path: root/main/glib/memcpy.c

#include "config.h"
#include <ctype.h>
#include "genlib.h"
#include "stddefs.h"

#ifndef MEMCPY_CHUNK
#define MEMCPY_CHUNK (256*1024)
#endif

/* memcpy():
 *  Copy n bytes from 'from' to 'to'; return 'to'.
 *  This version of memcpy() tries to take advantage of address alignment.
 *  The goal is to do as many of the copies on 4-byte aligned addresses,
 *  falling back to 2-byte alignment, and finally, if there is no other
 *  way, simple byte-by-byte copy.
 *  Note that there is some point where the amount of overhead may exceed
 *  the byte count; hence, this will take longer for small byte counts.
 *  The assumption here is that small byte count memcpy() calls don't really
 *  care.
 */
char *
memcpy(char *to,char *from,int count)
{
    char    *to_copy, *end;
#if INCLUDE_QUICKMEMCPY
    char    *tend;
#endif

    to_copy = to;

#if INCLUDE_QUICKMEMCPY
    /* If count is greater than 8, get fancy, else just do byte-copy... */
    if(count > 8) {
        /* Attempt to optimize the transfer here... */
        if(((int)to & 3) && ((int)from & 3)) {
            /* If from and to pointers are both unaligned to the
             * same degree then we can do a few char copies to get them
             * 4-byte aligned and then do a lot of 4-byte aligned copies.
             */
            if(((int)to & 3) == ((int)from & 3)) {
                while((int)to & 3) {
                    *to++ = *from++;
                    count--;
                }
            }
            /* If from and to pointers are both odd, but different, then
             * we can increment them both by 1 and do a bunch of 2-byte
             * aligned copies...
             */
            else if(((int)to & 1) && ((int)from & 1)) {
                *to++ = *from++;
                count--;
            }
        }

        /* If both pointers are now 4-byte aligned or 2-byte aligned,
         * take advantage of that here...
         */
        if(!((int)to & 3) && !((int)from & 3)) {
            tend = end = to + (count & ~3);
            count = count & 3;
#ifdef WATCHDOG_ENABLED
            do {
                tend = (end - to <= MEMCPY_CHUNK) ? end : to + MEMCPY_CHUNK;
#endif
                while(to < tend) {
                    *(ulong *)to = *(ulong *)from;
                    from += 4;
                    to += 4;
                }
#ifdef WATCHDOG_ENABLED
                WATCHDOG_MACRO;
            } while(tend != end);
#endif
        } else if(!((int)to & 1) && !((int)from & 1)) {
            tend = end = to + (count & ~1);
            count = count & 1;
#ifdef WATCHDOG_ENABLED
            do {
                tend = (end - to <= MEMCPY_CHUNK) ? end : to + MEMCPY_CHUNK;
#endif
                while(to < tend) {
                    *(ushort *)to = *(ushort *)from;
                    from += 2;
                    to += 2;
                }
#ifdef WATCHDOG_ENABLED
                WATCHDOG_MACRO;
            } while(tend != end);
#endif
        }
    }
#endif

    if(count) {
        end = to + count;
        while(to < end) {
            *to++ = *from++;
        }
    }
    return(to_copy);
}

void
bcopy(char *from, char *to, int size)
{
    memcpy(to,from,size);
}