commands/elle/sbbcpy.c

   1
   2 #include "sb.h"
   3
   4 /* BCOPY(from,to,cnt) - Copy string of bytes.
   5  *      Normally this routine is an assembly-language library routine,
   6  *      but not all systems have it.  Hence this C-language version
   7  *      which tries to be fairly machine-independent.
   8  *      Attempts to be clever about using word moves instead of byte moves.
   9  *      Does not hack overlapping backward moves.
  10  */
  11 bcopy(from, to, cnt)    /* Copy count bytes from -> to */
  12 register SBMA from;
  13 register SBMA to;
  14 register unsigned cnt;
  15 {
  16         if(!cnt)
  17                 return;
  18         while(rndrem((int)from))        /* Get source aligned */
  19           {     *to++ = *from++;
  20                 if(--cnt == 0) return;
  21           }
  22         if(rndrem((int)to) == 0)        /* Do word move if dest now aligned */
  23           {     register unsigned tmp;
  24                 tmp = cnt;
  25                 if((cnt = rnddiv(cnt)) > 4)
  26                   {     sbm_wcpy((int *)from, (int *)to, cnt);
  27                         if((cnt = rndrem(tmp)) == 0)
  28                                 return; /* No leftover bytes, all done */
  29                         tmp -= cnt;     /* Ugh, must update pointers */
  30                         from += tmp;
  31                         to += tmp;
  32                   }
  33                 else cnt = tmp;         /* Not worth call overhead */
  34           }
  35         do { *to++ = *from++; }         /* Finish up with byte loop */
  36         while(--cnt);
  37 }
  38
  39 /* SBM_WCPY - word-move auxiliary routine.
  40  *      This is a separate routine so that machines with only a few
  41  *      registers have a chance to use them for the word copy loop.
  42  *      This cannot be made part of BCOPY without doing some
  43  *      unnecessary pointer conversions and using extra variables
  44  *      (since most compilers will not accept type casts on lvalues,
  45  *      which are needed to treat (char *) as (int *)).
  46  */
  47 sbm_wcpy(from, to, cnt)
  48 register int *from, *to;
  49 register unsigned cnt;
  50 {
  51         if(cnt)
  52                 do { *to++ = *from++; }
  53                 while(--cnt);
  54 }