strbuf: strbuf_append_va

docs/technical/strbuf.txt

@@ -43,6 +43,26 @@ Functions
 
     Adds the formated-string 'fmt' to the end of ->buf.
 
+`strbuf_append_va()`::
+
+    Adds the formated-string 'fmt' (generated by a `va_list`) to the end of ->buf. +
+    Returns the number of characters that should have been written if ->buf was large enough. +
+    Therefor if the function returns zero. all characters has been written. +
+    +
+    Example usage:
++
+----
+va_start(va, fmt);
+len = strbuf_append_va(s, fmt, va);
+va_end(va);
+
+if (len > 0) {
+    strbuf_expand(s, len);
+    va_start(va, fmt);
+    len = strbuf_append_va(s, fmt, va);
+    va_end(va);
+}
+----
 `strbuf_append_str()`::
 
     Will add the 'str' C-string to the end of ->buf