snapshot: stupid debugging session

I spent a while building a little keyboard scancode printer:

  $ ./translate ex1.mu &&  qemu-system-i386 disk.img

..and wondering why up-arrow was 0x48 in hex but 724 in decimal. I ended
up paranoidly poking at a bunch of crap (though there _is_ a cool chromatography-based
debugging technique in 126write-int-decimal.subx) before I realized:

  - 724 just has one extra digit over the correct answer
  - the 0xe0 scan code is a 3-digit number in decimal -- and the final digit is '4'

There's nothing actually wrong.

6 files changed, 152 insertions, 123 deletions

diff --git a/126write-int-decimal.subx b/126write-int-decimal.subx
index bc4a510e..ed2077a2 100644
--- a/126write-int-decimal.subx
+++ b/126write-int-decimal.subx
@@ -43,18 +43,24 @@ write-int32-decimal:  # out: (addr stream byte), n: int
     51/push-ecx
     52/push-edx
     53/push-ebx
+    56/push-esi
     57/push-edi
+    be/copy-to-esi 3/imm32/x
     # const ten/ecx = 10
     b9/copy-to-ecx  0xa/imm32
     # push sentinel
     68/push  0/imm32/sentinel
     # var eax: int = abs(n)
     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           0/r32/eax   0xc/disp8       .                 # copy *(ebp+12) to eax
+    (draw-vertical-line-on-real-screen %eax 0x40 0x50 %eax)
+    81 0/subop/add %esi 3/imm32
     3d/compare-eax-with  0/imm32
     7d/jump-if->=  $write-int32-decimal:read-loop/disp8
 $write-int32-decimal:negative:
     f7          3/subop/negate      3/mod/direct    0/rm32/eax    .           .             .           .           .               .                 # negate eax
 $write-int32-decimal:read-loop:
+    (draw-vertical-line-on-real-screen %esi 0x80 0x90 %esi)
+    81 0/subop/add %esi 3/imm32
     # eax, edx = eax / 10, eax % 10
     99/sign-extend-eax-into-edx
     f7          7/subop/idiv        3/mod/direct    1/rm32/ecx    .           .             .           .           .               .                 # divide edx:eax by ecx, storing quotient in eax and remainder in edx
@@ -104,6 +110,7 @@ $write-int32-decimal:write-break:
 $write-int32-decimal:end:
     # . restore registers
     5f/pop-to-edi
+    5e/pop-to-esi
     5b/pop-to-ebx
     5a/pop-to-edx
     59/pop-to-ecx
diff --git a/501draw-text.mu b/501draw-text.mu
index ce87634e..6f0b8011 100644
--- a/501draw-text.mu
+++ b/501draw-text.mu
@@ -105,6 +105,15 @@ fn draw-text-rightward screen: (addr screen), text: (addr array byte), x: int, x
   return xcurr
 }
 
+fn draw-int32-decimal-rightward screen: (addr screen), n: int, x: int, xmax: int, y: int, color: int, background-color: int -> _/eax: int {
+  var stream-storage: (stream byte 0x100)
+  var stream/esi: (addr stream byte) <- address stream-storage
+  write-int32-decimal stream, n
+#?   write-int32-hex stream, n
+  var xcurr/eax: int <- draw-stream-rightward screen, stream, x, xmax, y, color, background-color
+  return xcurr
+}
+
 # draw a single-line stream from x, y to xmax
 # return the next 'x' coordinate
 # if there isn't enough space, truncate
@@ -244,23 +253,9 @@ fn draw-int32-hex-wrapping-right-then-down screen: (addr screen), n: int, xmin:
   var stream-storage: (stream byte 0x100)
   var stream/esi: (addr stream byte) <- address stream-storage
   write-int32-hex stream, n
-  var xcurr/edx: int <- copy x
+  var xcurr/eax: int <- copy x
   var ycurr/ecx: int <- copy y
-  {
-    var g/eax: grapheme <- read-grapheme stream
-    compare g, 0xffffffff/end-of-file
-    break-if-=
-    draw-grapheme screen, g, xcurr, ycurr, color, background-color
-    xcurr <- increment
-    compare xcurr, xmax
-    {
-      break-if-<
-      xcurr <- copy xmin
-      ycurr <- increment
-    }
-    loop
-  }
-  set-cursor-position screen, xcurr, ycurr
+  xcurr, ycurr <- draw-stream-wrapping-right-then-down screen, stream, xmin, ymin, xmax, ymax, x, y, color, background-color
   return xcurr, ycurr
 }
 
@@ -297,24 +292,17 @@ fn draw-int32-hex-wrapping-right-then-down-from-cursor-over-full-screen screen:
 fn draw-int32-decimal-wrapping-right-then-down screen: (addr screen), n: int, xmin: int, ymin: int, xmax: int, ymax: int, x: int, y: int, color: int, background-color: int -> _/eax: int, _/ecx: int {
   var stream-storage: (stream byte 0x100)
   var stream/esi: (addr stream byte) <- address stream-storage
+#?   compare n, 0x48
+#?   {
+#?     break-if-!=
+#?     abort "aa"
+#?   }
   write-int32-decimal stream, n
-  var xcurr/edx: int <- copy x
-  var ycurr/ecx: int <- copy y
-  {
-    var g/eax: grapheme <- read-grapheme stream
-    compare g, 0xffffffff/end-of-file
-    break-if-=
-    draw-grapheme screen, g, xcurr, ycurr, color, background-color
-    xcurr <- increment
-    compare xcurr, xmax
-    {
-      break-if-<
-      xcurr <- copy xmin
-      ycurr <- increment
-    }
-    loop
-  }
-  set-cursor-position screen, xcurr, ycurr
+#?   write-int32-decimal stream, 0x48
+#?   write-int32-hex stream, n
+  var xcurr/eax: int <- copy 0
+  var ycurr/ecx: int <- copy 0
+  xcurr, ycurr <- draw-stream-wrapping-right-then-down screen, stream, xmin, ymin, xmax, ymax, x, y, color, background-color
   return xcurr, ycurr
 }
 
diff --git a/boot.subx b/boot.subx
index 6982fccb..ed2d213e 100644
--- a/boot.subx
+++ b/boot.subx
@@ -359,96 +359,125 @@ keyboard-interrupt-handler:
   3c/compare-al-and 0/imm8
   75/jump-if-!= $keyboard-interrupt-handler:epilogue/disp8
   # - read keycode
+  31/xor %eax 0/r32/eax
   e4/read-port-into-al 0x60/imm8
-  # - key released
-  # if (al == 0xaa) shift = false  # left shift is being lifted
-  {
-    3c/compare-al-and 0xaa/imm8
-    75/jump-if-!= break/disp8
-    # *shift = 0
-    c7 0/subop/copy *Keyboard-shift-pressed? 0/imm32
-  }
-  # if (al == 0xb6) shift = false  # right shift is being lifted
-  {
-    3c/compare-al-and 0xb6/imm8
-    75/jump-if-!= break/disp8
-    # *shift = 0
-    c7 0/subop/copy *Keyboard-shift-pressed? 0/imm32
-  }
-  # if (al == 0x9d) ctrl = false  # ctrl is being lifted
-  {
-    3c/compare-al-and 0x9d/imm8
-    75/jump-if-!= break/disp8
-    # *ctrl = 0
-    c7 0/subop/copy *Keyboard-ctrl-pressed? 0/imm32
-  }
-  # if (al & 0x80) a key is being lifted; return
-  50/push-eax
-  24/and-al-with 0x80/imm8
-  3c/compare-al-and 0/imm8
-  58/pop-to-eax
-  75/jump-if-!= $keyboard-interrupt-handler:epilogue/disp8
-  # - key pressed
-  # if (al == 0x2a) shift = true, return  # left shift pressed
-  {
-    3c/compare-al-and 0x2a/imm8
-    75/jump-if-!= break/disp8
-    # *shift = 1
-    c7 0/subop/copy *Keyboard-shift-pressed? 1/imm32
-    # return
-    eb/jump $keyboard-interrupt-handler:epilogue/disp8
-  }
-  # if (al == 0x36) shift = true, return  # right shift pressed
-  {
-    3c/compare-al-and 0x36/imm8
-    75/jump-if-!= break/disp8
-    # *shift = 1
-    c7 0/subop/copy *Keyboard-shift-pressed? 1/imm32
-    # return
-    eb/jump $keyboard-interrupt-handler:epilogue/disp8
-  }
-  # if (al == 0x1d) ctrl = true, return
-  {
-    3c/compare-al-and 0x1d/imm8
-    75/jump-if-!= break/disp8
-    # *ctrl = 1
-    c7 0/subop/copy *Keyboard-ctrl-pressed? 1/imm32
-    # return
-    eb/jump $keyboard-interrupt-handler:epilogue/disp8
-  }
-  # - convert key to character
-  # if (shift) use keyboard shift map
-  {
-    81 7/subop/compare *Keyboard-shift-pressed? 0/imm32
-    74/jump-if-= break/disp8
-    # sigils don't currently support labels inside *(eax+label)
-    05/add-to-eax Keyboard-shift-map/imm32
-    8a/byte-> *eax 0/r32/al
-    eb/jump $keyboard-interrupt-handler:select-map-done/disp8
-  }
-  # if (ctrl) al = *(ctrl map + al)
-  {
-    81 7/subop/compare *Keyboard-ctrl-pressed? 0/imm32
-    74/jump-if-= break/disp8
-    05/add-to-eax Keyboard-ctrl-map/imm32
-    8a/byte-> *eax 0/r32/al
-    eb/jump $keyboard-interrupt-handler:select-map-done/disp8
-  }
-  # otherwise al = *(normal map + al)
-  05/add-to-eax Keyboard-normal-map/imm32
-  8a/byte-> *eax 0/r32/al
-$keyboard-interrupt-handler:select-map-done:
-  # - if there's no character mapping, return
-  {
-    3c/compare-al-and 0/imm8
-    74/jump-if-= break/disp8
-    # - store al in keyboard buffer
-    88/<- *ecx 0/r32/al
-    # increment index
-    fe/increment-byte *Keyboard-buffer:write
-    # clear top nibble of index (keyboard buffer is circular)
-    80 4/subop/and-byte *Keyboard-buffer:write 0x0f/imm8
-  }
+  #
+#?   50/push-eax
+#?   51/push-ecx
+#?   (draw-int32-hex-wrapping-right-then-down-over-full-screen 0 %eax 0 0 7 0)
+#?   59/pop-to-ecx
+#?   58/pop-to-eax
+  #
+#?   50/push-eax
+#?   51/push-ecx
+#?   (draw-int32-decimal-wrapping-right-then-down 0 %eax 0 2 0x400 2 0 2 7 0)
+  89/<- %ecx 0/r32/eax
+  # . . push args
+  68/push 0/imm32/bg
+  68/push 7/imm32/fg
+  68/push 2/imm32/y
+  68/push 0x400/imm32/xmax
+  68/push 0/imm32/xmin
+#?   68/push 0x48/imm32/n
+  51/push-ecx
+  68/push 0/imm32/screen
+  # . . call
+#?   e8/call draw-int32-hex-wrapping-right-then-down/disp32
+#?   e8/call draw-int32-decimal-wrapping-right-then-down/disp32
+  e8/call draw-int32-decimal-rightward/disp32
+  # . . discard args
+  81 0/subop/add %esp 0x1c/imm32
+#?   59/pop-to-ecx
+#?   58/pop-to-eax
+#?   # - key released
+#?   # if (al == 0xaa) shift = false  # left shift is being lifted
+#?   {
+#?     3c/compare-al-and 0xaa/imm8
+#?     75/jump-if-!= break/disp8
+#?     # *shift = 0
+#?     c7 0/subop/copy *Keyboard-shift-pressed? 0/imm32
+#?   }
+#?   # if (al == 0xb6) shift = false  # right shift is being lifted
+#?   {
+#?     3c/compare-al-and 0xb6/imm8
+#?     75/jump-if-!= break/disp8
+#?     # *shift = 0
+#?     c7 0/subop/copy *Keyboard-shift-pressed? 0/imm32
+#?   }
+#?   # if (al == 0x9d) ctrl = false  # ctrl is being lifted
+#?   {
+#?     3c/compare-al-and 0x9d/imm8
+#?     75/jump-if-!= break/disp8
+#?     # *ctrl = 0
+#?     c7 0/subop/copy *Keyboard-ctrl-pressed? 0/imm32
+#?   }
+#?   # if (al & 0x80) a key is being lifted; return
+#?   50/push-eax
+#?   24/and-al-with 0x80/imm8
+#?   3c/compare-al-and 0/imm8
+#?   58/pop-to-eax
+#?   75/jump-if-!= $keyboard-interrupt-handler:epilogue/disp8
+#?   # - key pressed
+#?   # if (al == 0x2a) shift = true, return  # left shift pressed
+#?   {
+#?     3c/compare-al-and 0x2a/imm8
+#?     75/jump-if-!= break/disp8
+#?     # *shift = 1
+#?     c7 0/subop/copy *Keyboard-shift-pressed? 1/imm32
+#?     # return
+#?     eb/jump $keyboard-interrupt-handler:epilogue/disp8
+#?   }
+#?   # if (al == 0x36) shift = true, return  # right shift pressed
+#?   {
+#?     3c/compare-al-and 0x36/imm8
+#?     75/jump-if-!= break/disp8
+#?     # *shift = 1
+#?     c7 0/subop/copy *Keyboard-shift-pressed? 1/imm32
+#?     # return
+#?     eb/jump $keyboard-interrupt-handler:epilogue/disp8
+#?   }
+#?   # if (al == 0x1d) ctrl = true, return
+#?   {
+#?     3c/compare-al-and 0x1d/imm8
+#?     75/jump-if-!= break/disp8
+#?     # *ctrl = 1
+#?     c7 0/subop/copy *Keyboard-ctrl-pressed? 1/imm32
+#?     # return
+#?     eb/jump $keyboard-interrupt-handler:epilogue/disp8
+#?   }
+#?   # - convert key to character
+#?   # if (shift) use keyboard shift map
+#?   {
+#?     81 7/subop/compare *Keyboard-shift-pressed? 0/imm32
+#?     74/jump-if-= break/disp8
+#?     # sigils don't currently support labels inside *(eax+label)
+#?     05/add-to-eax Keyboard-shift-map/imm32
+#?     8a/byte-> *eax 0/r32/al
+#?     eb/jump $keyboard-interrupt-handler:select-map-done/disp8
+#?   }
+#?   # if (ctrl) al = *(ctrl map + al)
+#?   {
+#?     81 7/subop/compare *Keyboard-ctrl-pressed? 0/imm32
+#?     74/jump-if-= break/disp8
+#?     05/add-to-eax Keyboard-ctrl-map/imm32
+#?     8a/byte-> *eax 0/r32/al
+#?     eb/jump $keyboard-interrupt-handler:select-map-done/disp8
+#?   }
+#?   # otherwise al = *(normal map + al)
+#?   05/add-to-eax Keyboard-normal-map/imm32
+#?   8a/byte-> *eax 0/r32/al
+#? $keyboard-interrupt-handler:select-map-done:
+#?   # - if there's no character mapping, return
+#?   {
+#?     3c/compare-al-and 0/imm8
+#?     74/jump-if-= break/disp8
+#?     # - store al in keyboard buffer
+#?     88/<- *ecx 0/r32/al
+#?     # increment index
+#?     fe/increment-byte *Keyboard-buffer:write
+#?     # clear top nibble of index (keyboard buffer is circular)
+#?     80 4/subop/and-byte *Keyboard-buffer:write 0x0f/imm8
+#?   }
 $keyboard-interrupt-handler:epilogue:
   # epilogue
   9d/pop-flags
diff --git a/ex1.mu b/ex1.mu
new file mode 100644
index 00000000..0b379f60
--- /dev/null
+++ b/ex1.mu
@@ -0,0 +1,3 @@
+fn main screen: (addr screen), keyboard: (addr keyboard), data-disk: (addr disk) {
+  loop
+}
diff --git a/linux/126write-int-decimal.subx b/linux/126write-int-decimal.subx
index bff585a7..d38e1a17 100644
--- a/linux/126write-int-decimal.subx
+++ b/linux/126write-int-decimal.subx
@@ -167,9 +167,10 @@ test-write-int32-decimal-zero:
     e8/call  clear-stream/disp32
     # . . discard args
     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    b8/copy-to-eax 0x48/imm32
     # write-int32-decimal(_test-stream, 0)
     # . . push args
-    68/push  0/imm32
+    50/push-eax
     68/push  _test-stream/imm32
     # . . call
     e8/call  write-int32-decimal/disp32
diff --git a/linux/ex1.subx b/linux/ex1.subx
index 183c014a..3a8f700c 100644
--- a/linux/ex1.subx
+++ b/linux/ex1.subx
@@ -11,6 +11,7 @@
 == code
 
 Entry:
+e8/call test-write-int32-decimal-zero/disp32
 # exit(42)
 bb/copy-to-ebx  0x2a/imm32  # 42 in hex
 e8/call  syscall_exit/disp32