+DEFINE_MUTEX(con_buf_mtx);
+
+/* is_double_width() is based on the wcwidth() implementation by
+ * Markus Kuhn -- 2007-05-26 (Unicode 5.0)
+ * Latest version: http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
+ */
+struct interval {
+ uint32_t first;
+ uint32_t last;
+};
+
+static int bisearch(uint32_t ucs, const struct interval *table, int max)
+{
+ int min = 0;
+ int mid;
+
+ if (ucs < table[0].first || ucs > table[max].last)
+ return 0;
+ while (max >= min) {
+ mid = (min + max) / 2;
+ if (ucs > table[mid].last)
+ min = mid + 1;
+ else if (ucs < table[mid].first)
+ max = mid - 1;
+ else
+ return 1;
+ }
+ return 0;
+}
+
+static int is_double_width(uint32_t ucs)
+{
+ static const struct interval double_width[] = {
+ { 0x1100, 0x115F }, { 0x2329, 0x232A }, { 0x2E80, 0x303E },
+ { 0x3040, 0xA4CF }, { 0xAC00, 0xD7A3 }, { 0xF900, 0xFAFF },
+ { 0xFE10, 0xFE19 }, { 0xFE30, 0xFE6F }, { 0xFF00, 0xFF60 },
+ { 0xFFE0, 0xFFE6 }, { 0x20000, 0x2FFFD }, { 0x30000, 0x3FFFD }
+ };
+ return bisearch(ucs, double_width, ARRAY_SIZE(double_width) - 1);
+}