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/*
* Copyright (C) 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "android-base/mapped_file.h"
#include <utility>
#include <errno.h>
namespace android {
namespace base {
static constexpr char kEmptyBuffer[] = {'0'};
static off64_t InitPageSize() {
#if defined(_WIN32)
SYSTEM_INFO si;
GetSystemInfo(&si);
return si.dwAllocationGranularity;
#else
return sysconf(_SC_PAGE_SIZE);
#endif
}
std::unique_ptr<MappedFile> MappedFile::FromFd(borrowed_fd fd, off64_t offset, size_t length,
int prot) {
#if defined(_WIN32)
return FromOsHandle(reinterpret_cast<HANDLE>(_get_osfhandle(fd.get())), offset, length, prot);
#else
return FromOsHandle(fd.get(), offset, length, prot);
#endif
}
std::unique_ptr<MappedFile> MappedFile::FromOsHandle(os_handle h, off64_t offset, size_t length,
int prot) {
static const off64_t page_size = InitPageSize();
size_t slop = offset % page_size;
off64_t file_offset = offset - slop;
off64_t file_length = length + slop;
#if defined(_WIN32)
HANDLE handle = CreateFileMappingW(
h, nullptr, (prot & PROT_WRITE) ? PAGE_READWRITE : PAGE_READONLY, 0, 0, nullptr);
if (handle == nullptr) {
// http://b/119818070 "app crashes when reading asset of zero length".
// Return a MappedFile that's only valid for reading the size.
if (length == 0 && ::GetLastError() == ERROR_FILE_INVALID) {
return std::unique_ptr<MappedFile>(
new MappedFile(const_cast<char*>(kEmptyBuffer), 0, 0, nullptr));
}
return nullptr;
}
void* base = MapViewOfFile(handle, (prot & PROT_WRITE) ? FILE_MAP_ALL_ACCESS : FILE_MAP_READ,
(file_offset >> 32), file_offset, file_length);
if (base == nullptr) {
CloseHandle(handle);
return nullptr;
}
return std::unique_ptr<MappedFile>(
new MappedFile(static_cast<char*>(base), length, slop, handle));
#else
void* base = mmap(nullptr, file_length, prot, MAP_SHARED, h, file_offset);
if (base == MAP_FAILED) {
// http://b/119818070 "app crashes when reading asset of zero length".
// mmap fails with EINVAL for a zero length region.
if (errno == EINVAL && length == 0) {
return std::unique_ptr<MappedFile>(new MappedFile(const_cast<char*>(kEmptyBuffer), 0, 0));
}
return nullptr;
}
return std::unique_ptr<MappedFile>(new MappedFile(static_cast<char*>(base), length, slop));
#endif
}
MappedFile::MappedFile(MappedFile&& other)
: base_(std::exchange(other.base_, nullptr)),
size_(std::exchange(other.size_, 0)),
offset_(std::exchange(other.offset_, 0))
#ifdef _WIN32
,
handle_(std::exchange(other.handle_, nullptr))
#endif
{
}
MappedFile& MappedFile::operator=(MappedFile&& other) {
Close();
base_ = std::exchange(other.base_, nullptr);
size_ = std::exchange(other.size_, 0);
offset_ = std::exchange(other.offset_, 0);
#ifdef _WIN32
handle_ = std::exchange(other.handle_, nullptr);
#endif
return *this;
}
MappedFile::~MappedFile() {
Close();
}
void MappedFile::Close() {
#if defined(_WIN32)
if (base_ != nullptr && size_ != 0) UnmapViewOfFile(base_);
if (handle_ != nullptr) CloseHandle(handle_);
handle_ = nullptr;
#else
if (base_ != nullptr && size_ != 0) munmap(base_, size_ + offset_);
#endif
base_ = nullptr;
offset_ = size_ = 0;
}
} // namespace base
} // namespace android
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