1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
|
// Copyright 2013 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 "base/files/memory_mapped_file.h"
#include <stddef.h>
#include <stdint.h>
#include <limits>
#include "base/files/file_path.h"
#include "base/strings/string16.h"
#include "base/threading/thread_restrictions.h"
namespace base {
MemoryMappedFile::MemoryMappedFile() : data_(NULL), length_(0) {
}
bool MemoryMappedFile::MapFileRegionToMemory(
const MemoryMappedFile::Region& region,
Access access) {
ThreadRestrictions::AssertIOAllowed();
if (!file_.IsValid())
return false;
int flags = 0;
uint32_t size_low = 0;
uint32_t size_high = 0;
switch (access) {
case READ_ONLY:
flags |= PAGE_READONLY;
break;
case READ_WRITE:
flags |= PAGE_READWRITE;
break;
case READ_WRITE_EXTEND:
flags |= PAGE_READWRITE;
size_high = static_cast<uint32_t>(region.size >> 32);
size_low = static_cast<uint32_t>(region.size & 0xFFFFFFFF);
break;
}
file_mapping_.Set(::CreateFileMapping(file_.GetPlatformFile(), NULL, flags,
size_high, size_low, NULL));
if (!file_mapping_.IsValid())
return false;
LARGE_INTEGER map_start = {};
SIZE_T map_size = 0;
int32_t data_offset = 0;
if (region == MemoryMappedFile::Region::kWholeFile) {
DCHECK_NE(READ_WRITE_EXTEND, access);
int64_t file_len = file_.GetLength();
if (file_len <= 0 || file_len > std::numeric_limits<int32_t>::max())
return false;
length_ = static_cast<size_t>(file_len);
} else {
// The region can be arbitrarily aligned. MapViewOfFile, instead, requires
// that the start address is aligned to the VM granularity (which is
// typically larger than a page size, for instance 32k).
// Also, conversely to POSIX's mmap, the |map_size| doesn't have to be
// aligned and must be less than or equal the mapped file size.
// We map here the outer region [|aligned_start|, |aligned_start+size|]
// which contains |region| and then add up the |data_offset| displacement.
int64_t aligned_start = 0;
int64_t ignored = 0;
CalculateVMAlignedBoundaries(
region.offset, region.size, &aligned_start, &ignored, &data_offset);
int64_t size = region.size + data_offset;
// Ensure that the casts below in the MapViewOfFile call are sane.
if (aligned_start < 0 || size < 0 ||
static_cast<uint64_t>(size) > std::numeric_limits<SIZE_T>::max()) {
DLOG(ERROR) << "Region bounds are not valid for MapViewOfFile";
return false;
}
map_start.QuadPart = aligned_start;
map_size = static_cast<SIZE_T>(size);
length_ = static_cast<size_t>(region.size);
}
data_ = static_cast<uint8_t*>(
::MapViewOfFile(file_mapping_.Get(),
(flags & PAGE_READONLY) ? FILE_MAP_READ : FILE_MAP_WRITE,
map_start.HighPart, map_start.LowPart, map_size));
if (data_ == NULL)
return false;
data_ += data_offset;
return true;
}
void MemoryMappedFile::CloseHandles() {
if (data_)
::UnmapViewOfFile(data_);
if (file_mapping_.IsValid())
file_mapping_.Close();
if (file_.IsValid())
file_.Close();
data_ = NULL;
length_ = 0;
}
} // namespace base
|
