Index: src/OFStream.h
==================================================================
--- src/OFStream.h
+++ src/OFStream.h
@@ -6,10 +6,12 @@
  *
  * This file is part of ObjFW. It may be distributed under the terms of the
  * Q Public License 1.0, which can be found in the file LICENSE included in
  * the packaging of this file.
  */
+
+#include <stdarg.h>
 
 #import "OFObject.h"
 
 @class OFString;
 @class OFDataArray;
@@ -264,10 +266,20 @@
  * \param fmt A string used as format
  * \return The number of bytes written
  */
 - (size_t)writeFormat: (OFString*)fmt, ...;
 
+/**
+ * Writes a formatted string into the stream.
+ *
+ * \param fmt A string used as format
+ * \param args The arguments used in the format string
+ * \return The number of bytes written
+ */
+- (size_t)writeFormat: (OFString*)fmt
+	withArguments: (va_list)args;
+
 /**
  * Closes the stream.
  */
 - close;
 @end

Index: src/OFStream.m
==================================================================
--- src/OFStream.m
+++ src/OFStream.m
@@ -611,26 +611,37 @@
 }
 
 - (size_t)writeFormat: (OFString*)fmt, ...
 {
 	va_list args;
-	char *t;
+	size_t ret;
+
+	va_start(args, fmt);
+	ret = [self writeFormat: fmt
+		  withArguments: args];
+	va_end(args);
+
+	return ret;
+}
+
+- (size_t)writeFormat: (OFString*)fmt
+	withArguments: (va_list)args
+{
 	size_t len;
+	char *t;
 
 	if (fmt == nil)
 		@throw [OFInvalidArgumentException newWithClass: isa
 						       selector: _cmd];
 
-	va_start(args, fmt);
 	if ((len = vasprintf(&t, [fmt cString], args)) == -1) {
 		/*
 		 * This is only the most likely error to happen. Unfortunately,
 		 * there is no good way to check what really happened.
 		 */
 		@throw [OFOutOfMemoryException newWithClass: isa];
 	}
-	va_end(args);
 
 	@try {
 		return [self writeNBytes: len
 			      fromBuffer: t];
 	} @finally {