Split handler_loop from handler_listen

Some applications might set up a struct handler object to listen on any
port i.e., 0, but still need a way to determine which port number was
eventually selected by the implementation.

Therefore, handler_listen has been reduced to the server initialization
bit, whereas the main loop has been split into its own function, namely
handler_loop.

Because of these changes, it no longer made sense for libweb to write
the selected port to standard output, as this is something now
applications can do on their own.

handler.c

@@ -182,14 +182,20 @@ end:
     return ret;
 }
 
-int handler_listen(struct handler *const h, const unsigned short port)
+int handler_listen(struct handler *const h, const unsigned short port,
+    unsigned short *const outport)
 {
-    if (!(h->server = server_init(port)))
+    if (!(h->server = server_init(port, outport)))
     {
         fprintf(stderr, "%s: server_init failed\n", __func__);
         return -1;
     }
 
+    return 0;
+}
+
+int handler_loop(struct handler *const h)
+{
     for (;;)
     {
         bool exit, io;

include/libweb/handler.h

@@ -20,6 +20,8 @@ struct handler *handler_alloc(const struct handler_cfg *cfg);
 void handler_free(struct handler *h);
 int handler_add(struct handler *h, const char *url, enum http_op op,
     handler_fn f, void *user);
-int handler_listen(struct handler *h, unsigned short port);
+int handler_listen(struct handler *h, unsigned short port,
+    unsigned short *outport);
+int handler_loop(struct handler *h);
 
 #endif /* HANDLER_H */

include/libweb/server.h

@@ -4,7 +4,7 @@
 #include <stdbool.h>
 #include <stddef.h>
 
-struct server *server_init(unsigned short port);
+struct server *server_init(unsigned short port, unsigned short *outport);
 struct server_client *server_poll(struct server *s, bool *io, bool *exit);
 int server_read(void *buf, size_t n, struct server_client *c);
 int server_write(const void *buf, size_t n, struct server_client *c);

server.c

@@ -320,7 +320,8 @@ static int init_signals(void)
     return 0;
 }
 
-struct server *server_init(const unsigned short port)
+struct server *server_init(const unsigned short port,
+    unsigned short *const outport)
 {
     struct server *const s = malloc(sizeof *s);
 
@@ -373,8 +374,9 @@ struct server *server_init(const unsigned short port)
         fprintf(stderr, "%s: getsockname(2): %s\n", __func__, strerror(errno));
         goto failure;
     }
+    else if (outport)
+        *outport = ntohs(in.sin_port);
 
-    printf("Listening on port %hu\n", ntohs(in.sin_port));
     return s;
 
 failure: