147 lines
3.3 KiB
Nim
147 lines
3.3 KiB
Nim
import std/sugar
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import pkg/questionable
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import pkg/chronos
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type
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Function*[T, U] = proc(fut: T): U {.raises: [CatchableError], gcsafe, noSideEffect.}
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IsFinished* = proc(): bool {.raises: [], gcsafe, noSideEffect.}
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GenNext*[T] = proc(): T {.raises: [CatchableError], gcsafe.}
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Iter*[T] = ref object
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finished: bool
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next*: GenNext[T]
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AsyncIter*[T] = Iter[Future[T]]
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proc finish*[T](self: Iter[T]): void =
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self.finished = true
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proc finished*[T](self: Iter[T]): bool =
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self.finished
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iterator items*[T](self: Iter[T]): T =
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while not self.finished:
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yield self.next()
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iterator pairs*[T](self: Iter[T]): tuple[key: int, val: T] {.inline.} =
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var i = 0
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while not self.finished:
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yield (i, self.next())
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inc(i)
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proc map*[T, U](fut: Future[T], fn: Function[T, U]): Future[U] {.async.} =
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let t = await fut
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fn(t)
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proc new*[T](_: type Iter, genNext: GenNext[T], isFinished: IsFinished, finishOnErr: bool = true): Iter[T] =
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var iter = Iter[T]()
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proc next(): T {.raises: [CatchableError].} =
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if not iter.finished:
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var item: T
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try:
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item = genNext()
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except CatchableError as err:
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if finishOnErr or isFinished():
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iter.finish
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raise err
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if isFinished():
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iter.finish
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return item
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else:
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raise newException(CatchableError, "Iterator is finished but next item was requested")
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if isFinished():
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iter.finish
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iter.next = next
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return iter
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proc fromItems*[T](_: type Iter, items: seq[T]): Iter[T] =
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## Create new iterator from items
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##
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Iter.fromSlice(0..<items.len)
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.map((i: int) => items[i])
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proc fromSlice*[U, V: Ordinal](_: type Iter, slice: HSlice[U, V]): Iter[U] =
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## Creates new iterator from slice
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##
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Iter.fromRange(slice.a.int, slice.b.int, 1)
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proc fromRange*[U, V, S: Ordinal](_: type Iter, a: U, b: V, step: S = 1): Iter[U] =
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## Creates new iterator in range a..b with specified step (default 1)
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##
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var i = a
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proc genNext(): U =
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let u = i
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inc(i, step)
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u
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proc isFinished(): bool =
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(step > 0 and i > b) or
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(step < 0 and i < b)
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Iter.new(genNext, isFinished)
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proc map*[T, U](iter: Iter[T], fn: Function[T, U]): Iter[U] =
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Iter.new(
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genNext = () => fn(iter.next()),
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isFinished = () => iter.finished
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)
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proc filter*[T](iter: Iter[T], predicate: Function[T, bool]): Iter[T] =
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var nextT: Option[T]
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proc tryFetch(): void =
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nextT = T.none
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while not iter.finished:
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let t = iter.next()
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if predicate(t):
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nextT = some(t)
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break
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proc genNext(): T =
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let t = nextT.unsafeGet
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tryFetch()
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return t
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proc isFinished(): bool =
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nextT.isNone
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tryFetch()
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Iter.new(genNext, isFinished)
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proc prefetch*[T](iter: Iter[T], n: Positive): Iter[T] =
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var ringBuf = newSeq[T](n)
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var iterLen = int.high
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var i = 0
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proc tryFetch(j: int): void =
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if not iter.finished:
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let item = iter.next()
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ringBuf[j mod n] = item
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if iter.finished:
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iterLen = min(j + 1, iterLen)
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else:
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if j == 0:
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iterLen = 0
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proc genNext(): T =
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let item = ringBuf[i mod n]
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tryFetch(i + n)
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inc i
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return item
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proc isFinished(): bool =
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i >= iterLen
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# initialize ringBuf with n prefetched values
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for j in 0..<n:
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tryFetch(j)
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Iter.new(genNext, isFinished)
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