Game.LambdaHack.Common.File

Saving/loading to files, with serialization and compression.

Documentation

encodeEOF :: Binary b => FilePath -> Version -> b -> IO ()

Serialize, compress and save data with an EOF marker. The OK is used as an EOF marker to ensure any apparent problems with corrupted files are reported to the user ASAP.

strictDecodeEOF :: Binary b => FilePath -> IO (Version, b)

Read, decompress and deserialize data with an EOF marker. The OK EOF marker ensures any easily detectable file corruption is discovered and reported before any value is decoded from the second component and before the file handle is closed. OTOH, binary encoding corruption is not discovered until a version check elswere ensures that binary formats are compatible.

tryCreateDir :: FilePath -> IO ()

Try to create a directory, if it doesn't exist. We catch exceptions in case many clients try to do the same thing at the same time.

doesFileExist :: FilePath -> IO Bool

The operation doesFileExist returns True if the argument file exists and is not a directory, and False otherwise.

tryWriteFile :: FilePath -> Text -> IO ()

Try to write a file, given content, if the file not already there. We catch exceptions in case many clients and/or the server try to do the same thing at the same time. Using IO to avoid UTF conflicts with OS or filesystem.

readFile :: FilePath -> IO String

The readFile function reads a file and returns the contents of the file as a string. The file is read lazily, on demand, as with getContents.

renameFile :: FilePath -> FilePath -> IO ()

renameFile old new changes the name of an existing file system object from old to new. If the new object already exists, it is replaced by the old object. Neither path may refer to an existing directory. A conformant implementation need not support renaming files in all situations (e.g. renaming across different physical devices), but the constraints must be documented.

On Windows, this calls MoveFileEx with MOVEFILE_REPLACE_EXISTING set, which is not guaranteed to be atomic (https://github.com/haskell/directory/issues/109).

On other platforms, this operation is atomic.

The operation may fail with:

• HardwareFault A physical I/O error has occurred. [EIO]
• InvalidArgument Either operand is not a valid file name. [ENAMETOOLONG, ELOOP]
• isDoesNotExistError The original file does not exist, or there is no path to the target. [ENOENT, ENOTDIR]
• isPermissionError The process has insufficient privileges to perform the operation. [EROFS, EACCES, EPERM]
• isFullError Insufficient resources are available to perform the operation. [EDQUOT, ENOSPC, ENOMEM, EMLINK]
• UnsatisfiedConstraints Implementation-dependent constraints are not satisfied. [EBUSY]
• UnsupportedOperation The implementation does not support renaming in this situation. [EXDEV]
• InappropriateType Either path refers to an existing directory. [ENOTDIR, EISDIR, EINVAL, EEXIST, ENOTEMPTY]