sdcc/device/lib/mos6502/_memset.s

   1 ;-------------------------------------------------------------------------
   2 ;   _memset.s - standarc C library
   3 ;
   4 ;   Copyright (C) 2003, Ullrich von Bassewitz
   5 ;   Copyright (C) 2009, Christian Krueger
   6 ;   Copyright (C) 2023, Gabriele Gorla
   7 ;
   8 ;   This library is free software; you can redistribute it and/or modify it
   9 ;   under the terms of the GNU General Public License as published by the
  10 ;   Free Software Foundation; either version 2, or (at your option) any
  11 ;   later version.
  12 ;
  13 ;   This library is distributed in the hope that it will be useful,
  14 ;   but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 ;   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 ;   GNU General Public License for more details.
  17 ;
  18 ;   You should have received a copy of the GNU General Public License
  19 ;   along with this library; see the file COPYING. If not, write to the
  20 ;   Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  21 ;   MA 02110-1301, USA.
  22 ;
  23 ;   As a special exception, if you link this library with other files,
  24 ;   some of which are compiled with SDCC, to produce an executable,
  25 ;   this library does not by itself cause the resulting executable to
  26 ;   be covered by the GNU General Public License. This exception does
  27 ;   not however invalidate any other reasons why the executable file
  28 ;   might be covered by the GNU General Public License.
  29 ;-------------------------------------------------------------------------
  30
  31         .module _memset
  32
  33 ;--------------------------------------------------------
  34 ; exported symbols
  35 ;--------------------------------------------------------
  36         .globl _memset_PARM_2
  37         .globl _memset_PARM_3
  38         .globl _memset
  39
  40 ;--------------------------------------------------------
  41 ; overlayable function parameters in zero page
  42 ;--------------------------------------------------------
  43         .area   OSEG    (PAG, OVR)
  44 _memset_PARM_2:
  45         .ds 1
  46 _memset_PARM_3:
  47         .ds 2
  48
  49 ;--------------------------------------------------------
  50 ; local aliases
  51 ;--------------------------------------------------------
  52         .define save  "REGTEMP+0"
  53         .define dst   "DPTR"
  54         .define val   "_memset_PARM_2"
  55         .define count "_memset_PARM_3"
  56
  57 ;--------------------------------------------------------
  58 ; code
  59 ;--------------------------------------------------------
  60         .area CODE
  61
  62 _memset:
  63         sta     *save+0
  64         stx     *save+1
  65         sta     *dst+0
  66         stx     *dst+1
  67
  68         ldy     #0
  69         lda     *val
  70         ldx     *count+1
  71         beq     00002$
  72 00001$:
  73         sta     [dst],y
  74         iny
  75         sta     [dst],y
  76         iny
  77         bne     00001$
  78         inc     *dst+1
  79         dex
  80         bne     00001$
  81 00002$:
  82         ldx     *count+0
  83         beq     00004$
  84 00003$:
  85         sta     [dst],y
  86         iny
  87         dex
  88         bne     00003$
  89 00004$:
  90         lda     *save+0
  91         ldx     *save+1
  92         rts