Storage.Hashed.Tree

Contents

Description

The abstract representation of a Tree and useful abstract utilities to handle those.

Synopsis

Documentation

Abstraction of a filesystem tree. Please note that the Tree returned by the respective read operations will have TreeStub items in it. To obtain a Tree without such stubs, call expand on it, eg.:

 tree <- readDarcsPristine "." >>= expand

When a Tree is expanded, it becomes "final". All stubs are forced and the Tree can be traversed purely. Access to actual file contents stays in IO though.

A Tree may have a Hash associated with it. A pair of Tree's is identical whenever their hashes are (the reverse need not hold, since not all Trees come equipped with a hash).

Instances

Monad m => FilterTree Tree m

data Blob m Source

Constructors

Blob !(m ByteString) !Hash

data TreeItem m Source

Constructors

File !(Blob m)
SubTree !(Tree m)
Stub !(m (Tree m)) !Hash

data ItemType Source

Constructors

BlobType
TreeType

Instances

Eq ItemType
Show ItemType

data Hash Source

Constructors

SHA256 !ByteString
SHA1 !ByteString
NoHash

Instances

Eq Hash
Ord Hash
Read Hash
Show Hash

makeTree :: Monad m => [(Name, TreeItem m)] -> Tree mSource

makeTreeWithHash :: Monad m => [(Name, TreeItem m)] -> Hash -> Tree mSource

emptyTree :: Monad m => Tree mSource

emptyBlob :: Monad m => Blob mSource

makeBlob :: Monad m => ByteString -> Blob mSource

makeBlobBS :: Monad m => ByteString -> Blob mSource

Unfolding stubbed (lazy) Trees.

By default, Tree obtained by a read function is stubbed: it will contain Stub items that need to be executed in order to access the respective subtrees. expand will produce an unstubbed Tree.

expandUpdate :: Monad m => (AnchoredPath -> Tree m -> m (Tree m)) -> Tree m -> m (Tree m)Source

expand :: Monad m => Tree m -> m (Tree m)Source

Expand a stubbed Tree into a one with no stubs in it. You might want to filter the tree before expanding to save IO. This is the basic implementation, which may be overriden by some Tree instances (this is especially true of the Index case).

expandPath :: Monad m => Tree m -> AnchoredPath -> m (Tree m)Source

Unfold a path in a (stubbed) Tree, such that the leaf node of the path is reachable without crossing any stubs.

Tree access and lookup.

items :: Tree m -> Map Name (TreeItem m)Source

list :: Tree m -> [(AnchoredPath, TreeItem m)]Source

List all contents of a Tree.

listImmediate :: Tree m -> [(Name, TreeItem m)]Source

treeHash :: Tree m -> Hash Source

Get hash of a Tree. This is guaranteed to uniquely identify the Tree (including any blob content), as far as cryptographic hashes are concerned. Sha256 is recommended.

lookup :: Tree m -> Name -> Maybe (TreeItem m)Source

Look up a Tree item (an immediate subtree or blob).

find :: Tree m -> AnchoredPath -> Maybe (TreeItem m)Source

Find a TreeItem by its path. Gives Nothing if the path is invalid.

findFile :: Tree m -> AnchoredPath -> Maybe (Blob m)Source

Find a Blob by its path. Gives Nothing if the path is invalid, or does not point to a Blob.

findTree :: Tree m -> AnchoredPath -> Maybe (Tree m)Source

Find a Tree by its path. Gives Nothing if the path is invalid, or does not point to a Tree.

itemHash :: TreeItem m -> Hash Source

Get a hash of a TreeItem. May be Nothing.

itemType :: TreeItem m -> ItemType Source

zipCommonFiles :: (AnchoredPath -> Blob m -> Blob m -> a) -> Tree m -> Tree m -> [a]Source

For every pair of corresponding blobs from the two supplied trees, evaluate the supplied function and accumulate the results in a list. Hint: to get IO actions through, just use sequence on the resulting list. NB. This won't expand any stubs.

zipFiles :: (AnchoredPath -> Maybe (Blob m) -> Maybe (Blob m) -> a) -> Tree m -> Tree m -> [a]Source

For each file in each of the two supplied trees, evaluate the supplied function (supplying the corresponding file from the other tree, or Nothing) and accumulate the results in a list. Hint: to get IO actions through, just use sequence on the resulting list. NB. This won't expand any stubs.

zipTrees :: (AnchoredPath -> Maybe (TreeItem m) -> Maybe (TreeItem m) -> a) -> Tree m -> Tree m -> [a]Source

diffTrees :: forall m. (Functor m, Monad m) => Tree m -> Tree m -> m (Tree m, Tree m)Source

Cautiously extracts differing subtrees from a pair of Trees. It will never do any unneccessary expanding. Tree hashes are used to cut the comparison as high up the Tree branches as possible. The result is a pair of trees that do not share any identical subtrees. They are derived from the first and second parameters respectively and they are always fully expanded. It might be advantageous to feed the result into zipFiles or zipTrees.

Files (Blobs).

readBlob :: Blob m -> m ByteString Source

Read a Blob into a Lazy ByteString. Might be backed by an mmap, use with care.

Filtering trees.

class Monad m => FilterTree a m whereSource

Methods

filter :: (AnchoredPath -> TreeItem m -> Bool) -> a m -> a mSource

Given pred tree, produce a Tree that only has items for which pred returns True. The tree might contain stubs. When expanded, these will be subject to filtering as well.

Instances

Monad m => FilterTree Tree m
FilterTree IndexM IO

restrict :: (FilterTree t m, Monad n) => Tree n -> t m -> t mSource

Given two Trees, a guide and a tree, produces a new Tree that is a identical to tree, but only has those items that are present in both tree and guide. The guide Tree may not contain any stubs.

Manipulating trees.

modifyTree :: Monad m => Tree m -> AnchoredPath -> Maybe (TreeItem m) -> Tree mSource

Modify a Tree (by replacing, or removing or adding items).

updateTree :: (Functor m, Monad m) => (TreeItem m -> m (TreeItem m)) -> Tree m -> m (Tree m)Source

Does not expand the tree.

updateSubtrees :: (Tree m -> Tree m) -> Tree m -> Tree mSource

overlay :: (Functor m, Monad m) => Tree m -> Tree m -> Tree mSource

Lay one tree over another. The resulting Tree will look like the base (1st parameter) Tree, although any items also present in the overlay Tree will be taken from the overlay. It is not allowed to overlay a different kind of an object, nor it is allowed for the overlay to add new objects to base. This means that the overlay Tree should be a subset of the base Tree (although any extraneous items will be ignored by the implementation).