7490 - baremetal: draw a grapheme to screen
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@ -34,6 +34,8 @@
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# $ echo '*Foo' | ./bootstrap run apps/sigils
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# 0/mod 5/rm32/.disp32 Foo/disp32
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#
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# TODO: *(Foo+ecx<<2)
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#
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# Addition isn't commutative here. Template must always be (base+index<<scale+disp),
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# though some components are optional as described above.
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# In particular, global variables like 'Foo' above don't support displacement
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@ -0,0 +1,70 @@
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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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@ -1,2 +1,3 @@
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sig pixel screen: (addr screen), x: int, y: int, color: int
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sig read-key kbd: (addr keyboard) -> _/eax: byte
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sig draw-grapheme screen: (addr screen), g: grapheme, x: int, y: int, color: int
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@ -0,0 +1,15 @@
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# Draw a character using the built-in font (GNU unifont)
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#
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# To build a disk image:
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# ./translate_mu_baremetal baremetal/ex4.mu # emits disk.img
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# To run:
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# qemu-system-i386 disk.img
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# Or:
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# bochs -f baremetal/boot.bochsrc # boot.bochsrc loads disk.img
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#
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# Expected output: letter 'A' in green near the top-left corner of screen
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fn main {
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var g/eax: grapheme <- copy 0x41 # 'A'
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draw-grapheme 0, g, 0x10, 0x10, 0xa
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}
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