#include <limits.h>
#include <stdint.h>
#include <string.h>

#include "libc.h"

#define ALIGN (sizeof(size_t))
#define ONES ((size_t)-1 / UCHAR_MAX)
#define HIGHS (ONES * (UCHAR_MAX / 2 + 1))
#define HASZERO(x) (((x)-ONES) & ~(x)&HIGHS)

char* __strchrnul(const char* s, int c) {
  c = (unsigned char)c;
  if (!c)
    return (char*)s + strlen(s);

  for (; (uintptr_t)s % ALIGN; s++)
    if (!*s || *(unsigned char*)s == c)
      return (char*)s;
  const size_t* w = (const void*)s;
#if !__has_feature(address_sanitizer)
  // This reads past the end of the string, which is usually OK since it
  // won't cross a page boundary.  But under ASan, even one byte past the
  // actual end is diagnosed.
  size_t k = ONES * c;
  while (!HASZERO(*w) && !HASZERO(*w ^ k))
    ++w;
#endif
  for (s = (const void*)w; *s && *(unsigned char*)s != c; s++)
    ;
  return (char*)s;
}

weak_alias(__strchrnul, strchrnul);