base/files/memory_mapped_file.cc

   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 #include "base/files/memory_mapped_file.h"
   6
   7 #include "base/files/file_path.h"
   8 #include "base/logging.h"
   9 #include "base/sys_info.h"
  10
  11 namespace base {
  12
  13 const MemoryMappedFile::Region MemoryMappedFile::Region::kWholeFile(
  14     base::LINKER_INITIALIZED);
  15
  16 MemoryMappedFile::Region::Region(base::LinkerInitialized) : offset(0), size(0) {
  17 }
  18
  19 MemoryMappedFile::Region::Region(int64 offset, int64 size)
  20     : offset(offset), size(size) {
  21   DCHECK_GE(offset, 0);
  22   DCHECK_GT(size, 0);
  23 }
  24
  25 bool MemoryMappedFile::Region::operator==(
  26     const MemoryMappedFile::Region& other) const {
  27   return other.offset == offset && other.size == size;
  28 }
  29
  30 MemoryMappedFile::~MemoryMappedFile() {
  31   CloseHandles();
  32 }
  33
  34 bool MemoryMappedFile::Initialize(const FilePath& file_name) {
  35   if (IsValid())
  36     return false;
  37
  38   file_.Initialize(file_name, File::FLAG_OPEN | File::FLAG_READ);
  39
  40   if (!file_.IsValid()) {
  41     DLOG(ERROR) << "Couldn't open " << file_name.AsUTF8Unsafe();
  42     return false;
  43   }
  44
  45   if (!MapFileRegionToMemory(Region::kWholeFile)) {
  46     CloseHandles();
  47     return false;
  48   }
  49
  50   return true;
  51 }
  52
  53 bool MemoryMappedFile::Initialize(File file) {
  54   return Initialize(file.Pass(), Region::kWholeFile);
  55 }
  56
  57 bool MemoryMappedFile::Initialize(File file, const Region& region) {
  58   if (IsValid())
  59     return false;
  60
  61   file_ = file.Pass();
  62
  63   if (!MapFileRegionToMemory(region)) {
  64     CloseHandles();
  65     return false;
  66   }
  67
  68   return true;
  69 }
  70
  71 bool MemoryMappedFile::IsValid() const {
  72   return data_ != NULL;
  73 }
  74
  75 // static
  76 void MemoryMappedFile::CalculateVMAlignedBoundaries(int64 start,
  77                                                     int64 size,
  78                                                     int64* aligned_start,
  79                                                     int64* aligned_size,
  80                                                     int32* offset) {
  81   // Sadly, on Windows, the mmap alignment is not just equal to the page size.
  82   const int64 mask = static_cast<int64>(SysInfo::VMAllocationGranularity()) - 1;
  83   DCHECK_LT(mask, std::numeric_limits<int32>::max());
  84   *offset = start & mask;
  85   *aligned_start = start & ~mask;
  86   *aligned_size = (size + *offset + mask) & ~mask;
  87 }
  88
  89 }  // namespace base