57 lines
1.5 KiB
Nim
57 lines
1.5 KiB
Nim
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proc alloca(n: int): pointer {.importc, header: "<alloca.h>".}
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type
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StackArray*[T] = ptr object
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bufferLen: int
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buffer: UncheckedArray[T]
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template `[]`*(a: StackArray, i: int): auto =
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if i < 0 or i >= a.len: raise newException(RangeError, "index out of range")
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a.buffer[i]
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proc `[]=`*(a: StackArray, i: int, val: a.T) =
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if i < 0 or i >= a.len: raise newException(RangeError, "index out of range")
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a.buffer[i] = val
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proc len*(a: StackArray): int {.inline.} =
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a.bufferLen
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template high*(a: StackArray): int =
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a.bufferLen - 1
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template low*(a: StackArray): int =
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0
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iterator items*(a: StackArray): a.T =
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for i in 0 .. a.high:
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yield a.buffer[i]
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iterator mitems*(a: var StackArray): var a.T =
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for i in 0 .. a.high:
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yield a.buffer[i]
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iterator pairs*(a: StackArray): a.T =
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for i in 0 .. a.high:
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yield (i, a.buffer[i])
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iterator mpairs*(a: var StackArray): (int, var a.T) =
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for i in 0 .. a.high:
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yield (i, a.buffer[i])
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template allocStackArray*(T: typedesc, size: int): auto =
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if size < 0: raise newException(RangeError, "allocation with a negative size")
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# XXX: is it possible to perform a stack size check before
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# calling `alloca`? Nim has a stackBottom pointer in the
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# system module.
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var
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bufferSize = size * sizeof(T)
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totalSize = sizeof(int) + bufferSize
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arr = cast[StackArray[T]](alloca(totalSize))
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zeroMem(addr arr.buffer[0], bufferSize)
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arr.bufferLen = size
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arr
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template toOpenArray*(a: StackArray): auto =
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toOpenArray(a.buffer, 0, a.high)
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