Index: uspace/lib/c/generic/str.c
===================================================================
--- uspace/lib/c/generic/str.c	(revision 6d5e378b28e2c858f3813b5d4d57fa46f709d753)
+++ uspace/lib/c/generic/str.c	(revision 20dccf3f4f41fb6f49fd3071c60e29e100cdae1d)
@@ -134,4 +134,49 @@
 	
 	return ch;
+}
+
+/** Decode a single character from a string to the left.
+ *
+ * Decode a single character from a string of size @a size. Decoding starts
+ * at @a offset and this offset is moved to the beginning of the previous
+ * character. In case of decoding error, offset generally decreases at least
+ * by one. However, offset is never moved before 0.
+ *
+ * @param str    String (not necessarily NULL-terminated).
+ * @param offset Byte offset in string where to start decoding.
+ * @param size   Size of the string (in bytes).
+ *
+ * @return Value of decoded character, U_SPECIAL on decoding error or
+ *         NULL if attempt to decode beyond @a start of str.
+ *
+ */
+wchar_t str_decode_reverse(const char *str, size_t *offset, size_t size)
+{
+	if (*offset == 0)
+		return 0;
+	
+	size_t processed = 0;
+	/* Continue while continuation bytes found */
+	while (*offset > 0 && processed < 4) {
+		uint8_t b = (uint8_t) str[--(*offset)];
+		
+		if (processed == 0 && (b & 0x80) == 0) {
+			/* 0xxxxxxx (Plain ASCII) */
+			return b & 0x7f;
+		}
+		else if ((b & 0xe0) == 0xc0 || (b & 0xf0) == 0xe0 ||
+		    (b & 0xf8) == 0xf0) {
+			/* Start byte */
+			size_t start_offset = *offset;
+			return str_decode(str, &start_offset, size);
+		}
+		else if ((b & 0xc0) != 0x80) {
+			/* Not a continuation byte */
+			return U_SPECIAL;
+		}
+		processed++;
+	}
+	/* Too many continuation bytes */
+	return U_SPECIAL;
 }