https://github.com/akkartik/mu/blob/main/linux/crenshaw2-1.subx

      1 # Port of https://github.com/akkartik/crenshaw/blob/master/tutor2.1.pas
      2 # which corresponds to the section "single digits" in https://compilers.iecc.com/crenshaw/tutor2.txt
      3 # except that we support hex digits.
      4 #
      5 # To run:
      6 #   $ bootstrap/bootstrap translate [01]*.subx apps/crenshaw2-1.subx -o apps/crenshaw2-1
      7 #   $ echo '3'  |bootstrap/bootstrap run crenshaw2-1
      8 # Expected output:
      9 #   # syscall(exit, 3)
     10 #   bb/copy-to-ebx  3/imm32
     11 #   b8/copy-to-eax  1/imm32/exit
     12 #   cd/syscall  0x80/imm8
     13 #
     14 # To run the generated output:
     15 #   $ echo '3'  |bootstrap/bootstrap run crenshaw2-1 > z1.subx
     16 #   $ bootstrap/bootstrap translate z1.subx -o z1
     17 #   $ bootstrap/bootstrap run z1
     18 #   $ echo $?
     19 #   3
     20 #
     21 # Stdin must contain just a single hex digit. Other input will print an error:
     22 #   $ echo 'xyz'  |bootstrap/bootstrap run crenshaw2-1
     23 #   Error: integer expected
     24 #
     25 # Names in this file sometimes follow Crenshaw's original rather than my usual
     26 # naming conventions.
     27
     28 == code
     29 #   instruction                     effective address                                                   register    displacement    immediate
     30 # . op          subop               mod             rm32          base        index         scale       r32
     31 # . 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
     32
     33 Entry:  # run tests if necessary, call 'compile' if not
     34     # . prologue
     35     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
     36
     37     # initialize heap
     38     # . Heap = new-segment(Heap-size)
     39     # . . push args
     40     68/push  Heap/imm32
     41     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Heap-size/disp32                  # push *Heap-size
     42     # . . call
     43     e8/call  new-segment/disp32
     44     # . . discard args
     45     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
     46
     47     # - if argc > 1 and argv[1] == "test", then return run_tests()
     48     # if (argc <= 1) goto run-main
     49     81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0/disp8         1/imm32           # compare *ebp
     50     7e/jump-if-<=  $run-main/disp8
     51     # if (!kernel-string-equal?(argv[1], "test")) goto run-main
     52     # . eax = kernel-string-equal?(argv[1], "test")
     53     # . . push args
     54     68/push  "test"/imm32
     55     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
     56     # . . call
     57     e8/call  kernel-string-equal?/disp32
     58     # . . discard args
     59     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
     60     # . if (eax == false) goto run-main
     61     3d/compare-eax-and  0/imm32/false
     62     74/jump-if-=  $run-main/disp8
     63     # run-tests()
     64     e8/call  run-tests/disp32
     65     # syscall(exit, *Num-test-failures)
     66     8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           3/r32/ebx   Num-test-failures/disp32          # copy *Num-test-failures to ebx
     67     eb/jump  $main:end/disp8
     68 $run-main:
     69     # - otherwise read a program from stdin and emit its translation to stdout
     70     # . compile(Stdin, 1/stdout, 2/stderr, ed)
     71     # . . push args
     72     68/push  0/imm32/exit-descriptor
     73     68/push  2/imm32/stderr
     74     68/push  1/imm32/stdout
     75     68/push  Stdin/imm32
     76     # . . call
     77     e8/call  compile/disp32
     78     # . . discard args
     79     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
     80     # syscall(exit, 0)
     81     bb/copy-to-ebx  0/imm32
     82 $main:end:
     83     e8/call  syscall_exit/disp32
     84
     85 # the main entry point
     86 compile:  # in: (addr buffered-file), out: fd or (addr stream byte), err: fd or (addr stream byte), ed: (addr exit-descriptor)
     87     # . prologue
     88     55/push-ebp
     89     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
     90     # . save registers
     91     50/push-eax
     92     51/push-ecx
     93     # prime the pump
     94     # . Look = get-char(in)
     95     # . . push args
     96     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8      .                    # push *(ebp+8)
     97     # . . call
     98     e8/call  get-char/disp32
     99     # . . discard args
    100     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    101     # var num/ecx: (stream byte 7)
    102     # Numbers can be 32 bits or 8 hex bytes long. One of them will be in 'Look', so we need space for 7 bytes.
    103     # Sizing the stream just right buys us overflow-handling for free inside 'get-num'.
    104     # Add 12 bytes for 'read', 'write' and 'size' fields, for a total of 19 bytes, or 0x13 in hex.
    105     # The stack pointer is no longer aligned, so dump_stack() can be misleading past this point.
    106     81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               0x13/imm32        # subtract from esp
    107     89/copy                         3/mod/direct    1/rm32/ecx    .           .             .           4/r32/esp   .               .                 # copy esp to ecx
    108     # initialize the stream
    109     # . num->size = 7
    110     c7          0/subop/copy        1/mod/*+disp8   1/rm32/ecx    .           .             .           .           8/disp8         7/imm32           # copy to *(ecx+8)
    111     # . clear-stream(num)
    112     # . . push args
    113     51/push-ecx
    114     # . . call
    115     e8/call  clear-stream/disp32
    116     # . . discard args
    117     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    118     # read a digit from 'in' into 'num'
    119     # . get-num(in, num, err, ed)
    120     # . . push args
    121     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x14/disp8      .                 # push *(ebp+20)
    122     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
    123     51/push-ecx/num
    124     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8      .                    # push *(ebp+8)
    125     # . . call
    126     e8/call  get-num/disp32
    127     # . . discard args
    128     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
    129     # render 'num' into the following template on 'out':
    130     #   bb/copy-to-ebx  _num_
    131     #   b8/copy-to-eax  1/imm32/exit
    132     #   cd/syscall  0x80/imm8
    133     #
    134     # . write(out, "bb/copy-to-ebx  ")
    135     # . . push args
    136     68/push  "bb/copy-to-ebx  "/imm32
    137     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    138     # . . call
    139     e8/call  write/disp32
    140     # . . discard args
    141     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    142     # . write-stream(out, num)
    143     # . . push args
    144     51/push-ecx/num
    145     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    146     # . . call
    147     e8/call  write-stream/disp32
    148     # . . discard args
    149     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    150     # . write(out, Newline)
    151     # . . push args
    152     68/push  Newline/imm32
    153     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    154     # . . call
    155     e8/call  write/disp32
    156     # . . discard args
    157     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    158     # . write(out, "b8/copy-to-eax  1/imm32/exit\n")
    159     # . . push args
    160     68/push  "b8/copy-to-eax  1/imm32/exit\n"/imm32
    161     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    162     # . . call
    163     e8/call  write/disp32
    164     # . . discard args
    165     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    166     # . write(out, "cd/syscall  0x80/imm8\n")
    167     # . . push args
    168     68/push  "cd/syscall  0x80/imm8\n"/imm32
    169     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    170     # . . call
    171     e8/call  write/disp32
    172     # . . discard args
    173     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    174 $compile:end:
    175     # . restore registers
    176     59/pop-to-ecx
    177     58/pop-to-eax
    178     # . epilogue
    179     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    180     5d/pop-to-ebp
    181     c3/return
    182
    183 # Read a single digit into 'out'. Abort if there are none, or if there is no
    184 # space in 'out'.
    185 # Input comes from the global variable 'Look' (first byte) and the argument
    186 # 'in' (rest). We leave the next byte from 'in' into 'Look' on exit.
    187 get-num:  # in: (addr buffered-file), out: (addr stream byte), err: fd or (addr stream byte), ed: (addr exit-descriptor)
    188     # pseudocode:
    189     #   if (!digit?(Look)) expected(ed, err, "integer")
    190     #   if out->write >= out->size
    191     #     write(err, "Error: too many digits in number\n")
    192     #     stop(ed, 1)
    193     #   out->data[out->write] = LSB(Look)
    194     #   ++out->write
    195     #   Look = get-char(in)
    196     #
    197     # registers:
    198     #   in: esi
    199     #   out: edi
    200     #   out->write: ecx (cached copy; need to keep in sync)
    201     #   out->size: edx
    202     #   temporaries: eax, ebx
    203     # We can't allocate Look to a register because it gets written implicitly in
    204     # get-char in each iteration of the loop. (Thereby demonstrating that it's
    205     # not the right interface for us. But we'll keep it just to follow Crenshaw.)
    206     #
    207     # . prologue
    208     55/push-ebp
    209     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    210     # - if (digit?(Look)) expected(ed, err, "integer")
    211     # . eax = digit?(Look)
    212     # . . push args
    213     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Look/disp32     .                 # push *Look
    214     # . . call
    215     e8/call  digit?/disp32
    216     # . . discard args
    217     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    218     # . if (eax == false)
    219     3d/compare-eax-and  0/imm32/false
    220     75/jump-if-!=  $get-num:main/disp8
    221     # . expected(ed, err, "integer")
    222     # . . push args
    223     68/push  "integer"/imm32
    224     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
    225     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x14/disp8      .                 # push *(ebp+20)
    226     # . . call
    227     e8/call  expected/disp32  # never returns
    228     # . . discard args
    229     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    230 $get-num:main:
    231     # - otherwise read a digit
    232     # . save registers
    233     50/push-eax
    234     51/push-ecx
    235     52/push-edx
    236     53/push-ebx
    237     56/push-esi
    238     57/push-edi
    239     # read necessary variables to registers
    240     # esi = in
    241     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           6/r32/esi   8/disp8         .                 # copy *(ebp+8) to esi
    242     # edi = out
    243     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           7/r32/edi   0xc/disp8       .                 # copy *(ebp+12) to edi
    244     # ecx = out->write
    245     8b/copy                         0/mod/indirect  7/rm32/edi    .           .             .           1/r32/ecx   .               .                 # copy *edi to ecx
    246     # edx = out->size
    247     8b/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           2/r32/edx   8/disp8         .                 # copy *(edi+8) to edx
    248 $get-num:loop:
    249     # if (out->write >= out->size) error
    250     39/compare                      3/mod/direct    2/rm32/edx    .           .             .           1/r32/ecx   .               .                 # compare edx with ecx
    251     7d/jump-if-<  $get-num:stage2/disp8
    252     # . error(ed, err, msg)  # TODO: show full number
    253     # . . push args
    254     68/push  "get-num: too many digits in number"/imm32
    255     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
    256     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x14/disp8      .                 # push *(ebp+20)
    257     # . . call
    258     e8/call  error/disp32  # never returns
    259     # . . discard args
    260     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    261 $get-num:stage2:
    262     # out->data[out->write] = LSB(Look)
    263     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    7/base/edi  1/index/ecx   .           3/r32/ebx   0xc/disp8       .                 # copy edi+ecx+12 to ebx
    264     8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Look/disp32     .                 # copy *Look to eax
    265     88/copy-byte                    0/mod/indirect  3/rm32/ebx    .           .             .           0/r32/AL    .               .                 # copy byte at AL to *ebx
    266     # ++out->write
    267     41/increment-ecx
    268     # Look = get-char(in)
    269     # . . push args
    270     56/push-esi
    271     # . . call
    272     e8/call  get-char/disp32
    273     # . . discard args
    274     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    275 $get-num:loop-end:
    276     # persist necessary variables from registers
    277     89/copy                         0/mod/indirect  7/rm32/edi    .           .             .           1/r32/ecx   .               .                 # copy ecx to *edi
    278 $get-num:end:
    279     # . restore registers
    280     5f/pop-to-edi
    281     5e/pop-to-esi
    282     5b/pop-to-ebx
    283     5a/pop-to-edx
    284     59/pop-to-ecx
    285     58/pop-to-eax
    286     # . epilogue
    287     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    288     5d/pop-to-ebp
    289     c3/return
    290
    291 test-get-num-reads-single-digit:
    292     # - check that get-num returns first character if it's a digit
    293     # This test uses exit-descriptors. Use ebp for setting up local variables.
    294     55/push-ebp
    295     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    296     # clear all streams
    297     # . clear-stream(_test-stream)
    298     # . . push args
    299     68/push  _test-stream/imm32
    300     # . . call
    301     e8/call  clear-stream/disp32
    302     # . . discard args
    303     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    304     # . clear-stream($_test-buffered-file->buffer)
    305     # . . push args
    306     68/push  $_test-buffered-file->buffer/imm32
    307     # . . call
    308     e8/call  clear-stream/disp32
    309     # . . discard args
    310     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    311     # . clear-stream(_test-output-stream)
    312     # . . push args
    313     68/push  _test-output-stream/imm32
    314     # . . call
    315     e8/call  clear-stream/disp32
    316     # . . discard args
    317     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    318     # . clear-stream(_test-error-stream)
    319     # . . push args
    320     68/push  _test-error-stream/imm32
    321     # . . call
    322     e8/call  clear-stream/disp32
    323     # . . discard args
    324     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    325     # initialize 'in'
    326     # . write(_test-stream, "3")
    327     # . . push args
    328     68/push  "3"/imm32
    329     68/push  _test-stream/imm32
    330     # . . call
    331     e8/call  write/disp32
    332     # . . discard args
    333     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    334     # initialize exit-descriptor 'ed' for the call to 'get-num' below
    335     # . var ed/eax: exit-descriptor
    336     81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # subtract from esp
    337     89/copy                         3/mod/direct    0/rm32/eax    .           .             .           4/r32/esp   .               .                 # copy esp to eax
    338     # . tailor-exit-descriptor(ed, 16)
    339     # . . push args
    340     68/push  0x10/imm32/nbytes-of-args-for-get-num
    341     50/push-eax/ed
    342     # . . call
    343     e8/call  tailor-exit-descriptor/disp32
    344     # . . discard args
    345     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    346     # prime the pump
    347     # . get-char(_test-buffered-file)
    348     # . . push args
    349     68/push  _test-buffered-file/imm32
    350     # . . call
    351     e8/call  get-char/disp32
    352     # . . discard args
    353     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    354     # get-num(in, out, err, ed)
    355     # . . push args
    356     50/push-eax/ed
    357     68/push  _test-error-stream/imm32
    358     68/push  _test-output-stream/imm32
    359     68/push  _test-buffered-file/imm32
    360     # . . call
    361     e8/call  get-num/disp32
    362     # registers except esp may be clobbered at this point
    363     # . . discard args
    364     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
    365     # check-ints-equal(*_test-output-stream->data, '3', msg)
    366     # . . push args
    367     68/push  "F - test-get-num-reads-single-digit"/imm32
    368     68/push  0x33/imm32
    369     b8/copy-to-eax  _test-output-stream/imm32
    370     ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           0xc/disp8       .                 # push *(eax+12)
    371     # . . call
    372     e8/call  check-ints-equal/disp32
    373     # . . discard args
    374     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    375     # . reclaim locals
    376     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    377     5d/pop-to-ebp
    378     c3/return
    379
    380 test-get-num-aborts-on-non-digit-in-Look:
    381     # - check that get-num returns first character if it's a digit
    382     # This test uses exit-descriptors. Use ebp for setting up local variables.
    383     55/push-ebp
    384     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    385     # clear all streams
    386     # . clear-stream(_test-stream)
    387     # . . push args
    388     68/push  _test-stream/imm32
    389     # . . call
    390     e8/call  clear-stream/disp32
    391     # . . discard args
    392     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    393     # . clear-stream($_test-buffered-file->buffer)
    394     # . . push args
    395     68/push  $_test-buffered-file->buffer/imm32
    396     # . . call
    397     e8/call  clear-stream/disp32
    398     # . . discard args
    399     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    400     # . clear-stream(_test-output-stream)
    401     # . . push args
    402     68/push  _test-output-stream/imm32
    403     # . . call
    404     e8/call  clear-stream/disp32
    405     # . . discard args
    406     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    407     # . clear-stream(_test-error-stream)
    408     # . . push args
    409     68/push  _test-error-stream/imm32
    410     # . . call
    411     e8/call  clear-stream/disp32
    412     # . . discard args
    413     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    414     # initialize 'in'
    415     # . write(_test-stream, "3")
    416     # . . push args
    417     68/push  "3"/imm32
    418     68/push  _test-stream/imm32
    419     # . . call
    420     e8/call  write/disp32
    421     # . . discard args
    422     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    423     # initialize exit-descriptor 'ed' for the call to 'get-num' below
    424     # . var ed/eax: exit-descriptor
    425     81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # subtract from esp
    426     89/copy                         3/mod/direct    0/rm32/eax    .           .             .           4/r32/esp   .               .                 # copy esp to eax
    427     # . tailor-exit-descriptor(ed, 16)
    428     # . . push args
    429     68/push  0x10/imm32/nbytes-of-args-for-get-num
    430     50/push-eax/ed
    431     # . . call
    432     e8/call  tailor-exit-descriptor/disp32
    433     # . . discard args
    434     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    435     # *don't* prime the pump
    436     # get-num(in, out, err, ed)
    437     # . . push args
    438     50/push-eax/ed
    439     68/push  _test-error-stream/imm32
    440     68/push  _test-output-stream/imm32
    441     68/push  _test-buffered-file/imm32
    442     # . . call
    443     e8/call  get-num/disp32
    444     # registers except esp may be clobbered at this point
    445     # . . discard args
    446     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
    447     # check that get-num tried to call exit(1)
    448     # . check-ints-equal(ed->value, 2, msg)  # i.e. stop was called with value 1
    449     # . . push args
    450     68/push  "F - test-get-num-aborts-on-non-digit-in-Look"/imm32
    451     68/push  2/imm32
    452     # . . push ed->value
    453     ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         .                 # push *(eax+4)
    454     # . . call
    455     e8/call  check-ints-equal/disp32
    456     # . . discard args
    457     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    458     # . reclaim locals
    459     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    460     5d/pop-to-ebp
    461     c3/return
    462
    463 ## helpers
    464
    465 # write(f, "Error: "+s+" expected\n") then stop(ed, 1)
    466 expected:  # ed: (addr exit-descriptor), f: fd or (addr stream byte), s: (addr array byte)
    467     # . prologue
    468     55/push-ebp
    469     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    470     # write(f, "Error: ")
    471     # . . push args
    472     68/push  "Error: "/imm32
    473     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    474     # . . call
    475     e8/call  write/disp32
    476     # . . discard args
    477     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    478     # write(f, s)
    479     # . . push args
    480     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0x10/disp8      .                 # push *(ebp+16)
    481     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    482     # . . call
    483     e8/call  write/disp32
    484     # . . discard args
    485     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    486     # write(f, " expected\n")
    487     # . . push args
    488     68/push  " expected\n"/imm32
    489     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    490     # . . call
    491     e8/call  write/disp32
    492     # . . discard args
    493     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    494     # stop(ed, 1)
    495     # . . push args
    496     68/push  1/imm32
    497     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    498     # . . call
    499     e8/call  stop/disp32
    500     # should never get past this point
    501 $expected:dead-end:
    502     # . epilogue
    503     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    504     5d/pop-to-ebp
    505     c3/return
    506
    507 # read a byte from 'f', and save it in 'Look'
    508 get-char:  # f: (addr buffered-file)
    509     # . prologue
    510     55/push-ebp
    511     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    512     # . save registers
    513     50/push-eax
    514     # eax = read-byte-buffered(f)
    515     # . . push args
    516     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    517     # . . call
    518     e8/call  read-byte-buffered/disp32
    519     # . . discard args
    520     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    521     # save eax to Look
    522     89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Look/disp32     .                 # copy eax to *Look
    523 $get-char:end:
    524     # . restore registers
    525     58/pop-to-eax
    526     # . epilogue
    527     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    528     5d/pop-to-ebp
    529     c3/return
    530
    531 digit?:  # c: int -> eax: boolean
    532     # . prologue
    533     55/push-ebp
    534     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    535     # eax = false
    536     b8/copy-to-eax  0/imm32
    537     # if (c < '0') return false
    538     81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         0x30/imm32        # compare *(ebp+8)
    539     7c/jump-if-<  $digit?:end/disp8
    540     # if (c > '9') return false
    541     81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         0x39/imm32        # compare *(ebp+8)
    542     7f/jump-if->  $digit?:end/disp8
    543     # otherwise return true
    544     b8/copy-to-eax  1/imm32
    545 $digit?:end:
    546     # . epilogue
    547     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    548     5d/pop-to-ebp
    549     c3/return
    550
    551 == data
    552
    553 Look:  # (char with some extra padding)
    554     0/imm32
    555
    556 # . . vim:nowrap:textwidth=0