/
SDL_vbltimer.S
128 lines (95 loc) · 2.24 KB
/
SDL_vbltimer.S
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/*
SDL - Simple DirectMedia Layer
Copyright (C) 1997-2006 Sam Lantinga
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Sam Lantinga
slouken@libsdl.org
*/
/*
* VBL queue routine
*
* Patrice Mandin
*/
#define _vbl_queue 0x456
.text
.globl _SDL_AtariVblInstall
.globl _SDL_AtariVblUninstall
/*--- Vector installer ---*/
_SDL_AtariVblInstall:
movel sp@(4),my_vector
lea _my_vbl,a0
clrw vbl_mutex
/* Stop interrupts */
movew #0x2700,sr
/* Read vbl_queue pointer */
movel _vbl_queue.w,a1
/* Search a free place */
moveq #7,d0
bcl_search_place:
movel (a1),d1
beqs place_found
addql #4,a1
dbra d0,bcl_search_place
/* Not found */
moveq #1,d0
bras exit_vbl_queue
/* Then install ourselves */
place_found:
movel a0,(a1)
moveq #0,d0
exit_vbl_queue:
/* Restart interrupts */
movew #0x2300,sr
rts
/*--- Vector uninstaller ---*/
_SDL_AtariVblUninstall:
movel sp@(4),d0
cmpl my_vector,d0
bnes badvector
movel #_my_vbl,d0
/* Stop interrupts */
movew #0x2700,sr
/* Read vbl_queue pointer */
movel _vbl_queue.w,a1
/* Search where we are */
moveq #7,d1
bcl2_search_place:
cmpl (a1),d0
bnes next_place
clrl (a1)
moveq #0,d1
next_place:
addql #4,a1
dbra d1,bcl2_search_place
/* Restart interrupts */
movew #0x2300,sr
badvector:
rts
/*--- Our vbl ---*/
_my_vbl:
/* Verify if this is not already running */
tstw vbl_mutex
bnes vbl_end
notw vbl_mutex
moveml d0-d7/a0-a6,sp@-
movel my_vector,a0
jsr a0@
moveml sp@+,d0-d7/a0-a6
clrw vbl_mutex
vbl_end:
rts
.data
.even
.comm vbl_mutex,2*1
.even
.comm my_vector,4*1