/* See the end of this file for copyright and license terms. */

#include <gay/types.h>

#include <string.h>

/*
 * The two and four byte routines use the same trick as strlen(),
 * see the respective file for details and where it's from.
 */

static inline void fourbyte_strcpy(char *to, const char *from)
{
	/* make sure we are aligned first */
#pragma unroll(3)
	while ((uintptr_t)to % 4) {
		if ((*to++ = *from++) == '\0')
			return;
	}

	/* copy in chunks of 4 bytes until there is a terminator */
	u32 *to32 = (u32 *)to;
	const u32 *from32 = (const u32 *)from;
	while ( ((*from32 - 0x01010101) & (~*from32 & 0x80808080)) == 0 )
		*to32++ = *from32++;

	to = (char *)to32;
	from = (const char *)from32;

	/* copy the remaining bytes (can only be within 1 and 4) */
#pragma unroll(4)
	while ((*to++ = *from++) != '\0');
		/* nothing */
}

static inline void twobyte_strcpy(char *to, const char *from)
{
	if ((uintptr_t)to % 2) {
		if ((*to++ = *from++) == '\0')
			return;
	}

	u16 *to16 = (u16 *)to;
	const u16 *from16 = (const u16 *)from;
	while ( ((*from16 - 0x0101) & (~*from16 & 0x8080)) == 0 )
		*to16++ = *from16++;

	to = (char *)to16;
	from = (const char *)from16;

	/* copy the remaining bytes (can only be within 1 and 2) */
#pragma unroll(2)
	while ((*to++ = *from++) != '\0');
		/* nothing */
}

#ifdef WEAK_STRCPY
#define STRCPY_NAME __strcpy
#else
#define STRCPY_NAME strcpy
#endif

char *STRCPY_NAME(char *restrict to, const char *restrict from)
{
	char *save = to;

	/*
	 * Check if the pointers can both be aligned to 2 or 4 bytes and copy
	 * in whole blocks of 2 or 4 bytes respectively if that's the case.
	 * This optimization is utterly useless because i'm almost certainly
	 * gonna write (or "import", rather) dedicated assembly routines but
	 * hey it can't hurt to introduce new sources for bugs right?
	 */
	if (((uintptr_t)to % 4) == ((uintptr_t)from % 4)) {
		fourbyte_strcpy(to, from);
	} else if (((uintptr_t)to % 2) == ((uintptr_t)from % 2)) {
		twobyte_strcpy(to, from);
	} else {
		while ((*to++ = *from++) != '\0');
			/* nothing */
	}

	return save;
}

#ifdef WEAK_STRCPY
#include <gay/cdefs.h>
__weak __alias(__strcpy) char *strcpy(char *restrict, const char *restrict);
#endif /* WEAK_STRCPY */

/*
 * This file is part of GayBSD.
 * Copyright (c) 2021 fef <owo@fef.moe>.
 *
 * GayBSD is nonviolent software: you may only use, redistribute, and/or
 * modify it under the terms of the Cooperative Nonviolent Public License
 * (CNPL) as found in the LICENSE file in the source code root directory
 * or at <https://git.pixie.town/thufie/npl-builder>; either version 7
 * of the license, or (at your option) any later version.
 *
 * GayBSD comes with ABSOLUTELY NO WARRANTY, to the extent
 * permitted by applicable law.  See the CNPL for details.
 *
 * ==========================================================================
 *
 * This file is derived from FreeBSD source code.
 *
 * Copyright (c) 1988, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD$
 */