367 lines
12 KiB
Standard ML
367 lines
12 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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| _ => false
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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 (cursorIdx, 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 cursorIdx,
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* then we want to return an empty tree,
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* splitting everything *)
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if cursorIdx < start then
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empty
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else if cursorIdx > Vector.sub (sizes, Vector.length sizes - 1) then
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(* if all items are before cursorIdx,
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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 (cursorIdx, 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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end
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