Append directly to base string in vstr printf hooks

src/libstrongswan/printf_hook.c

@@ -141,14 +141,13 @@ static int custom_arginfo(const struct printf_info *info, size_t n, int *argtype
  */
 static int custom_fmt_cb(Vstr_base *base, size_t pos, Vstr_fmt_spec *fmt_spec)
 {
-	int i, written;
-	char buf[PRINTF_BUF_LEN];
+	int i;
 	const void *args[ARGS_MAX];
 	printf_hook_spec_t spec;
 	printf_hook_handler_t *handler = printf_hooks[SPEC_TO_INDEX(fmt_spec->name[0])];
 	printf_hook_data_t data = {
-		.buf = buf,
-		.buflen = sizeof(buf),
+		.base = base,
+		.pos = pos,
 	};
 
 	for (i = 0; i < handler->numargs; i++)
@@ -168,11 +167,7 @@ static int custom_fmt_cb(Vstr_base *base, size_t pos, Vstr_fmt_spec *fmt_spec)
 	spec.minus = fmt_spec->fmt_minus;
 	spec.width = fmt_spec->fmt_field_width;
 
-	written = handler->hook(&data, &spec, args);
-	if (written > 0)
-	{
-		vstr_add_buf(base, pos, buf, written);
-	}
+	handler->hook(&data, &spec, args);
 	return 1;
 }
 

src/libstrongswan/printf_hook.h

@@ -115,27 +115,22 @@ int vstr_wrapper_vasprintf(char **str, const char *format, va_list ap);
 struct printf_hook_data_t {
 
 	/**
-	 * Buffer to write to
+	 * Base to append printf to
 	 */
-	char *buf;
+	Vstr_base *base;
 
 	/**
-	 * Size of the buffer
+	 * Position in base to write to
 	 */
-	size_t buflen;
+	size_t pos;
 };
 
 /**
  * Helper macro to be used in printf hook callbacks.
  */
 #define print_in_hook(data, fmt, ...) ({\
-	int _written = snprintf(data->buf, data->buflen, fmt, ##__VA_ARGS__);\
-	if (_written < 0 || _written >= data->buflen)\
-	{\
-		_written = data->buflen - 1;\
-	}\
-	data->buf += _written;\
-	data->buflen -= _written;\
+	int _written =  vstr_add_fmt(data->base, data->pos, fmt, ##__VA_ARGS__);\
+	data->pos += _written;\
 	_written;\
 })