+static void
+replace_whitespace (string *str)
+{
+ vsize i = 0;
+ vsize n = str->size ();
+
+ while (i < n)
+ {
+ vsize char_len = 1;
+ char cur = (*str)[i];
+
+ // U+10000 - U+10FFFF
+ if ((cur & 0x11110000) == 0x11110000)
+ char_len = 4;
+ // U+0800 - U+FFFF
+ else if ((cur & 0x11100000) == 0x11100000)
+ char_len = 3;
+ // U+0080 - U+07FF
+ else if ((cur & 0x11000000) == 0x11000000)
+ char_len = 2;
+ else if (cur & 0x10000000)
+ programming_error ("invalid utf-8 string");
+ else
+ // avoid the locale-dependent isspace
+ if (cur == '\n' || cur == '\t' || cur == '\v')
+ (*str)[i] = ' ';
+
+ i += char_len;
+ }
+}
+