Index: src/OFStream.h
==================================================================
--- src/OFStream.h
+++ src/OFStream.h
@@ -142,10 +142,18 @@
  * \param str The string from which the data is written to the stream
  * \return The number of bytes written
  */
 - (size_t)writeLine: (OFString*)str;
 
+/**
+ * Writes a formatted string into the stream.
+ *
+ * \param fmt A string used as format
+ * \return The number of bytes written
+ */
+- (size_t)writeFormat: (OFString*)fmt, ...;
+
 /**
  * Closes the stream.
  */
 - close;
 @end

Index: src/OFStream.m
==================================================================
--- src/OFStream.m
+++ src/OFStream.m
@@ -9,11 +9,13 @@
  * the packaging of this file.
  */
 
 #include "config.h"
 
+#include <stdlib.h>
 #include <string.h>
+
 #include <assert.h>
 
 #import "OFStream.h"
 #import "OFString.h"
 #import "OFDataArray.h"
@@ -406,10 +408,41 @@
 		return [self writeNBytes: len + 1
 			      fromBuffer: tmp];
 	} @finally {
 		[self freeMemory: tmp];
 	}
+
+	/* Get rid of a warning, never reached anyway */
+	assert(0);
+}
+
+- (size_t)writeFormat: (OFString*)fmt, ...
+{
+	va_list args;
+	char *t;
+	size_t len;
+
+	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 {
+		free(t);
+	}
 
 	/* Get rid of a warning, never reached anyway */
 	assert(0);
 }