lib/i86/string/memset.s

   1 !       memset()                                        Author: Kees J. Bot
   2 !                                                               27 Jan 1994
   3 .sect .text; .sect .rom; .sect .data; .sect .bss
   4
   5 ! void *memset(void *s, int c, size_t n)
   6 !       Set a chunk of memory to the same byte value.
   7 !
   8 .sect .text
   9 .define _memset
  10 _memset:
  11         push    bp
  12         mov     bp, sp
  13         push    di
  14         mov     di, 4(bp)       ! The string
  15         movb    al, 6(bp)       ! The fill byte
  16         mov     cx, 8(bp)       ! Length
  17         cld
  18         cmp     cx, #16
  19         jb      sbyte           ! Don't bother being smart with short arrays
  20         test    di, #1
  21         jnz     sbyte           ! Bit 0 set, use byte store
  22 sword:  movb    ah, al          ! One byte to two bytes
  23         sar     cx, #1
  24     rep stos                    ! Store words
  25         adc     cx, cx          ! One more byte?
  26 sbyte:
  27     rep stosb                   ! Store bytes
  28 done:   mov     ax, 4(bp)       ! Return some value you have no need for
  29         pop     di
  30         pop     bp
  31         ret