Implement proper zero size wait semantics for Posix stream sockets.

source/eventcore/drivers/posix.d

@@ -399,10 +399,10 @@ final class PosixEventDriverSockets(Loop : PosixEventLoop) : EventDriverSockets
 
 	final override void read(StreamSocketFD socket, ubyte[] buffer, IOMode mode, IOCallback on_read_finish)
 	{
-		if (buffer.length == 0) {
+		/*if (buffer.length == 0) {
 			on_read_finish(socket, IOStatus.ok, 0);
 			return;
-		}
+		}*/
 
 		sizediff_t ret;
 		() @trusted { ret = .recv(socket, buffer.ptr, buffer.length, 0); } ();
@@ -417,11 +417,13 @@ final class PosixEventDriverSockets(Loop : PosixEventLoop) : EventDriverSockets
 		}
 
 		if (ret == 0) {
+			print("disconnect");
 			on_read_finish(socket, IOStatus.disconnected, 0);
 			return;
 		}
 
 		if (ret < 0 && mode == IOMode.immediate) {
+			print("wouldblock");
 			on_read_finish(socket, IOStatus.wouldBlock, 0);
 			return;
 		}
@@ -469,8 +471,9 @@ final class PosixEventDriverSockets(Loop : PosixEventLoop) : EventDriverSockets
 			slot.readCallback(socket, status, slot.bytesRead);
 		}
 
-		sizediff_t ret;
+		sizediff_t ret = 0;
-		() @trusted { ret = .recv(socket, slot.readBuffer.ptr, slot.readBuffer.length, 0); } ();
+		if (!slot.readBuffer.length)
+			() @trusted { ret = .recv(socket, slot.readBuffer.ptr, slot.readBuffer.length, 0); } ();
 		if (ret < 0) {
 			auto err = getSocketError();
 			if (!err.among!(EAGAIN, EINPROGRESS)) {
@@ -479,13 +482,13 @@ final class PosixEventDriverSockets(Loop : PosixEventLoop) : EventDriverSockets
 			}
 		}
 
-		if (ret == 0) {
+		if (ret == 0 && slot.readBuffer.length) {
 			slot.state = ConnectionState.passiveClose;
 			finalize(IOStatus.disconnected);
 			return;
 		}
 
-		if (ret > 0) {
+		if (ret > 0 || !slot.readBuffer.length) {
 			slot.bytesRead += ret;
 			slot.readBuffer = slot.readBuffer[ret .. $];
 			if (slot.readMode != IOMode.all || slot.readBuffer.length == 0) {

tests/0-tcp-readwait.d

@@ -0,0 +1,66 @@
+/++ dub.sdl:
+	name "test"
+	dependency "eventcore" path=".."
++/
+module test;
+
+import eventcore.core;
+import eventcore.socket;
+import std.socket : InternetAddress;
+import core.time : Duration, msecs;
+
+ubyte[256] s_rbuf;
+bool s_done;
+
+void main()
+{
+	static ubyte[] pack1 = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
+
+	auto baddr 	= new InternetAddress(0x7F000001, 40002);
+	auto server = listenStream(baddr);
+	StreamSocket client;
+	StreamSocket incoming;
+
+	server.waitForConnections!((incoming_, addr) {
+		incoming = incoming_; // work around ref counting issue
+		incoming.read!((status, bts) {
+			assert(status == IOStatus.ok);
+			assert(bts == 0);
+
+			incoming.read!((status, bts) {
+				assert(status == IOStatus.ok);
+				assert(bts == pack1.length);
+				assert(s_rbuf[0 .. bts] == pack1);
+
+				destroy(incoming);
+				destroy(server);
+				destroy(client);
+				s_done = true;
+
+				// FIXME: this shouldn't ne necessary:
+				eventDriver.core.exit();
+			})(s_rbuf, IOMode.immediate);
+		})(s_rbuf[0 .. 0], IOMode.once);
+	});
+
+	connectStream!((sock, status) {
+		assert(status == ConnectStatus.connected);
+		client = sock;
+
+		auto tm = eventDriver.timers.create();
+		eventDriver.timers.set(tm, 100.msecs, 0.msecs);
+		eventDriver.timers.wait(tm, (tm) {
+			client.write!((wstatus, bytes) {
+				assert(wstatus == IOStatus.ok);
+				assert(bytes == 10);
+			})(pack1, IOMode.all);
+		});
+	})(baddr);
+
+	ExitReason er;
+	do er = eventDriver.core.processEvents(Duration.max);
+	while (er == ExitReason.idle);
+	//assert(er == ExitReason.outOfWaiters); // FIXME: see above
+	assert(s_done);
+	s_done = false;
+}