| // Copyright 2019 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 PLATFORM_IMPL_TLS_WRITE_BUFFER_H_ |
| #define PLATFORM_IMPL_TLS_WRITE_BUFFER_H_ |
| |
| #include <atomic> |
| #include <memory> |
| |
| #include "absl/types/span.h" |
| #include "platform/base/macros.h" |
| |
| namespace openscreen { |
| |
| // This class is responsible for buffering TLS Write data. The approach taken by |
| // this class is to allow for a single thread to act as a publisher of data and |
| // for a separate thread to act as the consumer of that data. The data in |
| // question is written to a lockless FIFO queue. |
| class TlsWriteBuffer { |
| public: |
| TlsWriteBuffer(); |
| ~TlsWriteBuffer(); |
| |
| // Pushes the provided data into the buffer, returning true if successful. |
| // Returns false if there was insufficient space left. Either all or none of |
| // the data is pushed into the buffer. |
| bool Push(const void* data, size_t len); |
| |
| // Returns a subset of the readable region of data. At time of reading, more |
| // data may be available for reading than what is represented in this Span. |
| absl::Span<const uint8_t> GetReadableRegion(); |
| |
| // Marks the provided number of bytes as consumed by the consumer thread. |
| void Consume(size_t byte_count); |
| |
| // The amount of space to allocate in the buffer. |
| static constexpr size_t kBufferSizeBytes = 1 << 19; // 0.5 MB. |
| |
| private: |
| // Buffer where data to be written over the TLS connection is stored. |
| uint8_t buffer_[kBufferSizeBytes]; |
| |
| // Total number of bytes read or written so far. Atomics are used both to |
| // ensure that read and write operations are atomic for uint64s on all systems |
| // and to ensure that different values for these values aren't loaded from |
| // each CPU's physical cache. |
| std::atomic_size_t bytes_read_so_far_{0}; |
| std::atomic_size_t bytes_written_so_far_{0}; |
| |
| OSP_DISALLOW_COPY_AND_ASSIGN(TlsWriteBuffer); |
| }; |
| |
| } // namespace openscreen |
| |
| #endif // PLATFORM_IMPL_TLS_WRITE_BUFFER_H_ |