7329 - snapshot: advent day 4 part 2

I've found two bugs in SubX libraries:

1. next-word had an out-of-bounds read
2. next-word was skipping comments, because that's what I need during bootstrapping.
I've created a new variant called next-raw-word that doesn't skip comments.
These really need better names.

We're now at the point where 4b.mu has the right structure and returns
identical result to 4a.mu.

127next-word.subx

@@ -5,7 +5,8 @@
 # . op          subop               mod             rm32          base        index         scale       r32
 # . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
 
-# (re)compute the bounds of the next word in the line
+# (re)compute the bounds of the next word in the line (surrounded by whitespace,
+# treating '#' comments as a single word)
 # return empty string on reaching end of file
 next-word:  # line: (addr stream byte), out: (addr slice)
     # . prologue
@@ -56,6 +57,7 @@ $next-word:comment:
     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    6/base/esi  0/index/eax   .           0/r32/eax   0xc/disp8       .                 # copy esi+eax+12 to eax
     89/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           0/r32/eax   4/disp8         .                 # copy eax to *(edi+4)
     # . line->read = line->write
+    8b/copy                         0/mod/indirect  6/rm32/esi    .           .             .           0/r32/eax   .               .                 # copy *esi to eax
     89/copy                         1/mod/*+disp8   6/rm32/esi    .           .             .           0/r32/eax   4/disp8         .                 # copy eax to *(esi+4)
     # . return
     eb/jump  $next-word:end/disp8
@@ -298,3 +300,63 @@ test-next-word-returns-empty-string-on-newline:
     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
     5d/pop-to-ebp
     c3/return
+
+# (re)compute the bounds of the next word in the line (separated by whitespace)
+# return empty string on reaching end of file
+next-raw-word:  # line: (addr stream byte), out: (addr slice)
+    # . prologue
+    55/push-ebp
+    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+    # . save registers
+    50/push-eax
+    51/push-ecx
+    56/push-esi
+    57/push-edi
+    # esi = line
+    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           6/r32/esi   8/disp8         .                 # copy *(ebp+8) to esi
+    # edi = out
+    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           7/r32/edi   0xc/disp8       .                 # copy *(ebp+12) to edi
+    # skip-chars-matching-whitespace(line)
+    # . . push args
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
+    # . . call
+    e8/call  skip-chars-matching-whitespace/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+$next-raw-word:check0:
+    # if (line->read >= line->write) clear out and return
+    # . eax = line->read
+    8b/copy                         1/mod/*+disp8   6/rm32/esi    .           .             .           0/r32/eax   4/disp8         .                 # copy *(esi+4) to eax
+    # . if (eax < line->write) goto next check
+    3b/compare                      0/mod/indirect  6/rm32/esi    .           .             .           0/r32/eax   .               .                 # compare eax with *esi
+    7c/jump-if-<  $next-raw-word:word-exists/disp8
+    # . return out
+    c7          0/subop/copy        0/mod/direct    7/rm32/edi    .           .             .           .           .               0/imm32           # copy to *edi
+    c7          0/subop/copy        1/mod/*+disp8   7/rm32/edi    .           .             .           .           4/disp8         0/imm32           # copy to *(edi+4)
+    eb/jump  $next-raw-word:end/disp8
+$next-raw-word:word-exists:
+    # out->start = &line->data[line->read]
+    8b/copy                         1/mod/*+disp8   6/rm32/esi    .           .             .           1/r32/ecx   4/disp8         .                 # copy *(esi+4) to ecx
+    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    6/base/esi  1/index/ecx   .           0/r32/eax   0xc/disp8       .                 # copy esi+ecx+12 to eax
+    89/copy                         0/mod/indirect  7/rm32/edi    .           .             .           0/r32/eax   .               .                 # copy eax to *edi
+    # skip-chars-not-matching-whitespace(line)  # including trailing newline
+    # . . push args
+    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
+    # . . call
+    e8/call  skip-chars-not-matching-whitespace/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
+    # out->end = &line->data[line->read]
+    8b/copy                         1/mod/*+disp8   6/rm32/esi    .           .             .           1/r32/ecx   4/disp8         .                 # copy *(esi+4) to ecx
+    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    6/base/esi  1/index/ecx   .           0/r32/eax   0xc/disp8       .                 # copy esi+ecx+12 to eax
+    89/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           0/r32/eax   4/disp8         .                 # copy eax to *(edi+4)
+$next-raw-word:end:
+    # . restore registers
+    5f/pop-to-edi
+    5e/pop-to-esi
+    59/pop-to-ecx
+    58/pop-to-eax
+    # . epilogue
+    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
+    5d/pop-to-ebp
+    c3/return

400.mu

@@ -113,7 +113,8 @@ sig write-stream-data f: (addr buffered-file), s: (addr stream byte)
 sig write-int32-decimal out: (addr stream byte), n: int
 sig is-decimal-digit? c: grapheme -> _/eax: boolean
 sig to-decimal-digit in: grapheme -> _/eax: int
-sig next-word line: (addr stream byte), out: (addr slice)
+sig next-word line: (addr stream byte), out: (addr slice)  # skips '#' comments
+sig next-raw-word line: (addr stream byte), out: (addr slice)  # does not skip '#' comments
 sig has-metadata? word: (addr slice), s: (addr string) -> _/eax: boolean
 sig is-valid-name? in: (addr slice) -> _/eax: boolean
 sig is-label? word: (addr slice) -> _/eax: boolean

apps/advent2020/4b.mu

@@ -0,0 +1,82 @@
+# https://adventofcode.com/2020/day/4
+#
+# To run (on Linux):
+#   $ git clone https://github.com/akkartik/mu
+#   $ cd mu
+#   $ ./translate_mu apps/advent2020/4b.mu
+#   $ ./a.elf < input
+#
+# You'll need to register to download the 'input' file for yourself.
+
+fn main -> _/ebx: int {
+  var curr-passport-field-count/esi: int <- copy 0
+  var valid-passport-count/edi: int <- copy 0
+  var line-storage: (stream byte 0x100)  # 256 bytes
+  var line/ecx: (addr stream byte) <- address line-storage
+  var key-slice-storage: slice
+  var key-slice/edx: (addr slice) <- address key-slice-storage
+  var val-slice-storage: slice
+  var val-slice/ebx: (addr slice) <- address val-slice-storage
+  $main:line-loop: {
+    # read line from stdin
+    clear-stream line
+    read-line-from-real-keyboard line
+    # if line is empty (not even a newline), quit
+    var done?/eax: boolean <- stream-empty? line
+    compare done?, 0  # false
+    break-if-!=
+    print-stream-to-real-screen line
+    # if line has just a newline, process passport
+    skip-chars-matching-whitespace line
+    var new-passport?/eax: boolean <- stream-empty? line
+    {
+      compare new-passport?, 0  # false
+      break-if-=
+      compare curr-passport-field-count, 7
+      {
+        break-if-!=
+        valid-passport-count <- increment
+        print-string 0, "=> "
+        print-int32-decimal 0, valid-passport-count
+        print-string 0, "\n"
+      }
+      curr-passport-field-count <- copy 0
+      loop $main:line-loop
+    }
+    $main:word-loop: {
+      skip-chars-matching-whitespace line
+      var done?/eax: boolean <- stream-empty? line
+      compare done?, 0  # false
+      break-if-!=
+      next-token line, 0x3a, key-slice  # ':'
+      var dummy/eax: byte <- read-byte line  # skip ':'
+      next-raw-word line, val-slice
+      print-slice-to-real-screen key-slice
+      print-string 0, " : "
+      print-slice-to-real-screen val-slice
+      print-string 0, "\n"
+      # treat cid as optional
+      var optional?/eax: boolean <- slice-equal? key-slice, "cid"
+      compare optional?, 0  # false
+      {
+        break-if-!=
+        # otherwise assume there are no invalid fields and no duplicate fields
+        curr-passport-field-count <- increment
+        print-string 0, "-> "
+        print-int32-decimal 0, curr-passport-field-count
+        print-string 0, "\n"
+      }
+      loop
+    }
+    loop
+  }
+  # process final passport
+  compare curr-passport-field-count, 7
+  {
+    break-if-!=
+    valid-passport-count <- increment
+  }
+  print-int32-decimal 0, valid-passport-count
+  print-string 0, "\n"
+  return 0
+}