source: buchla-68k/vlib/vcputsv.s@ 84c0125

Last change on this file since 84c0125 was 84c0125, checked in by Thomas Lopatic <thomas@…>, 7 years ago

Fix * in comments.
  • Property mode set to 100644
File size: 4.5 KB
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1| ------------------------------------------------------------------------------
2| vcputsv.s -- output characters to a 4-bit / pixel graphics window
3| with variable vertical pitch
4| Version 2 -- 1987-08-03 -- D.N. Lynx Crowe
5| (c) Copyright 1987 -- D.N. Lynx Crowe
6| ------------------------------------------------------------------------------
7
8| vcputsv(obase, nw, fg, bg, row, col, str. pitch)
9| int *obase, nw, fg, bg, row, col, pitch;
10| char *str;
11
12| Outputs characters from the string at 'str' to an 'nw'
13| character wide 4-bit per pixel graphics window at 'obase'
14| at ('row','col'), using 'fg' as the foreground color, and
15| 'bg' as the background color. Uses cgtable[][256] as the
16| VSDD formatted character generator table. Assumes 12 bit
17| high characters in the cgtable. Uses 'pitch' as the vertical
18| spacing between character rows. No error checks are done.
19| The string must fit the output area (no overlaps, single line).
20
21| ------------------------------------------------------------------------------
22 .text
23
24 .xdef _vcputsv
25
26 .xref _cgtable
27
28| Argument offsets from a6:
29
30OBASE = 8 | LONG - Output area base address
31NW = 12 | WORD - Character width of output area
32FG = 14 | WORD - Foreground color
33BG = 16 | WORD - Background color
34ROW = 18 | WORD - Row
35COL = 20 | WORD - Column
36STR = 22 | LONG - String base address
37PITCH = 26 | WORD - Vertical spacing between rows
38
39| Program constant definitions:
40
41HPIX = 8 | Character width in pixels
42VPIX = 12 | Character height in pixels
43HCW = 4 | Horizontal character width (bytes)
44PSHIFT = 12 | Pixel shift into MS bits
45HSHIFT = 4 | Pixel right shift
46
47 .page
48
49| Register usage:
50
51| d0 output word and scratch
52| d1 CG word and scratch
53| d2 pixel counter
54
55| d3 foreground color (in the 4 ms bits)
56| d4 background color (in the 4 ms bits)
57| d5 width of the area in bytes
58| d6 scan line counter
59
60| a0 CG table pointer
61| a1 output area scan line pointer
62| a2 input string character pointer
63
64| a3 output area character base pointer
65
66| a6 frame pointer
67| a7 stack pointer
68
69 .page
70
71_vcputsv: link a6,#0 | Link stack frames
72 movem.l d3-d6/a3,-(a7) | Save registers we use
73 move.w #PSHIFT,d1 | Set shift constant
74 move.w FG(a6),d3 | Setup foreground color
75 lsl.w d1,d3 | ... in ms 4 bits of d3.W
76 move.w BG(a6),d4 | Setup background color
77 lsl.w d1,d4 | ... in ms 4 bits of d4.W
78 move.w NW(a6),d5 | Get line width in d5.W
79 lsl.w #2,d5 | Multiply width by 4 for offset
80 move.w ROW(a6),d0 | Calculate output address
81 move.w PITCH(a6),d1 | ... PITCH
82 mulu d1,d0 | ... * ROW
83 add.w #VPIX-1,d0 | ... + VPIX-1
84 mulu d5,d0 | ... * NW
85 clr.l d1 | ...
86 move.w COL(a6),d1 | ... +
87 lsl.w #2,d1 | ... COL * 4
88 add.l d1,d0 | ...
89 add.l OBASE(a6),d0 | ... + OBASE
90 movea.l d0,a3 | Leave output address in a3
91 movea.l STR(a6),a2 | Put string address in a2
92
93cgl0: clr.l d0 | Clear out upper bits of d0
94 move.b (a2)+,d0 | Get next character
95 beq cgl5 | Done if character EQ 0
96
97 movea.l a3,a1 | Establish output pointer in a1
98 adda.l #HCW,a3 | Update output pointer for next char.
99 lea _cgtable,a0 | Establish CG pointer in a0
100 lsl.w #1,d0 | ... 2 * character
101 adda.w d0,a0 | ... + _cgtable address
102 move.w #VPIX-1,d6 | Set scan line counter in d6
103
104 .page
105cgl1: move.w (a0),d1 | Get character generator word in d1
106 move.w #(HPIX/2)-1,d2 | Set pixel counter in d2
107
108cgl2: lsr.w #HSHIFT,d0 | Shift output word right 1 pixel
109 btst.l #0,d1 | Check CG word ls bit
110 beq cgl3 | Set background color if bit EQ 0
111
112 or.w d3,d0 | OR foreground color into output word
113 bra cgl4 | Go update CG word
114
115cgl3: or.w d4,d0 | OR background color into output word
116
117cgl4: lsr.w #1,d1 | Shift CG word right 1 pixel
118 dbf d2,cgl2 | Loop for first 4 pixels
119
120 move.w d0,(a1)+ | Store first output word in scan line
121 move.w #(HPIX/2)-1,d2 | Set pixel counter in d2
122
123cgl2a: lsr.w #HSHIFT,d0 | Shift output word right 1 pixel
124 btst.l #0,d1 | Check CG word ls bit
125 beq cgl3a | Set background color if bit EQ 0
126
127 or.w d3,d0 | OR foreground color into output word
128 bra cgl4a | Go update CG word
129
130cgl3a: or.w d4,d0 | OR background color into output word
131
132cgl4a: lsr.w #1,d1 | Shift CG word right 1 pixel
133 dbf d2,cgl2a | Loop for last 4 pixels
134
135 move.w d0,(a1) | Store second output word in scan line
136 suba.w d5,a1 | Update output pointer
137 suba.w #2,a1 | ...
138 adda.l #512,a0 | Update CG pointer for next scan line
139 dbf d6,cgl1 | Loop for all scan lines
140
141 bra cgl0 | Loop for next character
142
143cgl5: movem.l (a7)+,d3-d6/a3 | Restore registers
144 unlk a6 | Unlink stack frames
145 rts | Return to caller
146
147 .end
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