tar-0.5.0.3: Reading, writing and manipulating ".tar" archive files.

Copyright | (c) 2007 Bjorn Bringert, 2008 Andrea Vezzosi, 2008-2009 Duncan Coutts
License | BSD3
Maintainer | duncan@community.haskell.org
Portability | portable
Safe Haskell | None
Language | Haskell98

Codec.Archive.Tar.Entry

Contents

- Tar entry and associated types
- Constructing simple entry values
- Standard file permissions
- Constructing entries from disk files
- TarPath type
- LinkTarget type

Description

Types and functions to manipulate tar entries.

While the Codec.Archive.Tar module provides only the simple high level API, this module provides full access to the details of tar entries. This lets you inspect all the meta-data, construct entries and handle error cases more precisely.

This module uses common names and so is designed to be imported qualified:

    import qualified Codec.Archive.Tar       as Tar
    import qualified Codec.Archive.Tar.Entry as Tar

Synopsis

- data Entry = Entry {
  - entryTarPath :: !TarPath
  - entryContent :: !EntryContent
  - entryPermissions :: !Permissions
  - entryOwnership :: !Ownership
  - entryTime :: !EpochTime
  - entryFormat :: !Format
  }
- entryPath :: Entry -> FilePath
- data EntryContent
  - = NormalFile ByteString !FileSize
  - | Directory
  - | SymbolicLink !LinkTarget
  - | HardLink !LinkTarget
  - | CharacterDevice !DevMajor !DevMinor
  - | BlockDevice !DevMajor !DevMinor
  - | NamedPipe
  - | OtherEntryType !TypeCode ByteString !FileSize
- data Ownership = Ownership {
  - ownerName :: String
  - groupName :: String
  - ownerId :: !Int
  - groupId :: !Int
  }
- type FileSize = Int64
- type Permissions = FileMode
- type EpochTime = Int64
- type DevMajor = Int
- type DevMinor = Int
- type TypeCode = Char
- data Format
  - = V7Format
  - | UstarFormat
  - | GnuFormat
- simpleEntry :: TarPath -> EntryContent -> Entry
- fileEntry :: TarPath -> ByteString -> Entry
- directoryEntry :: TarPath -> Entry
- ordinaryFilePermissions :: Permissions
- executableFilePermissions :: Permissions
- directoryPermissions :: Permissions
- packFileEntry :: FilePath -> TarPath -> IO Entry
- packDirectoryEntry :: FilePath -> TarPath -> IO Entry
- getDirectoryContentsRecursive :: FilePath -> IO [FilePath]
- data TarPath
- toTarPath :: Bool -> FilePath -> Either String TarPath
- fromTarPath :: TarPath -> FilePath
- fromTarPathToPosixPath :: TarPath -> FilePath
- fromTarPathToWindowsPath :: TarPath -> FilePath
- data LinkTarget
- toLinkTarget :: FilePath -> Maybe LinkTarget
- fromLinkTarget :: LinkTarget -> FilePath
- fromLinkTargetToPosixPath :: LinkTarget -> FilePath
- fromLinkTargetToWindowsPath :: LinkTarget -> FilePath

# Tar entry and associated types

data Entry

Tar archive entry.

Constructors

Entry |
Fields entryTarPath :: !TarPath The path of the file or directory within the archive. This is in a tar-specific form. Use `entryPath` to get a native `FilePath`. entryContent :: !EntryContent The real content of the entry. For `NormalFile` this includes the file data. An entry usually contains a `NormalFile` or a `Directory`. entryPermissions :: !Permissions File permissions (Unix style file mode). entryOwnership :: !Ownership The user and group to which this file belongs. entryTime :: !EpochTime The time the file was last modified. entryFormat :: !Format The tar format the archive is using.

Instances

Eq Entry |
Show Entry |
NFData Entry |

entryPath :: Entry -> FilePath

Native `FilePath` of the file or directory within the archive.

data EntryContent

The content of a tar archive entry, which depends on the type of entry.

Portable archives should contain only `NormalFile` and `Directory`.

Constructors

NormalFile ByteString !FileSize |
Directory |
SymbolicLink !LinkTarget |
HardLink !LinkTarget |
CharacterDevice !DevMajor !DevMinor |
BlockDevice !DevMajor !DevMinor |
NamedPipe |
OtherEntryType !TypeCode ByteString !FileSize |

Instances

Eq EntryContent |
Ord EntryContent |
Show EntryContent |
NFData EntryContent |

data Ownership

Constructors

Ownership |
Fields ownerName :: String The owner user name. Should be set to `""` if unknown. groupName :: String The owner group name. Should be set to `""` if unknown. ownerId :: !Int Numeric owner user id. Should be set to `0` if unknown. groupId :: !Int Numeric owner group id. Should be set to `0` if unknown.

Instances

Eq Ownership |
Ord Ownership |
Show Ownership |
NFData Ownership |

type FileSize = Int64

type Permissions = FileMode

type EpochTime = Int64

The number of seconds since the UNIX epoch

type DevMajor = Int

type DevMinor = Int

type TypeCode = Char

data Format

There have been a number of extensions to the tar file format over the years. They all share the basic entry fields and put more meta-data in different extended headers.

Constructors

V7Format | This is the classic Unix V7 tar format. It does not support owner and group names, just numeric Ids. It also does not support device numbers.
UstarFormat | The "USTAR" format is an extension of the classic V7 format. It was later standardised by POSIX. It has some restrictions but is the most portable format.
GnuFormat | The GNU tar implementation also extends the classic V7 format, though in a slightly different way from the USTAR format. In general for new archives the standard USTAR/POSIX should be used.

Instances

Eq Format |
Ord Format |
Show Format |

# Constructing simple entry values

simpleEntry :: TarPath -> EntryContent -> Entry

An `Entry` with all default values except for the file name and type. It uses the portable USTAR/POSIX format (see `UstarHeader`).

You can use this as a basis and override specific fields, eg:

    (emptyEntry name HardLink) { linkTarget = target }

fileEntry :: TarPath -> ByteString -> Entry

A tar `Entry` for a file.

Entry fields such as file permissions and ownership have default values.

You can use this as a basis and override specific fields. For example if you need an executable file you could use:

    (fileEntry name content) { fileMode = executableFileMode }

directoryEntry :: TarPath -> Entry

A tar `Entry` for a directory.

Entry fields such as file permissions and ownership have default values.

# Standard file permissions

For maximum portability when constructing archives use only these file permissions.

ordinaryFilePermissions :: Permissions

`rw-r--r--` for normal files

executableFilePermissions :: Permissions

`rwxr-xr-x` for executable files

directoryPermissions :: Permissions

`rwxr-xr-x` for directories

# Constructing entries from disk files

packFileEntry

Arguments

:: FilePath | Full path to find the file on the local disk
-> TarPath | Path to use for the tar Entry in the archive
-> IO Entry |

Construct a tar `Entry` based on a local file.

This sets the entry size, the data contained in the file and the file's modification time. If the file is executable then that information is also preserved. File ownership and detailed permissions are not preserved.

- The file contents is read lazily.

packDirectoryEntry

Arguments

:: FilePath | Full path to find the file on the local disk
-> TarPath | Path to use for the tar Entry in the archive
-> IO Entry |

Construct a tar `Entry` based on a local directory (but not its contents).

The only attribute of the directory that is used is its modification time. Directory ownership and detailed permissions are not preserved.

getDirectoryContentsRecursive :: FilePath -> IO [FilePath]

This is a utility function, much like `getDirectoryContents`. The difference is that it includes the contents of subdirectories.

The paths returned are all relative to the top directory. Directory paths are distinguishable by having a trailing path separator (see `hasTrailingPathSeparator`).

All directories are listed before the files that they contain. Amongst the contents of a directory, subdirectories are listed after normal files. The overall result is that files within a directory will be together in a single contiguous group. This tends to improve file layout and IO performance when creating or extracting tar archives.

- This function returns results lazily. Subdirectories are not scanned until the files entries in the parent directory have been consumed.

# TarPath type

data TarPath

The classic tar format allowed just 100 characters for the file name. The USTAR format extended this with an extra 155 characters, however it uses a complex method of splitting the name between the two sections.

Instead of just putting any overflow into the extended area, it uses the extended area as a prefix. The aggravating insane bit however is that the prefix (if any) must only contain a directory prefix. That is the split between the two areas must be on a directory separator boundary. So there is no simple calculation to work out if a file name is too long. Instead we have to try to find a valid split that makes the name fit in the two areas.

The rationale presumably was to make it a bit more compatible with old tar programs that only understand the classic format. A classic tar would be able to extract the file name and possibly some dir prefix, but not the full dir prefix. So the files would end up in the wrong place, but that's probably better than ending up with the wrong names too.

So it's understandable but rather annoying.

- Tar paths use Posix format (ie `'/'` directory separators), irrespective of the local path conventions.
- The directory separator between the prefix and name is not stored.

Instances

Eq TarPath |
Ord TarPath |
Show TarPath |
NFData TarPath |

toTarPath

Arguments

:: Bool | Is the path for a directory? This is needed because for directories a `TarPath` must always use a trailing `/`.
-> FilePath |
-> Either String TarPath |

Convert a native `FilePath` to a `TarPath`.

The conversion may fail if the `FilePath` is too long. See `TarPath` for a description of the problem with splitting long `FilePath`s.

fromTarPath :: TarPath -> FilePath

Convert a `TarPath` to a native `FilePath`.

The native `FilePath` will use the native directory separator but it is not otherwise checked for validity or sanity. In particular:

- The tar path may be invalid as a native path, eg the file name `"nul"` is not valid on Windows.
- The tar path may be an absolute path or may contain `".."` components. For security reasons this should not usually be allowed, but it is your responsibility to check for these conditions (eg using `checkSecurity`).

fromTarPathToPosixPath :: TarPath -> FilePath

Convert a `TarPath` to a Unix/Posix `FilePath`.

The difference compared to `fromTarPath` is that it always returns a Unix style path irrespective of the current operating system.

This is useful to check how a `TarPath` would be interpreted on a specific operating system, eg to perform portability checks.

fromTarPathToWindowsPath :: TarPath -> FilePath

Convert a `TarPath` to a Windows `FilePath`.

The only difference compared to `fromTarPath` is that it always returns a Windows style path irrespective of the current operating system.

This is useful to check how a `TarPath` would be interpreted on a specific operating system, eg to perform portability checks.

# LinkTarget type

data LinkTarget

The tar format allows just 100 ASCII characters for the `SymbolicLink` and `HardLink` entry types.

Instances

Eq LinkTarget |
Ord LinkTarget |
Show LinkTarget |
NFData LinkTarget |

toLinkTarget :: FilePath -> Maybe LinkTarget

Convert a native `FilePath` to a tar `LinkTarget`. This may fail if the string is longer than 100 characters or if it contains non-portable characters.

fromLinkTarget :: LinkTarget -> FilePath

Convert a tar `LinkTarget` to a native `FilePath`.

fromLinkTargetToPosixPath :: LinkTarget -> FilePath

Convert a tar `LinkTarget` to a Unix/Posix `FilePath`.

fromLinkTargetToWindowsPath :: LinkTarget -> FilePath

Convert a tar `LinkTarget` to a Windows `FilePath`.