71 lines
1.8 KiB
Plaintext
71 lines
1.8 KiB
Plaintext
draw-grapheme: # screen: (addr screen), g: grapheme, 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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# . save registers
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50/push-eax
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51/push-ecx
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52/push-edx
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53/push-ebx
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56/push-esi
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# var letter-bitmap/esi = font[g]
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8b/-> *(ebp+0xc) 6/r32/esi
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c1 4/subop/shift-left %esi 4/imm8
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8d/copy-address *(esi+0x8800) 6/r32/esi # font-start
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# if (letter-bitmap >= 0x9000) return # characters beyond ASCII currently not supported
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81 7/subop/compare %esi 0x9000/imm32
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7d/jump-if->= $draw-grapheme:end/disp8
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# edx = y
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8b/-> *(ebp+0x14) 2/r32/edx
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# var ymax/ebx: int = y + 16
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8b/-> *(ebp+0x14) 3/r32/ebx
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81 0/subop/add %ebx 0x10/imm32
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{
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# if (y >= ymax) break
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39/compare %edx 3/r32/ebx
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7d/jump-if->= break/disp8
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# eax = x + 7
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8b/-> *(ebp+0x10) 0/r32/eax
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81 0/subop/add %eax 7/imm32
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# var xmin/ecx: int = x
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8b/-> *(ebp+0x10) 1/r32/ecx
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# var row-bitmap/ebx: int = *letter-bitmap
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53/push-ebx
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8b/-> *esi 3/r32/ebx
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{
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# if (x < xmin) break
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39/compare %eax 1/r32/ecx
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7c/jump-if-< break/disp8
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# shift LSB from row-bitmap into carry flag (CF)
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c1 5/subop/shift-right-logical %ebx 1/imm8
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# if LSB, draw a pixel
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{
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73/jump-if-not-CF break/disp8
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(pixel *(ebp+8) %eax %edx *(ebp+0x18))
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}
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# --x
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48/decrement-eax
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#
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eb/jump loop/disp8
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}
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# reclaim row-bitmap
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5b/pop-to-ebx
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# ++y
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42/increment-edx
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# next bitmap row
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46/increment-esi
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#
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eb/jump loop/disp8
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}
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$draw-grapheme:end:
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# . restore registers
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5e/pop-to-esi
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5b/pop-to-ebx
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5a/pop-to-edx
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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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