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/strings/string16.h"
9#include "base/threading/thread_restrictions.h"
10
11namespace base {
12
13MemoryMappedFile::MemoryMappedFile() : data_(NULL), length_(0), image_(false) {
14}
15
16bool MemoryMappedFile::InitializeAsImageSection(const FilePath& file_name) {
17  image_ = true;
18  return Initialize(file_name);
19}
20
21bool MemoryMappedFile::MapFileRegionToMemory(
22    const MemoryMappedFile::Region& region) {
23  ThreadRestrictions::AssertIOAllowed();
24
25  if (!file_.IsValid())
26    return false;
27
28  int flags = image_ ? SEC_IMAGE | PAGE_READONLY : PAGE_READONLY;
29
30  file_mapping_.Set(::CreateFileMapping(file_.GetPlatformFile(), NULL,
31                                        flags, 0, 0, NULL));
32  if (!file_mapping_.IsValid())
33    return false;
34
35  LARGE_INTEGER map_start = {0};
36  SIZE_T map_size = 0;
37  int32 data_offset = 0;
38
39  if (region == MemoryMappedFile::Region::kWholeFile) {
40    int64 file_len = file_.GetLength();
41    if (file_len <= 0 || file_len > kint32max)
42      return false;
43    length_ = static_cast<size_t>(file_len);
44  } else {
45    // The region can be arbitrarily aligned. MapViewOfFile, instead, requires
46    // that the start address is aligned to the VM granularity (which is
47    // typically larger than a page size, for instance 32k).
48    // Also, conversely to POSIX's mmap, the |map_size| doesn't have to be
49    // aligned and must be less than or equal the mapped file size.
50    // We map here the outer region [|aligned_start|, |aligned_start+size|]
51    // which contains |region| and then add up the |data_offset| displacement.
52    int64 aligned_start = 0;
53    int64 ignored = 0;
54    CalculateVMAlignedBoundaries(
55        region.offset, region.size, &aligned_start, &ignored, &data_offset);
56    int64 size = region.size + data_offset;
57
58    // Ensure that the casts below in the MapViewOfFile call are sane.
59    if (aligned_start < 0 || size < 0 ||
60        static_cast<uint64>(size) > std::numeric_limits<SIZE_T>::max()) {
61      DLOG(ERROR) << "Region bounds are not valid for MapViewOfFile";
62      return false;
63    }
64    map_start.QuadPart = aligned_start;
65    map_size = static_cast<SIZE_T>(size);
66    length_ = static_cast<size_t>(region.size);
67  }
68
69  data_ = static_cast<uint8*>(::MapViewOfFile(file_mapping_.Get(),
70                                              FILE_MAP_READ,
71                                              map_start.HighPart,
72                                              map_start.LowPart,
73                                              map_size));
74  if (data_ == NULL)
75    return false;
76  data_ += data_offset;
77  return true;
78}
79
80void MemoryMappedFile::CloseHandles() {
81  if (data_)
82    ::UnmapViewOfFile(data_);
83  if (file_mapping_.IsValid())
84    file_mapping_.Close();
85  if (file_.IsValid())
86    file_.Close();
87
88  data_ = NULL;
89  length_ = 0;
90}
91
92}  // namespace base
93