/* rig file: fix.diff applied to the pristine body */
#include "prelude.h"

#if LONG_BIT != 32 && LONG_BIT != 64
#error Unsupported word size
#endif

#define	LONGPTR_MASK (sizeof(long) - 1)

#define	TESTBYTE				\
	do {					\
		if (*p != (unsigned char)c)	\
			goto done;		\
		p++;				\
	} while (0)

void *
memcchr(const void *begin, int c, size_t n)
{
	const unsigned long *lp;
	const unsigned char *p, *end;
	unsigned long word;

	/* Four or eight repetitions of `c'. */
	word = (unsigned char)c;
	word |= word << 8;
	word |= word << 16;
#if LONG_BIT >= 64
	word |= word << 32;
#endif

	/* Don't perform memory I/O when passing a zero-length buffer. */
	if (n == 0)
		return (NULL);

	end = (const unsigned char *)begin + n;

	/* Compare bytewise until word aligned: no loads below begin. */
	for (p = begin; p < end && ((uintptr_t)p & LONGPTR_MASK);)
		TESTBYTE;

	/* Compare one word at a time while the whole word is in range. */
	for (lp = (const unsigned long *)p;
	    (const unsigned char *)(lp + 1) <= end; lp++) {
		if (*lp != word) {
			p = (const unsigned char *)lp;
			TESTBYTE;
			TESTBYTE;
			TESTBYTE;
#if LONG_BIT >= 64
			TESTBYTE;
			TESTBYTE;
			TESTBYTE;
			TESTBYTE;
#endif
			goto done;
		}
	}

	/* Trailing bytes: no loads past end. */
	for (p = (const unsigned char *)lp; p < end;)
		TESTBYTE;

	return (NULL);

done:
	/*
	 * If the end of the buffer is not word aligned, the previous
	 * loops may obtain an address that's beyond the end of the
	 * buffer.
	 */
	if (p < end)
		return (__DECONST(void *, p));
	return (NULL);
}