/* nstrl.c - optimized strlcpy/strlcat implementation
 * Time-stamp: <2004-03-15 njk>
 *  
 * (C) 2003-2004 Nicholas J. Kain <njk@aerifal.cx>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * 
 */
#include <unistd.h>

#ifndef HAVE_STRLCPY
#define HAVE_STRLCPY 1

/* strlcat and strlcpy are optimized for strings of intermediate length
 * (greater than 8 bytes, but less than 512 bytes */
/* for very small and very large strings, it is suggested to instead use
 * *_s and *_l */

/* Note that strl* are inherently slower than a memcpy().  It's far more
 * efficient to just keep track of your string lengths externally and just
 * memcpy() data around, since it's then easy to use the rep movsl
 * instruction (or even faster mmx-based primitives on modern processors).
 *
 * When I bother to write a simple string library, nul-termination is going
 * to be the first thing to die...
 */

#ifdef USE_X86_ASM
unsigned int strlcpy(char *dest, char *src, unsigned int size) {
	unsigned int ret = size, sizeo;
	char *desto, *srco;
	asm (
			"cld				\n\t"
			"repnz movsb		\n\t"
			"dec %2				\n\t"
			"movb $0, (%2)		\n\t"
			: "=c"(sizeo), "=S"(srco), "=D"(desto)
			: "0"(size), "1"(src), "2"(dest)
			);
	return ret - sizeo;
}

unsigned int strlcat(char *dest, char *src, unsigned int size) {
	unsigned int ret = size, sizeo;
	char *desto, *srco;
	asm (
			"xor %%eax, %%eax	\n\t"
			"cld				\n\t"
			"repne scasb		\n\t"
			"dec %2				\n\t"
			"cld				\n\t"
			"repnz movsb		\n\t"
			"dec %2				\n\t"
			"movb $0, (%2)		\n\t"
			: "=c"(sizeo), "=S"(srco), "=D"(desto)
			: "0"(size), "1"(src), "2"(dest)
			: "%eax");
	return ret - sizeo;
}

/* TODO: write mmx-optimized strlcpy_l and strlcat_l */

#else
size_t strlcpy(char *dest, char *src, size_t size) 
{
	register unsigned int i;
	
	for (i=0; size > 0 && src[i] != '\0'; ++i, size--)
		dest[i] = src[i];

	dest[i] = '\0';

	return i;
}

size_t strlcat(char *dest, char *src, size_t size)
{
	register unsigned int i, j;
	
	for(i=0; size > 0 && dest[i] != '\0'; size--, i++);
	for(j=0; size > 0 && src[i] != '\0'; size--, i++, j++)
		dest[i] = src[j];

	dest[i] = '\0';
	return i;
}

size_t strlcpy_l(char *dest, char *src, size_t size) {
	return strlcpy(dest, src, size);
}
size_t strlcat_l(char *dest, char *src, size_t size) {
	return strlcat(dest, src, size);
}
#endif  /* USE_X86_ASM */
#endif  /* HAVE_STRLCPY */