howdoesiteven.c

#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>

// How does this work:
// https://github.com/nginx/nginx/blob/master/src/http/ngx_http_parse.c#L634

#define BYTE_TO_BINARY_PATTERN "%c%c%c%c%c%c%c%c"
#define BYTE_TO_BINARY(byte)  \
  (byte & 0x80 ? '1' : '0'), \
  (byte & 0x40 ? '1' : '0'), \
  (byte & 0x20 ? '1' : '0'), \
  (byte & 0x10 ? '1' : '0'), \
  (byte & 0x08 ? '1' : '0'), \
  (byte & 0x04 ? '1' : '0'), \
  (byte & 0x02 ? '1' : '0'), \
  (byte & 0x01 ? '1' : '0')


static uint32_t  usual[] = {
    0xffffdbfe, /* 1111 1111 1111 1111  1101 1011 1111 1110 */
                /* ?>=< ;:98 7654 3210  /.-, +*)( '&%$ #"!  */

    0x7fff37d6, /* 0111 1111 1111 1111  0011 0111 1101 0110 */
                /* _^]\ [ZYX WVUT SRQP  ONML KJIH GFED CBA@ */


    0xffffffff, /* 1111 1111 1111 1111  1111 1111 1111 1111 */
                /*  ~}| {zyx wvut srqp  onml kjih gfed cba` */

    0xffffffff, /* 1111 1111 1111 1111  1111 1111 1111 1111 */
    0xffffffff, /* 1111 1111 1111 1111  1111 1111 1111 1111 */
    0xffffffff, /* 1111 1111 1111 1111  1111 1111 1111 1111 */
    0xffffffff  /* 1111 1111 1111 1111  1111 1111 1111 1111 */
};


int main(int argc, char const *argv[]) {
  uint8_t  ch = '';
  for (size_t i = 0; i < 126; i++) {
    ch = i;
    printf("-> [%d] "BYTE_TO_BINARY_PATTERN"\n", ch >> 5, BYTE_TO_BINARY((1U << (ch & 0x1f))));
    if (usual[ch >> 5] & (1U << (ch & 0x1f))) {
      printf("BREAK: %c\n", ch);
    } else {
      printf("OK: %c\n", ch);
    }
  }

  return 0;
}