net/disk_cache/blockfile/mapped_file_avoid_mmap_posix.cc

   1 // Copyright (c) 2012 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 #include "net/disk_cache/blockfile/mapped_file.h"
   6
   7 #include <stdlib.h>
   8
   9 #include "base/files/file_path.h"
  10 #include "base/logging.h"
  11
  12 namespace disk_cache {
  13
  14 void* MappedFile::Init(const base::FilePath& name, size_t size) {
  15   DCHECK(!init_);
  16   if (init_ || !File::Init(name))
  17     return NULL;
  18
  19   if (!size)
  20     size = GetLength();
  21
  22   buffer_ = malloc(size);
  23   snapshot_ = malloc(size);
  24   if (buffer_ && snapshot_ && Read(buffer_, size, 0)) {
  25     memcpy(snapshot_, buffer_, size);
  26   } else {
  27     free(buffer_);
  28     free(snapshot_);
  29     buffer_ = snapshot_ = 0;
  30   }
  31
  32   init_ = true;
  33   view_size_ = size;
  34   return buffer_;
  35 }
  36
  37 void MappedFile::Flush() {
  38   DCHECK(buffer_);
  39   DCHECK(snapshot_);
  40   const char* buffer_ptr = static_cast<const char*>(buffer_);
  41   char* snapshot_ptr = static_cast<char*>(snapshot_);
  42   const size_t block_size = 4096;
  43   for (size_t offset = 0; offset < view_size_; offset += block_size) {
  44     size_t size = std::min(view_size_ - offset, block_size);
  45     if (memcmp(snapshot_ptr + offset, buffer_ptr + offset, size)) {
  46       memcpy(snapshot_ptr + offset, buffer_ptr + offset, size);
  47       Write(snapshot_ptr + offset, size, offset);
  48     }
  49   }
  50 }
  51
  52 MappedFile::~MappedFile() {
  53   if (!init_)
  54     return;
  55
  56   if (buffer_ && snapshot_) {
  57     Flush();
  58   }
  59   free(buffer_);
  60   free(snapshot_);
  61 }
  62
  63 }  // namespace disk_cache