Various fixes to FutureStreams based on PR feedback.

lib/pure/asyncdispatch.nim

@@ -9,7 +9,7 @@
 
 include "system/inclrtl"
 
-import os, oids, tables, strutils, times, heapqueue, queues
+import os, oids, tables, strutils, times, heapqueue
 
 import nativesockets, net, deques
 
@@ -1387,6 +1387,17 @@ proc send*(socket: AsyncFD, data: string,
 # -- Await Macro
 include asyncmacro
 
+proc readAll*(future: FutureStream[string]): Future[string] {.async.} =
+  ## Returns a future that will complete when all the string data from the
+  ## specified future stream is retrieved.
+  result = ""
+  while true:
+    let (hasValue, value) = await future.read()
+    if hasValue:
+      result.add(value)
+    else:
+      break
+
 proc recvLine*(socket: AsyncFD): Future[string] {.async, deprecated.} =
   ## Reads a line of data from ``socket``. Returned future will complete once
   ## a full line is read or an error occurs.

lib/pure/asyncfile.nim

@@ -476,13 +476,16 @@ proc close*(f: AsyncFile) =
     if close(f.fd.cint) == -1:
       raiseOSError(osLastError())
 
-proc writeFromStream(f: AsyncFile, fut: FutureStream[string]) {.async.} =
+proc writeFromStream*(f: AsyncFile, fs: FutureStream[string]) {.async.} =
+  ## Reads data from the specified future stream until it is completed.
+  ## The data which is read is written to the file immediately and
+  ## freed from memory.
+  ##
+  ## This procedure is perfect for saving streamed data to a file without
+  ## wasting memory.
   while true:
-    let (hasValue, value) = await fut.take()
+    let (hasValue, value) = await fs.read()
     if hasValue:
       await f.write(value)
     else:
       break
-
-proc setWriteStream*(f: AsyncFile; fut: FutureStream[string]) {.async.} =
-  await writeFromStream(f, fut)

lib/pure/collections/deques.nim

@@ -129,7 +129,7 @@ proc expandIfNeeded[T](deq: var Deque[T]) =
   var cap = deq.mask + 1
   if unlikely(deq.count >= cap):
     var n = newSeq[T](cap * 2)
-    for i, x in deq:  # don't use copyMem because the GC and because it's slower.
+    for i, x in pairs(deq):  # don't use copyMem because the GC and because it's slower.
       shallowCopy(n[i], x)
     shallowCopy(deq.data, n)
     deq.mask = cap * 2 - 1

lib/pure/httpclient.nim

@@ -131,7 +131,7 @@ type
     version*: string
     status*: string
     headers*: HttpHeaders
-    body: string # TODO: here for compatibility with old httpclient procs.
+    body: string
     bodyStream*: Stream
 
   AsyncResponse* = ref object
@@ -163,19 +163,6 @@ proc `body=`*(response: Response, value: string) {.deprecated.} =
   ## **This is deprecated and should not be used**.
   response.body = value
 
-proc readAll*(future: FutureStream[string]): Future[string] {.async.} =
-  ## Returns a future that will complete when all the string data from the
-  ## specified future stream is retrieved.
-
-  # TODO: Move this to asyncfutures.
-  result = ""
-  while true:
-    let (hasValue, value) = await future.take()
-    if hasValue:
-      result.add(value)
-    else:
-      break
-
 proc body*(response: AsyncResponse): Future[string] {.async.} =
   ## Reads the response's body and caches it. The read is performed only
   ## once.
@@ -650,7 +637,7 @@ proc post*(url: string, extraHeaders = "", body = "",
   ## **Deprecated since version 0.15.0**: use ``HttpClient.post`` instead.
   let (mpHeaders, mpBody) = format(multipart)
 
-  template withNewLine(x): expr =
+  template withNewLine(x): untyped =
     if x.len > 0 and not x.endsWith("\c\L"):
       x & "\c\L"
     else:
@@ -891,10 +878,7 @@ proc recvFull(client: HttpClient | AsyncHttpClient, size: int, timeout: int,
 
     readLen.inc(data.len)
     if keep:
-      when client.socket is Socket:
-        client.bodyStream.write(data)
-      else:
-        await client.bodyStream.put(data)
+      await client.bodyStream.write(data)
 
     await reportProgress(client, data.len)
 
@@ -1253,11 +1237,15 @@ proc downloadFile*(client: HttpClient | AsyncHttpClient,
     parseBody(client, resp.headers, resp.version)
     client.bodyStream.close()
   else:
-    client.bodyStream = newFutureStream[string]()
-    var f = openAsync(filename, fmWrite)
+    client.bodyStream = newFutureStream[string]("downloadFile")
+    var file = openAsync(filename, fmWrite)
+    # Let `parseBody` write response data into client.bodyStream in the
+    # background.
     asyncCheck parseBody(client, resp.headers, resp.version)
-    await f.setWriteStream(client.bodyStream)
-    f.close()
+    # The `writeFromStream` proc will complete once all the data in the
+    # `bodyStream` has been written to the file.
+    await file.writeFromStream(client.bodyStream)
+    file.close()
 
   if resp.code.is4xx or resp.code.is5xx:
     raise newException(HttpRequestError, resp.status)

lib/pure/includes/asyncfutures.nim

@@ -17,8 +17,10 @@ type
   FutureVar*[T] = distinct Future[T]
 
   FutureStream*[T] = ref object of FutureBase   ## Special future that acts as
-                                                ## a queue.
-    queue: Queue[T]
+                                                ## a queue. Its API is still
+                                                ## experimental and so is
+                                                ## subject to change.
+    queue: Deque[T]
 
   FutureError* = object of Exception
     cause*: FutureBase
@@ -30,7 +32,7 @@ when not defined(release):
 
 proc callSoon*(cbproc: proc ()) {.gcsafe.}
 
-template setupFutureBase(fromProc: string): stmt =
+template setupFutureBase(fromProc: string) =
   new(result)
   result.finished = false
   when not defined(release):
@@ -55,13 +57,20 @@ proc newFutureVar*[T](fromProc = "unspecified"): FutureVar[T] =
   result = FutureVar[T](newFuture[T](fromProc))
 
 proc newFutureStream*[T](fromProc = "unspecified"): FutureStream[T] =
-  ## Create a new ``FutureStream``. This Future type's callback can be activated
-  ## multiple times when new data is written to it.
+  ## Create a new ``FutureStream``. This future's callback is activated when
+  ## two events occur:
+  ##
+  ## * New data is written into the future stream.
+  ## * The future stream is completed (this means that no more data will be
+  ##   written).
   ##
   ## 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.
+  ##
+  ## **Note:** The API of FutureStream is still new and so has a higher
+  ## likelihood of changing in the future.
   setupFutureBase(fromProc)
-  result.queue = initQueue[T]()
+  result.queue = initDeque[T]()
 
 proc clean*[T](future: FutureVar[T]) =
   ## Resets the ``finished`` status of ``future``.
@@ -130,7 +139,7 @@ proc complete*[T](future: FutureVar[T], val: T) =
     fut.cb()
 
 proc complete*[T](future: FutureStream[T]) =
-  ## Completes a ``FutureStream`` signifying the end of data.
+  ## Completes a ``FutureStream`` signalling the end of data.
   future.finished = true
   if not future.cb.isNil():
     future.cb()
@@ -179,8 +188,8 @@ proc `callback=`*[T](future: FutureStream[T],
   ## The callback is also called when the future is completed. So you should
   ## use ``finished`` to check whether data is available.
   ##
-  ## If the future stream already has data then ``cb`` will be called
-  ## immediately.
+  ## If the future stream already has data or is finished then ``cb`` will be
+  ## called immediately.
   future.cb = proc () = cb(future)
   if future.queue.len > 0 or future.finished:
     callSoon(future.cb)
@@ -236,8 +245,9 @@ proc finished*[T](future: Future[T] | FutureVar[T] | FutureStream[T]): bool =
   ##
   ## ``True`` may indicate an error or a value. Use ``failed`` to distinguish.
   ##
-  ## For a ``FutureStream`` this signifies that no more data will be placed
-  ## inside it and that there is no data waiting to be retrieved.
+  ## For a ``FutureStream`` a ``true`` value means that no more data will be
+  ## placed inside the stream _and_ that there is no data waiting to be
+  ## retrieved.
   when future is FutureVar[T]:
     result = (Future[T](future)).finished
   elif future is FutureStream[T]:
@@ -249,7 +259,7 @@ proc failed*(future: FutureBase): bool =
   ## Determines whether ``future`` completed with an error.
   return future.error != nil
 
-proc put*[T](future: FutureStream[T], value: T): Future[void] =
+proc write*[T](future: FutureStream[T], value: T): Future[void] =
   ## Writes the specified value inside the specified future stream.
   ##
   ## This will raise ``ValueError`` if ``future`` is finished.
@@ -258,12 +268,13 @@ proc put*[T](future: FutureStream[T], value: T): Future[void] =
     let msg = "FutureStream is finished and so no longer accepts new data."
     result.fail(newException(ValueError, msg))
     return
-  # TODO: Buffering.
-  future.queue.enqueue(value)
+  # TODO: Implement limiting of the streams storage to prevent it growing
+  # infinitely when no reads are occuring.
+  future.queue.addLast(value)
   if not future.cb.isNil: future.cb()
   result.complete()
 
-proc take*[T](future: FutureStream[T]): Future[(bool, T)] =
+proc read*[T](future: FutureStream[T]): Future[(bool, T)] =
   ## Returns a future that will complete when the ``FutureStream`` has data
   ## placed into it. The future will be completed with the oldest
   ## value stored inside the stream. The return value will also determine
@@ -286,7 +297,7 @@ proc take*[T](future: FutureStream[T]): Future[(bool, T)] =
         res[0] = false
       else:
         res[0] = true
-        res[1] = fs.queue.dequeue()
+        res[1] = fs.queue.popLast()
 
       if not resFut.finished:
         resFut.complete(res)

lib/upcoming/asyncdispatch.nim

@@ -1664,6 +1664,17 @@ proc accept*(socket: AsyncFD,
 # -- Await Macro
 include asyncmacro
 
+proc readAll*(future: FutureStream[string]): Future[string] {.async.} =
+  ## Returns a future that will complete when all the string data from the
+  ## specified future stream is retrieved.
+  result = ""
+  while true:
+    let (hasValue, value) = await future.take()
+    if hasValue:
+      result.add(value)
+    else:
+      break
+
 proc recvLine*(socket: AsyncFD): Future[string] {.async.} =
   ## Reads a line of data from ``socket``. Returned future will complete once
   ## a full line is read or an error occurs.

tests/async/tfuturestream.nim

@@ -19,14 +19,14 @@ var fs = newFutureStream[int]()
 proc alpha() {.async.} =
   for i in 0 .. 5:
     await sleepAsync(1000)
-    await fs.put(i)
+    await fs.write(i)
 
   echo("Done")
   fs.complete()
 
 proc beta() {.async.} =
   while not fs.finished:
-    let (hasValue, value) = await fs.take()
+    let (hasValue, value) = await fs.read()
     if hasValue:
       echo(value)