68 lines
1.8 KiB
Common Lisp
68 lines
1.8 KiB
Common Lisp
((code
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(label main
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; Open screen
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(load-immediate $0 &screen-namespace)
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(load-immediate $1 0)
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(syscall DEVICE-OPEN $0 $1)
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; Draw red box at (10, 20)
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(load-immediate $1 0xE0) ; color
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(push $1)
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(load-immediate $1 10) ; x
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(push $1)
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(load-immediate $1 20) ; y
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(push $1)
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(call &draw-box)
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; Draw green box at (10, 40)
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(load-immediate $1 0x1C) ; RGB332 green (00011100)
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(push $1)
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(load-immediate $1 10)
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(push $1)
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(load-immediate $1 40)
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(push $1)
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(call &draw-box)
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; Flush and halt
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(syscall DEVICE-WRITE $0 $0 $0)
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(halt))
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; draw-box(color, x, y)
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; Pops: y, x, color
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(label draw-box
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; Pop arguments (reverse order)
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(pop $13) ; y_start
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(pop $11) ; x_start
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(pop $3) ; color
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; Constants
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(load-immediate $1 1) ; increment
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(load-immediate $2 640) ; row stride
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(load-immediate $10 36) ; framebuffer base
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(load-immediate $12 20) ; width
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(load-immediate $14 20) ; height
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; Compute start address: base + y*640 + x
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(mul-int $15 $13 $2) ; $15 = y * 640
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(add-int $15 $15 $11) ; $15 += x
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(add-int $4 $10 $15) ; $4 = base + offset
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; Outer loop: height times
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(register-move $5 $14) ; $5 = row counter
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(label draw-box-outer
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(add-int $6 $4 $12) ; $6 = row end = current + width
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(register-move $7 $4) ; $7 = pixel pointer
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(label draw-box-inner
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(store-8 $7 $3) ; write color
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(add-int $7 $7 $1) ; next pixel
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(jump-lt-int &draw-box-inner $7 $6))
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(add-int $4 $4 $2) ; next row (+= 640)
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(sub-int $5 $5 $1) ; decrement row count
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(jump-gt-int &draw-box-outer $5 0))
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(return)))
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(data
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(label screen-namespace "/dev/screen/0")))
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