elib_memmove.c

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/* ``The contents of this file are subject to the Erlang Public License,
 * Version 1.1, (the "License"); you may not use this file except in
 * compliance with the License. You should have received a copy of the
 * Erlang Public License along with this software. If not, it can be
 * retrieved via the world wide web at http://www.erlang.org/.
 * 
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 * 
 * The Initial Developer of the Original Code is Ericsson Utvecklings AB.
 * Portions created by Ericsson are Copyright 1999, Ericsson Utvecklings
 * AB. All Rights Reserved.''
 * 
 *     $Id$
 */
/* 
 * This memmove assumes that both src and dst are aligned on an address
 * divisible by 4 and that n is a multiple of four.
 */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#ifndef HAVE_MEMMOVE

#define MEMCPY_LIMIT 12
typedef unsigned long  u_long;
typedef unsigned short u_short;

static void copy_high(dst, src, n)
char* dst; char* src; int n;
{
    dst += n;
    src += n;

    if (n >= MEMCPY_LIMIT) {
	while(((u_long) dst) & 3) {
	    *--dst = *--src;
	    n--;
	}
	if ((((u_long) src) & 3) == 0) {
	    while(n >= sizeof(u_long)) {
		src -= sizeof(u_long);
		dst -= sizeof(u_long);
		*((u_long*)dst) = *((u_long*)src);
		n -= sizeof(u_long);
	    }
	}
	else if ((((u_short) src) & 3) == 2) {
	    while(n >= sizeof(u_short)) {
		src -= sizeof(u_short);
		dst -= sizeof(u_short);
		*((u_short*)dst) = *((u_short*)src);
		n -= sizeof(u_short);
	    }
	}
    }
    while(n > 0) {
	*--dst = *--src;
	n--;
    }
}

static void copy_low(dst, src, n)
char* dst; char* src; int n;
{
    if (n >= MEMCPY_LIMIT) {
	while(((u_long) dst) & 3) {
	    *dst++ = *src++;
	    n--;
	}
	if ((((u_long) src) & 3) == 0) {
	    while(n >= sizeof(u_long)) {
		*((u_long*)dst) = *((u_long*)src);
		src += sizeof(u_long);
		dst += sizeof(u_long);
		n -= sizeof(u_long);
	    }
	}
	else if ((((u_long) src) & 3) == 2) {
	    while(n >= sizeof(u_short)) {
		*((u_short*)dst) = *((u_short*)src);
		src += sizeof(u_short);
		dst += sizeof(u_short);
		n -= sizeof(u_short);
	    }
	}
    }
    while(n > 0) {
	*dst++ = *src++;
	n--;
    }
}

/*
** Move memory (with overlap)
*/
void* memmove(dst, src, n)
char* dst; char* src; int n;
{
    if (dst < src)
	copy_low(dst, src, n);
    else if (dst > src)
	copy_high(dst, src, n);
    return dst;
}

#endif /* HAVE_MEMMOVE */