Add API to resolve host name in background

CMakeLists.txt

@@ -37,6 +37,7 @@ set(PLUGIN_SOURCES
 	src/vban-output.c
 	src/vban-output-thread.c
 	src/vban-filter.c
+	src/resolve-thread.c
 )
 
 add_library(${PROJECT_NAME} MODULE ${PLUGIN_SOURCES})

src/resolve-thread.c

@@ -0,0 +1,111 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <obs-module.h>
+#include <util/threading.h>
+#ifndef _WIN32
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netdb.h>
+#include <ctype.h>
+#else
+#include <ws2tcpip.h>
+#endif
+#include "plugin-macros.generated.h"
+#include "resolve-thread.h"
+
+struct resolve_thread_s
+{
+	char *name;
+	resolve_thread_resolved_cb resolved_cb;
+	resolve_thread_failed_cb failed_cb;
+	void *cb_data;
+};
+
+static void *resolve_thread_main(void *data);
+
+static bool is_valid_hostname(const char *host)
+{
+	if (!host)
+		return false;
+
+	bool mid = false;
+	bool prev_was_alnum = false;
+
+	while (*host) {
+		char c = *host++;
+		if (c == '.') {
+			if (!prev_was_alnum)
+				return false;
+			mid = false;
+			prev_was_alnum = false;
+		}
+		else if (c == '-') {
+			if (!mid)
+				return false;
+			prev_was_alnum = false;
+		}
+		else if (isalnum((unsigned char)c)) {
+			mid = true;
+			prev_was_alnum = true;
+		}
+	}
+
+	return prev_was_alnum;
+}
+
+bool resolve_thread_start(const char *name, void *cb_data, resolve_thread_resolved_cb resolved_cb,
+			  resolve_thread_failed_cb failed_cb)
+{
+	if (!is_valid_hostname(name)) {
+		if (failed_cb)
+			failed_cb(cb_data);
+		return false;
+	}
+
+	struct resolve_thread_s *ctx = bzalloc(sizeof(struct resolve_thread_s));
+	ctx->name = bstrdup(name);
+	ctx->resolved_cb = resolved_cb;
+	ctx->failed_cb = failed_cb;
+	ctx->cb_data = cb_data;
+
+	pthread_t thread;
+	if (pthread_create(&thread, NULL, resolve_thread_main, ctx)) {
+		blog(LOG_ERROR, "Failed to create resolving thread for '%s'", ctx->name);
+		return false;
+	}
+
+	pthread_detach(thread);
+
+	return true;
+}
+
+static void *resolve_thread_main(void *data)
+{
+	struct resolve_thread_s *ctx = data;
+
+	struct addrinfo hints = {
+		.ai_family = AF_INET,
+		.ai_socktype = SOCK_DGRAM,
+		.ai_protocol = IPPROTO_UDP,
+		.ai_flags = 0,
+	};
+
+	struct addrinfo *res;
+
+	if (getaddrinfo(ctx->name, NULL, &hints, &res) == 0) {
+		struct in_addr addr = {0};
+		addr.s_addr = ((struct sockaddr_in *)res->ai_addr)->sin_addr.s_addr;
+		freeaddrinfo(res);
+
+		if (ctx->resolved_cb)
+			ctx->resolved_cb(ctx->cb_data, &addr);
+	}
+	else {
+		if (ctx->failed_cb)
+			ctx->failed_cb(ctx->cb_data);
+	}
+
+	bfree(ctx->name);
+	bfree(ctx);
+	return NULL;
+}

src/resolve-thread.h

@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* The API resolves host name in a newly created thread.
+ * If the resolution has succeeded, `resolved` will be called.
+ * Otherwise, `failed` will be called.
+ */
+
+typedef void (*resolve_thread_resolved_cb)(void *data, const struct in_addr *addr);
+typedef void (*resolve_thread_failed_cb)(void *data);
+
+bool resolve_thread_start(const char *name, void *cb_data, resolve_thread_resolved_cb resolved_cb,
+			  resolve_thread_failed_cb failed_cb);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif