source: buchla-68k/orig/IOLIB/VCPUTSV.S@ 06ccda2

Last change on this file since 06ccda2 was 3ae31e9, checked in by Thomas Lopatic <thomas@…>, 8 years ago

Imported original source code.
  • Property mode set to 100755
File size: 4.7 KB
Line 
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 .equ 8 * LONG - Output area base address
31NW .equ 12 * WORD - Character width of output area
32FG .equ 14 * WORD - Foreground color
33BG .equ 16 * WORD - Background color
34ROW .equ 18 * WORD - Row
35COL .equ 20 * WORD - Column
36STR .equ 22 * LONG - String base address
37PITCH .equ 26 * WORD - Vertical spacing between rows
38*
39* Program constant definitions:
40*
41HPIX .equ 8 * Character width in pixels
42VPIX .equ 12 * Character height in pixels
43HCW .equ 4 * Horizontal character width (bytes)
44PSHIFT .equ 12 * Pixel shift into MS bits
45HSHIFT .equ 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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