implement group status/nick changes, various fixes

src/misc_tools.c

@@ -295,13 +295,19 @@ int get_group_nick_truncate(Tox *m, char *buf, int peernum, int groupnum)
 }
 
 /* copies data to msg buffer.
-   returns length of msg, which will be no larger than size-1 */
+   returns length of msg.
+   returns 0 and nulls msg if length is too big for buffer size */
 uint16_t copy_tox_str(char *msg, size_t size, const char *data, uint16_t length)
 {
-    int len = MIN(length, size - 1);
-    memcpy(msg, data, len);
-    msg[len] = '\0';
-    return len;
+    if (length > size - 1) {
+        length = 0;
+        msg[0] = '\0';
+        return length;
+    }
+
+    memcpy(msg, data, length);
+    msg[length] = '\0';
+    return length;
 }
 
 /* returns index of the first instance of ch in s starting at idx.