https://github.com/akkartik/mu/blob/main/linux/107trace.subx

      1 # primitives for emitting traces to a 'trace' stream, and for tests to make assertions on its contents
      2 #
      3 # A trace stream looks like a regular stream:
      4 #   write: int  # index at which writes go
      5 #   read: int  # index that we've read until
      6 #   data: (array byte)  # prefixed by size as usual
      7 # Usually the trace stream will be in a separate segment set aside for the purpose.
      8 #
      9 # primitives for operating on traces (arguments in quotes):
     10 #   - initialize-trace-stream: populates Trace-stream with a new segment of the given 'size'
     11 #   - trace: adds a 'line' to Trace-stream
     12 #   - check-trace-contains: scans from Trace-stream's start for a matching 'line', prints a 'message' to stderr on failure
     13 #   - check-trace-scans-to: scans from Trace-stream's read pointer for a matching 'line', prints a 'message' to stderr on failure
     14
     15 == data
     16
     17 Trace-stream:  # (addr stream byte)  # TODO: make this a handle
     18     0/imm32
     19
     20 Trace-segment:
     21     0/imm32/curr
     22     0/imm32/limit
     23
     24 # Fake trace-stream for tests.
     25 # Also illustrates the layout of the real trace-stream (segment).
     26 _test-trace-stream:  # (stream byte)
     27     # current write index
     28     0/imm32
     29     # current read index
     30     0/imm32
     31     # size
     32     8/imm32
     33     # data
     34     00 00 00 00 00 00 00 00  # 8 bytes
     35
     36 == code
     37 #   instruction                     effective address                                                   register    displacement    immediate
     38 # . op          subop               mod             rm32          base        index         scale       r32
     39 # . 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
     40
     41 # Allocate a new segment for the trace stream, initialize its size, and save its address to Trace-stream.
     42 # The Trace-stream segment will consist of variable-length lines separated by newlines (0x0a)
     43 initialize-trace-stream:  # n: int
     44     # . prologue
     45     55/push-ebp
     46     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
     47     # . save registers
     48     50/push-eax
     49     51/push-ecx
     50     # ecx = n
     51     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           1/r32/ecx   8/disp8         .                 # copy *(ebp+8) to ecx
     52     # Trace-segment = new-segment(n)
     53     # . . push args
     54     68/push  Trace-segment/imm32
     55     51/push-ecx
     56     # . . call
     57     e8/call  new-segment/disp32
     58     # . . discard args
     59     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
     60     # copy Trace-segment->curr to *Trace-stream
     61     8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-segment/disp32              # copy *Trace-segment to eax
     62 #?     # watch point to catch Trace-stream leaks
     63 #? $watch-1:
     64     89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
     65     # Trace-stream->size = n - 12
     66     # . ecx -= 12
     67     81          5/subop/subtract    3/mod/direct    1/rm32/ecx    .           .             .           .           .               0xc/imm32         # subtract from ecx
     68     # . Trace-stream->size = ecx
     69     89/copy                         1/mod/*+disp8   0/rm32/eax    .           .             .           1/r32/ecx   8/disp8         .                 # copy ecx to *(eax+8)
     70 $initialize-trace-stream:end:
     71     # . restore registers
     72     59/pop-to-ecx
     73     58/pop-to-eax
     74     # . epilogue
     75     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
     76     5d/pop-to-ebp
     77     c3/return
     78
     79 # Append a string to the given trace stream.
     80 # Silently give up if it's already full. Or truncate the string if there isn't enough room.
     81 trace:  # line: (addr array byte)
     82     # . prologue
     83     55/push-ebp
     84     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
     85     # . save registers
     86     50/push-eax
     87     51/push-ecx
     88     52/push-edx
     89     53/push-ebx
     90     56/push-esi
     91     57/push-edi
     92     # var edi: (addr stream byte) = *Trace-stream
     93     8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           7/r32/edi   Trace-stream/disp32               # copy *Trace-stream to edi
     94     # esi = line
     95     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         6/r32/esi   8/disp8         .                 # copy *(ebp+8) to esi
     96     # var ecx: int = t->write
     97     8b/copy                         0/mod/indirect  7/rm32/edi    .           .             .           1/r32/ecx   .               .                 # copy *edi to ecx
     98     # var edx: int = t->size
     99     8b/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           2/r32/edx   8/disp8         .                 # copy *(edi+8) to edx
    100     # eax = _append-3(&t->data[t->write], &t->data[t->size], line)
    101     # . . push line
    102     56/push-esi
    103     # . . push &t->data[t->size]
    104     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    7/base/edi  2/index/edx   .           3/r32/ebx   0xc/disp8       .                 # copy edi+edx+12 to ebx
    105     53/push-ebx
    106     # . . push &t->data[t->write]
    107     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
    108     53/push-ebx
    109     # . . call
    110     e8/call  _append-3/disp32
    111     # . . discard args
    112     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    113     # if (eax == 0) return
    114     3d/compare-eax-and  0/imm32
    115     74/jump-if-=  $trace:end/disp8
    116     # t->write += eax
    117     01/add                          0/mod/indirect  7/rm32/edi    .           .             .           0/r32/eax   .               .                 # add eax to *edi
    118     # refresh ecx = t->write
    119     8b/copy                         0/mod/indirect  7/rm32/edi    .           .             .           1/r32/ecx   .               .                 # copy *edi to ecx
    120     # eax = _append-3(&t->data[t->write], &t->data[t->size], line)
    121     # . . push line
    122     68/push  Newline/imm32
    123     # . . push &t->data[t->size]
    124     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    7/base/edi  2/index/edx   .           3/r32/ebx   0xc/disp8       .                 # copy edi+edx+12 to ebx
    125     53/push-ebx
    126     # . . push &t->data[t->write]
    127     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
    128     53/push-ebx
    129     # . . call
    130     e8/call  _append-3/disp32
    131     # . . discard args
    132     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    133     # t->write += eax
    134     01/add                          0/mod/indirect  7/rm32/edi    .           .             .           0/r32/eax   .               .                 # add eax to *edi
    135 $trace:end:
    136     # . restore registers
    137     5f/pop-to-edi
    138     5e/pop-to-esi
    139     5b/pop-to-ebx
    140     5a/pop-to-edx
    141     59/pop-to-ecx
    142     58/pop-to-eax
    143     # . epilogue
    144     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    145     5d/pop-to-ebp
    146     c3/return
    147
    148 test-trace-single:
    149     # push *Trace-stream
    150     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    151     # *Trace-stream = _test-trace-stream
    152     b8/copy-to-eax  _test-trace-stream/imm32
    153     89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    154     # clear-trace-stream()
    155     e8/call  clear-trace-stream/disp32
    156     # trace("Ab")
    157     # . . push args
    158     68/push  "Ab"/imm32
    159     # . . call
    160     e8/call  trace/disp32
    161     # . . discard args
    162     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    163     # check-ints-equal(*_test-trace-stream->data, 41/A 62/b 0a/newline 00, msg)
    164     # . . push args
    165     68/push  "F - test-trace-single"/imm32
    166     68/push  0x0a6241/imm32/Ab-newline
    167     # . . push *_test-trace-stream->data
    168     b8/copy-to-eax  _test-trace-stream/imm32
    169     ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           0xc/disp8       .                 # push *(eax+12)
    170     # . . call
    171     e8/call  check-ints-equal/disp32
    172     # . . discard args
    173     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    174     # pop into *Trace-stream
    175     8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    176     # end
    177     c3/return
    178
    179 test-trace-appends:
    180     # push *Trace-stream
    181     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    182     # *Trace-stream = _test-trace-stream
    183     b8/copy-to-eax  _test-trace-stream/imm32
    184     89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    185     # clear-trace-stream()
    186     e8/call  clear-trace-stream/disp32
    187     # trace("C")
    188     # . . push args
    189     68/push  "C"/imm32
    190     # . . call
    191     e8/call  trace/disp32
    192     # . . discard args
    193     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    194     # trace("D")
    195     # . . push args
    196     68/push  "D"/imm32
    197     # . . call
    198     e8/call  trace/disp32
    199     # . . discard args
    200     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    201     # check-ints-equal(*_test-trace-stream->data, 43/C 0a/newline 44/D 0a/newline, msg)
    202     # . . push args
    203     68/push  "F - test-trace-appends"/imm32
    204     68/push  0x0a440a43/imm32/C-newline-D-newline
    205     # . . push *_test-trace-stream->data
    206     b8/copy-to-eax  _test-trace-stream/imm32
    207     ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           0xc/disp8       .                 # push *(eax+12)
    208     # . . call
    209     e8/call  check-ints-equal/disp32
    210     # . . discard args
    211     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    212     # pop into *Trace-stream
    213     8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    214     # end
    215     c3/return
    216
    217 test-trace-empty-line:
    218     # push *Trace-stream
    219     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    220     # *Trace-stream = _test-trace-stream
    221     b8/copy-to-eax  _test-trace-stream/imm32
    222     89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    223     # clear-trace-stream()
    224     e8/call  clear-trace-stream/disp32
    225     # trace("")
    226     # . . push args
    227     68/push  ""/imm32
    228     # . . call
    229     e8/call  trace/disp32
    230     # . . discard args
    231     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    232     # check-ints-equal(*_test-trace-stream->data, 0, msg)
    233     # . . push args
    234     68/push  "F - test-trace-empty-line"/imm32
    235     68/push  0/imm32
    236     # . . push *_test-trace-stream->data
    237     b8/copy-to-eax  _test-trace-stream/imm32
    238     ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           0xc/disp8       .                 # push *(eax+12)
    239     # . . call
    240     e8/call  check-ints-equal/disp32
    241     # . . discard args
    242     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    243     # pop into *Trace-stream
    244     8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    245     # end
    246     c3/return
    247
    248 check-trace-contains:  # line: (addr string), msg: (addr string)
    249     # . prologue
    250     55/push-ebp
    251     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    252     # rewind-stream(*Trace-stream)
    253     # . . push args
    254     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    255     # . . call
    256     e8/call  rewind-stream/disp32
    257     # . . discard args
    258     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    259     # check-trace-scans-to(line, msg)
    260     # . . push args
    261     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    262     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    263     # . . call
    264     e8/call  check-trace-scans-to/disp32
    265     # . . discard args
    266     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    267 $check-trace-contains:end:
    268     # . epilogue
    269     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    270     5d/pop-to-ebp
    271     c3/return
    272
    273 check-trace-scans-to:  # line: (addr string), msg: (addr string)
    274     # . prologue
    275     55/push-ebp
    276     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    277     # . save registers
    278     50/push-eax
    279     # eax = trace-scan(line)
    280     # . . push args
    281     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    282     # . . call
    283     e8/call  trace-scan/disp32
    284     # . . discard args
    285     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    286     # check-ints-equal(eax, 1, msg)
    287     # . . push args
    288     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    289     68/push  1/imm32
    290     50/push-eax
    291     # . . call
    292     e8/call check-ints-equal/disp32
    293     # . . discard args
    294     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    295 $check-trace-scans-to:end:
    296     # . restore registers
    297     58/pop-to-eax
    298     # . epilogue
    299     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    300     5d/pop-to-ebp
    301     c3/return
    302
    303 # Start scanning from Trace-stream->read for 'line'. If found, update Trace-stream->read and return true.
    304 trace-scan:  # line: (addr array byte) -> result/eax: boolean
    305     # pseudocode:
    306     #   push Trace-stream->read
    307     #   while true:
    308     #     if Trace-stream->read >= Trace-stream->write
    309     #       break
    310     #     if next-line-matches?(Trace-stream, line)
    311     #       skip-next-line(Trace-stream)
    312     #       dump saved copy of Trace-stream->read
    313     #       return true
    314     #     skip-next-line(Trace-stream)
    315     #   pop saved copy of Trace-stream->read
    316     #   return false
    317     #
    318     # . prologue
    319     55/push-ebp
    320     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    321     # . save registers
    322     51/push-ecx
    323     56/push-esi
    324     # esi = *Trace-stream
    325     8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           6/r32/esi   Trace-stream/disp32               # copy *Trace-stream to esi
    326     # ecx = Trace-stream->write
    327     8b/copy                         0/mod/indirect  6/rm32/esi    .           .             .           1/r32/ecx                   .                 # copy *esi to ecx
    328     # push Trace-stream->read
    329     ff          6/subop/push        1/mod/*+disp8   6/rm32/esi    .           .             .           .           4/disp8         .                 # push *(esi+4)
    330 $trace-scan:loop:
    331     # if (Trace-stream->read >= Trace-stream->write) return false
    332     39/compare                      1/mod/*+disp8   6/rm32/esi    .           .             .           1/r32/ecx   4/disp8         .                 # compare ecx with *(esi+4)
    333     7d/jump-if->=  $trace-scan:false/disp8
    334     # eax = next-line-matches?(Trace-stream, line)
    335     # . . push args
    336     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    337     56/push-esi
    338     # . . call
    339     e8/call  next-line-matches?/disp32
    340     # . . discard args
    341     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    342     # if (eax == false) continue
    343     3d/compare-eax-and  0/imm32/false
    344     74/jump-if-=  $trace-scan:continue/disp8
    345 $trace-scan:true:
    346     # skip-next-line(Trace-stream)
    347     # . . push args
    348     56/push-esi
    349     # . . call
    350     e8/call  skip-next-line/disp32
    351     # . . discard args
    352     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    353     # dump saved copy of Trace-stream->read
    354     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    355     # return true
    356     b8/copy-to-eax  1/imm32/true
    357     eb/jump  $trace-scan:end/disp8
    358 $trace-scan:continue:
    359     # skip-next-line(Trace-stream)
    360     # . . push args
    361     56/push-esi
    362     # . . call
    363     e8/call  skip-next-line/disp32
    364     # . . discard args
    365     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    366     eb/jump  $trace-scan:loop/disp8
    367 $trace-scan:false:
    368     # restore saved copy of Trace-stream->read
    369     8f          0/subop/pop         1/mod/*+disp8   6/rm32/esi    .           .             .           .           4/disp8         .                 # pop to *(esi+4)
    370     # return false
    371     b8/copy-to-eax  0/imm32/false
    372 $trace-scan:end:
    373     # . restore registers
    374     59/pop-to-ecx
    375     # . epilogue
    376     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    377     5d/pop-to-ebp
    378     c3/return
    379
    380 test-trace-scan-first:
    381     # push *Trace-stream
    382     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    383     # setup
    384     # . *Trace-stream = _test-trace-stream
    385     b8/copy-to-eax  _test-trace-stream/imm32
    386     89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    387     # . clear-trace-stream()
    388     e8/call  clear-trace-stream/disp32
    389     # . trace("Ab")
    390     # . . push args
    391     68/push  "Ab"/imm32
    392     # . . call
    393     e8/call  trace/disp32
    394     # . . discard args
    395     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    396     # eax = trace-scan("Ab")
    397     # . . push args
    398     68/push  "Ab"/imm32
    399     # . . call
    400     e8/call  trace-scan/disp32
    401     # . . discard args
    402     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    403     # check-ints-equal(eax, 1, msg)
    404     # . . push args
    405     68/push  "F - test-trace-scan-first"/imm32
    406     68/push  1/imm32
    407     50/push-eax
    408     # . . call
    409     e8/call check-ints-equal/disp32
    410     # . . discard args
    411     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    412     # pop into *Trace-stream
    413     8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    414     # . end
    415     c3/return
    416
    417 test-trace-scan-skips-lines-until-found:
    418     # push *Trace-stream
    419     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    420     # setup
    421     # . *Trace-stream = _test-trace-stream
    422     b8/copy-to-eax  _test-trace-stream/imm32
    423     89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    424     # . clear-trace-stream()
    425     e8/call  clear-trace-stream/disp32
    426     # . trace("Ab")
    427     # . . push args
    428     68/push  "Ab"/imm32
    429     # . . call
    430     e8/call  trace/disp32
    431     # . . discard args
    432     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    433     # . trace("cd")
    434     # . . push args
    435     68/push  "cd"/imm32
    436     # . . call
    437     e8/call  trace/disp32
    438     # . . discard args
    439     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    440     # eax = trace-scan("cd")
    441     # . . push args
    442     68/push  "cd"/imm32
    443     # . . call
    444     e8/call  trace-scan/disp32
    445     # . . discard args
    446     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    447     # check-ints-equal(eax, 1, msg)
    448     # . . push args
    449     68/push  "F - test-trace-scan-skips-lines-until-found"/imm32
    450     68/push  1/imm32
    451     50/push-eax
    452     # . . call
    453     e8/call check-ints-equal/disp32
    454     # . . discard args
    455     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    456     # pop into *Trace-stream
    457     8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    458     # . end
    459     c3/return
    460
    461 test-trace-second-scan-starts-where-first-left-off:
    462     # push *Trace-stream
    463     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    464     # setup
    465     # . *Trace-stream = _test-trace-stream
    466     b8/copy-to-eax  _test-trace-stream/imm32
    467     89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    468     # . clear-trace-stream()
    469     e8/call  clear-trace-stream/disp32
    470     # . trace("Ab")
    471     # . . push args
    472     68/push  "Ab"/imm32
    473     # . . call
    474     e8/call  trace/disp32
    475     # . . discard args
    476     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    477     # . eax = trace-scan("Ab")
    478     # . . push args
    479     68/push  "Ab"/imm32
    480     # . . call
    481     e8/call  trace-scan/disp32
    482     # . . discard args
    483     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    484     # second scan fails
    485     # . eax = trace-scan("Ab")
    486     # . . push args
    487     68/push  "Ab"/imm32
    488     # . . call
    489     e8/call  trace-scan/disp32
    490     # . . discard args
    491     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    492     # check-ints-equal(eax, 0, msg)
    493     # . . push args
    494     68/push  "F - test-trace-second-scan-starts-where-first-left-off"/imm32
    495     68/push  0/imm32
    496     50/push-eax
    497     # . . call
    498     e8/call check-ints-equal/disp32
    499     # . . discard args
    500     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    501     # pop into *Trace-stream
    502     8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    503     # . end
    504     c3/return
    505
    506 test-trace-scan-failure-leaves-read-index-untouched:
    507     # push *Trace-stream
    508     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    509     # setup
    510     # . *Trace-stream = _test-trace-stream
    511     b8/copy-to-eax  _test-trace-stream/imm32
    512     89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    513     # . clear-trace-stream()
    514     e8/call  clear-trace-stream/disp32
    515     # . trace("Ab")
    516     # . . push args
    517     68/push  "Ab"/imm32
    518     # . . call
    519     e8/call  trace/disp32
    520     # . . discard args
    521     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    522     # . check-ints-equal(_test-trace-stream->read, 0, msg)
    523     # . . push args
    524     68/push  "F - test-trace-scan-failure-leaves-read-index-untouched/precondition-failure"/imm32
    525     68/push  0/imm32
    526     b8/copy-to-eax  _test-trace-stream/imm32
    527     ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         .                 # push *(eax+4)
    528     # . . call
    529     e8/call check-ints-equal/disp32
    530     # . . discard args
    531     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    532     # perform a failing scan
    533     # . eax = trace-scan("Ax")
    534     # . . push args
    535     68/push  "Ax"/imm32
    536     # . . call
    537     e8/call  trace-scan/disp32
    538     # . . discard args
    539     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    540     # no change in read index
    541     # . check-ints-equal(_test-trace-stream->read, 0, msg)
    542     # . . push args
    543     68/push  "F - test-trace-scan-failure-leaves-read-index-untouched"/imm32
    544     68/push  0/imm32
    545     b8/copy-to-eax  _test-trace-stream/imm32
    546     ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         .                 # push *(eax+4)
    547     # . . call
    548     e8/call check-ints-equal/disp32
    549     # . . discard args
    550     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    551     # pop into *Trace-stream
    552     8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    553     # . end
    554     c3/return
    555
    556 next-line-matches?:  # t: (addr stream byte), line: (addr array byte) -> result/eax: boolean
    557     # pseudocode:
    558     #   while true:
    559     #     if (currl >= maxl) break
    560     #     if (currt >= maxt) return false
    561     #     if (*currt != *currl) return false
    562     #     ++currt
    563     #     ++currl
    564     #   return *currt == '\n'
    565     #
    566     # . prologue
    567     55/push-ebp
    568     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    569     # . save registers
    570     51/push-ecx
    571     52/push-edx
    572     53/push-ebx
    573     56/push-esi
    574     57/push-edi
    575     # edx = line
    576     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         2/r32/edx   0xc/disp8       .                 # copy *(ebp+12) to edx
    577     # var currl/esi: (addr byte) = line->data
    578     # . esi = line/edx->data
    579     8d/copy-address                 1/mod/*+disp8   2/rm32/edx    .           .             .           6/r32/esi   4/disp8         .                 # copy edx+4 to esi
    580     # var maxl/ecx: (addr byte) = &line->data[line->size]
    581     # . eax = line/edx->size
    582     8b/copy                         0/mod/indirect  2/rm32/edx    .           .                         0/r32/eax   .               .                 # copy *edx to eax
    583     # . maxl = &line->data[line->size]
    584     8d/copy-address                 0/mod/indirect  4/rm32/sib    6/base/esi  0/index/eax   .           1/r32/ecx   .               .                 # copy edx+eax to ecx
    585     # edi = t
    586     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         7/r32/edi   8/disp8         .                 # copy *(ebp+8) to edi
    587     # var ebx: (addr byte) = t->data
    588     8d/copy-address                 1/mod/*+disp8   7/rm32/edi    .           .             .           3/r32/ebx   0xc/disp8       .                 # copy edi+12 to ebx
    589     # var maxt/edx: (addr byte) = &t->data[t->write]
    590     # . eax = t->write
    591     8b/copy                         0/mod/indirect  7/rm32/edi    .           .                         0/r32/eax   .               .                 # copy *edi to eax
    592     # . maxt = &t->data[t->write]
    593     8d/copy-address                 0/mod/indirect  4/rm32/sib    3/base/ebx  0/index/eax   .           2/r32/edx   .               .                 # copy ebx+eax to edx
    594     # var currt/edi: (addr byte) = &t->data[t->read]
    595     # . eax = t/edi->read
    596     8b/copy                         1/mod/*+disp8   7/rm32/edi    .           .                         0/r32/eax   4/disp8         .                 # copy *(edi+4) to eax
    597     # . currt = &t->data[t->read]
    598     8d/copy-address                 0/mod/indirect  4/rm32/sib    3/base/ebx  0/index/eax   .           7/r32/edi   .               .                 # copy ebx+eax to edi
    599 $next-line-matches?:loop:
    600     # if (currl >= maxl) break
    601     39/compare                      3/mod/direct    6/rm32/esi    .           .             .           1/r32/ecx   .               .                 # compare esi and ecx
    602     73/jump-if-addr>=  $next-line-matches?:break/disp8
    603     # if (currt >= maxt) return false
    604     # . eax = false
    605     b8/copy-to-eax  0/imm32/false
    606     39/compare                      3/mod/direct    7/rm32/edi    .           .             .           2/r32/edx   .               .                 # compare edi and edx
    607     73/jump-if-addr>=  $next-line-matches?:end/disp8
    608     # if (*currt != *currl) return false
    609     31/xor                          3/mod/direct    0/rm32/eax    .           .             .           0/r32/eax   .               .                 # clear eax
    610     31/xor                          3/mod/direct    3/rm32/eax    .           .             .           3/r32/eax   .               .                 # clear ebx
    611     # . eax: byte = *currt
    612     8a/copy-byte                    0/mod/indirect  7/rm32/edi    .           .                         0/r32/eax   .               .                 # copy *edi to eax
    613     # . ebx: byte = *currl
    614     8a/copy-byte                    0/mod/indirect  6/rm32/esi    .           .                         3/r32/ebx   .               .                 # copy *esi to ebx
    615     # . eax >= ebx
    616     39/compare                      3/mod/direct    0/rm32/eax    .           .             .           3/r32/ebx   .               .                 # compare eax and ebx
    617     # . eax = false
    618     b8/copy-to-eax  0/imm32/false
    619     75/jump-if-!=  $next-line-matches?:end/disp8
    620     # ++currt
    621     47/increment-edi
    622     # ++currl
    623     46/increment-esi
    624     eb/jump  $next-line-matches?:loop/disp8
    625 $next-line-matches?:break:
    626     # return *currt == '\n'
    627     31/xor                          3/mod/direct    0/rm32/eax    .           .             .           0/r32/eax   .               .                 # clear eax
    628     # . eax: byte = *currt
    629     8a/copy-byte                    0/mod/indirect  7/rm32/edi    .           .                         0/r32/eax   .               .                 # copy *edi to eax
    630     3d/compare-eax-and  0xa/imm32/newline
    631     # . eax = false
    632     b8/copy-to-eax  1/imm32/true
    633     74/jump-if-=  $next-line-matches?:end/disp8
    634     b8/copy-to-eax  0/imm32/true
    635 $next-line-matches?:end:
    636     # . restore registers
    637     5f/pop-to-edi
    638     5e/pop-to-esi
    639     5b/pop-to-ebx
    640     5a/pop-to-edx
    641     59/pop-to-ecx
    642     # . epilogue
    643     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    644     5d/pop-to-ebp
    645     c3/return
    646
    647 test-next-line-matches?-no-match-1:
    648     # next line of "ABABA" does not match "blah blah"
    649     # . eax = next-line-matches?(_test-stream-line-ABABA, "blah blah")
    650     # . . push args
    651     68/push  "blah blah"/imm32
    652     68/push  _test-stream-line-ABABA/imm32
    653     # . . call
    654     e8/call  next-line-matches?/disp32
    655     # . . discard args
    656     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    657     # . check-ints-equal(eax, 0, msg)
    658     # . . push args
    659     68/push  "F - test-next-line-matches?-no-match-1"/imm32
    660     68/push  0/imm32
    661     50/push-eax
    662     # . . call
    663     e8/call  check-ints-equal/disp32
    664     # . . discard args
    665     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    666     c3/return
    667
    668 test-next-line-matches?-no-match-2:
    669     # next line of "ABABA" does not match ""
    670     # . eax = next-line-matches?(_test-stream-line-ABABA, "")
    671     # . . push args
    672     68/push  ""/imm32
    673     68/push  _test-stream-line-ABABA/imm32
    674     # . . call
    675     e8/call  next-line-matches?/disp32
    676     # . . discard args
    677     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    678     # . check-ints-equal(eax, 0, msg)
    679     # . . push args
    680     68/push  "F - test-next-line-matches?-no-match-2"/imm32
    681     68/push  0/imm32
    682     50/push-eax
    683     # . . call
    684     e8/call  check-ints-equal/disp32
    685     # . . discard args
    686     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    687     c3/return
    688
    689 test-next-line-matches?-no-match-3:
    690     # next line of "ABABA" does not match  "AA"
    691     # . eax = next-line-matches?(_test-stream-line-ABABA, "AA")
    692     # . . push args
    693     68/push  "AA"/imm32
    694     68/push  _test-stream-line-ABABA/imm32
    695     # . . call
    696     e8/call  next-line-matches?/disp32
    697     # . . discard args
    698     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    699     # . check-ints-equal(eax, 0, msg)
    700     # . . push args
    701     68/push  "F - test-next-line-matches?-no-match-3"/imm32
    702     68/push  0/imm32
    703     50/push-eax
    704     # . . call
    705     e8/call  check-ints-equal/disp32
    706     # . . discard args
    707     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    708     c3/return
    709
    710 test-next-line-matches?-match:
    711     # next line of "ABABA" matches "ABABA"
    712     # . eax = next-line-matches?(_test-stream-line-ABABA, "ABABA")
    713     # . . push args
    714     68/push  "ABABA"/imm32
    715     68/push  _test-stream-line-ABABA/imm32
    716     # . . call
    717     e8/call  next-line-matches?/disp32
    718     # . . discard args
    719     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    720     # . check-ints-equal(eax, 1, msg)
    721     # . . push args
    722     68/push  "F - test-next-line-matches?-match"/imm32
    723     68/push  1/imm32
    724     50/push-eax
    725     # . . call
    726     e8/call  check-ints-equal/disp32
    727     # . . discard args
    728     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    729     c3/return
    730
    731 # move t->read to _after_ next newline
    732 skip-next-line:  # t: (addr stream byte)
    733     # pseudocode:
    734     #   max = &t->data[t->write]
    735     #   i = t->read
    736     #   curr = &t->data[t->read]
    737     #   while true
    738     #     if (curr >= max) break
    739     #     ++i
    740     #     if (*curr == '\n') break
    741     #     ++curr
    742     #   t->read = i
    743     #
    744     # . prologue
    745     55/push-ebp
    746     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    747     # . save registers
    748     50/push-eax
    749     51/push-ecx
    750     52/push-edx
    751     53/push-ebx
    752     # ecx = t
    753     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         1/r32/ecx   8/disp8         .                 # copy *(ebp+8) to ecx
    754     # edx = t->data
    755     8d/copy-address                 1/mod/*+disp8   1/rm32/ecx    .           .             .           2/r32/edx   0xc/disp8       .                 # copy ecx+12 to edx
    756     # eax = t->write
    757     8b/copy                         0/mod/indirect  1/rm32/ecx    .           .             .           0/r32/eax   .               .                 # copy *ecx to eax
    758     # var max/ebx: (addr byte) = &t->data[t->write]
    759     8d/copy-address                 0/mod/indirect  4/rm32/sib    2/base/edx  0/index/eax   .           3/r32/ebx   .               .                 # copy edx+eax to ebx
    760     # eax = t->read
    761     8b/copy                         1/mod/*+disp8   1/rm32/ecx    .           .             .           0/r32/eax   4/disp8         .                 # copy *(ecx+4) to edx
    762     # var curr/ecx: (addr byte) = &t->data[t->read]
    763     8d/copy-address                 0/mod/indirect  4/rm32/sib    2/base/edx  0/index/eax   .           1/r32/ecx   .               .                 # copy edx+eax to ecx
    764     # var i/edx: int = t->read
    765     89/copy                         3/mod/direct    2/rm32/edx    .           .             .           0/r32/eax   .               .                 # copy eax to edx
    766 $skip-next-line:loop:
    767     # if (curr >= max) break
    768     39/compare                      3/mod/direct    1/rm32/ecx    .           .             .           3/r32/ebx   .               .                 # compare ecx and ebx
    769     73/jump-if-addr>=  $skip-next-line:end/disp8
    770     # ++i
    771     42/increment-edx
    772     # if (*curr == '\n') break
    773     31/xor                          3/mod/direct    0/rm32/eax    .           .             .           0/r32/eax   .               .                 # clear eax
    774     8a/copy-byte                    0/mod/indirect  1/rm32/ecx    .           .             .           0/r32/eax   .               .                 # copy *ecx to eax
    775     3d/compare-eax-and  0a/imm32/newline
    776     74/jump-if-=  $skip-next-line:end/disp8
    777     # ++curr
    778     41/increment-ecx
    779     # loop
    780     eb/jump  $skip-next-line:loop/disp8
    781 $skip-next-line:end:
    782     # ecx = t
    783     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         1/r32/ecx   8/disp8         .                 # copy *(ebp+8) to ecx
    784     # t->read = i
    785     89/copy                         1/mod/*+disp8   1/rm32/ecx    .           .             .           2/r32/edx   4/disp8         .                 # copy edx to *(ecx+4)
    786     # . restore registers
    787     5b/pop-to-ebx
    788     5a/pop-to-edx
    789     59/pop-to-ecx
    790     58/pop-to-eax
    791     # . epilogue
    792     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    793     5d/pop-to-ebp
    794     c3/return
    795
    796 test-skip-next-line-empty:
    797     # skipping next line in empty stream leaves read pointer at 0
    798     # . skip-next-line(_test-stream-empty)
    799     # . . push args
    800     68/push  _test-stream-empty/imm32
    801     # . . call
    802     e8/call  skip-next-line/disp32
    803     # . . discard args
    804     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    805     # . check-ints-equal(_test-stream-empty->read, 0, msg)
    806     # . . push args
    807     68/push  "F - test-skip-next-line-empty"/imm32
    808     68/push  0/imm32
    809     b8/copy-to-eax  _test-stream-empty/imm32
    810     8b/copy                         1/mod/*+disp8   0/rm32/eax    .           .             .           0/r32/eax   4/disp8         .                 # copy *(eax+4) to eax
    811     50/push-eax
    812     # . . call
    813     e8/call  check-ints-equal/disp32
    814     # . . discard args
    815     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    816     c3/return
    817
    818 test-skip-next-line-filled:
    819     # skipping next line increments read pointer by length of line + 1 (for newline)
    820     # . skip-next-line(_test-stream-filled)
    821     # . . push args
    822     68/push  _test-stream-filled/imm32
    823     # . . call
    824     e8/call  skip-next-line/disp32
    825     # . . discard args
    826     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    827     # . check-ints-equal(_test-stream-filled->read, 5, msg)
    828     # . . push args
    829     68/push  "F - test-skip-next-line-filled"/imm32
    830     68/push  5/imm32
    831     b8/copy-to-eax  _test-stream-filled/imm32
    832     8b/copy                         1/mod/*+disp8   0/rm32/eax    .           .             .           0/r32/eax   4/disp8         .                 # copy *(eax+4) to eax
    833     50/push-eax
    834     # . . call
    835     e8/call  check-ints-equal/disp32
    836     # . . discard args
    837     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    838     c3/return
    839
    840 clear-trace-stream:
    841     # . prologue
    842     55/push-ebp
    843     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    844     # clear-stream(*Trace-stream)
    845     # . . push args
    846     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    847     # . . call
    848     e8/call  clear-stream/disp32
    849     # . . discard args
    850     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    851 $clear-trace-stream:end:
    852     # . epilogue
    853     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    854     5d/pop-to-ebp
    855     c3/return
    856
    857 # - helpers
    858
    859 # 3-argument variant of _append
    860 _append-3:  # out: (addr byte), outend: (addr byte), s: (addr array byte) -> num_bytes_appended/eax
    861     # . prologue
    862     55/push-ebp
    863     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    864     # . save registers
    865     51/push-ecx
    866     # eax = _append-4(out, outend, &s->data[0], &s->data[s->size])
    867     # . . push &s->data[s->size]
    868     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         0/r32/eax   0x10/disp8      .                 # copy *(ebp+16) to eax
    869     8b/copy                         0/mod/indirect  0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # copy *eax to ecx
    870     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    0/base/eax  1/index/ecx   .           1/r32/ecx   4/disp8         .                 # copy eax+ecx+4 to ecx
    871     51/push-ecx
    872     # . . push &s->data[0]
    873     8d/copy-address                 1/mod/*+disp8   0/rm32/eax    .           .             .           1/r32/ecx   4/disp8         .                 # copy eax+4 to ecx
    874     51/push-ecx
    875     # . . push outend
    876     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    877     # . . push out
    878     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    879     # . . call
    880     e8/call  _append-4/disp32
    881     # . . discard args
    882     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
    883 $_append-3:end:
    884     # . restore registers
    885     59/pop-to-ecx
    886     # . epilogue
    887     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    888     5d/pop-to-ebp
    889     c3/return
    890
    891 # 4-argument variant of _append
    892 _append-4:  # out: (addr byte), outend: (addr byte), in: (addr byte), inend: (addr byte) -> num_bytes_appended/eax: int
    893     # . prologue
    894     55/push-ebp
    895     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    896     # . save registers
    897     51/push-ecx
    898     52/push-edx
    899     53/push-ebx
    900     56/push-esi
    901     57/push-edi
    902     # num_bytes_appended = 0
    903     b8/copy-to-eax  0/imm32
    904     # edi = out
    905     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           7/r32/edi   8/disp8         .                 # copy *(ebp+8) to edi
    906     # edx = outend
    907     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           2/r32/edx   0xc/disp8       .                 # copy *(ebp+12) to edx
    908     # esi = in
    909     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           6/r32/esi   0x10/disp8      .                 # copy *(ebp+16) to esi
    910     # ecx = inend
    911     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           1/r32/ecx   0x14/disp8      .                 # copy *(ebp+20) to ecx
    912 $_append-4:loop:
    913     # if (in >= inend) break
    914     39/compare                      3/mod/direct    6/rm32/esi    .           .             .           1/r32/ecx   .               .                 # compare esi with ecx
    915     73/jump-if-addr>=  $_append-4:end/disp8
    916     # if (out >= outend) abort  # just to catch test failures fast
    917     39/compare                      3/mod/direct    7/rm32/edi    .           .             .           2/r32/edx   .               .                 # compare edi with edx
    918     73/jump-if-addr>=  $_append-4:abort/disp8
    919     # *out = *in
    920     8a/copy-byte                    0/mod/indirect  6/rm32/esi    .           .             .           3/r32/BL    .               .                 # copy byte at *esi to BL
    921     88/copy-byte                    0/mod/indirect  7/rm32/edi    .           .             .           3/r32/BL    .               .                 # copy byte at BL to *edi
    922     # ++num_bytes_appended
    923     40/increment-eax
    924     # ++in
    925     46/increment-esi
    926     # ++out
    927     47/increment-edi
    928     eb/jump  $_append-4:loop/disp8
    929 $_append-4:end:
    930     # . restore registers
    931     5f/pop-to-edi
    932     5e/pop-to-esi
    933     5b/pop-to-ebx
    934     5a/pop-to-edx
    935     59/pop-to-ecx
    936     # . epilogue
    937     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    938     5d/pop-to-ebp
    939     c3/return
    940
    941 $_append-4:abort:
    942     # . _write(2/stderr, error)
    943     # . . push args
    944     68/push  "stream overflow\n"/imm32
    945     68/push  2/imm32/stderr
    946     # . . call
    947     e8/call  _write/disp32
    948     # . . discard args
    949     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    950     # . syscall(exit, 1)
    951     bb/copy-to-ebx  1/imm32
    952     e8/call  syscall_exit/disp32
    953     # never gets here
    954
    955 == data
    956
    957 _test-stream-line-ABABA:  # (stream byte)
    958     # write
    959     8/imm32
    960     # read
    961     0/imm32
    962     # size
    963     8/imm32
    964     # data
    965     41 42 41 42 41 0a 00 00  # 8 bytes
    966
    967 _test-stream-empty:  # (stream byte)
    968     # write
    969     0/imm32
    970     # read
    971     0/imm32
    972     # size
    973     8/imm32
    974     # data
    975     00 00 00 00 00 00 00 00  # 8 bytes
    976
    977 _test-stream-filled:  # (stream byte)
    978     # write
    979     8/imm32
    980     # read
    981     0/imm32
    982     # size
    983     8/imm32
    984     # data
    985     41 41 41 41 0a 41 41 41  # 8 bytes
    986
    987 # . . vim:nowrap:textwidth=0