Add callback based EchoServer implementation

apps/EchoServerCallback.cpp

+// SPDX-License-Identifier: LGPL-3.0-or-later
+// Copyright © 2020-2021 Florian Fischer
+#include <sys/socket.h>
+
+#include <array>
+#include <cerrno>
+#include <cstdint>
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <string>
+
+#include "Common.hpp"
+#include "Debug.hpp"
+#include "Runtime.hpp"
+#include "io.hpp"
+#include "io/Future.hpp"
+
+using SendFuture = emper::io::SendFuture;
+using RecvFuture = emper::io::RecvFuture;
+
+const std::string HOST = "::";
+const std::string PORT = "12345";
+
+const size_t BUF_SIZE = 1024;
+
+class Client {
+ public:
+	int sockfd;
+	size_t bytes_recv;
+	size_t bytes_send;
+	std::array<char, BUF_SIZE> buf;
+
+	Client(int socket) : sockfd(socket), bytes_recv(0), bytes_send(0) {}
+
+	void submitSend() {
+		SendFuture sf(sockfd, &buf[bytes_send], bytes_recv - bytes_send, MSG_NOSIGNAL);
+		sf.setCallback([this](int32_t bytes_send) { this->onSend(bytes_send); });
+		sf.submit();
+	}
+
+	void onSend(int32_t res) {
+		if (unlikely(res < 0)) {
+			LOGE("server send failed: " << strerror(errno));
+			emper::io::closeAndForget(sockfd);
+			return;
+		}
+
+		bytes_send += res;
+
+		// Send again
+		if (bytes_send < bytes_recv) {
+			submitSend();
+			return;
+		}
+
+		submitRecv();
+	}
+
+	void submitRecv() {
+		bytes_send = 0;
+		RecvFuture rf(sockfd, buf.data(), BUF_SIZE, 0);
+		rf.setCallback([this](int32_t bytes_recv) { this->onRecv(bytes_recv); });
+		rf.submit();
+	}
+
+	void onRecv(int32_t res) {
+		if (unlikely(res <= 0)) {
+			// socket was shutdown
+			if (res < 0) {
+				LOGE("server read failed:" << strerror(errno));
+			}
+
+			emper::io::closeAndForget(sockfd);
+			return;
+		}
+
+		bytes_recv = res;
+
+		if (unlikely(bytes_recv == 5 && strncmp("quit\n", buf.data(), bytes_recv) == 0)) {
+			exit(EXIT_SUCCESS);
+		}
+
+		submitSend();
+	}
+};
+
+auto main(int argc, char* argv[]) -> int {
+	std::string host = HOST;
+	std::string port = PORT;
+
+	if (argc > 2) {
+		std::cerr << "Usage: " << argv[0] << " [port]" << std::endl;
+		exit(EXIT_FAILURE);
+	}
+
+	if (argc > 1) {
+		port = std::string(argv[1]);
+	}
+
+	std::cout << "Echoserver listening on " << host << ":" << port << std::endl;
+
+	Runtime runtime;
+	auto* listener = emper::io::tcp_listener(host, port, [](int socket) {
+		auto* client = new Client(socket);
+		client->submitRecv();
+	});
+
+	if (!listener) {
+		exit(EXIT_FAILURE);
+	}
+
+	runtime.scheduleFromAnywhere(*listener);
+
+	runtime.waitUntilFinished();
+
+	return EXIT_FAILURE;
+}

apps/meson.build

@@ -16,6 +16,12 @@ echoserver_exe = executable(
   dependencies: emper_dep,
 )
 
+echoserver_callback_exe = executable(
+  'echoserver_callback',
+  'EchoServerCallback.cpp',
+  dependencies: emper_dep,
+)
+
 echoclient_exe = executable(
   'echoclient',
   'EchoClient.cpp',