add runewidth

Makefile

@@ -34,6 +34,7 @@ SRC = $(GEN) \
 	src/runestrstr.c \
 	src/runetochar.c \
 	src/runetype.c \
+	src/runewidth.c \
 	src/utfecpy.c \
 	src/utflen.c \
 	src/utfnlen.c \

include/utf.h

@@ -76,6 +76,7 @@ Rune *runestrrchr(const Rune *, Rune);
 Rune *runestrdup(const Rune *);
 Rune *runestrstr(const Rune *, const Rune *);
 
+int runewidth(Rune);
 int utftorunestr(Rune *, const char *);
 
 #ifdef __cplusplus

src/runewidth.c

@@ -0,0 +1,29 @@
+/* See LICENSE file for copyright and license details. */
+#include "utf.h"
+
+int
+runewidth(Rune r)
+{
+	/* Adapted from Markus Kuhn's wcwidth() */
+
+	if(r == 0)
+		return 0;
+	else if(iscntrlrune(r))
+		return -1;
+	else if(iscombiningrune(r))
+		return 0;
+	else if((r >= 0x1100 && r <= 0x115F)
+	     || (r >= 0x2329 && r <= 0x232A)
+	     || (r >= 0x2E80 && r <= 0xA4CF && r != 0x303F)
+	     || (r >= 0xAC00 && r <= 0xD7A3)
+	     || (r >= 0xF900 && r <= 0xFAFF)
+	     || (r >= 0xFE10 && r <= 0xFE19)
+	     || (r >= 0xFE30 && r <= 0xFE6F)
+	     || (r >= 0xFF00 && r <= 0xFF60)
+	     || (r >= 0xFFE0 && r <= 0xFFE6)
+	     || (r >= RUNE_C(0x20000) && r <= RUNE_C(0x2FFFD))
+	     || (r >= RUNE_C(0x30000) && r <= RUNE_C(0x3FFFD)))
+		return 2;
+	else
+		return 1;
+}