#include <strings.h>
#include <ctype.h>
#include <stdint.h>

#define aliases __attribute__((__may_alias__))
#define byte_repeat(x) ((size_t)~0 / 0xff * (x))
#define word_has_zero(x) (((x) - byte_repeat(0x01)) & ~(x) & byte_repeat(0x80))
#define word_tag_range(x, t, s, e) ((((x) | byte_repeat(t)) \
- byte_repeat(s) & ~((x) | byte_repeat(t)) - \
byte_repeat((e) + 1)) & (~(x) & byte_repeat(t)))
#define word_to_tolower(x) ((x) - (word_tag_range((x), 'a', 'z', 0x80)) >> 2)
#define weak_alias(o, n) extern __typeof__(o) n __attribute__((weak, alias(#o)))

int strncasecmp(const char *_l, const char *_r, size_t n)
{
	const unsigned char *l = (const void *)_l, *r = (const void *)_r;
	const size_t aliases *wl, aliases *wr;

	if (!n--) return 0;

	if (n < sizeof(size_t) * 3 || ((uintptr_t)l | (uintptr_t)r)
	    & sizeof(size_t) - 1) goto bytewise;

	for (;(uintptr_t)l & sizeof(size_t) - 1 && *l
	     && tolower(*l) == tolower(*r); l++, r++, n--);
	if ((uintptr_t)l & sizeof(size_t) - 1) return tolower(*l) - tolower(*r);

	wl = (const void *)l;
	wr = (const void *)r;
	for (; n >= sizeof(size_t) && !word_has_zero(*wl)
	       && word_to_tolower(*wl) == word_to_tolower(*wr)
	     ; wl++, wr++, n -= sizeof(size_t));
	l = (const void *)wl;
	r = (const void *)wr;

bytewise:
	for (; n && *l && tolower(*l) == tolower(*r); l++, r++, n--);

	return tolower(*l) - tolower(*r);
}

int __strncasecmp_l(const char *l, const char *r, size_t n, locale_t unused)
{
	return strncasecmp(l, r, n);
}

weak_alias(__strncasecmp_l, strncasecmp_l);