Stores all the buffered frames' start offset, length and arrival time. |
| std::map<QuicStreamOffset, FrameInfo> frame_arrival_time_map_; |
| |
| DISALLOW_COPY_AND_ASSIGN(StreamSequencerBuffer); |
| }; |
| } // namespace net |
| |
| #endif // NET_QUIC_STREAM_SEQUENCER_BUFFER_H_ |