sdcc/device/lib/ez80_z80/__strreverse.s

   1 ;--------------------------------------------------------------------------
   2 ;  __strreverse.s
   3 ;
   4 ;  Copyright (C) 2020, Sergey Belyashov
   5 ;
   6 ;  This library is free software; you can redistribute it and/or modify it
   7 ;  under the terms of the GNU General Public License as published by the
   8 ;  Free Software Foundation; either version 2, or (at your option) any
   9 ;  later version.
  10 ;
  11 ;  This library is distributed in the hope that it will be useful,
  12 ;  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 ;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 ;  GNU General Public License for more details.
  15 ;
  16 ;  You should have received a copy of the GNU General Public License
  17 ;  along with this library; see the file COPYING. If not, write to the
  18 ;  Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  19 ;   MA 02110-1301, USA.
  20 ;
  21 ;  As a special exception, if you link this library with other files,
  22 ;  some of which are compiled with SDCC, to produce an executable,
  23 ;  this library does not by itself cause the resulting executable to
  24 ;  be covered by the GNU General Public License. This exception does
  25 ;  not however invalidate any other reasons why the executable file
  26 ;   might be covered by the GNU General Public License.
  27 ;--------------------------------------------------------------------------
  28
  29         .area   _CODE
  30
  31         .globl ___strreverse
  32         .globl ___strreverse_reg
  33 ;
  34 ;void __reverse(char *beg, char *end);
  35 ;
  36 ___strreverse::
  37         pop     bc
  38         pop     de
  39         push    bc
  40         ex      de, hl
  41 ;
  42 ;in: HL - pointer to end of string (null symbol), DE - pointer to start of string
  43 ;
  44 ___strreverse_reg::
  45         jr      110$
  46 100$:
  47         add     hl, de
  48         ld      a, (de)
  49         ld      c, (hl)
  50         ld      (hl), a
  51         ld      a, c
  52         ld      (de), a
  53         inc     de
  54 110$:
  55         dec     hl
  56         or      a, a
  57         sbc     hl, de
  58         jr      NC, 100$
  59         ret