Simplifying ContentBrowserClient::GetAdditionalMappedFiles...()

content/browser/file_descriptor_info_impl.cc

 // Copyright (c) 2012 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 "content/browser/file_descriptor_info_impl.h"
 
 #include <utility>
 
 #include "base/stl_util.h"
 
 namespace content {
 
 // static
 std::unique_ptr<FileDescriptorInfo> FileDescriptorInfoImpl::Create() {
   return std::unique_ptr<FileDescriptorInfo>(new FileDescriptorInfoImpl());
 }
 
 FileDescriptorInfoImpl::FileDescriptorInfoImpl() {
 }
 
 FileDescriptorInfoImpl::~FileDescriptorInfoImpl() {
 }
 
 void FileDescriptorInfoImpl::Share(int id, base::PlatformFile fd) {
-  AddToMapping(id, fd);
+  ShareWithRegion(id, fd, base::MemoryMappedFile::Region::kWholeFile);
+}
+
+void FileDescriptorInfoImpl::ShareWithRegion(int id, base::PlatformFile fd,
+    const base::MemoryMappedFile::Region& region) {
+  AddToMapping(id, fd, region);
 }
 
 void FileDescriptorInfoImpl::Transfer(int id, base::ScopedFD fd) {
-  AddToMapping(id, fd.get());
+  AddToMapping(id, fd.get(), base::MemoryMappedFile::Region::kWholeFile);
   owned_descriptors_.push_back(std::move(fd));
 }
 
 base::PlatformFile FileDescriptorInfoImpl::GetFDAt(size_t i) const {
   return mapping_[i].first;
 }
 
 int FileDescriptorInfoImpl::GetIDAt(size_t i) const {
   return mapping_[i].second;
 }
 
+const base::MemoryMappedFile::Region& FileDescriptorInfoImpl::GetRegionAt(
+    size_t i) const {
+  auto iter = ids_to_regions_.find(GetIDAt(i));
+  return (iter != ids_to_regions_.end()) ?
+      iter->second : base::MemoryMappedFile::Region::kWholeFile;
+}
+
 size_t FileDescriptorInfoImpl::GetMappingSize() const {
   return mapping_.size();
 }
 
 bool FileDescriptorInfoImpl::HasID(int id) const {
   for (unsigned i = 0; i < mapping_.size(); ++i) {
     if (mapping_[i].second == id)
       return true;
   }
 
@@ skipping 10 matching lines @@
   base::ScopedFD fd;
   auto found =
       std::find(owned_descriptors_.begin(), owned_descriptors_.end(), file);
 
   std::swap(*found, fd);
   owned_descriptors_.erase(found);
 
   return fd;
 }
 
-void FileDescriptorInfoImpl::AddToMapping(int id, base::PlatformFile fd) {
+void FileDescriptorInfoImpl::AddToMapping(int id, base::PlatformFile fd,
+    const base::MemoryMappedFile::Region& region) {
   DCHECK(!HasID(id));
   mapping_.push_back(std::make_pair(fd, id));
+  if (region != base::MemoryMappedFile::Region::kWholeFile)
+    ids_to_regions_[id] = region;
 }
 
 const base::FileHandleMappingVector& FileDescriptorInfoImpl::GetMapping()
     const {
   return mapping_;
 }
 
 base::FileHandleMappingVector
 FileDescriptorInfoImpl::GetMappingWithIDAdjustment(int delta) const {
   base::FileHandleMappingVector result = mapping_;
   // Adding delta to each ID.
   for (unsigned i = 0; i < mapping_.size(); ++i)
     result[i].second += delta;
   return result;
 }
 
 }  // namespace content