Pass file Regions along with FDs to child processes on Android

base/files/memory_mapped_file.cc

 // 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 "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/sys_info.h"
 
 namespace base {
 
 const MemoryMappedFile::Region MemoryMappedFile::Region::kWholeFile(
     base::LINKER_INITIALIZED);
 
 MemoryMappedFile::Region::Region(base::LinkerInitialized) : offset(0), size(0) {
 }
 
+MemoryMappedFile::Region::Region() : offset(-1), size(-1) {
+}
+
 MemoryMappedFile::Region::Region(int64 offset, int64 size)
     : offset(offset), size(size) {
-  DCHECK_GE(offset, 0);
-  DCHECK_GT(size, 0);
 }
 
 bool MemoryMappedFile::Region::operator==(
     const MemoryMappedFile::Region& other) const {
   return other.offset == offset && other.size == size;
 }
 
+bool MemoryMappedFile::Region::operator!=(
+    const MemoryMappedFile::Region& other) const {
+  return other.offset != offset || other.size != size;

[Lei Zhang, 2015/06/02 20:25:43]

Some people just do !(this == other) here, especially if the comparison gets
more complicated.

+}
+
 MemoryMappedFile::~MemoryMappedFile() {
   CloseHandles();
 }
 
 #if !defined(OS_NACL)
 bool MemoryMappedFile::Initialize(const FilePath& file_name) {
   if (IsValid())
     return false;
 
   file_.Initialize(file_name, File::FLAG_OPEN | File::FLAG_READ);
@@ skipping 12 matching lines @@
 }
 
 bool MemoryMappedFile::Initialize(File file) {
   return Initialize(file.Pass(), Region::kWholeFile);
 }
 
 bool MemoryMappedFile::Initialize(File file, const Region& region) {
   if (IsValid())
     return false;
 
+  if (region != Region::kWholeFile) {
+    DCHECK_GE(region.offset, 0);
+    DCHECK_GT(region.size, 0);
+  }
+
   file_ = file.Pass();
 
   if (!MapFileRegionToMemory(region)) {
     CloseHandles();
     return false;
   }
 
   return true;
 }
 
@@ skipping 10 matching lines @@
   // Sadly, on Windows, the mmap alignment is not just equal to the page size.
   const int64 mask = static_cast<int64>(SysInfo::VMAllocationGranularity()) - 1;
   DCHECK_LT(mask, std::numeric_limits<int32>::max());
   *offset = start & mask;
   *aligned_start = start & ~mask;
   *aligned_size = (size + *offset + mask) & ~mask;
 }
 #endif
 
 }  // namespace base