560 lines
18 KiB
Standard ML
560 lines
18 KiB
Standard ML
structure PersistentVector =
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struct
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(* Clojure-style persistent vector, for building search list.
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* There is an "int table" too, which stores the last index
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* at the node with the same index.
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* We can use the size table for binary search.
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* *)
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datatype t =
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BRANCH of t vector * int vector
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| LEAF of {start: int, finish: int} vector * int vector
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val maxSize = 32
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val halfSize = 16
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fun isEmpty t =
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case t of
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LEAF (_, sizes) => Vector.length sizes = 0
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| BRANCH (_, sizes) => Vector.length sizes = 0
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val empty = LEAF (#[], #[])
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datatype append_result = APPEND of t | UPDATE of t
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fun isInRange (checkIdx, t) =
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case t of
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BRANCH (nodes, sizes) =>
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let
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val searchIdx = BinSearch.equalOrMore (checkIdx, sizes)
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in
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if searchIdx = ~1 then
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false
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else if searchIdx = 0 then
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isInRange (checkIdx, Vector.sub (nodes, searchIdx))
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else
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let
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val nextCheckIdx = checkIdx - Vector.sub (sizes, searchIdx - 1)
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in
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isInRange (nextCheckIdx, Vector.sub (nodes, searchIdx))
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end
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end
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| LEAF (values, sizes) =>
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let
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val searchIdx = BinSearch.equalOrMore (checkIdx, sizes)
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in
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if searchIdx = ~1 then
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false
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else
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let
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val {start, finish} = Vector.sub (values, searchIdx)
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in
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checkIdx >= start andalso checkIdx <= finish
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end
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end
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fun getFinishIdx t =
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case t of
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BRANCH (_, sizes) => Vector.sub (sizes, Vector.length sizes - 1)
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| LEAF (_, sizes) => Vector.sub (sizes, Vector.length sizes - 1)
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fun helpAppend (start, finish, tree) =
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case tree of
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BRANCH (nodes, sizes) =>
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let
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val lastNode = Vector.sub (nodes, Vector.length nodes - 1)
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val prevSize =
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if Vector.length sizes > 1 then
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Vector.sub (sizes, Vector.length sizes - 2)
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else
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0
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in
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case helpAppend (start - prevSize, finish - prevSize, lastNode) of
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UPDATE newLast =>
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let
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val lastPos = Vector.length nodes - 1
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val newNode = Vector.update (nodes, lastPos, newLast)
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val newSizes = Vector.update (sizes, lastPos, finish)
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val newNode = BRANCH (newNode, newSizes)
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in
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UPDATE newNode
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end
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| APPEND newVec =>
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if Vector.length nodes = maxSize then
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let
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(* adjust "finish" so that it does not consider
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* offset for "lower" vector *)
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val finish = finish - Vector.sub (sizes, Vector.length sizes - 1)
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val newNode = BRANCH (#[newVec], #[finish])
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in
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APPEND newNode
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end
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else
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let
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val newNodes = Vector.concat [nodes, #[newVec]]
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val newSizes = Vector.concat [sizes, #[finish]]
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val newNodes = BRANCH (newNodes, newSizes)
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in
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UPDATE newNodes
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end
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end
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| LEAF (values, sizes) =>
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if Vector.length values + 1 > maxSize then
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(* when we split a leaf into two vectors,
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* we want to adjust the start and finish parameters
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* so that they don't contain the offset relevant to the
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* "lower" vector, which was split from *)
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let
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val prevFinish = Vector.sub (sizes, Vector.length sizes - 1)
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val start = start - prevFinish
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val finish = finish - prevFinish
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val newNode = LEAF (#[{start = start, finish = finish}], #[finish])
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in
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APPEND newNode
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end
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else
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let
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val newNode = Vector.concat
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[values, #[{start = start, finish = finish}]]
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val newSizes = Vector.concat [sizes, #[finish]]
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val newNode = LEAF (newNode, newSizes)
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in
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UPDATE newNode
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end
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fun append (start, finish, tree) =
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case helpAppend (start, finish, tree) of
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UPDATE t => t
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| APPEND newNode =>
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let
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val maxSize = getFinishIdx tree
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in
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BRANCH (#[tree, newNode], #[maxSize, finish])
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end
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fun getStart tree =
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case tree of
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LEAF (values, _) => Vector.sub (values, 0)
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| BRANCH (nodes, _) => getStart (Vector.sub (nodes, 0))
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fun helpNextMatch (cursorIdx, tree, absOffset) =
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case tree of
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LEAF (values, sizes) =>
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let
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val idx = BinSearch.equalOrMore (cursorIdx, sizes)
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in
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if idx = ~1 then {start = ~1, finish = ~1}
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else
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let
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val {start, finish} = Vector.sub (values, idx)
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in
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{start = start + absOffset, finish = finish + absOffset}
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end
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end
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| BRANCH (nodes, sizes) =>
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let
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val idx = BinSearch.equalOrMore (cursorIdx, sizes)
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in
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if idx = ~1 then
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{start = ~1, finish = ~1}
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else if idx = 0 then
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helpNextMatch (cursorIdx, Vector.sub (nodes, idx), absOffset)
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else
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let
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val prevSize = Vector.sub (sizes, idx - 1)
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val cursorIdx = cursorIdx - prevSize
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val absOffset = absOffset + prevSize
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in
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helpNextMatch (cursorIdx, Vector.sub (nodes, idx), absOffset)
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end
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end
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fun loopNextMatch (prevStart, prevFinish, tree, count) =
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if count = 0 then
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prevStart
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else
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let
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val {start, finish} = helpNextMatch (prevFinish + 1, tree, 0)
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in
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if start = ~1 then
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let val {start, finish} = getStart tree
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in loopNextMatch (start, finish, tree, count - 1)
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end
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else
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loopNextMatch (start, finish, tree, count - 1)
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end
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fun nextMatch (cursorIdx, tree, count) =
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if isEmpty tree then
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~1
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else
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let
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val {start, finish} = helpNextMatch (cursorIdx, tree, 0)
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in
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if start = ~1 then
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let val {start, finish} = getStart tree
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in loopNextMatch (start, finish, tree, count - 1)
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end
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else if cursorIdx >= start andalso cursorIdx <= finish then
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loopNextMatch (start, finish, tree, count)
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else
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loopNextMatch (start, finish, tree, count - 1)
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end
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fun getLast (tree, absOffset) =
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case tree of
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LEAF (values, _) =>
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let
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val {start, finish} = Vector.sub (values, Vector.length values - 1)
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in
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{start = start + absOffset, finish = finish + absOffset}
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end
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| BRANCH (nodes, sizes) =>
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let
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val prevSize =
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if Vector.length sizes - 2 >= 0 then
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Vector.sub (sizes, Vector.length sizes - 2)
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else
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0
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val absOffset = absOffset + prevSize
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in
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getLast (Vector.sub (nodes, Vector.length nodes - 1), absOffset)
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end
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(* slightly tricky.
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* The `sizes` vector contains the last/finish position of the item
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* at the corresponding index in the `nodes` or `values` vector
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* However, what we when searching for the previous match
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* is different: we want the node that has a start prior
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* to the cursorIdx.
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* This information cannot be retrieved with 100% accuracy
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* using the `sizes` vector.
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* To get what we want, we recurse downwards using the `sizes` vector.
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* If we found the node we want, we return it.
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* Otherwise, we return a state meaning "no node at this position"
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* and we use the call stack to descend down the node at the previous index.
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* There might not be a previous index because the current index is 0.
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* In this case, either the call stack will handle it,
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* or the caller to `helpPrevMatch` will. *)
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fun helpPrevMatch (cursorIdx, tree, absOffset) =
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case tree of
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LEAF (values, sizes) =>
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let
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val idx = BinSearch.equalOrMore (cursorIdx, sizes)
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in
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if idx < 0 then
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{start = ~1, finish = ~1}
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else if idx = 0 then
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let
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val {start, finish} = Vector.sub (values, 0)
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in
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if start < cursorIdx then
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{start = start + absOffset, finish = finish + absOffset}
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else
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{start = ~1, finish = ~1}
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end
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else
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let
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val {start, finish} = Vector.sub (values, idx)
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in
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if cursorIdx > start then
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{start = start + absOffset, finish = finish + absOffset}
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else
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let
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val {start, finish} = Vector.sub (values, idx - 1)
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in
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{start = start + absOffset, finish = finish + absOffset}
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end
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end
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end
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| BRANCH (nodes, sizes) =>
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let
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val idx = BinSearch.equalOrMore (cursorIdx, sizes)
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in
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if idx < 0 then
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{start = ~1, finish = ~1}
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else if idx = 0 then
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helpPrevMatch (cursorIdx, Vector.sub (nodes, idx), absOffset)
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else
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let
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val prevSize = Vector.sub (sizes, idx - 1)
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val node = Vector.sub (nodes, idx)
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val result =
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helpPrevMatch (cursorIdx - prevSize, node, absOffset + prevSize)
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in
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if #start result = ~1 then
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let
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val prevSize =
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if idx - 2 >= 0 then
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Vector.sub (sizes, idx - 2)
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else
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0
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val absOffset = absOffset + prevSize
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in
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getLast (Vector.sub (nodes, idx - 1), absOffset)
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end
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else result
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end
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end
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fun loopPrevMatch (prevStart, prevFinish, tree, count) =
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if count = 0 then
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prevStart
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else
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let
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val {start, finish} = helpPrevMatch (prevFinish - 1, tree, 0)
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in
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if start = ~1 then
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let val {start, finish} = getLast (tree, 0)
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in loopPrevMatch (start, finish, tree, count - 1)
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end
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else
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loopPrevMatch (start, finish, tree, count - 1)
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end
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fun prevMatch (cursorIdx, tree, count) =
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if isEmpty tree then
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~1
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else
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let
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val {start, finish} = helpPrevMatch (cursorIdx, tree, 0)
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in
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if start = ~1 then
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let val {start, finish} = getLast (tree, 0)
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in loopPrevMatch (start, finish, tree, count - 1)
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end
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else if cursorIdx >= start andalso cursorIdx <= finish then
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loopPrevMatch (start, finish, tree, count)
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else
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loopPrevMatch (start, finish, tree, count - 1)
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end
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fun splitLeft (splitIdx, tree) =
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case tree of
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LEAF (items, sizes) =>
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if Vector.length items = 0 then
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(* if tree is empty, then just return tree *)
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tree
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else
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let
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val {start, ...} = Vector.sub (items, 0)
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in
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(* if all items are after splitIdx,
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* then we want to return an empty tree,
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* splitting everything *)
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if splitIdx < start then
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empty
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else if splitIdx > Vector.sub (sizes, Vector.length sizes - 1) then
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(* if all items are before splitIdx,
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* then we want to return the same tree,
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* splitting nothing *)
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tree
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else
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(* we want to split from somewhere in middle, keeping left *)
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let
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val idx = BinSearch.equalOrMore (splitIdx, sizes)
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val idx = SOME idx
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val items = VectorSlice.slice (items, 0, idx)
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val items = VectorSlice.vector items
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val sizes = VectorSlice.slice (sizes, 0, idx)
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val sizes = VectorSlice.vector sizes
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in
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LEAF (items, sizes)
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end
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end
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| BRANCH (nodes, sizes) =>
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if Vector.length nodes = 0 then
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tree
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else
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if splitIdx < Vector.sub (sizes, 0) then
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(* we want to split first node from rest *)
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splitLeft (splitIdx, Vector.sub (nodes, 0))
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else if splitIdx > Vector.sub (sizes, Vector.length sizes - 1) then
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(* split point is after this subtree,
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* so return this subtree unchanged *)
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tree
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else
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(* we want to split from somewhere in middle *)
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let
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val idx = BinSearch.equalOrMore (splitIdx, sizes)
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val prevSize =
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if idx = 0 then
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0
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else
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Vector.sub (sizes, idx - 1)
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val child =
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splitLeft (splitIdx - prevSize, Vector.sub (nodes, idx))
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val sizes = VectorSlice.slice (sizes, 0, SOME idx)
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val nodes = VectorSlice.slice (nodes, 0, SOME idx)
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in
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if isEmpty child then
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let
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val sizes = VectorSlice.vector sizes
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val nodes = VectorSlice.vector nodes
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in
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BRANCH (nodes, sizes)
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end
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else
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let
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val childSize = VectorSlice.full #[getFinishIdx child + prevSize]
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val sizes =VectorSlice.concat [sizes, childSize]
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val childNode = VectorSlice.full #[child]
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val nodes = VectorSlice.concat [nodes, childNode]
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in
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BRANCH (nodes, sizes)
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end
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end
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(* When we split in this function,
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* we always want to update the sizes vector
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* so that the relative rope-like metadata is valid *)
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fun splitRight (splitIdx, tree) =
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case tree of
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BRANCH (nodes, sizes) =>
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if splitIdx > Vector.sub (sizes, Vector.length sizes - 1) then
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(* splitIdx is greater than largest element,
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* so we want to remove everything;
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* or, in other words, we want to return an empty vec *)
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empty
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else
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let
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val idx = BinSearch.equalOrMore (splitIdx, sizes)
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val prevSize =
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if idx = 0 then
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0
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else
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Vector.sub (sizes, idx - 1)
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val oldChildSize = Vector.sub (sizes, idx)
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val child = splitRight (splitIdx - prevSize, Vector.sub (nodes, idx))
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val len = Vector.length nodes - (idx + 1)
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val sizesSlice = VectorSlice.slice (sizes, idx + 1, SOME len)
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val nodesSlice = VectorSlice.slice (nodes, idx + 1, SOME len)
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in
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if isEmpty child then
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if VectorSlice.length sizesSlice = 0 then
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(* if we descended down last node and last node became empty,
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* then return empty vector *)
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empty
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else
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let
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val nodes = VectorSlice.vector nodesSlice
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val sizes = VectorSlice.map (fn el => el - prevSize) sizesSlice
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in
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BRANCH (nodes, sizes)
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end
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else
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let
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val newChildSize = getFinishIdx child
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val difference = oldChildSize - newChildSize
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val sizes = Vector.tabulate (VectorSlice.length sizesSlice + 1,
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fn i =>
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if i = 0 then
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newChildSize
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else
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VectorSlice.sub (sizesSlice, i - 1) - difference
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)
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val child = VectorSlice.full #[child]
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val nodes = VectorSlice.concat [child, nodesSlice]
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in
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BRANCH (nodes, sizes)
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end
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end
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| LEAF (items, sizes) =>
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if Vector.length items = 0 then
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tree
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else
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if splitIdx > Vector.sub (sizes, Vector.length sizes - 1) then
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empty
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else if splitIdx < Vector.sub (sizes, 0) then
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tree
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else
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let
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val idx = BinSearch.equalOrMore (splitIdx, sizes)
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val {start, finish} = Vector.sub (items, idx)
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val idx =
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if splitIdx >= start then
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idx + 1
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else
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idx
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in
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if idx >= Vector.length items then
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empty
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else
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let
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val len = Vector.length items - idx
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val itemsSlice = VectorSlice.slice (items, idx, SOME len)
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val items = VectorSlice.map
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(fn {start, finish} =>
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{start = start - splitIdx, finish = finish - splitIdx}
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)
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itemsSlice
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val sizes = Vector.map #finish items
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in
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LEAF (items, sizes)
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end
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end
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|
|
(* functions only for testing *)
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fun fromListLoop (lst, acc) =
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case lst of
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{start, finish} :: tl =>
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let
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val acc = append (start, finish, acc)
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in
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fromListLoop (tl, acc)
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end
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| [] => acc
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fun fromList coords = fromListLoop (coords, empty)
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fun toListLoop (tree, acc) =
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case tree of
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BRANCH (nodes, _) =>
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let
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fun branchLoop (pos, acc) =
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if pos = Vector.length nodes then
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acc
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else
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let
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val acc = toListLoop (Vector.sub (nodes, pos), acc)
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in
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branchLoop (pos + 1, acc)
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end
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in
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branchLoop (0, acc)
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end
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| LEAF (items, _) =>
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let
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fun itemLoop (pos, acc, offset) =
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if pos = Vector.length items then
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acc
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else
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let
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val {start, finish} = Vector.sub (items, pos)
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val item = {start = start + offset, finish = finish + offset}
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in
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itemLoop (pos + 1, item :: acc, offset)
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end
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val offset =
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case acc of
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{finish, ...} :: _ => finish
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| [] => 0
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in
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itemLoop (0, acc, offset)
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end
|
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fun toList tree =
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let
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val result = toListLoop (tree, [])
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in
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List.rev result
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end
|
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end
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