content/renderer/shared_memory_seqlock_reader.h

   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:
  42   SharedMemorySeqLockReader() : buffer_(0) { }
  43   virtual ~SharedMemorySeqLockReader() { }
  44
  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
  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_