gbdk-2020 | GameBoy Development Kit |
| download: https://git.y1.nz/archives/gbdk.tar.gz | |
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gbdk-lib/libc/asm/z80/memmove.s
1 ;--------------------------------------------------------------------------
2 ; memmove.s
3 ;
4 ; Copyright (C) 2008-2009, Philipp Klaus Krause, Marco Bodrato
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 _memmove
32
33 ; The Z80 has the ldir and lddr instructions, which are perfect for implementing memmove().
34
35 _memmove:
36 pop af
37 pop hl
38 pop de
39 pop bc
40 push bc
41 push de
42 push hl
43 push af
44 ld a, c
45 or a, b
46 ret Z
47 push hl
48 sbc hl, de ; or above cleared carry.
49 add hl, de ; same carry as the line before
50 jr C, memmove_up
51 memmove_down:
52 dec bc
53 add hl, bc
54 ex de, hl
55 add hl, bc
56 inc bc
57 lddr
58 pop hl
59 ret
60 memmove_up:
61 ex de, hl
62 ldir
63 pop hl
64 ret
65
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