nim-dagger/dagger/utils/asyncheapqueue.nim

327 lines
9.3 KiB
Nim

## Nim-Dagger
## Copyright (c) 2021 Status Research & Development GmbH
## Licensed under either of
## * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
## * MIT license ([LICENSE-MIT](LICENSE-MIT))
## at your option.
## This file may not be copied, modified, or distributed except according to
## those terms.
import std/sequtils
import pkg/chronos
import pkg/stew/results
# Based on chronos AsyncHeapQueue and std/heapqueue
type
QueueType* {.pure.} = enum
Min, Max
AsyncHeapQueue*[T] = ref object of RootRef
## A priority queue
##
## If ``maxsize`` is less than or equal to zero, the queue size is
## infinite. If it is an integer greater than ``0``, then "await put()"
## will block when the queue reaches ``maxsize``, until an item is
## removed by "await get()".
queueType: QueueType
getters: seq[Future[void]]
putters: seq[Future[void]]
queue: seq[T]
maxsize: int
AsyncHQErrors* {.pure.} = enum
Empty, Full
proc newAsyncHeapQueue*[T](
maxsize: int = 0,
queueType: QueueType = QueueType.Min): AsyncHeapQueue[T] =
## Creates a new asynchronous queue ``AsyncHeapQueue``.
##
AsyncHeapQueue[T](
getters: newSeq[Future[void]](),
putters: newSeq[Future[void]](),
queue: newSeqOfCap[T](maxsize),
maxsize: maxsize,
queueType: queueType,
)
proc wakeupNext(waiters: var seq[Future[void]]) {.inline.} =
var i = 0
while i < len(waiters):
var waiter = waiters[i]
inc(i)
if not(waiter.finished()):
waiter.complete()
break
if i > 0:
waiters.delete(0, i - 1)
proc heapCmp[T](x, y: T, max: bool = false): bool {.inline.} =
if max:
return (y < x)
else:
return (x < y)
proc siftdown[T](heap: AsyncHeapQueue[T], startpos, p: int) =
## 'heap' is a heap at all indices >= startpos, except
## possibly for pos. pos is the index of a leaf with a
## possibly out-of-order value. Restore the heap invariant.
##
var pos = p
var newitem = heap[pos]
# Follow the path to the root, moving parents down until
# finding a place newitem fits.
while pos > startpos:
let parentpos = (pos - 1) shr 1
let parent = heap[parentpos]
if heapCmp(newitem, parent, heap.queueType == QueueType.Max):
heap.queue[pos] = parent
pos = parentpos
else:
break
heap.queue[pos] = newitem
proc siftup[T](heap: AsyncHeapQueue[T], p: int) =
let endpos = len(heap)
var pos = p
let startpos = pos
let newitem = heap[pos]
# Bubble up the smaller child until hitting a leaf.
var childpos = 2*pos + 1 # leftmost child position
while childpos < endpos:
# Set childpos to index of smaller child.
let rightpos = childpos + 1
if rightpos < endpos and
not heapCmp(heap[childpos], heap[rightpos], heap.queueType == QueueType.Max):
childpos = rightpos
# Move the smaller child up.
heap.queue[pos] = heap[childpos]
pos = childpos
childpos = 2*pos + 1
# The leaf at pos is empty now. Put newitem there, and bubble it up
# to its final resting place (by sifting its parents down).
heap.queue[pos] = newitem
siftdown(heap, startpos, pos)
proc full*[T](heap: AsyncHeapQueue[T]): bool {.inline.} =
## Return ``true`` if there are ``maxsize`` items in the queue.
##
## Note: If the ``heap`` was initialized with ``maxsize = 0`` (default),
## then ``full()`` is never ``true``.
if heap.maxsize <= 0:
false
else:
(len(heap.queue) >= heap.maxsize)
proc empty*[T](heap: AsyncHeapQueue[T]): bool {.inline.} =
## Return ``true`` if the queue is empty, ``false`` otherwise.
(len(heap.queue) == 0)
proc pushNoWait*[T](heap: AsyncHeapQueue[T], item: T): Result[void, AsyncHQErrors] =
## Push `item` onto heap, maintaining the heap invariant.
##
if heap.full():
return err(AsyncHQErrors.Full)
heap.queue.add(item)
siftdown(heap, 0, len(heap)-1)
heap.getters.wakeupNext()
return ok()
proc push*[T](heap: AsyncHeapQueue[T], item: T) {.async, gcsafe.} =
## Push item into the queue, awaiting for an available slot
## when it's full
##
while heap.full():
var putter = newFuture[void]("AsyncHeapQueue.push")
heap.putters.add(putter)
try:
await putter
except CatchableError as exc:
if not(heap.full()) and not(putter.cancelled()):
heap.putters.wakeupNext()
raise exc
heap.pushNoWait(item).tryGet()
proc popNoWait*[T](heap: AsyncHeapQueue[T]): Result[T, AsyncHQErrors] =
## Pop and return the smallest item from `heap`,
## maintaining the heap invariant.
##
if heap.empty():
return err(AsyncHQErrors.Empty)
let lastelt = heap.queue.pop()
if heap.len > 0:
result = ok(heap[0])
heap.queue[0] = lastelt
siftup(heap, 0)
else:
result = ok(lastelt)
heap.putters.wakeupNext()
proc pop*[T](heap: AsyncHeapQueue[T]): Future[T] {.async.} =
## Remove and return an ``item`` from the beginning of the queue ``heap``.
## If the queue is empty, wait until an item is available.
while heap.empty():
var getter = newFuture[void]("AsyncHeapQueue.pop")
heap.getters.add(getter)
try:
await getter
except CatchableError as exc:
if not(heap.empty()) and not(getter.cancelled()):
heap.getters.wakeupNext()
raise exc
return heap.popNoWait().tryGet()
proc del*[T](heap: AsyncHeapQueue[T], index: Natural) =
## Removes the element at `index` from `heap`,
## maintaining the heap invariant.
##
if heap.empty():
return
swap(heap.queue[^1], heap.queue[index])
let newLen = heap.len - 1
heap.queue.setLen(newLen)
if index < newLen:
heap.siftup(index)
heap.putters.wakeupNext()
proc delete*[T](heap: AsyncHeapQueue[T], item: T) =
## Find and delete an `item` from the `heap`
##
let index = heap.find(item)
if index > -1:
heap.del(index)
proc update*[T](heap: AsyncHeapQueue[T], item: T): bool =
## Update an entry in the heap by reshufling its
## possition, maintaining the heap invariant.
##
let index = heap.find(item)
if index > -1:
# replace item with new one in case it's a copy
heap.queue[index] = item
# re-establish heap order
# TODO: don't start at 0 to avoid reshuffling
# entire heap
heap.siftup(0)
return true
proc pushOrUpdateNoWait*[T](heap: AsyncHeapQueue[T], item: T): Result[void, AsyncHQErrors] =
## Update an item if it exists or push a new one
##
if heap.update(item):
return ok()
return heap.pushNoWait(item)
proc pushOrUpdate*[T](heap: AsyncHeapQueue[T], item: T) {.async.} =
## Update an item if it exists or push a new one
## awaiting until a slot becomes available
##
if not heap.update(item):
await heap.push(item)
proc replace*[T](heap: AsyncHeapQueue[T], item: T): Result[T, AsyncHQErrors] =
## Pop and return the current smallest value, and add the new item.
## This is more efficient than pop() followed by push(), and can be
## more appropriate when using a fixed-size heap. Note that the value
## returned may be larger than item! That constrains reasonable uses of
## this routine unless written as part of a conditional replacement:
##
## .. code-block:: nim
## if item > heap[0]:
## item = replace(heap, item)
##
if heap.empty():
error(AsyncHQErrors.Empty)
result = heap[0]
heap.queue[0] = item
siftup(heap, 0)
proc pushPopNoWait*[T](heap: AsyncHeapQueue[T], item: T): Result[T, AsyncHQErrors] =
## Fast version of a push followed by a pop.
##
if heap.empty():
err(AsyncHQErrors.Empty)
if heap.len > 0 and heapCmp(heap[0], item, heap.queueType == QueueType.Max):
swap(item, heap[0])
siftup(heap, 0)
return item
proc clear*[T](heap: AsyncHeapQueue[T]) {.inline.} =
## Clears all elements of queue ``heap``.
heap.queue.setLen(0)
proc len*[T](heap: AsyncHeapQueue[T]): int {.inline.} =
## Return the number of elements in ``heap``.
len(heap.queue)
proc size*[T](heap: AsyncHeapQueue[T]): int {.inline.} =
## Return the maximum number of elements in ``heap``.
len(heap.maxsize)
proc `[]`*[T](heap: AsyncHeapQueue[T], i: Natural) : T {.inline.} =
## Access the i-th element of ``heap`` by order from first to last.
## ``heap[0]`` is the first element, ``heap[^1]`` is the last element.
heap.queue[i]
proc `[]`*[T](heap: AsyncHeapQueue[T], i: BackwardsIndex) : T {.inline.} =
## Access the i-th element of ``heap`` by order from first to last.
## ``heap[0]`` is the first element, ``heap[^1]`` is the last element.
heap.queue[len(heap.queue) - int(i)]
iterator items*[T](heap: AsyncHeapQueue[T]): T {.inline.} =
## Yield every element of ``heap``.
for item in heap.queue.items():
yield item
iterator mitems*[T](heap: AsyncHeapQueue[T]): var T {.inline.} =
## Yield every element of ``heap``.
for mitem in heap.queue.mitems():
yield mitem
iterator pairs*[T](heap: AsyncHeapQueue[T]): tuple[key: int, val: T] {.inline.} =
## Yield every (position, value) of ``heap``.
for pair in heap.queue.pairs():
yield pair
proc contains*[T](heap: AsyncHeapQueue[T], item: T): bool {.inline.} =
## Return true if ``item`` is in ``heap`` or false if not found. Usually used
## via the ``in`` operator.
for e in heap.queue.items():
if e == item: return true
return false
proc `$`*[T](heap: AsyncHeapQueue[T]): string =
## Turn an async queue ``heap`` into its string representation.
var res = "["
for item in heap.queue.items():
if len(res) > 1: res.add(", ")
res.addQuoted(item)
res.add("]")
res