(NEXT_CHAR_BOUNDARY, PREV_CHAR_BOUNDARY): New macros.

1 files changed, 28 insertions, 0 deletions

diff --git a/src/charset.h b/src/charset.h
index 2b58f88f840..23a46326678 100644
--- a/src/charset.h
+++ b/src/charset.h
@@ -634,6 +634,34 @@ else
    ? 1                                                  \
    : multibyte_form_length (str, len))
 
+/* If P is before LIMIT, advance P to the next character boundary.  It
+   assumes that P is already at a character boundary of the sane
+   mulitbyte form whose end address is LIMIT.  */
+
+#define NEXT_CHAR_BOUNDARY(p, limit)    \
+  do {                                  \
+    if ((p) < (limit))                  \
+      (p) += BYTES_BY_CHAR_HEAD (*(p)); \
+  } while (0)
+
+
+/* If P is after LIMIT, advance P to the previous character boundary.
+   It assumes that P is already at a character boundary of the sane
+   mulitbyte form whose beginning address is LIMIT.  */
+
+#define PREV_CHAR_BOUNDARY(p, limit)                                    \
+  do {                                                                  \
+    if ((p) > (limit))                                                  \
+      {                                                                 \
+        const unsigned char *p0 = (p);                                  \
+        do {                                                            \
+          p0--;                                                         \
+        } while (p0 >= limit && ! CHAR_HEAD_P (*p0));                   \
+        (p) = (BYTES_BY_CHAR_HEAD (*p0) == (p) - p0) ? p0 : (p) - 1;    \
+      }                                                                 \
+  } while (0)
+
+
 #ifdef emacs
 
 /* Increase the buffer byte position POS_BYTE of the current buffer to