format: use empty element to set default values

An empty string in the type, to and from uses a default value. For
example to send a message to the groupchat specified on the command
line:

~~~

m::::this is a test message
~~~

src/xmppipe.c

@@ -1236,7 +1236,7 @@ xmppipe_send_stanza(xmppipe_state_t *state, char *buf0, size_t len)
 
     buf = xmppipe_strdup(buf0);
 
-    tok[0] = strtok(buf, ":");
+    tok[0] = xmppipe_strtok(buf, ":");
     switch (tok[0][0]) {
       case 'm':
         j = 5;
@@ -1254,7 +1254,7 @@ xmppipe_send_stanza(xmppipe_state_t *state, char *buf0, size_t len)
 
     while (tok[i] != NULL && i < j) {
       i++;
-      tok[i] = strtok(NULL, ":");
+      tok[i] = xmppipe_strtok(NULL, ":");
 
       if (state->verbose)
           (void)fprintf(stderr, "message:%d:%s\n", i,
@@ -1268,6 +1268,9 @@ xmppipe_send_stanza(xmppipe_state_t *state, char *buf0, size_t len)
         return;
     }
 
+    if (strlen(tok[1]) == 0)
+        tok[1] = (state->opt & XMPPIPE_OPT_GROUPCHAT) ? "groupchat" : "chat";
+
     if (tok[2] == NULL) {
         if (state->verbose)
           (void)fprintf(stderr, "to address required\n");
@@ -1275,6 +1278,9 @@ xmppipe_send_stanza(xmppipe_state_t *state, char *buf0, size_t len)
         return;
     }
 
+    if (strlen(tok[2]) == 0)
+        tok[2] = state->out;
+
     if (tok[4] == NULL) {
         if (state->verbose)
           (void)fprintf(stderr, "body required\n");
@@ -1300,6 +1306,7 @@ xmppipe_send_stanza(xmppipe_state_t *state, char *buf0, size_t len)
     xmppipe_send_message(state, to, type, body, strlen(body));
 
 XMPPIPE_ERR:
+    free(buf);
     free(type);
     free(to);
     free(body);

src/xmppipe.h

@@ -117,6 +117,7 @@ char *xmppipe_getenv(const char *);
 char *xmppipe_strdup(const char *);
 void *xmppipe_malloc(size_t);
 void *xmppipe_calloc(size_t, size_t);
+char *xmppipe_strtok(char *str, char const *delims);
 
 xmpp_stanza_t *xmppipe_stanza_new(xmpp_ctx_t *);
 void xmppipe_stanza_set_attribute(xmpp_stanza_t * const, const char * const,

src/xmppipe_util.c

@@ -92,6 +92,30 @@ xmppipe_calloc(size_t nmemb, size_t size)
     return buf;
 }
 
+// https://stackoverflow.com/a/30295426
+    char
+*xmppipe_strtok(char *str, char const *delims)
+{
+    static char *src = NULL;
+    char *p, *ret = 0;
+
+    if (str != NULL) src = str;
+
+    if (src == NULL || *src == '\0')
+        return NULL;
+
+    ret = src;
+    if ((p = strpbrk(src, delims)) != NULL)
+    {
+        *p  = 0;
+        src = ++p;
+    }
+    else
+        src += strlen(src);
+
+    return ret;
+}
+
     xmpp_stanza_t *
 xmppipe_stanza_new(xmpp_ctx_t *ctx)
 {