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      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 <utility>
      8 
      9 #include "base/files/file_path.h"
     10 #include "base/logging.h"
     11 #include "base/sys_info.h"
     12 #include "build/build_config.h"
     13 
     14 namespace base {
     15 
     16 const MemoryMappedFile::Region MemoryMappedFile::Region::kWholeFile = {0, 0};
     17 
     18 bool MemoryMappedFile::Region::operator==(
     19     const MemoryMappedFile::Region& other) const {
     20   return other.offset == offset && other.size == size;
     21 }
     22 
     23 bool MemoryMappedFile::Region::operator!=(
     24     const MemoryMappedFile::Region& other) const {
     25   return other.offset != offset || other.size != size;
     26 }
     27 
     28 MemoryMappedFile::~MemoryMappedFile() {
     29   CloseHandles();
     30 }
     31 
     32 #if !defined(OS_NACL)
     33 bool MemoryMappedFile::Initialize(const FilePath& file_name) {
     34   if (IsValid())
     35     return false;
     36 
     37   file_.Initialize(file_name, File::FLAG_OPEN | File::FLAG_READ);
     38 
     39   if (!file_.IsValid()) {
     40     DLOG(ERROR) << "Couldn't open " << file_name.AsUTF8Unsafe();
     41     return false;
     42   }
     43 
     44   if (!MapFileRegionToMemory(Region::kWholeFile)) {
     45     CloseHandles();
     46     return false;
     47   }
     48 
     49   return true;
     50 }
     51 
     52 bool MemoryMappedFile::Initialize(File file) {
     53   return Initialize(std::move(file), Region::kWholeFile);
     54 }
     55 
     56 bool MemoryMappedFile::Initialize(File file, const Region& region) {
     57   if (IsValid())
     58     return false;
     59 
     60   if (region != Region::kWholeFile) {
     61     DCHECK_GE(region.offset, 0);
     62     DCHECK_GT(region.size, 0);
     63   }
     64 
     65   file_ = std::move(file);
     66 
     67   if (!MapFileRegionToMemory(region)) {
     68     CloseHandles();
     69     return false;
     70   }
     71 
     72   return true;
     73 }
     74 
     75 bool MemoryMappedFile::IsValid() const {
     76   return data_ != NULL;
     77 }
     78 
     79 // static
     80 void MemoryMappedFile::CalculateVMAlignedBoundaries(int64_t start,
     81                                                     int64_t size,
     82                                                     int64_t* aligned_start,
     83                                                     int64_t* aligned_size,
     84                                                     int32_t* offset) {
     85   // Sadly, on Windows, the mmap alignment is not just equal to the page size.
     86   const int64_t mask =
     87       static_cast<int64_t>(SysInfo::VMAllocationGranularity()) - 1;
     88   DCHECK_LT(mask, std::numeric_limits<int32_t>::max());
     89   *offset = start & mask;
     90   *aligned_start = start & ~mask;
     91   *aligned_size = (size + *offset + mask) & ~mask;
     92 }
     93 #endif
     94 
     95 }  // namespace base
     96