+#define FULL_LO 0xff00
+#define FULL_HI 0xff5e
+#define HALF_LO 0x20
+
+#define isFullWidth(ch) ((int)(ch) >= FULL_LO && (int)(ch) <= FULL_HI)
+#define ToNormalWidth(ch) (wchar_t) (((int)(ch) - FULL_LO) + HALF_LO)
+#define ToFullWidth(ch) (wchar_t) (((int)(ch) - HALF_LO) + FULL_LO)
+
+/*
+ * Returns an ASCII code in [32..126]
+ */
+static wchar_t
+normal_wchar(int ch)
+{
+ wchar_t result = (wchar_t) ch;
+ if (isFullWidth(ch))
+ result = ToNormalWidth(ch);
+ return result;
+}
+
+/*
+ * Returns either an ASCII code in in [32..126] or full-width in
+ * [0xff00..0xff5e], according to use_fullwidth setting.
+ */
+static wchar_t
+target_wchar(int ch)
+{
+ wchar_t result = (wchar_t) ch;
+ if (use_fullwidth) {
+ if (!isFullWidth(ch))
+ result = ToFullWidth(ch);
+ } else {
+ if (isFullWidth(ch))
+ result = ToNormalWidth(ch);
+ }
+ return result;
+}
+