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base/file_descriptor_store.cc

+// Copyright 2017 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/file_descriptor_store.h"
+
+#include <utility>
+
+#include "base/logging.h"
+
+namespace base {
+
+FileDescriptorStore::Descriptor::Descriptor(const std::string& key,
+                                            base::ScopedFD fd)
+    : key(key),
+      fd(std::move(fd)),
+      region(base::MemoryMappedFile::Region::kWholeFile) {}
+
+FileDescriptorStore::Descriptor::Descriptor(
+    const std::string& key,
+    base::ScopedFD fd,
+    base::MemoryMappedFile::Region region)
+    : key(key), fd(std::move(fd)), region(region) {}
+
+FileDescriptorStore::Descriptor::Descriptor(
+    FileDescriptorStore::Descriptor&& other)
+    : key(other.key), fd(std::move(other.fd)), region(other.region) {}
+
+FileDescriptorStore::Descriptor::~Descriptor() {}
+
+FileDescriptorStore::Descriptor& FileDescriptorStore::Descriptor::operator=(
+    FileDescriptorStore::Descriptor&& other) {

[dcheng, 2017/02/10 08:44:15]

I think this and the move ctor can be explicitly defaulted.

[Jay Civelli, 2017/02/13 18:48:25]

If I default the  move constructor, I get a "Complex class/struct needs an
explicit out-of-line copy constructor."
The = operator works though.

[dcheng, 2017/02/15 08:05:27]

Sorry, to clarify, they should only be declared in the header, not defined.

Then the .cc file can write
FileDescriptorStore::Descriptor::Descriptor(Descriptor&&) = default;

+  key = other.key;
+  fd = std::move(other.fd);
+  region = other.region;
+  return *this;
+}
+
+// static
+FileDescriptorStore& FileDescriptorStore::GetInstance() {
+  static FileDescriptorStore* store = new FileDescriptorStore;
+  return *store;
+}
+
+base::ScopedFD FileDescriptorStore::TakeFD(
+    const std::string& key,
+    base::MemoryMappedFile::Region* region) {
+  base::ScopedFD fd = MaybeTakeFD(key, region);
+  if (!fd.is_valid())
+    DLOG(FATAL) << "Unknown global descriptor: " << key;
+  return fd;
+}
+
+base::ScopedFD FileDescriptorStore::MaybeTakeFD(
+    const std::string& key,
+    base::MemoryMappedFile::Region* region) {
+  auto iter = descriptors_.find(key);
+  if (iter == descriptors_.end())
+    return base::ScopedFD();
+  descriptors_.erase(iter);
+  if (region)
+    *region = iter->second.region;

[dcheng, 2017/02/10 08:44:15]

Isn't referencing |iter| here undefined behavior? From [associative.reqmts]/9:
The insert and emplace members shall not affect the validity of iterators and
references to the container,
and the erase members shall invalidate only iterators and references to the
erased elements.

[Jay Civelli, 2017/02/13 18:48:25]

You are right! Fixed.

+  return std::move(iter->second.fd);
+}
+
+void FileDescriptorStore::Set(const std::string& key, base::ScopedFD fd) {
+  Set(key, std::move(fd), base::MemoryMappedFile::Region::kWholeFile);
+}
+
+void FileDescriptorStore::Set(const std::string& key,
+                              base::ScopedFD fd,
+                              base::MemoryMappedFile::Region region) {
+  Descriptor descriptor(key, std::move(fd), region);
+  descriptors_.insert(std::make_pair(key, std::move(descriptor)));
+}
+
+FileDescriptorStore::FileDescriptorStore() {}
+
+FileDescriptorStore::~FileDescriptorStore() {}
+
+}  // namespace base