misc: Add `vformat_len_copy()`

This works the same as `vformat_len()`, except that it copies `args`
into a temporary `va_list`.

This can be useful when you're already using a `va_list`, and thus need
to copy the list already.

1 files changed, 9 insertions, 0 deletions

diff --git a/misc.c b/misc.c
index 3f82b64..36bbad4 100644
--- a/misc.c
+++ b/misc.c
@@ -201,6 +201,15 @@ char *skip_whitespace(const char *str) {
 	}
 }
 
+int vformat_len_copy(const char *fmt, va_list args) {
+	int len;
+	va_list tmp_args;
+	va_copy(tmp_args, args);
+	len = vformat_len(fmt, tmp_args);
+	va_end(tmp_args);
+	return len;
+}
+
 int vformat_len(const char *fmt, va_list args) {
 	return vsnprintf(NULL, 0, fmt, args);
 }