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#
# Chronos
#
# (c) Copyright 2015 Dominik Picheta
# (c) Copyright 2018-Present Status Research & Development GmbH
#
# Licensed under either of
# Apache License, version 2.0, (LICENSE-APACHEv2)
# MIT license (LICENSE-MIT)
import std/[os, tables, strutils, heapqueue, options, deques, cstrutils, sequtils]
import srcloc
export srcloc
const
LocCreateIndex* = 0
LocCompleteIndex* = 1
when defined(chronosStackTrace):
type StackTrace = string
type
FutureState* {.pure.} = enum
Pending, Finished, Cancelled, Failed
FutureBase* = ref object of RootObj ## Untyped future.
location*: array[2, ptr SrcLoc]
callbacks: seq[AsyncCallback]
cancelcb*: CallbackFunc
child*: FutureBase
state*: FutureState
error*: ref Exception ## Stored exception
mustCancel*: bool
id*: int
when defined(chronosStackTrace):
errorStackTrace*: StackTrace
stackTrace: StackTrace ## For debugging purposes only.
when defined(chronosFutureTracking):
next*: FutureBase
prev*: FutureBase
# ZAH: we have discussed some possible optimizations where
# the future can be stored within the caller's stack frame.
# How much refactoring is needed to make this a regular non-ref type?
# Obviously, it will still be allocated on the heap when necessary.
Future*[T] = ref object of FutureBase ## Typed future.
value: T ## Stored value
FutureStr*[T] = ref object of Future[T]
## Future to hold GC strings
gcholder*: string
FutureSeq*[A, B] = ref object of Future[A]
## Future to hold GC seqs
gcholder*: seq[B]
FutureVar*[T] = distinct Future[T]
FutureDefect* = object of Defect
cause*: FutureBase
FutureError* = object of CatchableError
CancelledError* = object of FutureError
FutureList* = object
head*: FutureBase
tail*: FutureBase
count*: int
var currentID* {.threadvar.}: int
currentID = 0
when defined(chronosFutureTracking):
var futureList* {.threadvar.}: FutureList
futureList = FutureList()
template setupFutureBase(loc: ptr SrcLoc) =
new(result)
result.state = FutureState.Pending
when defined(chronosStackTrace):
result.stackTrace = getStackTrace()
result.id = currentID
result.location[LocCreateIndex] = loc
currentID.inc()
when defined(chronosFutureTracking):
result.next = nil
result.prev = futureList.tail
if not(isNil(futureList.tail)):
futureList.tail.next = result
futureList.tail = result
if isNil(futureList.head):
futureList.head = result
futureList.count.inc()
proc newFutureImpl[T](loc: ptr SrcLoc): Future[T] =
setupFutureBase(loc)
proc newFutureSeqImpl[A, B](loc: ptr SrcLoc): FutureSeq[A, B] =
setupFutureBase(loc)
proc newFutureStrImpl[T](loc: ptr SrcLoc): FutureStr[T] =
setupFutureBase(loc)
proc newFutureVarImpl[T](loc: ptr SrcLoc): FutureVar[T] =
FutureVar[T](newFutureImpl[T](loc))
template newFuture*[T](fromProc: static[string] = ""): Future[T] =
## Creates a new future.
##
## Specifying ``fromProc``, which is a string specifying the name of the proc
## that this future belongs to, is a good habit as it helps with debugging.
newFutureImpl[T](getSrcLocation(fromProc))
template newFutureSeq*[A, B](fromProc: static[string] = ""): FutureSeq[A, B] =
## Create a new future which can hold/preserve GC sequence until future will
## not be completed.
##
## Specifying ``fromProc``, which is a string specifying the name of the proc
## that this future belongs to, is a good habit as it helps with debugging.
newFutureSeqImpl[A, B](getSrcLocation(fromProc))
template newFutureStr*[T](fromProc: static[string] = ""): FutureStr[T] =
## Create a new future which can hold/preserve GC string until future will
## not be completed.
##
## Specifying ``fromProc``, which is a string specifying the name of the proc
## that this future belongs to, is a good habit as it helps with debugging.
newFutureStrImpl[T](getSrcLocation(fromProc))
template newFutureVar*[T](fromProc: static[string] = ""): FutureVar[T] =
## Create a new ``FutureVar``. This Future type is ideally suited for
## situations where you want to avoid unnecessary allocations of Futures.
##
## Specifying ``fromProc``, which is a string specifying the name of the proc
## that this future belongs to, is a good habit as it helps with debugging.
newFutureVarImpl[T](getSrcLocation(fromProc))
proc clean*[T](future: FutureVar[T]) =
## Resets the ``finished`` status of ``future``.
Future[T](future).state = FutureState.Pending
Future[T](future).value = default(T)
Future[T](future).error = nil
proc finished*(future: FutureBase | FutureVar): bool {.inline.} =
## Determines whether ``future`` has completed, i.e. ``future`` state changed
## from state ``Pending`` to one of the states (``Finished``, ``Cancelled``,
## ``Failed``).
when future is FutureVar:
result = (FutureBase(future).state != FutureState.Pending)
else:
result = (future.state != FutureState.Pending)
proc cancelled*(future: FutureBase): bool {.inline.} =
## Determines whether ``future`` has cancelled.
(future.state == FutureState.Cancelled)
proc failed*(future: FutureBase): bool {.inline.} =
## Determines whether ``future`` completed with an error.
(future.state == FutureState.Failed)
proc completed*(future: FutureBase): bool {.inline.} =
## Determines whether ``future`` completed without an error.
(future.state == FutureState.Finished)
proc done*(future: FutureBase): bool {.inline.} =
## This is an alias for ``completed(future)`` procedure.
completed(future)
when defined(chronosFutureTracking):
proc futureDestructor(udata: pointer) {.gcsafe.} =
## This procedure will be called when Future[T] got finished, cancelled or
## failed and all Future[T].callbacks are already scheduled and processed.
let future = cast[FutureBase](udata)
if future == futureList.tail: futureList.tail = future.prev
if future == futureList.head: futureList.head = future.next
if not(isNil(future.next)): future.next.prev = future.prev
if not(isNil(future.prev)): future.prev.next = future.next
futureList.count.dec()
proc scheduleDestructor(future: FutureBase) {.inline.} =
callSoon(futureDestructor, cast[pointer](future))
proc checkFinished(future: FutureBase, loc: ptr SrcLoc) =
## Checks whether `future` is finished. If it is then raises a
## ``FutureDefect``.
if future.finished():
var msg = ""
msg.add("An attempt was made to complete a Future more than once. ")
msg.add("Details:")
msg.add("\n Future ID: " & $future.id)
msg.add("\n Creation location:")
msg.add("\n " & $future.location[LocCreateIndex])
msg.add("\n First completion location:")
msg.add("\n " & $future.location[LocCompleteIndex])
msg.add("\n Second completion location:")
msg.add("\n " & $loc)
when defined(chronosStackTrace):
msg.add("\n Stack trace to moment of creation:")
msg.add("\n" & indent(future.stackTrace.strip(), 4))
msg.add("\n Stack trace to moment of secondary completion:")
msg.add("\n" & indent(getStackTrace().strip(), 4))
msg.add("\n\n")
var err = newException(FutureDefect, msg)
err.cause = future
raise err
else:
future.location[LocCompleteIndex] = loc
proc finish(fut: FutureBase, state: FutureState) =
# We do not perform any checks here, because:
# 1. `finish()` is a private procedure and `state` is under our control.
# 2. `fut.state` is checked by `checkFinished()`.
fut.state = state
fut.cancelcb = nil # release cancellation callback memory
for item in fut.callbacks.mitems():
if not(isNil(item.function)):
callSoon(item)
item = default(AsyncCallback) # release memory as early as possible
fut.callbacks = default(seq[AsyncCallback]) # release seq as well
when defined(chronosFutureTracking):
scheduleDestructor(fut)
proc complete[T](future: Future[T], val: T, loc: ptr SrcLoc) =
if not(future.cancelled()):
checkFinished(FutureBase(future), loc)
doAssert(isNil(future.error))
future.value = val
future.finish(FutureState.Finished)
template complete*[T](future: Future[T], val: T) =
## Completes ``future`` with value ``val``.
complete(future, val, getSrcLocation())
proc complete(future: Future[void], loc: ptr SrcLoc) =
if not(future.cancelled()):
checkFinished(FutureBase(future), loc)
doAssert(isNil(future.error))
future.finish(FutureState.Finished)
template complete*(future: Future[void]) =
## Completes a void ``future``.
complete(future, getSrcLocation())
proc complete[T](future: FutureVar[T], loc: ptr SrcLoc) =
if not(future.cancelled()):
template fut: untyped = Future[T](future)
checkFinished(FutureBase(fut), loc)
doAssert(isNil(fut.error))
fut.finish(FutureState.Finished)
template complete*[T](futvar: FutureVar[T]) =
## Completes a ``FutureVar``.
complete(futvar, getSrcLocation())
proc complete[T](futvar: FutureVar[T], val: T, loc: ptr SrcLoc) =
if not(futvar.cancelled()):
template fut: untyped = Future[T](futvar)
checkFinished(FutureBase(fut), loc)
doAssert(isNil(fut.error))
fut.value = val
fut.finish(FutureState.Finished)
template complete*[T](futvar: FutureVar[T], val: T) =
## Completes a ``FutureVar`` with value ``val``.
##
## Any previously stored value will be overwritten.
complete(futvar, val, getSrcLocation())
proc fail[T](future: Future[T], error: ref Exception, loc: ptr SrcLoc) =
if not(future.cancelled()):
checkFinished(FutureBase(future), loc)
future.error = error
when defined(chronosStackTrace):
future.errorStackTrace = if getStackTrace(error) == "":
getStackTrace()
else:
getStackTrace(error)
future.finish(FutureState.Failed)
template fail*[T](future: Future[T], error: ref Exception) =
## Completes ``future`` with ``error``.
fail(future, error, getSrcLocation())
template newCancelledError(): ref CancelledError =
(ref CancelledError)(msg: "Future operation cancelled!")
proc cancelAndSchedule(future: FutureBase, loc: ptr SrcLoc) =
if not(future.finished()):
checkFinished(future, loc)
future.error = newCancelledError()
when defined(chronosStackTrace):
future.errorStackTrace = getStackTrace()
future.finish(FutureState.Cancelled)
template cancelAndSchedule*[T](future: Future[T]) =
cancelAndSchedule(FutureBase(future), getSrcLocation())
proc cancel(future: FutureBase, loc: ptr SrcLoc): bool =
## Request that Future ``future`` cancel itself.
##
## This arranges for a `CancelledError` to be thrown into procedure which
## waits for ``future`` on the next cycle through the event loop.
## The procedure then has a chance to clean up or even deny the request
## using `try/except/finally`.
##
## This call do not guarantee that the ``future`` will be cancelled: the
## exception might be caught and acted upon, delaying cancellation of the
## ``future`` or preventing cancellation completely. The ``future`` may also
## return value or raise different exception.
##
## Immediately after this procedure is called, ``future.cancelled()`` will
## not return ``true`` (unless the Future was already cancelled).
if future.finished():
return false
if not(isNil(future.child)):
if cancel(future.child, getSrcLocation()):
return true
else:
if not(isNil(future.cancelcb)):
future.cancelcb(cast[pointer](future))
future.cancelcb = nil
cancelAndSchedule(future, getSrcLocation())
future.mustCancel = true
return true
template cancel*[T](future: Future[T]) =
## Cancel ``future``.
discard cancel(FutureBase(future), getSrcLocation())
proc clearCallbacks(future: FutureBase) =
future.callbacks = default(seq[AsyncCallback])
proc addCallback*(future: FutureBase, cb: CallbackFunc, udata: pointer = nil) =
## Adds the callbacks proc to be called when the future completes.
##
## If future has already completed then ``cb`` will be called immediately.
doAssert(not isNil(cb))
if future.finished():
callSoon(cb, udata)
else:
let acb = AsyncCallback(function: cb, udata: udata)
future.callbacks.add acb
proc addCallback*[T](future: Future[T], cb: CallbackFunc) =
## Adds the callbacks proc to be called when the future completes.
##
## If future has already completed then ``cb`` will be called immediately.
future.addCallback(cb, cast[pointer](future))
proc removeCallback*(future: FutureBase, cb: CallbackFunc,
udata: pointer = nil) =
## Remove future from list of callbacks - this operation may be slow if there
## are many registered callbacks!
doAssert(not isNil(cb))
# Make sure to release memory associated with callback, or reference chains
# may be created!
future.callbacks.keepItIf:
it.function != cb or it.udata != udata
proc removeCallback*[T](future: Future[T], cb: CallbackFunc) =
future.removeCallback(cb, cast[pointer](future))
proc `callback=`*(future: FutureBase, cb: CallbackFunc, udata: pointer = nil) =
## Clears the list of callbacks and sets the callback proc to be called when
## the future completes.
##
## If future has already completed then ``cb`` will be called immediately.
##
## It's recommended to use ``addCallback`` or ``then`` instead.
# ZAH: how about `setLen(1); callbacks[0] = cb`
future.clearCallbacks
future.addCallback(cb, udata)
proc `callback=`*[T](future: Future[T], cb: CallbackFunc) =
## Sets the callback proc to be called when the future completes.
##
## If future has already completed then ``cb`` will be called immediately.
`callback=`(future, cb, cast[pointer](future))
proc `cancelCallback=`*[T](future: Future[T], cb: CallbackFunc) =
## Sets the callback procedure to be called when the future is cancelled.
##
## This callback will be called immediately as ``future.cancel()`` invoked.
future.cancelcb = cb
proc getHint(entry: StackTraceEntry): string =
## We try to provide some hints about stack trace entries that the user
## may not be familiar with, in particular calls inside the stdlib.
result = ""
if entry.procname == "processPendingCallbacks":
if cmpIgnoreStyle(entry.filename, "asyncdispatch.nim") == 0:
return "Executes pending callbacks"
elif entry.procname == "poll":
if cmpIgnoreStyle(entry.filename, "asyncdispatch.nim") == 0:
return "Processes asynchronous completion events"
if entry.procname.endsWith("_continue"):
if cmpIgnoreStyle(entry.filename, "asyncmacro.nim") == 0:
return "Resumes an async procedure"
proc `$`*(entries: seq[StackTraceEntry]): string =
result = ""
# Find longest filename & line number combo for alignment purposes.
var longestLeft = 0
for entry in entries:
if isNil(entry.procName): continue
let left = $entry.filename & $entry.line
if left.len > longestLeft:
longestLeft = left.len
var indent = 2
# Format the entries.
for entry in entries:
if isNil(entry.procName):
if entry.line == -10:
result.add(spaces(indent) & "#[\n")
indent.inc(2)
else:
indent.dec(2)
result.add(spaces(indent) & "]#\n")
continue
let left = "$#($#)" % [$entry.filename, $entry.line]
result.add((spaces(indent) & "$#$# $#\n") % [
left,
spaces(longestLeft - left.len + 2),
$entry.procName
])
let hint = getHint(entry)
if hint.len > 0:
result.add(spaces(indent+2) & "## " & hint & "\n")
when defined(chronosStackTrace):
proc injectStacktrace(future: FutureBase) =
const header = "\nAsync traceback:\n"
var exceptionMsg = future.error.msg
if header in exceptionMsg:
# This is messy: extract the original exception message from the msg
# containing the async traceback.
let start = exceptionMsg.find(header)
exceptionMsg = exceptionMsg[0..<start]
var newMsg = exceptionMsg & header
let entries = getStackTraceEntries(future.error)
newMsg.add($entries)
newMsg.add("Exception message: " & exceptionMsg & "\n")
newMsg.add("Exception type:")
# # For debugging purposes
# for entry in getStackTraceEntries(future.error):
# newMsg.add "\n" & $entry
future.error.msg = newMsg
proc internalCheckComplete*(fut: FutureBase) =
# For internal use only. Used in asyncmacro
if not(isNil(fut.error)):
when defined(chronosStackTrace):
injectStacktrace(fut)
raise fut.error
proc internalRead*[T](fut: Future[T] | FutureVar[T]): T {.inline.} =
# For internal use only. Used in asyncmacro
when T isnot void:
return fut.value
proc read*[T](future: Future[T] | FutureVar[T]): T =
## Retrieves the value of ``future``. Future must be finished otherwise
## this function will fail with a ``ValueError`` exception.
##
## If the result of the future is an error then that error will be raised.
{.push hint[ConvFromXtoItselfNotNeeded]: off.}
let fut = Future[T](future)
{.pop.}
if fut.finished():
internalCheckComplete(future)
internalRead(future)
else:
# TODO: Make a custom exception type for this?
raise newException(ValueError, "Future still in progress.")
proc readError*[T](future: Future[T]): ref Exception =
## Retrieves the exception stored in ``future``.
##
## An ``ValueError`` exception will be thrown if no exception exists
## in the specified Future.
if not(isNil(future.error)):
return future.error
else:
# TODO: Make a custom exception type for this?
raise newException(ValueError, "No error in future.")
proc mget*[T](future: FutureVar[T]): var T =
## Returns a mutable value stored in ``future``.
##
## Unlike ``read``, this function will not raise an exception if the
## Future has not been finished.
result = Future[T](future).value
proc asyncCheck*[T](future: Future[T]) =
## Sets a callback on ``future`` which raises an exception if the future
## finished with an error.
##
## This should be used instead of ``discard`` to discard void futures.
doAssert(not isNil(future), "Future is nil")
proc cb(data: pointer) =
if future.failed() or future.cancelled():
when defined(chronosStackTrace):
injectStacktrace(future)
raise future.error
future.callback = cb
proc asyncSpawn*(future: Future[void]) =
## Spawns a new concurrent async task.
##
## Tasks may not raise exceptions or be cancelled - a ``Defect`` will be
## raised when this happens.
##
## This should be used instead of ``discard`` and ``asyncCheck`` when calling
## an ``async`` procedure without ``await``, to ensure exceptions in the
## returned future are not silently discarded.
##
## Note, that if passed ``future`` is already finished, it will be checked
## and processed immediately.
doAssert(not isNil(future), "Future is nil")
template getFutureLocation(): string =
let loc = future.location[0]
"[" & (
if len(loc.procedure) == 0: "[unspecified]" else: $loc.procedure & "()"
) & " at " & $loc.file & ":" & $(loc.line) & "]"
template getErrorMessage(): string =
"Asynchronous task " & getFutureLocation() &
" finished with an exception \"" & $future.error.name & "\"!"
template getCancelMessage(): string =
"Asynchronous task " & getFutureLocation() & " was cancelled!"
proc cb(data: pointer) =
if future.failed():
raise newException(FutureDefect, getErrorMessage())
elif future.cancelled():
raise newException(FutureDefect, getCancelMessage())
if not(future.finished()):
# We adding completion callback only if ``future`` is not finished yet.
future.addCallback(cb)
else:
if future.failed():
raise newException(FutureDefect, getErrorMessage())
elif future.cancelled():
raise newException(FutureDefect, getCancelMessage())
proc asyncDiscard*[T](future: Future[T]) {.deprecated.} = discard
## This is async workaround for discard ``Future[T]``.
proc `and`*[T, Y](fut1: Future[T], fut2: Future[Y]): Future[void] {.
deprecated: "Use allFutures[T](varargs[Future[T]])".} =
## Returns a future which will complete once both ``fut1`` and ``fut2``
## complete.
##
## If cancelled, ``fut1`` and ``fut2`` futures WILL NOT BE cancelled.
var retFuture = newFuture[void]("chronos.`and`")
proc cb(data: pointer) =
if not(retFuture.finished()):
if fut1.finished() and fut2.finished():
if cast[pointer](fut1) == data:
if fut1.failed():
retFuture.fail(fut1.error)
else:
retFuture.complete()
else:
if fut2.failed():
retFuture.fail(fut2.error)
else:
retFuture.complete()
fut1.callback = cb
fut2.callback = cb
proc cancellation(udata: pointer) {.gcsafe.} =
# On cancel we remove all our callbacks only.
if not(fut1.finished()):
fut1.removeCallback(cb)
if not(fut2.finished()):
fut2.removeCallback(cb)
retFuture.cancelCallback = cancellation
return retFuture
proc `or`*[T, Y](fut1: Future[T], fut2: Future[Y]): Future[void] =
## Returns a future which will complete once either ``fut1`` or ``fut2``
## complete.
##
## If ``fut1`` or ``fut2`` future is failed, the result future will also be
## failed with an error stored in ``fut1`` or ``fut2`` respectively.
##
## If both ``fut1`` and ``fut2`` future are completed or failed, the result
## future will depend on the state of ``fut1`` future. So if ``fut1`` future
## is failed, the result future will also be failed, if ``fut1`` future is
## completed, the result future will also be completed.
##
## If cancelled, ``fut1`` and ``fut2`` futures WILL NOT BE cancelled.
var retFuture = newFuture[void]("chronos.or")
proc cb(udata: pointer) {.gcsafe.} =
if not(retFuture.finished()):
var fut = cast[FutureBase](udata)
if cast[pointer](fut1) == udata:
fut2.removeCallback(cb)
else:
fut1.removeCallback(cb)
if fut.failed():
retFuture.fail(fut.error)
else:
retFuture.complete()
proc cancellation(udata: pointer) {.gcsafe.} =
# On cancel we remove all our callbacks only.
if not(fut1.finished()):
fut1.removeCallback(cb)
if not(fut2.finished()):
fut2.removeCallback(cb)
if fut1.finished():
if fut1.failed():
retFuture.fail(fut1.error)
else:
retFuture.complete()
return retFuture
if fut2.finished():
if fut2.failed():
retFuture.fail(fut2.error)
else:
retFuture.complete()
return retFuture
fut1.addCallback(cb)
fut2.addCallback(cb)
retFuture.cancelCallback = cancellation
return retFuture
proc all*[T](futs: varargs[Future[T]]): auto {.
deprecated: "Use allFutures(varargs[Future[T]])".} =
## Returns a future which will complete once all futures in ``futs`` complete.
## If the argument is empty, the returned future completes immediately.
##
## If the awaited futures are not ``Future[void]``, the returned future
## will hold the values of all awaited futures in a sequence.
##
## If the awaited futures *are* ``Future[void]``, this proc returns
## ``Future[void]``.
##
## Note, that if one of the futures in ``futs`` will fail, result of ``all()``
## will also be failed with error from failed future.
##
## TODO: This procedure has bug on handling cancelled futures from ``futs``.
## So if future from ``futs`` list become cancelled, what must be returned?
## You can't cancel result ``retFuture`` because in such way infinite
## recursion will happen.
let totalFutures = len(futs)
var completedFutures = 0
# Because we can't capture varargs[T] in closures we need to create copy.
var nfuts = @futs
when T is void:
var retFuture = newFuture[void]("chronos.all(void)")
proc cb(udata: pointer) {.gcsafe.} =
if not(retFuture.finished()):
inc(completedFutures)
if completedFutures == totalFutures:
for nfut in nfuts:
if nfut.failed():
retFuture.fail(nfut.error)
break
if not(retFuture.failed()):
retFuture.complete()
for fut in nfuts:
fut.addCallback(cb)
if len(nfuts) == 0:
retFuture.complete()
return retFuture
else:
var retFuture = newFuture[seq[T]]("chronos.all(T)")
var retValues = newSeq[T](totalFutures)
proc cb(udata: pointer) {.gcsafe.} =
if not(retFuture.finished()):
inc(completedFutures)
if completedFutures == totalFutures:
for k, nfut in nfuts:
if nfut.failed():
retFuture.fail(nfut.error)
break
else:
retValues[k] = nfut.read()
if not(retFuture.failed()):
retFuture.complete(retValues)
for fut in nfuts:
fut.addCallback(cb)
if len(nfuts) == 0:
retFuture.complete(retValues)
return retFuture
proc oneIndex*[T](futs: varargs[Future[T]]): Future[int] {.
deprecated: "Use one[T](varargs[Future[T]])".} =
## Returns a future which will complete once one of the futures in ``futs``
## complete.
##
## If the argument is empty, the returned future FAILS immediately.
##
## Returned future will hold index of completed/failed future in ``futs``
## argument.
var nfuts = @futs
var retFuture = newFuture[int]("chronos.oneIndex(T)")
proc cb(udata: pointer) {.gcsafe.} =
var res = -1
if not(retFuture.finished()):
var rfut = cast[FutureBase](udata)
for i in 0..<len(nfuts):
if cast[FutureBase](nfuts[i]) != rfut:
nfuts[i].removeCallback(cb)
else:
res = i
retFuture.complete(res)
for fut in nfuts:
fut.addCallback(cb)
if len(nfuts) == 0:
retFuture.fail(newException(ValueError, "Empty Future[T] list"))
return retFuture
proc oneValue*[T](futs: varargs[Future[T]]): Future[T] {.
deprecated: "Use one[T](varargs[Future[T]])".} =
## Returns a future which will complete once one of the futures in ``futs``
## complete.
##
## If the argument is empty, returned future FAILS immediately.
##
## Returned future will hold value of completed ``futs`` future, or error
## if future was failed.
var nfuts = @futs
var retFuture = newFuture[T]("chronos.oneValue(T)")
proc cb(udata: pointer) {.gcsafe.} =
var resFut: Future[T]
if not(retFuture.finished()):
var rfut = cast[FutureBase](udata)
for i in 0..<len(nfuts):
if cast[FutureBase](nfuts[i]) != rfut:
nfuts[i].removeCallback(cb)
else:
resFut = nfuts[i]
if resFut.failed():
retFuture.fail(resFut.error)
else:
when T is void:
retFuture.complete()
else:
retFuture.complete(resFut.read())
for fut in nfuts:
fut.addCallback(cb)
if len(nfuts) == 0:
retFuture.fail(newException(ValueError, "Empty Future[T] list"))
return retFuture
proc cancelAndWait*[T](fut: Future[T]): Future[void] =
## Initiate cancellation process for Future ``fut`` and wait until ``fut`` is
## done e.g. changes its state (become completed, failed or cancelled).
##
## If ``fut`` is already finished (completed, failed or cancelled) result
## Future[void] object will be returned complete.
var retFuture = newFuture[void]("chronos.cancelAndWait(T)")
proc continuation(udata: pointer) {.gcsafe.} =
if not(retFuture.finished()):
retFuture.complete()
proc cancellation(udata: pointer) {.gcsafe.} =
if not(fut.finished()):
fut.removeCallback(continuation)
if fut.finished():
retFuture.complete()
else:
fut.addCallback(continuation)
retFuture.cancelCallback = cancellation
# Initiate cancellation process.
fut.cancel()
return retFuture
proc allFutures*[T](futs: varargs[Future[T]]): Future[void] =
## Returns a future which will complete only when all futures in ``futs``
## will be completed, failed or canceled.
##
## If the argument is empty, the returned future COMPLETES immediately.
##
## On cancel all the awaited futures ``futs`` WILL NOT BE cancelled.
var retFuture = newFuture[void]("chronos.allFutures()")
let totalFutures = len(futs)
var completedFutures = 0
# Because we can't capture varargs[T] in closures we need to create copy.
var nfuts = @futs
proc cb(udata: pointer) {.gcsafe.} =
if not(retFuture.finished()):
inc(completedFutures)
if completedFutures == totalFutures:
retFuture.complete()
proc cancellation(udata: pointer) {.gcsafe.} =
# On cancel we remove all our callbacks only.
for i in 0..<len(nfuts):
if not(nfuts[i].finished()):
nfuts[i].removeCallback(cb)
for fut in nfuts:
if not(fut.finished()):
fut.addCallback(cb)
else:
inc(completedFutures)
retFuture.cancelCallback = cancellation
if len(nfuts) == 0 or len(nfuts) == completedFutures:
retFuture.complete()
return retFuture
proc allFinished*[T](futs: varargs[Future[T]]): Future[seq[Future[T]]] =
## Returns a future which will complete only when all futures in ``futs``
## will be completed, failed or canceled.
##
## Returned sequence will hold all the Future[T] objects passed to
## ``allCompleted`` with the order preserved.
##
## If the argument is empty, the returned future COMPLETES immediately.
##
## On cancel all the awaited futures ``futs`` WILL NOT BE cancelled.
var retFuture = newFuture[seq[Future[T]]]("chronos.allFinished()")
let totalFutures = len(futs)
var completedFutures = 0
var nfuts = @futs
proc cb(udata: pointer) {.gcsafe.} =
if not(retFuture.finished()):
inc(completedFutures)
if completedFutures == totalFutures:
retFuture.complete(nfuts)
proc cancellation(udata: pointer) {.gcsafe.} =
# On cancel we remove all our callbacks only.
for fut in nfuts.mitems():
if not(fut.finished()):
fut.removeCallback(cb)
for fut in nfuts:
if not(fut.finished()):
fut.addCallback(cb)
else:
inc(completedFutures)
retFuture.cancelCallback = cancellation
if len(nfuts) == 0 or len(nfuts) == completedFutures:
retFuture.complete(nfuts)
return retFuture
proc one*[T](futs: varargs[Future[T]]): Future[Future[T]] =
## Returns a future which will complete and return completed Future[T] inside,
## when one of the futures in ``futs`` will be completed, failed or canceled.
##
## If the argument is empty, the returned future FAILS immediately.
##
## On success returned Future will hold finished Future[T].
##
## On cancel futures in ``futs`` WILL NOT BE cancelled.
var retFuture = newFuture[Future[T]]("chronos.one()")
# Because we can't capture varargs[T] in closures we need to create copy.
var nfuts = @futs
proc cb(udata: pointer) {.gcsafe.} =
if not(retFuture.finished()):
var res: Future[T]
var rfut = cast[FutureBase](udata)
for i in 0..<len(nfuts):
if cast[FutureBase](nfuts[i]) != rfut:
nfuts[i].removeCallback(cb)
else:
res = nfuts[i]
retFuture.complete(res)
proc cancellation(udata: pointer) {.gcsafe.} =
# On cancel we remove all our callbacks only.
for i in 0..<len(nfuts):
if not(nfuts[i].finished()):
nfuts[i].removeCallback(cb)
# If one of the Future[T] already finished we return it as result
for fut in nfuts:
if fut.finished():
retFuture.complete(fut)
return retFuture
for fut in nfuts:
fut.addCallback(cb)
if len(nfuts) == 0:
retFuture.fail(newException(ValueError, "Empty Future[T] list"))
retFuture.cancelCallback = cancellation
return retFuture
proc race*(futs: varargs[FutureBase]): Future[FutureBase] =
## Returns a future which will complete and return completed FutureBase,
## when one of the futures in ``futs`` will be completed, failed or canceled.
##
## If the argument is empty, the returned future FAILS immediately.
##
## On success returned Future will hold finished FutureBase.
##
## On cancel futures in ``futs`` WILL NOT BE cancelled.
var retFuture = newFuture[FutureBase]("chronos.race()")
# Because we can't capture varargs[T] in closures we need to create copy.
var nfuts = @futs
proc cb(udata: pointer) {.gcsafe.} =
if not(retFuture.finished()):
var res: FutureBase
var rfut = cast[FutureBase](udata)
for i in 0..<len(nfuts):
if nfuts[i] != rfut:
nfuts[i].removeCallback(cb)
else:
res = nfuts[i]
retFuture.complete(res)
proc cancellation(udata: pointer) {.gcsafe.} =
# On cancel we remove all our callbacks only.
for i in 0..<len(nfuts):
if not(nfuts[i].finished()):
nfuts[i].removeCallback(cb)
# If one of the Future[T] already finished we return it as result
for fut in nfuts:
if fut.finished():
retFuture.complete(fut)
return retFuture
for fut in nfuts:
fut.addCallback(cb, cast[pointer](fut))
if len(nfuts) == 0:
retFuture.fail(newException(ValueError, "Empty Future[T] list"))
retFuture.cancelCallback = cancellation
return retFuture
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