base/files/memory_mapped_file_posix.cc

   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 <sys/mman.h>
   8 #include <sys/stat.h>
   9 #include <unistd.h>
  10
  11 #include "base/logging.h"
  12 #include "base/threading/thread_restrictions.h"
  13
  14 namespace base {
  15
  16 MemoryMappedFile::MemoryMappedFile() : data_(NULL), length_(0) {
  17 }
  18
  19 #if !defined(OS_NACL)
  20 bool MemoryMappedFile::MapFileRegionToMemory(
  21     const MemoryMappedFile::Region& region) {
  22   ThreadRestrictions::AssertIOAllowed();
  23
  24   off_t map_start = 0;
  25   size_t map_size = 0;
  26   int32 data_offset = 0;
  27
  28   if (region == MemoryMappedFile::Region::kWholeFile) {
  29     int64 file_len = file_.GetLength();
  30     if (file_len == -1) {
  31       DPLOG(ERROR) << "fstat " << file_.GetPlatformFile();
  32       return false;
  33     }
  34     map_size = static_cast<size_t>(file_len);
  35     length_ = map_size;
  36   } else {
  37     // The region can be arbitrarily aligned. mmap, instead, requires both the
  38     // start and size to be page-aligned. Hence, we map here the page-aligned
  39     // outer region [|aligned_start|, |aligned_start| + |size|] which contains
  40     // |region| and then add up the |data_offset| displacement.
  41     int64 aligned_start = 0;
  42     int64 aligned_size = 0;
  43     CalculateVMAlignedBoundaries(region.offset,
  44                                  region.size,
  45                                  &aligned_start,
  46                                  &aligned_size,
  47                                  &data_offset);
  48
  49     // Ensure that the casts in the mmap call below are sane.
  50     if (aligned_start < 0 || aligned_size < 0 ||
  51         aligned_start > std::numeric_limits<off_t>::max() ||
  52         static_cast<uint64>(aligned_size) >
  53             std::numeric_limits<size_t>::max() ||
  54         static_cast<uint64>(region.size) > std::numeric_limits<size_t>::max()) {
  55       DLOG(ERROR) << "Region bounds are not valid for mmap";
  56       return false;
  57     }
  58
  59     map_start = static_cast<off_t>(aligned_start);
  60     map_size = static_cast<size_t>(aligned_size);
  61     length_ = static_cast<size_t>(region.size);
  62   }
  63
  64   data_ = static_cast<uint8*>(mmap(NULL,
  65                                    map_size,
  66                                    PROT_READ,
  67                                    MAP_SHARED,
  68                                    file_.GetPlatformFile(),
  69                                    map_start));
  70   if (data_ == MAP_FAILED) {
  71     DPLOG(ERROR) << "mmap " << file_.GetPlatformFile();
  72     return false;
  73   }
  74
  75   data_ += data_offset;
  76   return true;
  77 }
  78 #endif
  79
  80 void MemoryMappedFile::CloseHandles() {
  81   ThreadRestrictions::AssertIOAllowed();
  82
  83   if (data_ != NULL)
  84     munmap(data_, length_);
  85   file_.Close();
  86
  87   data_ = NULL;
  88   length_ = 0;
  89 }
  90
  91 }  // namespace base