davidcorne / file-locker

Locked File

Purpose

This is a project to get a good RAII class for locking a file for reading and writing. This is implemented in C++.

The Purpose of Locking Files

The main use of file locking is to stop someone writing to a file between you reading it and writing it back out changed. It also becomes important implementing databases and websites.

Contents

The main class in this repository is LockedFile. In the repository there is this class and some supporting error classes. There is also a comprehensive unit test.

Application

There is a sample application which uses the file locking. What this does is lock the files you give it on the command line.

Implementation Details

This repository is indended to be built using make and the Microsoft C++ compiler. This repository currently only works on windows.

Running Unit Test

The entire project is built and the test run, by typing

make test

This should give output which looks like this.

===============================================================================
utest_LockedFile::test_file_exists
===============================================================================

Pass: File should exist

===============================================================================
utest_LockedFile::test_non_existant_file
===============================================================================

Pass: File should not exist
Pass: This is not PathNotFoundError

===============================================================================
utest_LockedFile::test_file_write_lock
===============================================================================

Pass: File should lock ok.
Pass: Should not write correctly.
Pass: Should write correctly.

===============================================================================
utest_LockedFile::test_file_deletion
===============================================================================

Pass: Should be no error from LockedFile
Pass: Should not be able to delete locked file.
Pass: File shouldn't be locked any more.

===============================================================================
utest_LockedFile::test_nested_locks
===============================================================================

Pass: First lock should work.
Pass: Second lock should not work.
Pass: This is not FileInUseError
Pass: Third lock should work.

Building the Application

It is built using

make

in the application directory. The executable is found under exe.

Implementation Problems

• The dependencies in the makefile are not well set up. Somethimes if you change a header you need to manually remake other files (or make -B) to get them to compile.
• The reading and writing in LockedFile says nothing about encoding.