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/* ****************************************************************************
 * string/memset.c -- Initialize the content of a memory area.
 * Copyright (C) 2017 Thomas "Cakeisalie5" Touhey <thomas@touhey.fr>
 *
 * This file is part of the 'all/core' module,
 * in libcarrot, an experimental modular libc project.
 *
 * This file is free software: you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option)
 * any later version.
 *
 * This file is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Lesser Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this file.  If not, see <http://www.gnu.org/licenses/>.
 * ************************************************************************* */
#include <string.h>
#include <stdint.h>

/**
 *	setlil:
 *	Set a little zone of memory.
 *
 *	@arg	dword
 *
 *	@arg	dword		the word to set.
 *	@arg	full		the character fullarized.
 *	@arg	start		the starting byte.
 *	@arg	end			the ending byte.
 */

static __inline void setlil(unsigned int *p, unsigned char c, size_t count)
{
	switch (count % 8) {
		case 7: *p++ = c;
		case 6: *p++ = c;
		case 5: *p++ = c;
		case 4: *p++ = c;
		case 3: *p++ = c;
		case 2: *p++ = c;
		case 1: *p++ = c;
		case 0: break;
	}
}

/**
 *	memset:
 *	Initialize a memory area with a value.
 *
 *	@arg	s		the void thingy.
 *	@arg	c		the character.
 *	@arg	n		the size.
 *	@return			the memory area.
 */

void *memset(void *s, int c, size_t n)
{
	unsigned int lc;
	__uintptr_t mask;
	unsigned int *p;
	int count;

	if (!n) return (s);

	/* prepare the full character */
	lc = c & 0xFF;
	lc |= lc << 8;
#if __SIZEOF_INT__ > 2
	lc |= lc << 16;
# if __SIZEOF_INT__ > 4
	lc |= lc << 32;
# endif
#endif

	/* get the initial pointer */
	mask = (__uintptr_t)&((unsigned int*)NULL)[1] - 1;
	p = (unsigned int*)((__uintptr_t)s & ~mask) + 1;
	count = (int)((__uintptr_t)p - (__uintptr_t)s);
	n -= count;

	/* initial bytes */
	setlil(s, c, count);

	/* main loop */
	for (; n >= sizeof(unsigned int); n -= sizeof(unsigned int))
		*p++ = lc;

	/* final bytes */
	setlil(p, c, n);

	/* return destination */
	return (s);
}