1 // Copyright 2013 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef CONTENT_RENDERER_SHARED_MEMORY_SEQLOCK_READER_H_ 6 #define CONTENT_RENDERER_SHARED_MEMORY_SEQLOCK_READER_H_ 7 8 #include "base/logging.h" 9 #include "base/memory/scoped_ptr.h" 10 #include "base/memory/shared_memory.h" 11 #include "content/common/shared_memory_seqlock_buffer.h" 12 13 namespace internal { 14 15 class SharedMemorySeqLockReaderBase { 16 protected: 17 SharedMemorySeqLockReaderBase(); 18 virtual ~SharedMemorySeqLockReaderBase(); 19 20 void* InitializeSharedMemory( 21 base::SharedMemoryHandle shared_memory_handle, 22 size_t buffer_size); 23 24 bool FetchFromBuffer(content::OneWriterSeqLock* seqlock, void* final, 25 void* temp, void* from, size_t size); 26 27 static const int kMaximumContentionCount = 10; 28 base::SharedMemoryHandle renderer_shared_memory_handle_; 29 scoped_ptr<base::SharedMemory> renderer_shared_memory_; 30 }; 31 32 } // namespace internal 33 34 namespace content { 35 36 // Template argument Data should be a pod-like structure only containing 37 // data fields, such that it is copyable by memcpy method. 38 template<typename Data> 39 class SharedMemorySeqLockReader 40 : private internal::SharedMemorySeqLockReaderBase { 41 public: SharedMemorySeqLockReader()42 SharedMemorySeqLockReader() : buffer_(0) { } ~SharedMemorySeqLockReader()43 virtual ~SharedMemorySeqLockReader() { } 44 GetLatestData(Data * data)45 bool GetLatestData(Data* data) { 46 DCHECK(buffer_); 47 DCHECK(sizeof(*data) == sizeof(*temp_buffer_)); 48 return FetchFromBuffer(&buffer_->seqlock, data, temp_buffer_.get(), 49 &buffer_->data, sizeof(*temp_buffer_)); 50 } 51 Initialize(base::SharedMemoryHandle shared_memory_handle)52 bool Initialize(base::SharedMemoryHandle shared_memory_handle) { 53 if (void* memory = InitializeSharedMemory( 54 shared_memory_handle, sizeof(SharedMemorySeqLockBuffer<Data>))) { 55 buffer_ = static_cast<SharedMemorySeqLockBuffer<Data>*>(memory); 56 temp_buffer_.reset(new Data); 57 return true; 58 } 59 return false; 60 } 61 62 private: 63 SharedMemorySeqLockBuffer<Data>* buffer_; 64 scoped_ptr<Data> temp_buffer_; 65 66 DISALLOW_COPY_AND_ASSIGN(SharedMemorySeqLockReader); 67 }; 68 69 } // namespace content 70 71 #endif // CONTENT_RENDERER_SHARED_MEMORY_SEQLOCK_READER_H_ 72