| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell2010 |
Darcs.Util.Tree.Monad
Description
A monad transformer for Tree mutation. The main idea is to simulate
IO-ish manipulation of real filesystem (that's the state part of the monad),
and to keep memory usage down by reasonably often dumping the intermediate
data to disk and forgetting it.
The implementation is configured by passing a procedure of type DumpItem
to runTreeMonad.
This module provides the pre-configured virtualTreeIO that never
writes any changes, but may trigger filesystem reads as appropriate.
Synopsis
- type TreeMonad m = RWST (DumpItem m) () (TreeState m) m
- data TreeState m
- runTreeMonad :: Monad m => TreeMonad m a -> Tree m -> DumpItem m -> m (a, Tree m)
- virtualTreeMonad :: Monad m => TreeMonad m a -> Tree m -> m (a, Tree m)
- type TreeIO = TreeMonad IO
- virtualTreeIO :: TreeIO a -> Tree IO -> IO (a, Tree IO)
- readFile :: MonadThrow m => AnchoredPath -> TreeMonad m ByteString
- exists :: MonadThrow m => AnchoredPath -> TreeMonad m Bool
- directoryExists :: Monad m => AnchoredPath -> TreeMonad m Bool
- fileExists :: Monad m => AnchoredPath -> TreeMonad m Bool
- writeFile :: MonadThrow m => AnchoredPath -> ByteString -> TreeMonad m ()
- createDirectory :: Monad m => AnchoredPath -> TreeMonad m ()
- unlink :: Monad m => AnchoredPath -> TreeMonad m ()
- rename :: MonadThrow m => AnchoredPath -> AnchoredPath -> TreeMonad m ()
- copy :: MonadThrow m => AnchoredPath -> AnchoredPath -> TreeMonad m ()
- findM :: Monad m => Tree m -> AnchoredPath -> m (Maybe (TreeItem m))
- findFileM :: Monad m => Tree m -> AnchoredPath -> m (Maybe (Blob m))
- findTreeM :: Monad m => Tree m -> AnchoredPath -> m (Maybe (Tree m))
TreeMonad
type TreeMonad m = RWST (DumpItem m) () (TreeState m) m Source #
A monad transformer that adds state of type TreeState and an environment
of type DumpItem.
Instances
| MonadThrow m => ApplyMonad Tree (TreeMonad m) Source # | |
Defined in Darcs.Patch.ApplyMonad Methods readFilePS :: ObjectIdOf Tree -> TreeMonad m ByteString Source # | |
| MonadThrow m => ApplyMonadTree (TreeMonad m) Source # | |
Defined in Darcs.Patch.ApplyMonad Methods mDoesDirectoryExist :: AnchoredPath -> TreeMonad m Bool Source # mDoesFileExist :: AnchoredPath -> TreeMonad m Bool Source # mReadFilePS :: AnchoredPath -> TreeMonad m ByteString Source # mCreateDirectory :: AnchoredPath -> TreeMonad m () Source # mRemoveDirectory :: AnchoredPath -> TreeMonad m () Source # mCreateFile :: AnchoredPath -> TreeMonad m () Source # mRemoveFile :: AnchoredPath -> TreeMonad m () Source # mRename :: AnchoredPath -> AnchoredPath -> TreeMonad m () Source # mModifyFilePS :: AnchoredPath -> (ByteString -> TreeMonad m ByteString) -> TreeMonad m () Source # mChangePref :: String -> String -> String -> TreeMonad m () Source # | |
virtualTreeMonad :: Monad m => TreeMonad m a -> Tree m -> m (a, Tree m) Source #
Run a TreeMonad action without storing any changes. This is useful for
running monadic tree mutations for obtaining the resulting Tree (as opposed
to their effect of writing a modified tree to disk). The actions can do both
read and write -- reads are passed through to the actual filesystem, but the
writes are held in memory in the form of a modified Tree.
Specializing to IO
Read actions
readFile :: MonadThrow m => AnchoredPath -> TreeMonad m ByteString Source #
Grab content of a file in the current Tree at the given path.
exists :: MonadThrow m => AnchoredPath -> TreeMonad m Bool Source #
Check for existence of a node (file or directory, doesn't matter).
directoryExists :: Monad m => AnchoredPath -> TreeMonad m Bool Source #
Check for existence of a directory.
fileExists :: Monad m => AnchoredPath -> TreeMonad m Bool Source #
Check for existence of a file.
Write actions
writeFile :: MonadThrow m => AnchoredPath -> ByteString -> TreeMonad m () Source #
Change content of a file at a given path. The change will be eventually flushed to disk, but might be buffered for some time.
createDirectory :: Monad m => AnchoredPath -> TreeMonad m () Source #
Create a directory.
rename :: MonadThrow m => AnchoredPath -> AnchoredPath -> TreeMonad m () Source #
Rename the item at a path.
copy :: MonadThrow m => AnchoredPath -> AnchoredPath -> TreeMonad m () Source #
Copy an item from some path to another path. Doing this with a SubTree is weird... it means copy recursively, but with lazy copy-on-write semantics. What happens when we flush that? Seems to work, though, as it is used in Darcs.UI.Commands.Convert.Import