ascii-utf8-table.c

static unsigned char map[256] = {
        /* 0 1 2 3 4 5 6 7 8 9 A B C D E F */
/* 0x00 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // <CTRL> ...
/* 0x10 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // <CTRL> ...
/* 0x20 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  //   ! " # $ % & ' ( ) * + , - . /
/* 0x30 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // 0 1 2 3 4 5 6 7 8 9 : ; < = > ?
/* 0x40 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // @ A B C D E F G H I J K L M N O
/* 0x50 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // P Q R S T U V W X Y Z [ \ ] ^ _
/* 0x60 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // ` a b c d e f g h i j k l m n o
/* 0x70 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // p q r s t u v w x y z { | } ~ <DEL>
/* 0x80 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // <CTRL> ...
/* 0x90 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // <CTRL> ...
/* 0xA0 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // <NBSP> ¡ ¢ £ ¤ ¥ ¦ § ¨ © ª « ¬ <SOFTHYPEN> ® ¯
/* 0xB0 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // ° ± ² ³ ´ µ ¶ · ¸ ¹ º » ¼ ½ ¾ ¿
/* 0xC0 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // À Á Â Ã Ä Å Æ Ç È É Ê Ë Ì Í Î Ï
/* 0xD0 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // Ð Ñ Ò Ó Ô Õ Ö × Ø Ù Ú Û Ü Ý Þ ß
/* 0xE0 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,  // à á â ã ä å æ ç è é ê ë ì í î ï
/* 0xF0 */ 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0   // ð ñ ò ó ô õ ö ÷ ø ù ú û ü ý þ ÿ
};

example.c

static size_t WBufAppendSlug(WBuf* b, const char* pch, size_t len) {
  WBufReserve(b, len);
  const char* start = b->ptr;
  char c = 0, pc = 0;
  for (size_t i = 0; i < len; i++) {
    u8 x = (u8)pch[i];
    if (x >= 0x80) {
      // decode UTF8-encoded character as Latin-1
      if ((x >> 5) == 0x6 && i+1 < len) {
        u32 cp = ((x << 6) & 0x7ff) + ((pch[++i]) & 0x3f);
        x = cp <= 0xFF ? cp : 0;
      } else {
        x = 0;
      }
    }
    c = slugMap[x];
    if (c != '-' || pc != '-' && pc) {
      // note: check "pc" to trim leading '-'
      *(b->ptr++) = c;
      pc = c;
    }
  }
  if (pc == '-') {
    // trim trailing '-'
    b->ptr--;
  }
  return b->ptr - start;
}