System.IO.HVFS

MissingH-1.1.1.0: Large utility library

Portability | portable
Stability | provisional
Maintainer | John Goerzen <jgoerzen@complete.org>

System.IO.HVFS

Contents

- Implementation Classes / Types
- Re-exported types from other modules

Description

Haskell Virtual FS -- generic support for real or virtual filesystem in Haskell

Copyright (c) 2004-2005 John Goerzen, jgoerzen@complete.org

The idea of this module is to provide virtualization of filesystem calls. In addition to the "real" system filesystem, you can also provide access to other, virtual, filesystems using the same set of calls. Examples of such virtual filesystems might include a remote FTP server, WebDAV server, a local Hashtable, a ConfigParser object, or any other data structure you can represent as a tree of named nodes containing strings.

Each `HVFS` function takes a `HVFS` "handle" (`HVFS` instance) as its first parameter. If you wish to operate on the standard system filesystem, you can just use `SystemFS`.

The MissingH.HVFS.IO.InstanceHelpers module contains some code to help you make your own HVFS instances.

The `HVFSOpenable` class works together with the System.IO.HVIO module to provide a complete virtual filesystem and I/O model that allows you to open up virtual filesystem files and act upon them in a manner similar to standard Handles.

Synopsis

- class Show a => HVFS a where
  - vGetCurrentDirectory :: a -> IO FilePath
  - vSetCurrentDirectory :: a -> FilePath -> IO ()
  - vGetDirectoryContents :: a -> FilePath -> IO [FilePath]
  - vDoesFileExist :: a -> FilePath -> IO Bool
  - vDoesDirectoryExist :: a -> FilePath -> IO Bool
  - vDoesExist :: a -> FilePath -> IO Bool
  - vCreateDirectory :: a -> FilePath -> IO ()
  - vRemoveDirectory :: a -> FilePath -> IO ()
  - vRenameDirectory :: a -> FilePath -> FilePath -> IO ()
  - vRemoveFile :: a -> FilePath -> IO ()
  - vRenameFile :: a -> FilePath -> FilePath -> IO ()
  - vGetFileStatus :: a -> FilePath -> IO HVFSStatEncap
  - vGetSymbolicLinkStatus :: a -> FilePath -> IO HVFSStatEncap
  - vGetModificationTime :: a -> FilePath -> IO ClockTime
  - vRaiseError :: a -> IOErrorType -> String -> Maybe FilePath -> IO c
  - vCreateSymbolicLink :: a -> FilePath -> FilePath -> IO ()
  - vReadSymbolicLink :: a -> FilePath -> IO FilePath
  - vCreateLink :: a -> FilePath -> FilePath -> IO ()
- class Show a => HVFSStat a where
  - vDeviceID :: a -> DeviceID
  - vFileID :: a -> FileID
  - vFileMode :: a -> FileMode
  - vLinkCount :: a -> LinkCount
  - vFileOwner :: a -> UserID
  - vFileGroup :: a -> GroupID
  - vSpecialDeviceID :: a -> DeviceID
  - vFileSize :: a -> FileOffset
  - vAccessTime :: a -> EpochTime
  - vModificationTime :: a -> EpochTime
  - vStatusChangeTime :: a -> EpochTime
  - vIsBlockDevice :: a -> Bool
  - vIsCharacterDevice :: a -> Bool
  - vIsNamedPipe :: a -> Bool
  - vIsRegularFile :: a -> Bool
  - vIsDirectory :: a -> Bool
  - vIsSymbolicLink :: a -> Bool
  - vIsSocket :: a -> Bool
- class HVFS a => HVFSOpenable a where
  - vOpen :: a -> FilePath -> IOMode -> IO HVFSOpenEncap
  - vReadFile :: a -> FilePath -> IO String
  - vWriteFile :: a -> FilePath -> String -> IO ()
  - vOpenBinaryFile :: a -> FilePath -> IOMode -> IO HVFSOpenEncap
- data HVFSOpenEncap = forall a . HVIO a => HVFSOpenEncap a
- data HVFSStatEncap = forall a . HVFSStat a => HVFSStatEncap a
- withStat :: forall b. HVFSStatEncap -> (forall a. HVFSStat a => a -> b) -> b
- withOpen :: forall b. HVFSOpenEncap -> (forall a. HVIO a => a -> b) -> b
- data SystemFS = SystemFS
- type FilePath = String
- type DeviceID = CDev
- type FileID = CIno
- type FileMode = CMode
- type LinkCount = CNlink
- type UserID = CUid
- type GroupID = CGid
- type FileOffset = COff
- type EpochTime = CTime
- data IOMode

# Implementation Classes / Types

class Show a => HVFS a where

The main HVFS class.

Default implementations of these functions are provided:

- `vGetModificationTime` -- implemented in terms of `vGetFileStatus`
- `vRaiseError`
- `vDoesFileExist` -- implemented in terms of `vGetFileStatus`
- `vDoesDirectoryExist` -- implemented in terms of `vGetFileStatus`
- `vDoesExist` -- implemented in terms of `vGetSymbolicLinkStatus`
- `vGetSymbolicLinkStatus` -- set to call `vGetFileStatus`.

Default implementations of all other functions will generate an isIllegalOperation error, since they are assumed to be un-implemented.

You should always provide at least a `vGetFileStatus` call, and almost certainly several of the others.

Most of these functions correspond to functions in System.Directory or System.Posix.Files. Please see detailed documentation on them there.

Methods

vGetCurrentDirectory :: a -> IO FilePath

vSetCurrentDirectory :: a -> FilePath -> IO ()

vGetDirectoryContents :: a -> FilePath -> IO [FilePath]

vDoesFileExist :: a -> FilePath -> IO Bool

vDoesDirectoryExist :: a -> FilePath -> IO Bool

vDoesExist :: a -> FilePath -> IO Bool

True if the file exists, regardless of what type it is. This is even True if the given path is a broken symlink.

vCreateDirectory :: a -> FilePath -> IO ()

vRemoveDirectory :: a -> FilePath -> IO ()

vRenameDirectory :: a -> FilePath -> FilePath -> IO ()

vRemoveFile :: a -> FilePath -> IO ()

vRenameFile :: a -> FilePath -> FilePath -> IO ()

vGetFileStatus :: a -> FilePath -> IO HVFSStatEncap

vGetSymbolicLinkStatus :: a -> FilePath -> IO HVFSStatEncap

vGetModificationTime :: a -> FilePath -> IO ClockTime

vRaiseError :: a -> IOErrorType -> String -> Maybe FilePath -> IO c

Raise an error relating to actions on this class.

vCreateSymbolicLink :: a -> FilePath -> FilePath -> IO ()

vReadSymbolicLink :: a -> FilePath -> IO FilePath

vCreateLink :: a -> FilePath -> FilePath -> IO ()

Instances

HVFS SystemFS |
HVFS MemoryVFS |
HVFS a => HVFS (HVFSChroot a) |
HVFS a => HVFS (HVFSReadOnly a) |

class Show a => HVFSStat a where

Evaluating types of files and information about them.

This corresponds to the System.Posix.Types.FileStatus type, and indeed, that is one instance of this class.

Inplementators must, at minimum, implement `vIsDirectory` and `vIsRegularFile`.

Default implementations of everything else are provided, returning reasonable values.

A default implementation of this is not currently present on Windows.

Methods

vDeviceID :: a -> DeviceID

vFileID :: a -> FileID

vFileMode :: a -> FileMode

Refers to file permissions, NOT the st_mode field from stat(2)

vLinkCount :: a -> LinkCount

vFileOwner :: a -> UserID

vFileGroup :: a -> GroupID

vSpecialDeviceID :: a -> DeviceID

vFileSize :: a -> FileOffset

vAccessTime :: a -> EpochTime

vModificationTime :: a -> EpochTime

vStatusChangeTime :: a -> EpochTime

vIsBlockDevice :: a -> Bool

vIsCharacterDevice :: a -> Bool

vIsNamedPipe :: a -> Bool

vIsRegularFile :: a -> Bool

vIsDirectory :: a -> Bool

vIsSymbolicLink :: a -> Bool

vIsSocket :: a -> Bool

Instances

HVFSStat FileStatus |
HVFSStat SimpleStat |

class HVFS a => HVFSOpenable a where

Types that can open a HVIO object should be instances of this class. You need only implement `vOpen`.

Methods

vOpen :: a -> FilePath -> IOMode -> IO HVFSOpenEncap

vReadFile :: a -> FilePath -> IO String

vWriteFile :: a -> FilePath -> String -> IO ()

vOpenBinaryFile :: a -> FilePath -> IOMode -> IO HVFSOpenEncap

Instances

HVFSOpenable SystemFS |
HVFSOpenable MemoryVFS |
HVFSOpenable a => HVFSOpenable (HVFSChroot a) |
HVFSOpenable a => HVFSOpenable (HVFSReadOnly a) |

data HVFSOpenEncap

Similar to `HVFSStatEncap`, but for `vOpen` result.

Constructors

forall a . HVIO a => HVFSOpenEncap a |

data HVFSStatEncap

Encapsulate a `HVFSStat` result. This is required due to Haskell typing restrictions. You can get at it with:

     case encap of
        HVFSStatEncap x -> -- now use x

Constructors

forall a . HVFSStat a => HVFSStatEncap a |

withStat :: forall b. HVFSStatEncap -> (forall a. HVFSStat a => a -> b) -> b

Convenience function for working with stat -- takes a stat result and a function that uses it, and returns the result.

Here is an example from the HVFS source:

        vGetModificationTime fs fp =
           do s <- vGetFileStatus fs fp
              return $ epochToClockTime (withStat s vModificationTime)

See `epochToClockTime` for more information.

withOpen :: forall b. HVFSOpenEncap -> (forall a. HVIO a => a -> b) -> b

Similar to `withStat`, but for the `vOpen` result.

data SystemFS

Constructors

SystemFS |

Instances

Eq SystemFS |
Show SystemFS |
HVFSOpenable SystemFS |
HVFS SystemFS |

# Re-exported types from other modules

type FilePath = String

File and directory names are values of type `String`, whose precise meaning is operating system dependent. Files can be opened, yielding a handle which can then be used to operate on the contents of that file.

type DeviceID = CDev

type FileID = CIno

type FileMode = CMode

type LinkCount = CNlink

type UserID = CUid

type GroupID = CGid

type FileOffset = COff

type EpochTime = CTime

data IOMode

See `System.IO.openFile`

Instances

Enum IOMode |
Eq IOMode |
Ord IOMode |
Read IOMode |
Show IOMode |
Ix IOMode |