1 files changed, 9 insertions, 0 deletions

diff --git a/src/charset.h b/src/charset.h
index 0965bb29d2c..a8e162d1a30 100644
--- a/src/charset.h
+++ b/src/charset.h
@@ -412,6 +412,15 @@ extern Lisp_Object Vchar_charset_set;
    : decode_char ((charset), (code)))
 
 
+/* If CHARSET is a simple offset base charset, return it's offset,
+   otherwise return -1.  */
+#define CHARSET_OFFSET(charset)                         \
+  (((charset)->method == CHARSET_METHOD_OFFSET          \
+    && (charset)->code_linear_p                         \
+    && ! (charset)->unified_p)                          \
+   ? (charset)->code_offset - (charset)->min_code       \
+   : -1)
+
 extern Lisp_Object charset_work;
 
 /* Return a code point of CHAR in CHARSET.