sdcc/device/lib/mos65c02/_strlen.s

   1 ;-------------------------------------------------------------------------
   2 ;   _strlen.s - standard C library function
   3 ;
   4 ;   Copyright (C) 1998, Ullrich von Bassewitz
   5 ;   Copyright (C) 2023, Gabriele Gorla
   6 ;
   7 ;   This library is free software; you can redistribute it and/or modify it
   8 ;   under the terms of the GNU General Public License as published by the
   9 ;   Free Software Foundation; either version 2, or (at your option) any
  10 ;   later version.
  11 ;
  12 ;   This library is distributed in the hope that it will be useful,
  13 ;   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 ;   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 ;   GNU General Public License for more details.
  16 ;
  17 ;   You should have received a copy of the GNU General Public License
  18 ;   along with this library; see the file COPYING. If not, write to the
  19 ;   Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  20 ;   MA 02110-1301, USA.
  21 ;
  22 ;   As a special exception, if you link this library with other files,
  23 ;   some of which are compiled with SDCC, to produce an executable,
  24 ;   this library does not by itself cause the resulting executable to
  25 ;   be covered by the GNU General Public License. This exception does
  26 ;   not however invalidate any other reasons why the executable file
  27 ;   might be covered by the GNU General Public License.
  28 ;-------------------------------------------------------------------------
  29
  30         .module _strlen
  31
  32 ;--------------------------------------------------------
  33 ; exported symbols
  34 ;--------------------------------------------------------
  35         .globl _strlen
  36
  37 ;--------------------------------------------------------
  38 ; local aliases
  39 ;--------------------------------------------------------
  40         .define _src "DPTR"
  41
  42 ;--------------------------------------------------------
  43 ; code
  44 ;--------------------------------------------------------
  45         .area CODE
  46
  47 _strlen:
  48         sta     *_src+0
  49         stx     *_src+1
  50
  51         ldy     #0x00
  52         ldx     #0x00
  53 loop:
  54         lda     [_src],y
  55         beq     end
  56         iny
  57         bne     loop
  58         inc     *_src+1
  59         inx
  60         bne     loop
  61 end:
  62         tya
  63         rts