tasyncawait now works on Linux.

Reworked detection of a file descriptor being closed with epoll (in the
case of sockets it is when the remote host disconnects). Ensured that
events are only updated when they change.

lib/pure/asyncio2.nim

@@ -479,9 +479,11 @@ else:
       discard p.selector.update(sock, events)
   
   proc addRead(p: PDispatcher, sock: TSocketHandle, cb: TCallback) =
+    #echo("addRead")
     if sock notin p.selector:
       var data = PData(sock: sock, readCBs: @[cb], writeCBs: @[])
       p.selector.register(sock, {EvRead}, data.PObject)
+      #echo("registered")
     else:
       p.selector[sock].data.PData.readCBs.add(cb)
       p.update(sock, p.selector[sock].events + {EvRead})
@@ -498,7 +500,7 @@ else:
     for info in p.selector.select(timeout):
       let data = PData(info.key.data)
       assert data.sock == info.key.fd
-      
+      #echo("In poll ", data.sock.cint)
       if EvRead in info.events:
         # Callback may add items to ``data.readCBs`` which causes issues if
         # we are iterating over ``data.readCBs`` at the same time. We therefore
@@ -517,11 +519,17 @@ else:
           if not cb(data.sock):
             # Callback wants to be called again.
             data.writeCBs.add(cb)
-  
-      var newEvents: set[TEvent]
-      if data.readCBs.len != 0: newEvents = {EvRead}
-      if data.writeCBs.len != 0: newEvents = newEvents + {EvWrite}
-      p.update(data.sock, newEvents)
+      
+      if info.key in p.selector:
+        var newEvents: set[TEvent]
+        if data.readCBs.len != 0: newEvents = {EvRead}
+        if data.writeCBs.len != 0: newEvents = newEvents + {EvWrite}
+        if newEvents != info.key.events:
+          echo(info.key.events, " -> ", newEvents)
+          p.update(data.sock, newEvents)
+      else:
+        # FD no longer a part of the selector. Likely been closed
+        # (e.g. socket disconnected).
   
   proc connect*(p: PDispatcher, socket: TSocketHandle, address: string, port: TPort,
     af = AF_INET): PFuture[int] =
@@ -569,6 +577,7 @@ else:
       result = true
       let netSize = size - sizeRead
       let res = recv(sock, addr readBuffer[sizeRead], netSize, flags.cint)
+      #echo("recv cb res: ", res)
       if res < 0:
         let lastError = osLastError()
         if lastError.int32 notin {EINTR, EWOULDBLOCK, EAGAIN}: 
@@ -576,6 +585,7 @@ else:
         else:
           result = false # We still want this callback to be called.
       elif res == 0:
+        #echo("Disconnected recv: ", sizeRead)
         # Disconnected
         if sizeRead == 0:
           retFuture.complete("")
@@ -588,6 +598,7 @@ else:
           result = false # We want to read all the data requested.
         else:
           retFuture.complete(readBuffer)
+      #echo("Recv cb result: ", result)
   
     addRead(p, socket, cb)
     return retFuture
@@ -833,9 +844,13 @@ proc recvLine*(p: PDispatcher, socket: TSocketHandle): PFuture[string] {.async.}
   result = ""
   var c = ""
   while true:
+    #echo("1")
     c = await p.recv(socket, 1)
+    #echo("Received ", c.len)
     if c.len == 0:
+      #echo("returning")
       return
+    #echo("2")
     if c == "\r":
       c = await p.recv(socket, 1, MSG_PEEK)
       if c.len > 0 and c == "\L":
@@ -845,7 +860,9 @@ proc recvLine*(p: PDispatcher, socket: TSocketHandle): PFuture[string] {.async.}
     elif c == "\L":
       addNLIfEmpty()
       return
+    #echo("3")
     add(result.string, c)
+  #echo("4")
 
 when isMainModule:
   
@@ -859,6 +876,7 @@ when isMainModule:
     proc main(p: PDispatcher): PFuture[int] {.async.} =
       discard await p.connect(sock, "irc.freenode.net", TPort(6667))
       while true:
+        echo("recvLine")
         var line = await p.recvLine(sock)
         echo("Line is: ", line.repr)
         if line == "":
@@ -882,7 +900,7 @@ when isMainModule:
   else:
     when true:
 
-      var f = p.connect(sock, "irc.freenode.org", TPort(6667))
+      var f = p.connect(sock, "irc.poop.nl", TPort(6667))
       f.callback =
         proc (future: PFuture[int]) =
           echo("Connected in future!")
@@ -898,11 +916,13 @@ when isMainModule:
       sock.bindAddr(TPort(6667))
       sock.listen()
       proc onAccept(future: PFuture[TSocketHandle]) =
-        echo "Accepted"
-        var t = p.send(future.read, "test\c\L")
+        let client = future.read
+        echo "Accepted ", client.cint
+        var t = p.send(client, "test\c\L")
         t.callback =
           proc (future: PFuture[int]) =
-            echo(future.read)
+            echo("Send: ", future.read)
+            client.close()
         
         var f = p.accept(sock)
         f.callback = onAccept

lib/pure/selectors.nim

@@ -10,7 +10,6 @@
 # TODO: Docs.
 
 import tables, os, unsigned, hashes
-import sockets2
 
 when defined(linux): import posix, epoll
 elif defined(windows): import winlean
@@ -41,17 +40,14 @@ when defined(linux) or defined(nimdoc):
       result.events = EPOLLIN
     if EvWrite in events:
       result.events = result.events or EPOLLOUT
+    result.events = result.events or EPOLLRDHUP
     result.data.fd = fd.cint
   
   proc register*(s: PSelector, fd: TSocketHandle, events: set[TEvent],
       data: PObject): PSelectorKey {.discardable.} =
     ## Registers file descriptor ``fd`` to selector ``s`` with a set of TEvent
     ## ``events``.
-    if s.fds.hasKey(fd):
-      raise newException(EInvalidValue, "File descriptor already exists.")
-    
     var event = createEventStruct(events, fd)
-  
     if epoll_ctl(s.epollFD, EPOLL_CTL_ADD, fd, addr(event)) != 0:
       OSError(OSLastError())
   
@@ -63,30 +59,18 @@ when defined(linux) or defined(nimdoc):
   proc update*(s: PSelector, fd: TSocketHandle,
       events: set[TEvent]): PSelectorKey {.discardable.} =
     ## Updates the events which ``fd`` wants notifications for.
-    if not s.fds.hasKey(fd):
-      raise newException(EInvalidValue, "File descriptor not found.")
-    var event = createEventStruct(events, fd)
-    
-    s.fds[fd].events = events
-    if epoll_ctl(s.epollFD, EPOLL_CTL_MOD, fd, addr(event)) != 0:
-      if OSLastError().cint == ENOENT:
-        # Socket has been closed. Epoll automatically removes disconnected
-        # sockets.
-        s.fds.del(fd)
-        osError("Socket has been disconnected")
-        
-      OSError(OSLastError())
-    result = s.fds[fd]
+    if s.fds[fd].events != events:
+      echo("Update ", fd.cint, " to ", events)
+      var event = createEventStruct(events, fd)
+      
+      s.fds[fd].events = events
+      if epoll_ctl(s.epollFD, EPOLL_CTL_MOD, fd, addr(event)) != 0:
+        OSError(OSLastError())
+      result = s.fds[fd]
   
   proc unregister*(s: PSelector, fd: TSocketHandle): PSelectorKey {.discardable.} =
-    if not s.fds.hasKey(fd):
-      raise newException(EInvalidValue, "File descriptor not found.")
     if epoll_ctl(s.epollFD, EPOLL_CTL_DEL, fd, nil) != 0:
-      if osLastError().cint == ENOENT:
-        # Socket has been closed. Epoll automatically removes disconnected
-        # sockets so its already been removed.
-      else:
-        OSError(OSLastError())
+      OSError(OSLastError())
     result = s.fds[fd]
     s.fds.del(fd)
 
@@ -113,6 +97,14 @@ when defined(linux) or defined(nimdoc):
       assert selectorKey != nil
       result.add((selectorKey, evSet))
   
+      if (s.events[i].events and EPOLLHUP) != 0 or
+         (s.events[i].events and EPOLLRDHUP) != 0:
+        # fd closed
+        #echo("fd closed ", s.events[i].data.fd)
+        s.unregister(s.events[i].data.fd.TSocketHandle)
+  
+      #echo("Epoll: ", result[i].key.fd, " ", result[i].events, " ", result[i].key.events)
+  
   proc newSelector*(): PSelector =
     new result
     result.epollFD = epoll_create(64)
@@ -123,7 +115,26 @@ when defined(linux) or defined(nimdoc):
 
   proc contains*(s: PSelector, fd: TSocketHandle): bool =
     ## Determines whether selector contains a file descriptor.
-    return s.fds.hasKey(fd)
+    if s.fds.hasKey(fd):
+      result = true
+      
+      # Ensure the underlying epoll instance still contains this fd.
+      var event = createEventStruct(s.fds[fd].events, fd)
+      if epoll_ctl(s.epollFD, EPOLL_CTL_MOD, fd, addr(event)) != 0:
+        let err = osLastError()
+        if err.cint in {ENOENT, EBADF}:
+          return false
+        OSError(OSLastError())
+    else:
+      return false
+
+  proc contains*(s: PSelector, key: PSelectorKey): bool =
+    ## Determines whether selector contains this selector key. More accurate
+    ## than checking if the file descriptor is in the selector because it
+    ## ensures that the keys are equal. File descriptors may not always be
+    ## unique especially when an fd is closed and then a new one is opened,
+    ## the new one may have the same value.
+    return key.fd in s and s.fds[key.fd] == key
 
   proc `[]`*(s: PSelector, fd: TSocketHandle): PSelectorKey =
     ## Retrieves the selector key for ``fd``.

tests/async/tasyncawait.nim

@@ -15,24 +15,17 @@ const
 var clientCount = 0
 
 proc sendMessages(disp: PDispatcher, client: TSocketHandle): PFuture[int] {.async.} =
-  echo("entering sendMessages")
   for i in 0 .. <messagesToSend:
     discard await disp.send(client, "Message " & $i & "\c\L")
-  echo("returning sendMessages")
 
 proc launchSwarm(disp: PDispatcher, port: TPort): PFuture[int] {.async.} =
   for i in 0 .. <swarmSize:
     var sock = socket()
-    # TODO: We may need to explicitly register and unregister the fd.
-    # This is because when the socket is closed, selectors is not aware
-    # that it has been closed. While epoll is. Perhaps we should just unregister
-    # in close()?
-    echo(sock.cint)
+
     #disp.register(sock)
     discard await disp.connect(sock, "localhost", port)
     when true:
       discard await sendMessages(disp, sock)
-      echo("Calling close")
       sock.close()
     else:
       # Issue #932: https://github.com/Araq/Nimrod/issues/932