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#
# Asyncdispatch2
#
# (c) Coprygith 2015 Dominik Picheta
# (c) Copyright 2018 Status Research & Development GmbH
#
# Licensed under either of
# Apache License, version 2.0, (LICENSE-APACHEv2)
# MIT license (LICENSE-MIT)
include "system/inclrtl"
import os, tables, strutils, heapqueue, lists, options
import timer
import asyncfutures2 except callSoon
import nativesockets, net, deques
export Port, SocketFlag
export asyncfutures2, timer
#{.injectStmt: newGcInvariant().}
## AsyncDispatch
## *************
##
## This module implements asynchronous IO. This includes a dispatcher,
## a ``Future`` type implementation, and an ``async`` macro which allows
## asynchronous code to be written in a synchronous style with the ``await``
## keyword.
##
## The dispatcher acts as a kind of event loop. You must call ``poll`` on it
## (or a function which does so for you such as ``waitFor`` or ``runForever``)
## in order to poll for any outstanding events. The underlying implementation
## is based on epoll on Linux, IO Completion Ports on Windows and select on
## other operating systems.
##
## The ``poll`` function will not, on its own, return any events. Instead
## an appropriate ``Future`` object will be completed. A ``Future`` is a
## type which holds a value which is not yet available, but which *may* be
## available in the future. You can check whether a future is finished
## by using the ``finished`` function. When a future is finished it means that
## either the value that it holds is now available or it holds an error instead.
## The latter situation occurs when the operation to complete a future fails
## with an exception. You can distinguish between the two situations with the
## ``failed`` function.
##
## Future objects can also store a callback procedure which will be called
## automatically once the future completes.
##
## Futures therefore can be thought of as an implementation of the proactor
## pattern. In this
## pattern you make a request for an action, and once that action is fulfilled
## a future is completed with the result of that action. Requests can be
## made by calling the appropriate functions. For example: calling the ``recv``
## function will create a request for some data to be read from a socket. The
## future which the ``recv`` function returns will then complete once the
## requested amount of data is read **or** an exception occurs.
##
## Code to read some data from a socket may look something like this:
##
## .. code-block::nim
## var future = socket.recv(100)
## future.addCallback(
## proc () =
## echo(future.read)
## )
##
## All asynchronous functions returning a ``Future`` will not block. They
## will not however return immediately. An asynchronous function will have
## code which will be executed before an asynchronous request is made, in most
## cases this code sets up the request.
##
## In the above example, the ``recv`` function will return a brand new
## ``Future`` instance once the request for data to be read from the socket
## is made. This ``Future`` instance will complete once the requested amount
## of data is read, in this case it is 100 bytes. The second line sets a
## callback on this future which will be called once the future completes.
## All the callback does is write the data stored in the future to ``stdout``.
## The ``read`` function is used for this and it checks whether the future
## completes with an error for you (if it did it will simply raise the
## error), if there is no error however it returns the value of the future.
##
## Asynchronous procedures
## -----------------------
##
## Asynchronous procedures remove the pain of working with callbacks. They do
## this by allowing you to write asynchronous code the same way as you would
## write synchronous code.
##
## An asynchronous procedure is marked using the ``{.async.}`` pragma.
## When marking a procedure with the ``{.async.}`` pragma it must have a
## ``Future[T]`` return type or no return type at all. If you do not specify
## a return type then ``Future[void]`` is assumed.
##
## Inside asynchronous procedures ``await`` can be used to call any
## procedures which return a
## ``Future``; this includes asynchronous procedures. When a procedure is
## "awaited", the asynchronous procedure it is awaited in will
## suspend its execution
## until the awaited procedure's Future completes. At which point the
## asynchronous procedure will resume its execution. During the period
## when an asynchronous procedure is suspended other asynchronous procedures
## will be run by the dispatcher.
##
## The ``await`` call may be used in many contexts. It can be used on the right
## hand side of a variable declaration: ``var data = await socket.recv(100)``,
## in which case the variable will be set to the value of the future
## automatically. It can be used to await a ``Future`` object, and it can
## be used to await a procedure returning a ``Future[void]``:
## ``await socket.send("foobar")``.
##
## If an awaited future completes with an error, then ``await`` will re-raise
## this error. To avoid this, you can use the ``yield`` keyword instead of
## ``await``. The following section shows different ways that you can handle
## exceptions in async procs.
##
## Handling Exceptions
## ~~~~~~~~~~~~~~~~~~~
##
## The most reliable way to handle exceptions is to use ``yield`` on a future
## then check the future's ``failed`` property. For example:
##
## .. code-block:: Nim
## var future = sock.recv(100)
## yield future
## if future.failed:
## # Handle exception
##
## The ``async`` procedures also offer limited support for the try statement.
##
## .. code-block:: Nim
## try:
## let data = await sock.recv(100)
## echo("Received ", data)
## except:
## # Handle exception
##
## Unfortunately the semantics of the try statement may not always be correct,
## and occasionally the compilation may fail altogether.
## As such it is better to use the former style when possible.
##
##
## Discarding futures
## ------------------
##
## Futures should **never** be discarded. This is because they may contain
## errors. If you do not care for the result of a Future then you should
## use the ``asyncCheck`` procedure instead of the ``discard`` keyword.
##
## Examples
## --------
##
## For examples take a look at the documentation for the modules implementing
## asynchronous IO. A good place to start is the
## `asyncnet module <asyncnet.html>`_.
##
## Limitations/Bugs
## ----------------
##
## * The effect system (``raises: []``) does not work with async procedures.
## * Can't await in a ``except`` body
## * Forward declarations for async procs are broken,
## link includes workaround: https://github.com/nim-lang/Nim/issues/3182.
# TODO: Check if yielded future is nil and throw a more meaningful exception
type
AsyncError* = object of Exception
## Generic async exception
AsyncTimeoutError* = object of AsyncError
## Timeout exception
TimerCallback* = object
finishAt*: uint64
function*: AsyncCallback
PDispatcherBase = ref object of RootRef
timers*: HeapQueue[TimerCallback]
callbacks*: Deque[AsyncCallback]
proc `<`(a, b: TimerCallback): bool =
result = a.finishAt < b.finishAt
proc callSoon(cbproc: CallbackFunc, data: pointer = nil) {.gcsafe.}
proc initCallSoonProc() =
if asyncfutures2.getCallSoonProc().isNil:
asyncfutures2.setCallSoonProc(callSoon)
template processTimersGetTimeout(loop, timeout: untyped) =
var count = len(loop.timers)
if count > 0:
var lastFinish = curTime
while count > 0:
lastFinish = loop.timers[0].finishAt
if curTime < lastFinish:
break
loop.callbacks.addLast(loop.timers.pop().function)
dec(count)
if count > 0:
when defined(windows):
timeout = DWORD(lastFinish - curTime)
else:
timeout = int(lastFinish - curTime)
if timeout == 0:
if len(loop.callbacks) == 0:
when defined(windows):
timeout = INFINITE
else:
timeout = -1
else:
if len(loop.callbacks) != 0:
timeout = 0
template processTimers(loop: untyped) =
var curTime = fastEpochTime()
var count = len(loop.timers)
if count > 0:
while count > 0:
if curTime < loop.timers[0].finishAt:
break
loop.callbacks.addLast(loop.timers.pop().function)
dec(count)
template processCallbacks(loop: untyped) =
var count = len(loop.callbacks)
for i in 0..<count:
# This is mostly workaround for people which are using `waitFor` where
# it must be used `await`. While using `waitFor` inside of callbacks
# dispatcher's callback list is got decreased and length of
# `loop.callbacks` become not equal to `count`, its why `IndexError`
# can be generated.
if len(loop.callbacks) == 0: break
let callable = loop.callbacks.popFirst()
if not isNil(callable.function):
callable.function(callable.udata)
when defined(windows) or defined(nimdoc):
import winlean, sets, hashes
type
WSAPROC_TRANSMITFILE = proc(hSocket: SocketHandle, hFile: Handle,
nNumberOfBytesToWrite: DWORD,
nNumberOfBytesPerSend: DWORD,
lpOverlapped: POVERLAPPED,
lpTransmitBuffers: pointer,
dwReserved: DWORD): cint {.
stdcall.}
CompletionKey = ULONG_PTR
CompletionData* = object
fd*: AsyncFD
cb*: CallbackFunc
errCode*: OSErrorCode
bytesCount*: int32
udata*: pointer
CustomOverlapped* = object of OVERLAPPED
data*: CompletionData
PDispatcher* = ref object of PDispatcherBase
ioPort: Handle
handles: HashSet[AsyncFD]
connectEx*: WSAPROC_CONNECTEX
acceptEx*: WSAPROC_ACCEPTEX
getAcceptExSockAddrs*: WSAPROC_GETACCEPTEXSOCKADDRS
transmitFile*: WSAPROC_TRANSMITFILE
PtrCustomOverlapped* = ptr CustomOverlapped
RefCustomOverlapped* = ref CustomOverlapped
AsyncFD* = distinct int
proc hash(x: AsyncFD): Hash {.borrow.}
proc `==`*(x: AsyncFD, y: AsyncFD): bool {.borrow.}
proc newDispatcher*(): PDispatcher =
## Creates a new Dispatcher instance.
new result
result.ioPort = createIoCompletionPort(INVALID_HANDLE_VALUE, 0, 0, 1)
result.handles = initSet[AsyncFD]()
result.timers.newHeapQueue()
result.callbacks = initDeque[AsyncCallback](64)
var gDisp{.threadvar.}: PDispatcher ## Global dispatcher
proc setGlobalDispatcher*(disp: PDispatcher) =
## Set current thread's dispatcher instance to ``disp``.
if not gDisp.isNil:
assert gDisp.callbacks.len == 0
gDisp = disp
initCallSoonProc()
proc getGlobalDispatcher*(): PDispatcher =
## Returns current thread's dispatcher instance.
if gDisp.isNil:
setGlobalDispatcher(newDispatcher())
result = gDisp
proc getIoHandler*(disp: PDispatcher): Handle =
## Returns the underlying IO Completion Port handle (Windows) or selector
## (Unix) for the specified dispatcher.
return disp.ioPort
proc register*(fd: AsyncFD) =
## Register file descriptor ``fd`` in thread's dispatcher.
let loop = getGlobalDispatcher()
if createIoCompletionPort(fd.Handle, loop.ioPort,
cast[CompletionKey](fd), 1) == 0:
raiseOSError(osLastError())
loop.handles.incl(fd)
proc poll*() =
## Perform single asynchronous step.
let loop = getGlobalDispatcher()
var curTime = fastEpochTime()
var curTimeout = DWORD(0)
# Moving expired timers to `loop.callbacks` and calculate timeout
loop.processTimersGetTimeout(curTimeout)
# Processing handles
var lpNumberOfBytesTransferred: Dword
var lpCompletionKey: ULONG_PTR
var customOverlapped: PtrCustomOverlapped
let res = getQueuedCompletionStatus(
loop.ioPort, addr lpNumberOfBytesTransferred, addr lpCompletionKey,
cast[ptr POVERLAPPED](addr customOverlapped), curTimeout).bool
if res:
customOverlapped.data.bytesCount = lpNumberOfBytesTransferred
customOverlapped.data.errCode = OSErrorCode(-1)
let acb = AsyncCallback(function: customOverlapped.data.cb,
udata: cast[pointer](customOverlapped))
loop.callbacks.addLast(acb)
else:
let errCode = osLastError()
if customOverlapped != nil:
customOverlapped.data.errCode = errCode
let acb = AsyncCallback(function: customOverlapped.data.cb,
udata: cast[pointer](customOverlapped))
loop.callbacks.addLast(acb)
else:
if int32(errCode) != WAIT_TIMEOUT:
raiseOSError(errCode)
# Moving expired timers to `loop.callbacks`.
loop.processTimers()
# All callbacks which will be added in process will be processed on next
# poll() call.
loop.processCallbacks()
proc getFunc(s: SocketHandle, fun: var pointer, guid: var GUID): bool =
var bytesRet: DWORD
fun = nil
result = WSAIoctl(s, SIO_GET_EXTENSION_FUNCTION_POINTER, addr guid,
sizeof(GUID).DWORD, addr fun, sizeof(pointer).DWORD,
addr bytesRet, nil, nil) == 0
proc initAPI() =
var
WSAID_TRANSMITFILE = GUID(
D1: 0xb5367df0'i32, D2: 0xcbac'i16, D3: 0x11cf'i16,
D4: [0x95'i8, 0xca'i8, 0x00'i8, 0x80'i8,
0x5f'i8, 0x48'i8, 0xa1'i8, 0x92'i8])
let loop = getGlobalDispatcher()
var wsa: WSAData
if wsaStartup(0x0202'i16, addr wsa) != 0:
raiseOSError(osLastError())
let sock = winlean.socket(winlean.AF_INET, 1, 6)
if sock == INVALID_SOCKET:
raiseOSError(osLastError())
var funcPointer: pointer = nil
if not getFunc(sock, funcPointer, WSAID_CONNECTEX):
let err = osLastError()
close(sock)
raiseOSError(err)
loop.connectEx = cast[WSAPROC_CONNECTEX](funcPointer)
if not getFunc(sock, funcPointer, WSAID_ACCEPTEX):
let err = osLastError()
close(sock)
raiseOSError(err)
loop.acceptEx = cast[WSAPROC_ACCEPTEX](funcPointer)
if not getFunc(sock, funcPointer, WSAID_GETACCEPTEXSOCKADDRS):
let err = osLastError()
close(sock)
raiseOSError(err)
loop.getAcceptExSockAddrs = cast[WSAPROC_GETACCEPTEXSOCKADDRS](funcPointer)
if not getFunc(sock, funcPointer, WSAID_TRANSMITFILE):
let err = osLastError()
close(sock)
raiseOSError(err)
loop.transmitFile = cast[WSAPROC_TRANSMITFILE](funcPointer)
close(sock)
proc closeSocket*(fd: AsyncFD, aftercb: CallbackFunc = nil) =
## Closes a socket and ensures that it is unregistered.
let loop = getGlobalDispatcher()
loop.handles.excl(fd)
close(SocketHandle(fd))
if not isNil(aftercb):
var acb = AsyncCallback(function: aftercb)
loop.callbacks.addLast(acb)
proc closeHandle*(fd: AsyncFD, aftercb: CallbackFunc = nil) =
## Closes a (pipe/file) handle and ensures that it is unregistered.
let loop = getGlobalDispatcher()
loop.handles.excl(fd)
doAssert closeHandle(Handle(fd)) == 1
if not isNil(aftercb):
var acb = AsyncCallback(function: aftercb)
loop.callbacks.addLast(acb)
proc unregister*(fd: AsyncFD) =
## Unregisters ``fd``.
getGlobalDispatcher().handles.excl(fd)
proc contains*(disp: PDispatcher, fd: AsyncFD): bool =
## Returns ``true`` if ``fd`` is registered in thread's dispatcher.
return fd in disp.handles
else:
import selectors
from posix import EINTR, EAGAIN, EINPROGRESS, EWOULDBLOCK, MSG_PEEK,
MSG_NOSIGNAL
type
AsyncFD* = distinct cint
CompletionData* = object
fd*: AsyncFD
udata*: pointer
PCompletionData* = ptr CompletionData
SelectorData* = object
reader*: AsyncCallback
rdata*: CompletionData
writer*: AsyncCallback
wdata*: CompletionData
PDispatcher* = ref object of PDispatcherBase
selector: Selector[SelectorData]
keys: seq[ReadyKey]
proc `==`*(x, y: AsyncFD): bool {.borrow.}
proc newDispatcher*(): PDispatcher =
## Create new dispatcher.
new result
result.selector = newSelector[SelectorData]()
result.timers.newHeapQueue()
result.callbacks = initDeque[AsyncCallback](64)
result.keys = newSeq[ReadyKey](64)
var gDisp{.threadvar.}: PDispatcher ## Global dispatcher
proc setGlobalDispatcher*(disp: PDispatcher) =
## Set current thread's dispatcher instance to ``disp``.
if not gDisp.isNil:
assert gDisp.callbacks.len == 0
gDisp = disp
initCallSoonProc()
proc getGlobalDispatcher*(): PDispatcher =
## Returns current thread's dispatcher instance.
if gDisp.isNil:
setGlobalDispatcher(newDispatcher())
result = gDisp
proc getIoHandler*(disp: PDispatcher): Selector[SelectorData] =
## Returns system specific OS queue.
return disp.selector
proc register*(fd: AsyncFD) =
## Register file descriptor ``fd`` in thread's dispatcher.
let loop = getGlobalDispatcher()
var data: SelectorData
data.rdata.fd = fd
data.wdata.fd = fd
loop.selector.registerHandle(int(fd), {}, data)
proc unregister*(fd: AsyncFD) =
## Unregister file descriptor ``fd`` from thread's dispatcher.
getGlobalDispatcher().selector.unregister(int(fd))
proc contains*(disp: PDispatcher, fd: AsyncFd): bool {.inline.} =
## Returns ``true`` if ``fd`` is registered in thread's dispatcher.
result = int(fd) in disp.selector
proc addReader*(fd: AsyncFD, cb: CallbackFunc, udata: pointer = nil) =
## Start watching the file descriptor ``fd`` for read availability and then
## call the callback ``cb`` with specified argument ``udata``.
let loop = getGlobalDispatcher()
var newEvents = {Event.Read}
withData(loop.selector, int(fd), adata) do:
let acb = AsyncCallback(function: cb, udata: addr adata.rdata)
adata.reader = acb
adata.rdata = CompletionData(fd: fd, udata: udata)
newEvents.incl(Event.Read)
if not isNil(adata.writer.function): newEvents.incl(Event.Write)
do:
raise newException(ValueError, "File descriptor not registered.")
loop.selector.updateHandle(int(fd), newEvents)
proc removeReader*(fd: AsyncFD) =
## Stop watching the file descriptor ``fd`` for read availability.
let loop = getGlobalDispatcher()
var newEvents: set[Event]
withData(loop.selector, int(fd), adata) do:
# We need to clear `reader` data, because `selectors` don't do it
adata.reader.function = nil
# adata.rdata = CompletionData()
if not isNil(adata.writer.function): newEvents.incl(Event.Write)
do:
raise newException(ValueError, "File descriptor not registered.")
loop.selector.updateHandle(int(fd), newEvents)
proc addWriter*(fd: AsyncFD, cb: CallbackFunc, udata: pointer = nil) =
## Start watching the file descriptor ``fd`` for write availability and then
## call the callback ``cb`` with specified argument ``udata``.
let loop = getGlobalDispatcher()
var newEvents = {Event.Write}
withData(loop.selector, int(fd), adata) do:
let acb = AsyncCallback(function: cb, udata: addr adata.wdata)
adata.writer = acb
adata.wdata = CompletionData(fd: fd, udata: udata)
newEvents.incl(Event.Write)
if not isNil(adata.reader.function): newEvents.incl(Event.Read)
do:
raise newException(ValueError, "File descriptor not registered.")
loop.selector.updateHandle(int(fd), newEvents)
proc removeWriter*(fd: AsyncFD) =
## Stop watching the file descriptor ``fd`` for write availability.
let loop = getGlobalDispatcher()
var newEvents: set[Event]
withData(loop.selector, int(fd), adata) do:
# We need to clear `writer` data, because `selectors` don't do it
adata.writer.function = nil
# adata.wdata = CompletionData()
if not isNil(adata.reader.function): newEvents.incl(Event.Read)
do:
raise newException(ValueError, "File descriptor not registered.")
loop.selector.updateHandle(int(fd), newEvents)
proc closeSocket*(fd: AsyncFD, aftercb: CallbackFunc = nil) =
## Close asynchronous socket.
##
## Please note, that socket is not closed immediately. To avoid bugs with
## closing socket, while operation pending, socket will be closed as
## soon as all pending operations will be notified.
## You can execute ``aftercb`` before actual socket close operation.
let loop = getGlobalDispatcher()
proc continuation(udata: pointer) =
unregister(fd)
close(SocketHandle(fd))
if not isNil(aftercb):
aftercb(nil)
withData(loop.selector, int(fd), adata) do:
# We are scheduling reader and writer callbacks to be called
# explicitly, so they can get an error and continue work.
if not isNil(adata.reader.function):
if not adata.reader.deleted:
loop.callbacks.addLast(adata.reader)
if not isNil(adata.writer.function):
if not adata.writer.deleted:
loop.callbacks.addLast(adata.writer)
# Mark callbacks as deleted, we don't need to get REAL notifications
# from system queue for this reader and writer.
adata.reader.deleted = true
adata.writer.deleted = true
# We can't unregister file descriptor from system queue here, because
# in such case processing queue will stuck on poll() call, because there
# can be no file descriptors registered in system queue.
var acb = AsyncCallback(function: continuation)
loop.callbacks.addLast(acb)
when ioselSupportedPlatform:
proc addSignal*(signal: int, cb: CallbackFunc,
udata: pointer = nil): int =
## Start watching signal ``signal``, and when signal appears, call the
## callback ``cb`` with specified argument ``udata``. Returns signal
## identifier code, which can be used to remove signal callback
## via ``removeSignal``.
let loop = getGlobalDispatcher()
var data: SelectorData
result = loop.selector.registerSignal(signal, data)
withData(loop.selector, result, adata) do:
adata.reader = AsyncCallback(function: cb, udata: addr adata.rdata)
adata.rdata.fd = AsyncFD(result)
adata.rdata.udata = udata
do:
raise newException(ValueError, "File descriptor not registered.")
proc removeSignal*(sigfd: int) =
## Remove watching signal ``signal``.
let loop = getGlobalDispatcher()
loop.selector.unregister(sigfd)
proc poll*() =
## Perform single asynchronous step.
let loop = getGlobalDispatcher()
var curTime = fastEpochTime()
var curTimeout = 0
when ioselSupportedPlatform:
let customSet = {Event.Timer, Event.Signal, Event.Process,
Event.Vnode}
# Moving expired timers to `loop.callbacks` and calculate timeout.
loop.processTimersGetTimeout(curTimeout)
# Processing IO descriptors and all hardware events.
var count = loop.selector.selectInto(curTimeout, loop.keys)
for i in 0..<count:
let fd = loop.keys[i].fd
let events = loop.keys[i].events
withData(loop.selector, fd, adata) do:
if Event.Read in events or events == {Event.Error}:
if not adata.reader.deleted:
loop.callbacks.addLast(adata.reader)
if Event.Write in events or events == {Event.Error}:
if not adata.writer.deleted:
loop.callbacks.addLast(adata.writer)
if Event.User in events:
if not adata.reader.deleted:
loop.callbacks.addLast(adata.reader)
when ioselSupportedPlatform:
if customSet * events != {}:
if not adata.reader.deleted:
loop.callbacks.addLast(adata.reader)
# Moving expired timers to `loop.callbacks`.
loop.processTimers()
# All callbacks which will be added in process, will be processed on next
# poll() call.
loop.processCallbacks()
proc initAPI() =
discard getGlobalDispatcher()
proc addTimer*(at: uint64, cb: CallbackFunc, udata: pointer = nil) =
## Arrange for the callback ``cb`` to be called at the given absolute
## timestamp ``at``. You can also pass ``udata`` to callback.
let loop = getGlobalDispatcher()
var tcb = TimerCallback(finishAt: at,
function: AsyncCallback(function: cb, udata: udata))
loop.timers.push(tcb)
proc removeTimer*(at: uint64, cb: CallbackFunc, udata: pointer = nil) =
## Remove timer callback ``cb`` with absolute timestamp ``at`` from waiting
## queue.
let loop = getGlobalDispatcher()
var list = cast[seq[TimerCallback]](loop.timers)
var index = -1
for i in 0..<len(list):
if list[i].finishAt == at and list[i].function.function == cb and
list[i].function.udata == udata:
index = i
break
if index != -1:
loop.timers.del(index)
proc sleepAsync*(ms: int): Future[void] =
## Suspends the execution of the current async procedure for the next
## ``ms`` milliseconds.
var retFuture = newFuture[void]("sleepAsync")
proc completion(data: pointer) =
if not retFuture.finished:
retFuture.complete()
addTimer(fastEpochTime() + uint64(ms),
completion, cast[pointer](retFuture))
return retFuture
proc withTimeout*[T](fut: Future[T], timeout: int): Future[bool] =
## Returns a future which will complete once ``fut`` completes or after
## ``timeout`` milliseconds has elapsed.
##
## If ``fut`` completes first the returned future will hold true,
## otherwise, if ``timeout`` milliseconds has elapsed first, the returned
## future will hold false.
var retFuture = newFuture[bool]("asyncdispatch.`withTimeout`")
proc continuation(udata: pointer) {.gcsafe.} =
if not retFuture.finished:
if isNil(udata):
fut.removeCallback(continuation)
retFuture.complete(false)
else:
if not retFuture.finished:
retFuture.complete(true)
addTimer(fastEpochTime() + uint64(timeout), continuation, nil)
fut.addCallback(continuation)
return retFuture
proc wait*[T](fut: Future[T], timeout = -1): Future[T] =
## Returns a future which will complete once future ``fut`` completes
## or if timeout of ``timeout`` milliseconds has been expired.
##
## If ``timeout`` is ``-1``, then statement ``await wait(fut)`` is
## equal to ``await fut``.
var retFuture = newFuture[T]("asyncdispatch.wait")
proc continuation(udata: pointer) {.gcsafe.} =
if not retFuture.finished:
if isNil(udata):
fut.removeCallback(continuation)
retFuture.fail(newException(AsyncTimeoutError, ""))
else:
if not retFuture.finished:
if fut.failed:
retFuture.fail(fut.error)
else:
retFuture.complete(fut.read())
if timeout == -1:
retFuture = fut
elif timeout == 0:
if fut.finished:
if fut.failed:
retFuture.fail(fut.error)
else:
retFuture.complete(fut.read())
else:
retFuture.fail(newException(AsyncTimeoutError, ""))
else:
addTimer(fastEpochTime() + uint64(timeout), continuation, nil)
fut.addCallback(continuation)
return retFuture
include asyncmacro2
proc callSoon(cbproc: CallbackFunc, data: pointer = nil) =
## Schedule `cbproc` to be called as soon as possible.
## The callback is called when control returns to the event loop.
assert cbproc != nil
let acb = AsyncCallback(function: cbproc, udata: data)
getGlobalDispatcher().callbacks.addLast(acb)
proc runForever*() =
## Begins a never ending global dispatcher poll loop.
while true:
poll()
proc waitFor*[T](fut: Future[T]): T =
## **Blocks** the current thread until the specified future completes.
while not fut.finished:
poll()
fut.read
# Global API and callSoon() initialization.
initAPI()
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