libc.c

C++ 编写的EROS RTOS

/*
 * Copyright (C) 1998, 1999, Jonathan S. Shapiro.
 *
 * This file is part of the EROS Operating System.
 *
 * 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,
 * 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */


#include "system.h"
#include "tar.h"

typedef	long word;		/* "word" used for optimal copy speed */

#define	wsize	sizeof(word)
#define	wmask	(wsize - 1)

/*
 * Copy a block of memory, handling overlap.
 * This is the routine that actually implements
 * (the portable versions of) bcopy, memcpy, and memmove.
 */
#ifdef MEMCOPY
void *
memcpy(dst0, src0, length)
#else
#ifdef MEMMOVE
void *
memmove(dst0, src0, length)
#else
void
bcopy(src0, dst0, length)
#endif
#endif
	void *dst0;
	const void *src0;
	register size_t length;
{
	register char *dst = dst0;
	register const char *src = src0;
	register size_t t;

	if (length == 0 || dst == src)		/* nothing to do */
		goto done;

	/*
	 * Macros: loop-t-times; and loop-t-times, t>0
	 */
#define	TLOOP(s) if (t) TLOOP1(s)
#define	TLOOP1(s) do { s; } while (--t)

	if ((unsigned long)dst < (unsigned long)src) {
		/*
		 * Copy forward.
		 */
		t = (long)src;	/* only need low bits */
		if ((t | (long)dst) & wmask) {
			/*
			 * Try to align operands.  This cannot be done
			 * unless the low bits match.
			 */
			if ((t ^ (long)dst) & wmask || length < wsize)
				t = length;
			else
				t = wsize - (t & wmask);
			length -= t;
			TLOOP1(*dst++ = *src++);
		}
		/*
		 * Copy whole words, then mop up any trailing bytes.
		 */
		t = length / wsize;
		TLOOP(*(word *)dst = *(word *)src; src += wsize; dst += wsize);
		t = length & wmask;
		TLOOP(*dst++ = *src++);
	} else {
		/*
		 * Copy backwards.  Otherwise essentially the same.
		 * Alignment works as before, except that it takes
		 * (t&wmask) bytes to align, not wsize-(t&wmask).
		 */
		src += length;
		dst += length;
		t = (long)src;
		if ((t | (long)dst) & wmask) {
			if ((t ^ (long)dst) & wmask || length <= wsize)
				t = length;
			else
				t &= wmask;
			length -= t;
			TLOOP1(*--dst = *--src);
		}
		t = length / wsize;
		TLOOP(src -= wsize; dst -= wsize; *(word *)dst = *(word *)src);
		t = length & wmask;
		TLOOP(*--dst = *--src);
	}
done:
#if defined(MEMCOPY) || defined(MEMMOVE)
	return (dst0);
#else
	return;
#endif
}

int
strncmp(s1, s2, n)
	register const char *s1, *s2;
	register size_t n;
{

	if (n == 0)
		return (0);
	do {
		if (*s1 != *s2++)
			return (*(unsigned char *)s1 - *(unsigned char *)--s2);
		if (*s1++ == 0)
			break;
	} while (--n != 0);
	return (0);
}

char *

#ifdef STRCHR
strchr(p, ch)
#else
index(p, ch)
#endif
	register const char *p, ch;
{
	for (;; ++p) {
		if (*p == ch)
			return((char *)p);
		if (!*p)
			return((char *)NULL);
	}
	/* NOTREACHED */
}

char *
strcpy(to, from)
        register char *to;
        register const char *from;
{
        char *save = to;

        for (; (*to = *from) != '\0'; ++from, ++to);
        return(save);
}

/*
 * Copy src to dst, truncating or null-padding to always copy n bytes.
 * Return dst.
 */
char *
strncpy(dst, src, n)
	char *dst;
	const char *src;
	register size_t n;
{
	if (n != 0) {
		register char *d = dst;
		register const char *s = src;

		do {
			if ((*d++ = *s++) == 0) {
				/* NUL pad the remaining n-1 bytes */
				while (--n != 0)
					*d++ = 0;
				break;
			}
		} while (--n != 0);
	}
	return (dst);
}