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55 lines
1.6 KiB
55 lines
1.6 KiB
# Primitives for screen control. |
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# |
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# We need to do this in machine code because Mu doesn't have global variables |
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# yet (for the start of video memory). |
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== code |
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pixel-on-real-screen: # x: int, y: int, color: int |
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# . prologue |
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55/push-ebp |
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89/<- %ebp 4/r32/esp |
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# |
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(pixel-on-screen-buffer *Video-memory-addr *(ebp+8) *(ebp+0xc) *(ebp+0x10) 0x400 0x300) |
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$pixel-on-real-screen:end: |
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# . epilogue |
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89/<- %esp 5/r32/ebp |
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5d/pop-to-ebp |
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c3/return |
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# 'buffer' here is not a valid Mu type: a naked address without a length. |
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pixel-on-screen-buffer: # buffer: (addr byte), x: int, y: int, color: int, width: int, height: int |
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# . prologue |
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55/push-ebp |
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89/<- %ebp 4/r32/esp |
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# . save registers |
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50/push-eax |
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51/push-ecx |
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# bounds checks |
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8b/-> *(ebp+0xc) 0/r32/eax # foo |
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3d/compare-eax-and 0/imm32 |
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7c/jump-if-< $pixel-on-screen-buffer:end/disp8 |
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3b/compare 0/r32/eax *(ebp+0x18) |
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7d/jump-if->= $pixel-on-screen-buffer:end/disp8 |
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8b/-> *(ebp+0x10) 0/r32/eax |
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3d/compare-eax-and 0/imm32 |
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7c/jump-if-< $pixel-on-screen-buffer:end/disp8 |
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3b/compare 0/r32/eax *(ebp+0x1c) |
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7d/jump-if->= $pixel-on-screen-buffer:end/disp8 |
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# eax = y*width + x |
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8b/-> *(ebp+0x10) 0/r32/eax |
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0f af/multiply-> *(ebp+0x18) 0/r32/eax |
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03/add-> *(ebp+0xc) 0/r32/eax |
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# eax += location of frame buffer |
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03/add-> *(ebp+8) 0/r32/eax |
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# *eax = color |
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8b/-> *(ebp+0x14) 1/r32/ecx |
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88/byte<- *eax 1/r32/CL |
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$pixel-on-screen-buffer:end: |
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# . restore registers |
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59/pop-to-ecx |
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58/pop-to-eax |
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# . epilogue |
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89/<- %esp 5/r32/ebp |
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5d/pop-to-ebp |
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c3/return
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