1 /*
2 * Copyright (C) 2018 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include "android-base/mapped_file.h"
18
19 #include <utility>
20
21 #include <errno.h>
22
23 namespace android {
24 namespace base {
25
26 static constexpr char kEmptyBuffer[] = {'0'};
27
InitPageSize()28 static off64_t InitPageSize() {
29 #if defined(_WIN32)
30 SYSTEM_INFO si;
31 GetSystemInfo(&si);
32 return si.dwAllocationGranularity;
33 #else
34 return sysconf(_SC_PAGE_SIZE);
35 #endif
36 }
37
FromFd(borrowed_fd fd,off64_t offset,size_t length,int prot)38 std::unique_ptr<MappedFile> MappedFile::FromFd(borrowed_fd fd, off64_t offset, size_t length,
39 int prot) {
40 #if defined(_WIN32)
41 return FromOsHandle(reinterpret_cast<HANDLE>(_get_osfhandle(fd.get())), offset, length, prot);
42 #else
43 return FromOsHandle(fd.get(), offset, length, prot);
44 #endif
45 }
46
FromOsHandle(os_handle h,off64_t offset,size_t length,int prot)47 std::unique_ptr<MappedFile> MappedFile::FromOsHandle(os_handle h, off64_t offset, size_t length,
48 int prot) {
49 static const off64_t page_size = InitPageSize();
50 size_t slop = offset % page_size;
51 off64_t file_offset = offset - slop;
52 off64_t file_length = length + slop;
53
54 #if defined(_WIN32)
55 HANDLE handle = CreateFileMappingW(
56 h, nullptr, (prot & PROT_WRITE) ? PAGE_READWRITE : PAGE_READONLY, 0, 0, nullptr);
57 if (handle == nullptr) {
58 // http://b/119818070 "app crashes when reading asset of zero length".
59 // Return a MappedFile that's only valid for reading the size.
60 if (length == 0 && ::GetLastError() == ERROR_FILE_INVALID) {
61 return std::unique_ptr<MappedFile>(
62 new MappedFile(const_cast<char*>(kEmptyBuffer), 0, 0, nullptr));
63 }
64 return nullptr;
65 }
66 void* base = MapViewOfFile(handle, (prot & PROT_WRITE) ? FILE_MAP_ALL_ACCESS : FILE_MAP_READ, 0,
67 file_offset, file_length);
68 if (base == nullptr) {
69 CloseHandle(handle);
70 return nullptr;
71 }
72 return std::unique_ptr<MappedFile>(
73 new MappedFile(static_cast<char*>(base), length, slop, handle));
74 #else
75 void* base = mmap(nullptr, file_length, prot, MAP_SHARED, h, file_offset);
76 if (base == MAP_FAILED) {
77 // http://b/119818070 "app crashes when reading asset of zero length".
78 // mmap fails with EINVAL for a zero length region.
79 if (errno == EINVAL && length == 0) {
80 return std::unique_ptr<MappedFile>(new MappedFile(const_cast<char*>(kEmptyBuffer), 0, 0));
81 }
82 return nullptr;
83 }
84 return std::unique_ptr<MappedFile>(new MappedFile(static_cast<char*>(base), length, slop));
85 #endif
86 }
87
MappedFile(MappedFile && other)88 MappedFile::MappedFile(MappedFile&& other)
89 : base_(std::exchange(other.base_, nullptr)),
90 size_(std::exchange(other.size_, 0)),
91 offset_(std::exchange(other.offset_, 0))
92 #ifdef _WIN32
93 ,
94 handle_(std::exchange(other.handle_, nullptr))
95 #endif
96 {
97 }
98
operator =(MappedFile && other)99 MappedFile& MappedFile::operator=(MappedFile&& other) {
100 Close();
101 base_ = std::exchange(other.base_, nullptr);
102 size_ = std::exchange(other.size_, 0);
103 offset_ = std::exchange(other.offset_, 0);
104 #ifdef _WIN32
105 handle_ = std::exchange(other.handle_, nullptr);
106 #endif
107 return *this;
108 }
109
~MappedFile()110 MappedFile::~MappedFile() {
111 Close();
112 }
113
Close()114 void MappedFile::Close() {
115 #if defined(_WIN32)
116 if (base_ != nullptr && size_ != 0) UnmapViewOfFile(base_);
117 if (handle_ != nullptr) CloseHandle(handle_);
118 handle_ = nullptr;
119 #else
120 if (base_ != nullptr && size_ != 0) munmap(base_, size_ + offset_);
121 #endif
122
123 base_ = nullptr;
124 offset_ = size_ = 0;
125 }
126
127 } // namespace base
128 } // namespace android
129