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Merge pull request #21 from status-im/stackarrays

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Fixed potential memory corruption, added allocStackArrayNoInit
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Yuriy Glukhov 2018-07-20 17:09:03 +03:00 committed by GitHub
commit 179c03822a
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1 changed files with 20 additions and 14 deletions
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34
ranges/stackarrays.nim
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@ -38,9 +38,9 @@
##
type
StackArray*[T] = ptr object
StackArray*[T] = object
bufferLen: int32
buffer: UncheckedArray[T]
buffer: ptr UncheckedArray[T]
when defined(windows):
proc alloca(n: int): pointer {.importc, header: "<malloc.h>".}
@ -66,7 +66,7 @@ template `[]`*(a: StackArray, i: int): auto =
if i < 0 or i >= a.len: raiseOutOfRange()
a.buffer[i]
proc `[]=`*(a: StackArray, i: int, val: a.T) =
proc `[]=`*(a: StackArray, i: int, val: a.T) {.inline.} =
if i < 0 or i >= a.len: raiseOutOfRange()
a.buffer[i] = val
@ -94,28 +94,34 @@ iterator mpairs*(a: var StackArray): (int, var a.T) =
for i in 0 .. a.high:
yield (i, a.buffer[i])
template allocStackArray*(T: typedesc, size: int): auto =
template allocaAux(sz: int, init: static[bool]): pointer =
let s = sz
let b = alloca(s)
when init: zeroMem(b, s)
b
template allocStackArrayAux(T: typedesc, size: int, init: static[bool]): StackArray[T] =
let sz = int(size) # Evaluate size only once
if sz < 0: raiseRangeError "allocation with a negative size"
# XXX: is it possible to perform a stack size check before calling `alloca`?
# On thread init, Nim may record the base address and the capacity of the stack,
# so in theory we can verify that we still have enough room for the allocation.
# Research this.
var
bufferSize = sz * sizeof(T)
totalSize = sizeof(int32) + bufferSize
arr = cast[StackArray[T]](alloca(totalSize))
zeroMem(addr arr.buffer[0], bufferSize)
arr.bufferLen = int32(sz)
arr
StackArray[T](bufferLen: int32(sz), buffer: cast[ptr UncheckedArray[T]](allocaAux(sz * sizeof(T), init)))
template allocStackArray*(T: typedesc, size: int): StackArray[T] =
allocStackArrayAux(T, size, true)
template allocStackArrayNoInit*(T: typedesc, size: int): StackArray[T] =
allocStackArrayAux(T, size, false)
template toOpenArray*(a: StackArray): auto =
toOpenArray(a.buffer, 0, a.high)
toOpenArray(a.buffer[], 0, a.high)
template toOpenArray*(a: StackArray, first: int): auto =
if first < 0 or first >= a.len: raiseOutOfRange()
toOpenArray(a.buffer, first, a.high)
toOpenArray(a.buffer[], first, a.high)
template toOpenArray*(a: StackArray, first, last: int): auto =
if first < 0 or first >= last or last <= a.len: raiseOutOfRange()
toOpenArray(a.buffer, first, last)
toOpenArray(a.buffer[], first, last)