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gbdk-2020

GameBoy Development Kit
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gbdk-lib/libc/asm/sm83/strlen.s

      1 ;--------------------------------------------------------------------------
      2 ;  strlen.s
      3 ;
      4 ;  Copyright (C) 2020, Tony Pavlov
      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         .module strlen
     30 
     31         .area   _HOME
     32 
     33 _strlen::
     34         lda     HL, 2(SP)
     35         ld      A, (HL+)        
     36         ld      H, (HL)
     37         ld      L, A
     38 .strlen::       
     39         ld      DE, #0
     40 1$:     ld      A, (HL+)
     41         or      A
     42         ret     Z
     43         inc     DE
     44         jr      1$

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