Use LockFile/UnlockFile for Settings to port to Windows

client/settings.h

 // Copyright 2015 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
 #ifndef CRASHPAD_CLIENT_SETTINGS_H_
 #define CRASHPAD_CLIENT_SETTINGS_H_
 
 #include <time.h>
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/files/file_path.h"
+#include "base/scoped_generic.h"
 #include "util/file/file_io.h"
 #include "util/misc/initialization_state_dcheck.h"
 #include "util/misc/uuid.h"
 
 namespace crashpad {
 
+namespace internal {
+
+struct ScopedLockedFileHandleTraits {
+  static FileHandle InvalidValue();
+  static void Free(FileHandle handle);
+};
+
+}  // namespace internal
+
 //! \brief An interface for accessing and modifying the settings of a
 //!     CrashReportDatabase.
 //!
 //! This class must not be instantiated directly, but rather an instance of it
 //! should be retrieved via CrashReportDatabase::GetSettings().
 class Settings {
  public:
   explicit Settings(const base::FilePath& file_path);
   ~Settings();
 
@@ skipping 48 matching lines @@
   //!
   //! \param[in] time The last time at which a report was uploaded.
   //!
   //! \return On success, returns `true`, otherwise returns `false` with an
   //!     error logged.
   bool SetLastUploadAttemptTime(time_t time);
 
  private:
   struct Data;
 
+  // This must be constructed with MakeScopedLockedFileHandle(). It both unlocks
+  // and closes the file on destruction.
+  using ScopedLockedFileHandle =
+      base::ScopedGeneric<FileHandle,
+                          internal::ScopedLockedFileHandleTraits>;
+  static ScopedLockedFileHandle MakeScopedLockedFileHandle(FileHandle file,
+                                                           FileLocking locking);
+
   // Opens the settings file for reading. On error, logs a message and returns
   // the invalid handle.
-  ScopedFileHandle OpenForReading();
+  ScopedLockedFileHandle OpenForReading();
 
   // Opens the settings file for reading and writing. On error, logs a message
   // and returns the invalid handle.
-  ScopedFileHandle OpenForReadingAndWriting();
+  ScopedLockedFileHandle OpenForReadingAndWriting();
 
   // Opens the settings file and reads the data. If that fails, an error will
   // be logged and the settings will be recovered and re-initialized. If that
   // also fails, returns false with additional log data from recovery.
   bool OpenAndReadSettings(Data* out_data);
 
   // Opens the settings file for writing and reads the data. If reading fails,
   // recovery is attempted. Returns the opened file handle on success, or the
   // invalid file handle on failure, with an error logged.
-  ScopedFileHandle OpenForWritingAndReadSettings(Data* out_data);
+  ScopedLockedFileHandle OpenForWritingAndReadSettings(Data* out_data);
 
   // Reads the settings from |handle|. Logs an error and returns false on
   // failure. This does not perform recovery.
   bool ReadSettings(FileHandle handle, Data* out_data);
 
   // Writes the settings to |handle|. Logs an error and returns false on
   // failure. This does not perform recovery.
   bool WriteSettings(FileHandle handle, const Data& data);
 
   // Recovers the settings file by re-initializing the data. If |handle| is the
@@ skipping 13 matching lines @@
   base::FilePath file_path_;
 
   InitializationStateDcheck initialized_;
 
   DISALLOW_COPY_AND_ASSIGN(Settings);
 };
 
 }  // namespace crashpad
 
 #endif  // CRASHPAD_CLIENT_SETTINGS_H_