INitial commit.

README.md

@@ -1 +1,11 @@
 # asyncaddrinfo
+
+Asynchronous version of [getaddrinfo()](http://man7.org/linux/man-pages/man3/getaddrinfo.3.html).
+
+## Features
+
+* Uses getaddrinfo() underneath, so is quirk-compatible
+* Configurable number of resolver threads
+* Signals completion via a single file descriptor
+	* Compatible with select, poll, epoll, or blocking results
+* Simple API; splits getaddrinfo() into two functions, with a file descriptor in between

asyncaddrinfo.c

@@ -0,0 +1,125 @@
+#include <assert.h>
+#include <netdb.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "asyncaddrinfo.h"
+
+struct asyncaddrinfo_resolution {
+	int return_fd;
+
+	char *node;
+	char *service;
+	struct addrinfo _hints, *hints;
+
+	int err;
+	struct addrinfo *addrs;
+};
+
+static size_t asyncaddrinfo_num_threads;
+static pthread_t *asyncaddrinfo_threads = NULL;
+static int asyncaddrinfo_write_fd;
+
+static void *asyncaddrinfo_main(void *arg) {
+	int fd = (int) (intptr_t) arg;
+	struct asyncaddrinfo_resolution *res;
+	ssize_t len;
+	while ((len = recv(fd, &res, sizeof(res), 0)) == sizeof(res)) {
+		res->err = getaddrinfo(res->node, res->service, res->hints, &res->addrs);
+		int return_fd = res->return_fd;
+		res->return_fd = -1;
+		assert(send(return_fd, &res, sizeof(res), MSG_EOR) == sizeof(res));
+		// Main thread now owns res
+		assert(!close(return_fd));
+	}
+	assert(!len);
+	assert(!close(fd));
+	return NULL;
+}
+
+static void asyncaddrinfo_del(struct asyncaddrinfo_resolution *res) {
+	if (res->node) {
+		free(res->node);
+		res->node = NULL;
+	}
+	if (res->service) {
+		free(res->service);
+		res->service = NULL;
+	}
+	free(res);
+}
+
+void asyncaddrinfo_init(size_t threads) {
+	assert(!asyncaddrinfo_threads);
+
+	int fds[2];
+	assert(!socketpair(AF_UNIX, SOCK_SEQPACKET | SOCK_CLOEXEC, 0, fds));
+	asyncaddrinfo_write_fd = fds[1];
+
+	asyncaddrinfo_num_threads = threads;
+	asyncaddrinfo_threads = malloc(asyncaddrinfo_num_threads * sizeof(*asyncaddrinfo_threads));
+	assert(asyncaddrinfo_threads);
+
+	for (size_t i = 0; i < asyncaddrinfo_num_threads; i++) {
+		int subfd = dup(fds[0]);
+		assert(subfd >= 0);
+		assert(!pthread_create(&asyncaddrinfo_threads[i], NULL, asyncaddrinfo_main, (void *) (intptr_t) subfd));
+	}
+	assert(!close(fds[0]));
+}
+
+void asyncaddrinfo_cleanup() {
+	assert(asyncaddrinfo_threads);
+	assert(!close(asyncaddrinfo_write_fd));
+	asyncaddrinfo_write_fd = -1;
+	for (size_t i = 0; i < asyncaddrinfo_num_threads; i++) {
+		assert(!pthread_join(asyncaddrinfo_threads[i], NULL));
+	}
+	free(asyncaddrinfo_threads);
+	asyncaddrinfo_threads = NULL;
+}
+
+int asyncaddrinfo_resolve(const char *node, const char *service, struct addrinfo *hints) {
+	int fds[2];
+	assert(!socketpair(AF_UNIX, SOCK_SEQPACKET | SOCK_CLOEXEC, 0, fds));
+
+	struct asyncaddrinfo_resolution *res = malloc(sizeof(*res));
+	assert(res);
+	res->return_fd = fds[1];
+	if (node) {
+		res->node = strdup(node);
+		assert(res->node);
+	} else {
+		res->node = NULL;
+	}
+	if (service) {
+		res->service = strdup(service);
+		assert(res->service);
+	} else {
+		res->service = NULL;
+	}
+	if (hints) {
+		memcpy(&res->_hints, hints, sizeof(res->_hints));
+		res->hints = &res->_hints;
+	} else {
+		res->hints = NULL;
+	}
+	assert(send(asyncaddrinfo_write_fd, &res, sizeof(res), MSG_EOR) == sizeof(res));
+	// Resolve thread now owns res
+
+	return fds[0];
+}
+
+int asyncaddrinfo_result(int fd, struct addrinfo **addrs) {
+	struct asyncaddrinfo_resolution *res;
+	assert(recv(fd, &res, sizeof(res), 0) == sizeof(res));
+	assert(!close(fd));
+	*addrs = res->addrs;
+	int err = res->err;
+	asyncaddrinfo_del(res);
+	return err;
+}

asyncaddrinfo.h

@@ -0,0 +1,8 @@
+#pragma once
+
+struct addrinfo;
+
+void asyncaddrinfo_init(size_t threads);
+void asyncaddrinfo_cleanup(void);
+int asyncaddrinfo_resolve(const char *node, const char *service, struct addrinfo *hints);
+int asyncaddrinfo_result(int fd, struct addrinfo **addrs);