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// 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 <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include "base/logging.h"
#include "base/threading/thread_restrictions.h"
#include "build/build_config.h"
namespace base {
MemoryMappedFile::MemoryMappedFile() : data_(NULL), length_(0) {
}
#if !defined(OS_NACL)
bool MemoryMappedFile::MapFileRegionToMemory(
const MemoryMappedFile::Region& region,
Access access) {
ThreadRestrictions::AssertIOAllowed();
off_t map_start = 0;
size_t map_size = 0;
int32_t data_offset = 0;
if (region == MemoryMappedFile::Region::kWholeFile) {
int64_t file_len = file_.GetLength();
if (file_len == -1) {
DPLOG(ERROR) << "fstat " << file_.GetPlatformFile();
return false;
}
map_size = static_cast<size_t>(file_len);
length_ = map_size;
} else {
// The region can be arbitrarily aligned. mmap, instead, requires both the
// start and size to be page-aligned. Hence, we map here the page-aligned
// 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 aligned_size = 0;
CalculateVMAlignedBoundaries(region.offset,
region.size,
&aligned_start,
&aligned_size,
&data_offset);
// Ensure that the casts in the mmap call below are sane.
if (aligned_start < 0 || aligned_size < 0 ||
aligned_start > std::numeric_limits<off_t>::max() ||
static_cast<uint64_t>(aligned_size) >
std::numeric_limits<size_t>::max() ||
static_cast<uint64_t>(region.size) >
std::numeric_limits<size_t>::max()) {
DLOG(ERROR) << "Region bounds are not valid for mmap";
return false;
}
map_start = static_cast<off_t>(aligned_start);
map_size = static_cast<size_t>(aligned_size);
length_ = static_cast<size_t>(region.size);
}
int flags = 0;
switch (access) {
case READ_ONLY:
flags |= PROT_READ;
break;
case READ_WRITE:
flags |= PROT_READ | PROT_WRITE;
break;
case READ_WRITE_EXTEND:
// POSIX won't auto-extend the file when it is written so it must first
// be explicitly extended to the maximum size. Zeros will fill the new
// space.
file_.SetLength(std::max(file_.GetLength(), region.offset + region.size));
flags |= PROT_READ | PROT_WRITE;
break;
}
data_ = static_cast<uint8_t*>(mmap(NULL, map_size, flags, MAP_SHARED,
file_.GetPlatformFile(), map_start));
if (data_ == MAP_FAILED) {
DPLOG(ERROR) << "mmap " << file_.GetPlatformFile();
return false;
}
data_ += data_offset;
return true;
}
#endif
void MemoryMappedFile::CloseHandles() {
ThreadRestrictions::AssertIOAllowed();
if (data_ != NULL)
munmap(data_, length_);
file_.Close();
data_ = NULL;
length_ = 0;
}
} // namespace base
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