source: trunk/minix/commands/elle/sbbcpy.c@ 22

#include "sb.h"

/* BCOPY(from,to,cnt) - Copy string of bytes.
 *      Normally this routine is an assembly-language library routine,
 *      but not all systems have it.  Hence this C-language version
 *      which tries to be fairly machine-independent.
 *      Attempts to be clever about using word moves instead of byte moves.
 *      Does not hack overlapping backward moves.
 */
bcopy(from, to, cnt)    /* Copy count bytes from -> to */
register SBMA from;
register SBMA to;
register unsigned cnt;
{
        if(!cnt)
                return;
        while(rndrem((int)from))        /* Get source aligned */
          {     *to++ = *from++;
                if(--cnt == 0) return;
          }
        if(rndrem((int)to) == 0)        /* Do word move if dest now aligned */
          {     register unsigned tmp;
                tmp = cnt;
                if((cnt = rnddiv(cnt)) > 4)
                  {     sbm_wcpy((int *)from, (int *)to, cnt);
                        if((cnt = rndrem(tmp)) == 0)
                                return; /* No leftover bytes, all done */
                        tmp -= cnt;     /* Ugh, must update pointers */
                        from += tmp;
                        to += tmp;
                  }
                else cnt = tmp;         /* Not worth call overhead */
          }                             
        do { *to++ = *from++; }         /* Finish up with byte loop */
        while(--cnt);
}

/* SBM_WCPY - word-move auxiliary routine.
 *      This is a separate routine so that machines with only a few
 *      registers have a chance to use them for the word copy loop.
 *      This cannot be made part of BCOPY without doing some
 *      unnecessary pointer conversions and using extra variables
 *      (since most compilers will not accept type casts on lvalues,
 *      which are needed to treat (char *) as (int *)).
 */
sbm_wcpy(from, to, cnt)
register int *from, *to;
register unsigned cnt;
{
        if(cnt)
                do { *to++ = *from++; }
                while(--cnt);
}