text: // Copyright (c) 2012 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.
  
  #include "net/disk_cache/mapped_file.h"
  
  #include <errno.h>
  #include <sys/mman.h>
  
  #include "base/file_path.h"
  #include "base/logging.h"
  #include "net/disk_cache/disk_cache.h"
  
  namespace disk_cache {
  
  void* MappedFile::Init(const FilePath& name, size_t size) {
    DCHECK(!init_);
    if (init_ || !File::Init(name))
      return NULL;
  
    size_t temp_len = size ? size : 4096;
    if (!size)
      size = GetLength();
  
    buffer_ = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED,
                   platform_file(), 0);
    init_ = true;
    view_size_ = size;
    DCHECK(reinterpret_cast<intptr_t>(buffer_) != -1);
    if (reinterpret_cast<intptr_t>(buffer_) == -1)
      buffer_ = 0;
  
    // Make sure we detect hardware failures reading the headers.
    scoped_array<char> temp(new char[temp_len]);
    if (!Read(temp.get(), temp_len, 0))
      return NULL;
  
    return buffer_;
  }
  
  bool MappedFile::Load(const FileBlock* block) {
    size_t offset = block->offset() + view_size_;
    return Read(block->buffer(), block->size(), offset);
  }
  
  bool MappedFile::Store(const FileBlock* block) {
    size_t offset = block->offset() + view_size_;
    return Write(block->buffer(), block->size(), offset);
  }
  
  void MappedFile::Flush() {
  }
  
  MappedFile::~MappedFile() {
    if (!init_)
      return;
  
    if (buffer_) {
      int ret = munmap(buffer_, view_size_);
      DCHECK_EQ(0, ret);
    }
  }
  
  }  // namespace disk_cache
  