source: buchla-68k/vlib/vputp.s

Last change on this file was 8325447, checked in by Thomas Lopatic <thomas@…>, 7 years ago

Removed _ prefix.
  • Property mode set to 100644
File size: 2.6 KB
Line 
1| ------------------------------------------------------------------------------
2| vputp.s -- put a pixel into a 4-bit per pixel bitmap object
3| Version 4 -- 1987-08-04 -- D.N. Lynx Crowe
4| (c) Copyright 1987 -- D.N. Lynx Crowe
5| ------------------------------------------------------------------------------
6| int
7| vputp(octad, xloc, yloc, val)
8| struct octent *octad;
9| int xloc, yloc;
10
11| Puts the pixel value 'val' at ('xloc','yloc') in the
12| 4-bit per pixel bitmap object described by 'octad'.
13
14| -----
15| struct octent {
16
17| uint ysize,
18| xsize;
19
20| int objx,
21| objy;
22
23| uint |obase;
24
25| char opri,
26| obank;
27
28| uint odtw0,
29| odtw1;
30| };
31
32 .text
33
34 .xdef vputp
35
36OCTAD = 8
37XLOC = 12
38YLOC = 14
39VAL = 16
40
41YSIZE = 0
42XSIZE = 2
43OBJX = 4
44OBJY = 6
45OBASE = 8
46OPRI = 12
47OBANK = 13
48ODTW0 = 14
49ODTW1 = 16
50
51 .page
52
53vputp: link a6,#0 | Link stack frames
54 movea.l OCTAD(a6),a1 | Get OCTAD base into a1
55 move.w XLOC(a6),d0 | Get XLOC into d0
56 cmp.w XSIZE(a1),d0 | Check XLOC range
57 bge vputerr | ERROR if too large
58
59 tst.w d0 | Check XLOC sign
60 bmi vputerr | ERROR if negative
61
62 move.w YLOC(a6),d1 | Get YLOC into d1 to test
63 cmp.w YSIZE(a1),d1 | Check YLOC range
64 bge vputerr | ERROR if too large
65
66 tst.w d1 | Check YLOC sign
67 bmi vputerr | ERROR if negative
68
69 lsr.w #2,d0 | Divide XLOC by 4
70 move.w XSIZE(a1),d1 | Get width into d1
71 lsr.w #2,d1 | Divide width by 4
72 mulu YLOC(a6),d1 | Multiply width/4 by YLOC
73 ext.l d0 | Extend XLOC/4 to a long
74 add.l d0,d1 | ... and add it to d1
75 lsl.l #1,d1 | Make d1 a word offset
76 add.l OBASE(a1),d1 | Add OBASE to d1
77 movea.l d1,a0 | Make a0 point at bitmap data
78 move.w XLOC(a6),d0 | Get XLOC
79 andi.l #0x03,d0 | Mask to low 2 bits
80 add.l d0,d0 | Multiply by 2 for word index
81 move.l d0,d1 | Save index in d1
82 add.l #MTAB,d0 | Add mask table base
83 movea.l d0,a2 | a2 points at mask
84 add.l #STAB,d1 | Add shift table base to index
85 move.l d1,a1 | a1 points at shift count
86 move.w (a1),d0 | Get shift count in d0
87 move.w VAL(a6),d1 | Get new pixel in d1
88 andi.w #0x0F,d1 | Mask down to 4 bits
89 lsl.w d0,d1 | Shift into position for OR
90 move.w (a0),d0 | Get old bitmap word in d0
91 and.w (a2),d0 | Mask out old pixel
92 or.w d1,d0 | OR in new pixel
93 move.w d0,(a0) | Store updated word in bitmap
94 clr.l d0 | Set return value = 0 = OK
95
96vputexit: unlk a6 | Unlink stack frame
97 rts | Return to caller
98
99vputerr: moveq.l #-1,d0 | Set return value = -1 = ERROR
100 bra vputexit | Go unlink stack and return
101
102 .page
103
104 .data
105
106MTAB: .dc.w 0xFFF0,0xFF0F,0xF0FF,0x0FFF | Mask table
107STAB: .dc.w 0,4,8,12 | Shift table
108
109 .end
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