sdcc/device/lib/sm83/__initrleblock.s

   1 ;--------------------------------------------------------------------------
   2 ;  __initrleblock.s
   3 ;
   4 ;  Copyright (C) 2001, Michael Hope
   5 ;  Copyright (C) 2020, Sergey Belyashov
   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         .area   _CODE
  31
  32         ;; Special RLE decoder used for initing global data
  33         ;; input: DE - destination address
  34 __initrleblock::
  35         ;; Pop the return address
  36         pop     hl
  37 1$:
  38         ;; Fetch the run
  39         ld      a, (hl+)
  40         ld      c, a
  41         ;; Negative means a run
  42         bit     7, c
  43         jr      Z, 2$
  44         ;; Expanding a run
  45         ld      a, (hl+)
  46 3$:
  47         ld      (de), a
  48         inc     de
  49         inc     c
  50         jr      NZ, 3$
  51         jr      1$
  52 2$:
  53         ;; Zero means end of a block
  54         inc     c
  55         dec     c
  56         jr      Z, 4$
  57         ;; Expanding a block
  58 5$:
  59         ld      a, (hl+)
  60         ld      (de), a
  61         inc     de
  62         dec     c
  63         jr      NZ, 5$
  64         jr      1$
  65 4$:
  66         ;; Return back
  67         jp      (hl)