120 lines
3.9 KiB
Nim
120 lines
3.9 KiB
Nim
import ../pointerutils
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# configure stacks here
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import ../config
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#const boundsChecks = defined(debug)
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# boundsChecks default: false, true has a large performance impact, and emitting correct code is on the compiler's job
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# boundsChecking is only meant for debugging
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const growthFactor = 2
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# should be a natural number larger than 1
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type
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Stack*[T] = object
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top: ptr T
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start: ptr T
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cap*: int
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proc newStack*[T](startingCap: int): Stack[T] =
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result.start = cast[ptr T](alloc(startingCap * sizeof(T)))
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result.top = result.start.psub(sizeof(T))
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result.cap = startingCap
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proc free*[T](stack: var Stack[T]) =
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## dealloc's the stack object
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## if the stack contains pointers, those should be freed before destroying the stack
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stack.cap = 0
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stack.start.dealloc()
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stack.start = nil
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stack.top = nil
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proc grow[T](stack: var Stack[T], len: int) =
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## growth the stack's capacity and increments the top's index by one
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stack.cap *= growthFactor
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stack.start = cast[ptr T](realloc(stack.start, stack.cap * sizeof(T)))
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stack.top = stack.start.padd(len * sizeof(T))
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proc shrink[T](stack: var Stack[T]) =
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discard
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template high*[T](stack: Stack[T]): int =
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stack.top.pdiff(stack.start) div sizeof(T)
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template len*[T](stack: Stack[T]): int =
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stack.high() + 1
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proc push*[T](stack: var Stack[T], item: T) =
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let len = stack.len()
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if len == stack.cap:
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stack.grow(len)
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else:
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stack.top = stack.top.padd(sizeof(T))
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stack.top[]= item
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template add*[T](stack: var Stack[T], item: T) =
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stack.push(item)
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proc pop*[T](stack: var Stack[T]): T =
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when boundsChecks:
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if stack.top == nil or stack.top.pless(stack.start):
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raise newException(Defect, "Stacktop is nil or smaller than start.")
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result = stack.top[]
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stack.top = stack.top.psub(sizeof(T))
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proc peek*[T](stack: Stack[T]): var T =
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when boundsChecks:
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if stack.top == nil or stack.top.pless(stack.start):
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raise newException(Defect, "Stacktop is nil or smaller than start.")
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stack.top[]
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proc settip*[T](stack: var Stack[T], newtip: T) =
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when boundsChecks:
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if stack.top == nil or stack.top.pless(stack.start):
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raise newException(Defect, "Stacktop is nil or smaller than start")
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stack.top[]= newtip
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proc swap*[T](stack: var Stack[T]) =
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when boundsChecks:
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if stack.top == nil or stack.len() < 2:
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raise newException(Defect, "Stacktop is nil, or not high enough for swap.")
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let temp = stack.top[]
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var below = stack.top.psub(sizeof(T))
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stack.top[] = below[]
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below[] = temp
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proc deleteTopN*[T](stack: var Stack[T], n: Natural) =
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stack.top = stack.top.psub(sizeof(T) * n)
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when boundsChecks:
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if stack.top.pless(stack.start):
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raise newException(Defect, "Stacktop sunk below the start after a deleteTopN.")
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proc getIndex*[T](stack: Stack[T], index: int): var T =
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when boundsChecks:
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if index < 0 or index >= stack.len():
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raise newException(Defect, &"Attempt to getIndex with an index {index} which is out of bounds (len: {stack.len()}).")
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stack.start.padd(index * sizeof(T))[]
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proc getIndexNeg*[T](stack: Stack[T], index: int): var T =
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when boundsChecks:
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if index < 0 or index >= stack.len():
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raise newException(Defect, "Attempt to getIndexNeg with an index out of bounds.")
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stack.top.psub(index * sizeof(T))[]
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template `[]`*[T](stack: Stack[T], index: int): var T =
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stack.getIndex(index)
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proc setIndex*[T](stack: var Stack[T], index: int, item: T) =
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when boundsChecks:
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if index < 0 or index >= stack.len():
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raise newException(Defect, "Attempt to getIndex with an index out of bounds.")
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stack.start.padd(index * sizeof(T))[]= item
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proc setIndexNeg*[T](stack: Stack[T], index: int, item: T) =
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when boundsChecks:
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if index < 0 or index >= stack.len():
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raise newException(Defect, "Attempt to setIndexNeg with an index out of bounds.")
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stack.top.psub(index * sizeof(T))[] = item
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template `[]=`*[T](stack: var Stack[T], index: int, item: T) =
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stack.setIndex(index, item)
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