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| 2 | | vwputs.s -- output a character string to a 2-bit per pixel graphics window
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| 3 | | Version 9 -- 1987-07-28 -- D.N. Lynx Crowe
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| 4 | | (c) Copyright 1987 -- D.N. Lynx Crowe
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| 5 | | ------------------------------------------------------------------------------
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| 6 |
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| 7 | | vwputs(obase, nw, fg, bg, row, col, str)
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| 8 | | int *obase, nw, fg, bg, row, col;
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| 9 | | char *str;
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| 10 |
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| 11 | | Outputs characters from the string at 'str' to an 'nw'
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| 12 | | character wide 2-bit per pixel graphics window at 'obase'
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| 13 | | at ('row','col'), using 'fg' as the foreground color, and
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| 14 | | 'bg' as the background color. Uses cgtable[][256] as the
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| 15 | | VSDD formatted character generator table.
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| 16 | | No error checks are done.
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| 17 | | ------------------------------------------------------------------------------
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| 18 |
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| 19 | .text
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| 20 | .xdef _vwputs
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| 21 |
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| 22 | .xref _cgtable
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| 23 |
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| 24 | | Argument offsets from a6:
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| 25 |
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| 26 | OBASE = 8 | L: Output area base address
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| 27 | NW = 12 | W: Character width of output area
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| 28 | FG = 14 | W: Foreground color
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| 29 | BG = 16 | W: Background color
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| 30 | ROW = 18 | W: Row
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| 31 | COL = 20 | W: Column
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| 32 | STR = 22 | L: String base address
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| 33 |
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| 34 | | Miscellaneous constants:
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| 35 |
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| 36 | HPIX = 8 | Horizontal pixels in the character
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| 37 |
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| 38 | NVPIX = 12 | Vertical pixels in the character
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| 39 | VPITCH = 12 | Vertical pitch between characters
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| 40 |
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| 41 | | Register usage:
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| 42 |
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| 43 | | d0 output word and scratch
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| 44 | | d1 CG word and scratch
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| 45 | | d2 pixel counter
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| 46 | | d3 foreground color (in the 2 ms bits)
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| 47 | | d4 background color (in the 2 ms bits)
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| 48 | | d5 width of the area in bytes
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| 49 | | d6 scan line counter
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| 50 |
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| 51 | | a0 CG table pointer
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| 52 | | a1 output area scan line pointer
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| 53 | | a2 input character pointer
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| 54 | | a3 output area character pointer
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| 55 |
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| 56 | .page
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| 57 |
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| 58 | _vwputs: link a6,#0 | Link stack frames
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| 59 | movem.l d3-d6/a3,-(a7) | Save registers we use
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| 60 | move.w #14,d1 | Set shift constant
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| 61 | move.w FG(a6),d3 | Setup foreground color
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| 62 | lsl.w d1,d3 | ... in ms 2 bits of d3
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| 63 | move.w BG(a6),d4 | Setup background color
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| 64 | lsl.w d1,d4 | ... in ms 2 bits of d4
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| 65 | move.w NW(a6),d5 | Get width in characters in d5
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| 66 | lsl.w #1,d5 | ... make it words
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| 67 | move.w ROW(a6),d0 | Calculate output address
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| 68 | move.w #VPITCH,d1 | ...
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| 69 | mulu d1,d0 | ... ROW * VPITCH
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| 70 | add.w #NVPIX-1,d0 | ... + NVPIX-1
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| 71 | mulu d5,d0 | ... * NW
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| 72 | clr.l d1 | ...
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| 73 | move.w COL(a6),d1 | ... + (COL * 2)
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| 74 | lsl.l #1,d1 | ...
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| 75 | add.l d1,d0 | ...
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| 76 | add.l OBASE(a6),d0 | ... + OBASE
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| 77 | movea.l d0,a3 | Leave output address in a3
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| 78 | movea.l STR(a6),a2 | Put string address in a2
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| 79 |
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| 80 | .page
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| 81 | cgl0: clr.l d0 | Clear out upper bits of d0
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| 82 | move.b (a2)+,d0 | Get next character
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| 83 | beq cgl5 | Done if character EQ 0
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| 84 |
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| 85 | movea.l a3,a1 | Establish output pointer in a1
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| 86 | adda.l #2,a3 | Update output pointer for next char.
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| 87 | lea _cgtable,a0 | Establish CG pointer in a0
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| 88 | lsl.w #1,d0 | ... 2 * character
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| 89 | adda.w d0,a0 | ... + _cgtable address
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| 90 | move.w #NVPIX-1,d6 | Set scan line counter in d6
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| 91 |
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| 92 | cgl1: move.w #HPIX-1,d2 | Set pixel counter in d2
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| 93 | move.w (a0),d1 | Get character generator word in d1
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| 94 |
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| 95 | cgl2: lsr.w #2,d0 | Shift output word right 1 pixel
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| 96 | btst.l #0,d1 | Check CG word ls bit
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| 97 | beq cgl3 | Set background color if bit EQ 0
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| 98 |
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| 99 | or.w d3,d0 | OR foreground color into output word
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| 100 | bra cgl4 | Go update CG word
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| 101 |
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| 102 | cgl3: or.w d4,d0 | OR background color into output word
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| 103 |
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| 104 | cgl4: lsr.w #1,d1 | Shift CG word right 1 pixel
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| 105 | dbf d2,cgl2 | Loop for all 8 pixels
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| 106 |
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| 107 | move.w d0,(a1) | Store output word in output bitmap
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| 108 | suba.w d5,a1 | Update output pointer
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| 109 | adda.l #512,a0 | Update CG pointer for next scan line
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| 110 | dbf d6,cgl1 | Loop for all scan lines
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| 111 |
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| 112 | bra cgl0 | Loop for next character
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| 113 |
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| 114 | cgl5: movem.l (a7)+,d3-d6/a3 | Restore registers
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| 115 | unlk a6 | Unlink stack frames
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| 116 | rts | Return to caller
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| 117 |
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| 118 | .end
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