gbdk-2020 | GameBoy Development Kit |
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gbdk-lib/libc/asm/mos6502/_strcmp.s
1 ;-------------------------------------------------------------------------
2 ; _strcmp.s - standard C library function
3 ;
4 ; Copyright (C) 1998, Ullrich von Bassewitz
5 ; Copyright (C) 2022, 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 _strcmp
31
32 ;--------------------------------------------------------
33 ; exported symbols
34 ;--------------------------------------------------------
35 .globl _strcmp_PARM_2
36 .globl _strcmp
37
38 ;--------------------------------------------------------
39 ; overlayable function parameters in zero page
40 ;--------------------------------------------------------
41 .area OSEG (PAG, OVR)
42 _strcmp_PARM_2:
43 .ds 2
44
45 ;--------------------------------------------------------
46 ; local aliases
47 ;--------------------------------------------------------
48 .define _str2 "_strcmp_PARM_2"
49 .define _str1 "DPTR"
50 ;--------------------------------------------------------
51 ; code
52 ;--------------------------------------------------------
53 .area _CODE
54
55 _strcmp:
56 sta *_str1+0
57 stx *_str1+1
58
59 ldy #0
60 loop:
61 lda [_str1],y
62 cmp [_str2],y
63 bne L1
64 tax
65 beq end
66 iny
67 bne loop
68 inc *_str1+1
69 inc *_str2+1
70 bne loop
71 L1:
72 bcs L2
73 ldx #0xFF
74 ;// txa
75 rts
76 L2:
77 ldx #0x01
78 ;// txa
79 end:
80 rts
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