TCPConnection.waitForDataAsync

source/vibe/core/net.d

@@ -586,6 +586,61 @@ mixin(tracer);
 		return m_context.readBuffer.length > 0;
 	}
 
+	/** Waits asynchronously for new data to arrive.
+
+		This function can be used to detach the `TCPConnection` from a
+		running task while waiting for data, so that the associated memory
+		resources are available for other operations.
+
+		Note that `read_ready_callback` may be called from outside of a
+		task, so no blocking operations may be performed. Instead, an existing
+		task should be notified, or a new one started with `runTask`.
+
+		Params:
+			read_ready_callback = A callback taking a `bool` parameter that
+				signals the read-readiness of the connection
+			timeout = Optional timeout to limit the maximum wait time
+
+		Returns:
+			If the read readiness can be determined immediately, it will be
+			returned as  WaitForDataAsyncStatus.sataAvailable` or
+			`WaitForDataAsyncStatus.noModeData` and the callback will not be
+			invoked. Otherwise `WaitForDataAsyncStatus.waiting` is returned
+			and the callback will be invoked once the status can be
+			determined or the specified timeout is reached.
+	*/
+	WaitForDataAsyncStatus waitForDataAsync(CALLABLE)(CALLABLE read_ready_callback, Duration timeout = Duration.max)
+		if (is(typeof(read_ready_callback(true))))
+	{
+mixin(tracer);
+		import vibe.core.core : setTimer;
+
+		if (!m_context)
+			return WaitForDataAsyncStatus.noMoreData;
+
+		if (m_context.readBuffer.length > 0)
+			return WaitForDataAsyncStatus.dataAvailable;
+
+		if (timeout <= 0.seconds) {
+			auto rs = waitForData(0.seconds);
+			return rs ? WaitForDataAsyncStatus.dataAvailable : WaitForDataAsyncStatus.noMoreData;
+		}
+
+		auto tm = setTimer(timeout, {
+			eventDriver.sockets.cancelRead(m_socket);
+			read_ready_callback(false);
+		});
+		eventDriver.sockets.read(m_socket, m_context.readBuffer.peekDst(), IOMode.once,
+			(sock, st, nb) {
+				tm.stop();
+				assert(m_context.readBuffer.length == 0);
+				m_context.readBuffer.putN(nb);
+				read_ready_callback(m_context.readBuffer.length > 0);
+			});
+
+		return WaitForDataAsyncStatus.waiting;
+	}
+
 	const(ubyte)[] peek() { return m_context ? m_context.readBuffer.peek() : null; }
 
 	void skip(ulong count)
@@ -684,6 +739,16 @@ mixin(tracer);
 	}
 }
 
+/** Represents possible return values for
+    TCPConnection.waitForDataAsync.
+*/
+enum WaitForDataAsyncStatus {
+	noMoreData,
+	dataAvailable,
+	waiting,
+}
+
+
 mixin validateConnectionStream!TCPConnection;
 
 private void loopWithTimeout(alias LoopBody, ExceptionType = Exception)(Duration timeout)