Use LockFile/UnlockFile for Settings to port to Windows

util/file/file_io.h

 // Copyright 2014 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,
@@ skipping 170 matching lines @@
 //!     reading. Logs an error if the operation fails.
 //!
 //! \return The newly opened FileHandle, or an invalid FileHandle on failure.
 //!
 //! \sa ScopedFileHandle
 FileHandle LoggingOpenFileForRead(const base::FilePath& path);
 
 //! \brief Wraps `open()` or `CreateFile()`, creating a file for output. Logs
 //!     an error if the operation fails.
 //!
-//! \a write_mode determines the style (truncate, reuse, etc.) that is used to
-//! open the file. On POSIX, \a permissions determines the value that is passed
-//! as `mode` to `open()`. On Windows, the file is always opened in binary mode
+//! \a mode determines the style (truncate, reuse, etc.) that is used to open
+//! the file. On POSIX, \a permissions determines the value that is passed as
+//! `mode` to `open()`. On Windows, the file is always opened in binary mode
 //! (that is, no CRLF translation). On Windows, the file is opened for sharing,
 //! see LoggingLockFile() and LoggingUnlockFile() to control concurrent access.
 //!
 //! \return The newly opened FileHandle, or an invalid FileHandle on failure.
 //!
 //! \sa FileWriteMode
 //! \sa FilePermissions
 //! \sa ScopedFileHandle
 FileHandle LoggingOpenFileForWrite(const base::FilePath& path,
-                                   FileWriteMode write_mode,
+                                   FileWriteMode mode,
                                    FilePermissions permissions);
 
+//! \brief Wraps `open()` or `CreateFile()`, creating a file for both input and
+//!     output. Logs an error if the operation fails.
+//!
+//! \a mode determines the style (truncate, reuse, etc.) that is used to open
+//! the file. On POSIX, \a permissions determines the value that is passed as
+//! `mode` to `open()`. On Windows, the file is always opened in binary mode
+//! (that is, no CRLF translation). On Windows, the file is opened for sharing,
+//! see LoggingLockFile() and LoggingUnlockFile() to control concurrent access.
+//!
+//! \return The newly opened FileHandle, or an invalid FileHandle on failure.
+//!
+//! \sa FileWriteMode
+//! \sa FilePermissions
+//! \sa ScopedFileHandle
+FileHandle LoggingOpenFileForReadAndWrite(const base::FilePath& path,
+                                          FileWriteMode mode,
+                                          FilePermissions permissions);
+
 //! \brief Locks the given \a file using `flock()` on POSIX or `LockFileEx()` on
 //!     Windows.
 //!
 //! It is an error to attempt to lock a file in a different mode when it is
 //! already locked. This call will block until the lock is acquired. The
 //! entire file is locked.
 //!
 //! If \a locking is FileLocking::kShared, \a file must have been opened for
 //! reading, and if it's FileLocking::kExclusive, \a file must have been opened
 //! for writing.
@@ skipping 20 matching lines @@
 //!     operation fails.
 //!
 //! Repositions the offset of the open \a file to the specified \a offset,
 //! relative to \a whence. \a whence must be one of `SEEK_SET`, `SEEK_CUR`, or
 //! `SEEK_END`, and is interpreted in the usual way.
 //!
 //! \return The resulting offset in bytes from the beginning of the file, or
 //!     `-1` on failure.
 FileOffset LoggingSeekFile(FileHandle file, FileOffset offset, int whence);
 
+//! \brief Truncates the given \a file to zero bytes in length.
+//!
+//! \return `true` on success, or `false`, and a message will be logged.
+bool LoggingTruncateFile(FileHandle file);
+
 //! \brief Wraps `close()` or `CloseHandle()`, logging an error if the operation
 //!     fails.
 //!
 //! \return On success, `true` is returned. On failure, an error is logged and
 //!     `false` is returned.
 bool LoggingCloseFile(FileHandle file);
 
 //! \brief Wraps `close()` or `CloseHandle()`, ensuring that it succeeds.
 //!
 //! If the underlying function fails, this function causes execution to
 //! terminate without returning.
 void CheckedCloseFile(FileHandle file);
 
 }  // namespace crashpad
 
 #endif  // CRASHPAD_UTIL_FILE_FILE_IO_H_