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# example program: reading a URL over HTTP

def main [
  local-scope
  $print [aaa] 10/newline
  google:&:source:char <- start-reading-from-network null/real-resources, [google.com/]
  $print [bbb] 10/newline
  n:num <- copy 0
  buf:&:buffer:char <- new-buffer 30
  {
    c:char, done?:bool <- read google
    break-if done?
    n <- add n, 1
    buf <- append buf, c
    {
      _, a:num <- divide-with-remainder n, 100
      break-if a
      $print n 10/newline
    }
    loop
  }
  result:text <- buffer-to-array buf
  open-console
  clear-screen null/screen  # non-scrolling app
  len:num <- length *result
  print null/real-screen, result
  wait-for-some-interaction
  close-console
]
404'>404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009
# primitives for emitting traces to a 'trace' stream, and for tests to make assertions on its contents
#
# A trace stream looks like a regular stream:
#   write : int  # index at which writes go
#   read : int  # index that we've read until
#   data : (array byte)  # prefixed by length as usual
# Usually the trace stream will be in a separate segment set aside for the purpose.
#
# primitives for operating on traces (arguments in quotes):
#   - initialize-trace-stream: populates Trace-stream with a new segment of the given 'size'
#   - trace: adds a 'line' to Trace-stream
#   - check-trace-contains: scans from Trace-stream's start for a matching 'line', prints a 'message' to stderr on failure
#   - check-trace-scans-to: scans from Trace-stream's read pointer for a matching 'line', prints a 'message' to stderr on failure

== data

# We'll save the address of the trace segment here.
Trace-stream:
    0/imm32

Trace-segment:
    0/imm32/curr
    0/imm32/limit

# Fake trace-stream for tests.
# Also illustrates the layout of the real trace-stream (segment).
_test-trace-stream:
    # current write index
    0/imm32
    # current read index
    0/imm32
    # length
    8/imm32
    # data
    00 00 00 00 00 00 00 00  # 8 bytes

== code
#   instruction                     effective address                                                   register    displacement    immediate
# . op          subop               mod             rm32          base        index         scale       r32
# . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes

# Allocate a new segment for the trace stream, initialize its length, and save its address to Trace-stream.
# The Trace-stream segment will consist of variable-length lines separated by newlines (0x0a)
initialize-trace-stream:  # n : int
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    50/push-eax
    51/push-ecx
    # ecx = n
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           1/r32/ecx   8/disp8         .                 # copy *(ebp+8) to ecx
    # Trace-segment = new-segment(n)
    # . . push args
    68/push  Trace-segment/imm32
    51/push-ecx
    # . . call
    e8/call  new-segment/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # copy Trace-segment->curr to *Trace-stream
    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-segment/disp32              # copy *Trace-segment to eax
    # watch point to catch Trace-stream leaks
#? $watch-1:
    89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    # Trace-stream->length = n - 12
    # . ecx -= 12
    81          5/subop/subtract    3/mod/direct    1/rm32/ecx    .           .             .           .           .               0xc/imm32         # subtract from ecx
    # . Trace-stream->length = ecx
    89/copy                         1/mod/*+disp8   0/rm32/eax    .           .             .           1/r32/ecx   8/disp8         .                 # copy ecx to *(eax+8)
$initialize-trace-stream:end:
    # . restore registers
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

# Append a string to the given trace stream.
# Silently give up if it's already full. Or truncate the string if there isn't enough room.
trace:  # line : (address string)
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    50/push-eax
    51/push-ecx
    52/push-edx
    53/push-ebx
    56/push-esi
    57/push-edi
    # edi = *Trace-stream
    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           7/r32/edi   Trace-stream/disp32               # copy *Trace-stream to edi
    # esi = line
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         6/r32/esi   8/disp8         .                 # copy *(ebp+8) to esi
    # ecx = t->write
    8b/copy                         0/mod/indirect  7/rm32/edi    .           .             .           1/r32/ecx   .               .                 # copy *edi to ecx
    # edx = t->length
    8b/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           2/r32/edx   8/disp8         .                 # copy *(edi+8) to edx
    # eax = _append-3(&t->data[t->write], &t->data[t->length], line)
    # . . push line
    56/push-esi
    # . . push &t->data[t->length]
    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
    53/push-ebx
    # . . push &t->data[t->write]
    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
    53/push-ebx
    # . . call
    e8/call  _append-3/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # if (eax == 0) return
    3d/compare-eax-and  0/imm32
    74/jump-if-equal  $trace:end/disp8
    # t->write += eax
    01/add                          0/mod/indirect  7/rm32/edi    .           .             .           0/r32/eax   .               .                 # add eax to *edi
    # refresh ecx = t->write
    8b/copy                         0/mod/indirect  7/rm32/edi    .           .             .           1/r32/ecx   .               .                 # copy *edi to ecx
    # eax = _append-3(&t->data[t->write], &t->data[t->length], line)
    # . . push line
    68/push  Newline/imm32
    # . . push &t->data[t->length]
    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
    53/push-ebx
    # . . push &t->data[t->write]
    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
    53/push-ebx
    # . . call
    e8/call  _append-3/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # t->write += eax
    01/add                          0/mod/indirect  7/rm32/edi    .           .             .           0/r32/eax   .               .                 # add eax to *edi
$trace:end:
    # . restore registers
    5f/pop-to-edi
    5e/pop-to-esi
    5b/pop-to-ebx
    5a/pop-to-edx
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

test-trace-single:
    # push *Trace-stream
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    # *Trace-stream = _test-trace-stream
    b8/copy-to-eax  _test-trace-stream/imm32
    89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    # clear-trace-stream()
    e8/call  clear-trace-stream/disp32
    # trace("Ab")
    # . . push args
    68/push  "Ab"/imm32
    # . . call
    e8/call  trace/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # check-ints-equal(*_test-trace-stream->data, 41/A 62/b 0a/newline 00, msg)
    # . . push args
    68/push  "F - test-trace-single"/imm32
    68/push  0x0a6241/imm32/Ab-newline
    # . . push *_test-trace-stream->data
    b8/copy-to-eax  _test-trace-stream/imm32
    ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           0xc/disp8       .                 # push *(eax+12)
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # pop into *Trace-stream
    8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    # end
    c3/return

test-trace-appends:
    # push *Trace-stream
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    # *Trace-stream = _test-trace-stream
    b8/copy-to-eax  _test-trace-stream/imm32
    89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    # clear-trace-stream()
    e8/call  clear-trace-stream/disp32
    # trace("C")
    # . . push args
    68/push  "C"/imm32
    # . . call
    e8/call  trace/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # trace("D")
    # . . push args
    68/push  "D"/imm32
    # . . call
    e8/call  trace/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # check-ints-equal(*_test-trace-stream->data, 43/C 0a/newline 44/D 0a/newline, msg)
    # . . push args
    68/push  "F - test-trace-appends"/imm32
    68/push  0x0a440a43/imm32/C-newline-D-newline
    # . . push *_test-trace-stream->data
    b8/copy-to-eax  _test-trace-stream/imm32
    ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           0xc/disp8       .                 # push *(eax+12)
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # pop into *Trace-stream
    8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    # end
    c3/return

test-trace-empty-line:
    # push *Trace-stream
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    # *Trace-stream = _test-trace-stream
    b8/copy-to-eax  _test-trace-stream/imm32
    89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    # clear-trace-stream()
    e8/call  clear-trace-stream/disp32
    # trace("")
    # . . push args
    68/push  ""/imm32
    # . . call
    e8/call  trace/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # check-ints-equal(*_test-trace-stream->data, 0, msg)
    # . . push args
    68/push  "F - test-trace-empty-line"/imm32
    68/push  0/imm32
    # . . push *_test-trace-stream->data
    b8/copy-to-eax  _test-trace-stream/imm32
    ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           0xc/disp8       .                 # push *(eax+12)
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # pop into *Trace-stream
    8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    # end
    c3/return

check-trace-contains:  # line : (address string), msg : (address string)
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # rewind-stream(*Trace-stream)
    # . . push args
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    # . . call
    e8/call  rewind-stream/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # check-trace-scans-to(line, msg)
    # . . push args
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    # . . call
    e8/call  check-trace-scans-to/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
$check-trace-contains:end:
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

check-trace-scans-to:  # line : (address string), msg : (address string)
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    50/push-eax
    # eax = trace-scan(line)
    # . . push args
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    # . . call
    e8/call  trace-scan/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # check-ints-equal(eax, 1, msg)
    # . . push args
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    68/push  1/imm32
    50/push-eax
    # . . call
    e8/call check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
$check-trace-scans-to:end:
    # . restore registers
    58/pop-to-eax
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

# Start scanning from Trace-stream->read for 'line'. If found, update Trace-stream->read and return true.
trace-scan:  # line : (address string) -> result/eax : boolean
    # pseudocode:
    #   push Trace-stream->read
    #   while true:
    #     if Trace-stream->read >= Trace-stream->write
    #       break
    #     if next-line-matches?(Trace-stream, line)
    #       skip-next-line(Trace-stream)
    #       dump saved copy of Trace-stream->read
    #       return true
    #     skip-next-line(Trace-stream)
    #   pop saved copy of Trace-stream->read
    #   return false
    #
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    51/push-ecx
    56/push-esi
    # esi = *Trace-stream
    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           6/r32/esi   Trace-stream/disp32               # copy *Trace-stream to esi
    # ecx = Trace-stream->write
    8b/copy                         0/mod/indirect  6/rm32/esi    .           .             .           1/r32/ecx                   .                 # copy *esi to ecx
    # push Trace-stream->read
    ff          6/subop/push        1/mod/*+disp8   6/rm32/esi    .           .             .           .           4/disp8         .                 # push *(esi+4)
$trace-scan:loop:
    # if (Trace-stream->read >= Trace-stream->write) return false
    39/compare                      1/mod/*+disp8   6/rm32/esi    .           .             .           1/r32/ecx   4/disp8         .                 # compare ecx with *(esi+4)
    7d/jump-if-greater-or-equal  $trace-scan:false/disp8
    # eax = next-line-matches?(Trace-stream, line)
    # . . push args
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    56/push-esi
    # . . call
    e8/call  next-line-matches?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # if (eax == 0) continue
    3d/compare-eax-and  0/imm32
    74/jump-if-equal  $trace-scan:continue/disp8
$trace-scan:true:
    # skip-next-line(Trace-stream)
    # . . push args
    56/push-esi
    # . . call
    e8/call  skip-next-line/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # dump saved copy of Trace-stream->read
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # return true
    b8/copy-to-eax  1/imm32/true
    eb/jump  $trace-scan:end/disp8
$trace-scan:continue:
    # skip-next-line(Trace-stream)
    # . . push args
    56/push-esi
    # . . call
    e8/call  skip-next-line/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    eb/jump  $trace-scan:loop/disp8
$trace-scan:false:
    # restore saved copy of Trace-stream->read
    8f          0/subop/pop         1/mod/*+disp8   6/rm32/esi    .           .             .           .           4/disp8         .                 # pop to *(esi+4)
    # return false
    b8/copy-to-eax  0/imm32/false
$trace-scan:end:
    # . restore registers
    59/pop-to-ecx
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

test-trace-scan-first:
    # push *Trace-stream
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    # setup
    # . *Trace-stream = _test-trace-stream
    b8/copy-to-eax  _test-trace-stream/imm32
    89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    # . clear-trace-stream()
    e8/call  clear-trace-stream/disp32
    # . trace("Ab")
    # . . push args
    68/push  "Ab"/imm32
    # . . call
    e8/call  trace/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # eax = trace-scan("Ab")
    # . . push args
    68/push  "Ab"/imm32
    # . . call
    e8/call  trace-scan/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # check-ints-equal(eax, 1, msg)
    # . . push args
    68/push  "F - test-trace-scan-first"/imm32
    68/push  1/imm32
    50/push-eax
    # . . call
    e8/call check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # pop into *Trace-stream
    8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    # . end
    c3/return

test-trace-scan-skips-lines-until-found:
    # push *Trace-stream
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    # setup
    # . *Trace-stream = _test-trace-stream
    b8/copy-to-eax  _test-trace-stream/imm32
    89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    # . clear-trace-stream()
    e8/call  clear-trace-stream/disp32
    # . trace("Ab")
    # . . push args
    68/push  "Ab"/imm32
    # . . call
    e8/call  trace/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . trace("cd")
    # . . push args
    68/push  "cd"/imm32
    # . . call
    e8/call  trace/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # eax = trace-scan("cd")
    # . . push args
    68/push  "cd"/imm32
    # . . call
    e8/call  trace-scan/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # check-ints-equal(eax, 1, msg)
    # . . push args
    68/push  "F - test-trace-scan-skips-lines-until-found"/imm32
    68/push  1/imm32
    50/push-eax
    # . . call
    e8/call check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # pop into *Trace-stream
    8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    # . end
    c3/return

test-trace-second-scan-starts-where-first-left-off:
    # push *Trace-stream
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    # setup
    # . *Trace-stream = _test-trace-stream
    b8/copy-to-eax  _test-trace-stream/imm32
    89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    # . clear-trace-stream()
    e8/call  clear-trace-stream/disp32
    # . trace("Ab")
    # . . push args
    68/push  "Ab"/imm32
    # . . call
    e8/call  trace/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . eax = trace-scan("Ab")
    # . . push args
    68/push  "Ab"/imm32
    # . . call
    e8/call  trace-scan/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # second scan fails
    # . eax = trace-scan("Ab")
    # . . push args
    68/push  "Ab"/imm32
    # . . call
    e8/call  trace-scan/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # check-ints-equal(eax, 0, msg)
    # . . push args
    68/push  "F - test-trace-second-scan-starts-where-first-left-off"/imm32
    68/push  0/imm32
    50/push-eax
    # . . call
    e8/call check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # pop into *Trace-stream
    8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    # . end
    c3/return

test-trace-scan-failure-leaves-read-index-untouched:
    # push *Trace-stream
    ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # push *Trace-stream
    # setup
    # . *Trace-stream = _test-trace-stream
    b8/copy-to-eax  _test-trace-stream/imm32
    89/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy eax to *Trace-stream
    # . clear-trace-stream()
    e8/call  clear-trace-stream/disp32
    # . trace("Ab")
    # . . push args
    68/push  "Ab"/imm32
    # . . call
    e8/call  trace/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . check-ints-equal(_test-trace-stream->read, 0, msg)
    # . . push args
    68/push  "F - test-trace-second-scan-starts-where-first-left-off/precondition-failure"/imm32
    68/push  0/imm32
    b8/copy-to-eax  _test-trace-stream/imm32
    ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         .                 # push *(eax+4)
    # . . call
    e8/call check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # perform a failing scan
    # . eax = trace-scan("Ax")
    # . . push args
    68/push  "Ax"/imm32
    # . . call
    e8/call  trace-scan/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # no change in read index
    # . check-ints-equal(_test-trace-stream->read, 0, msg)
    # . . push args
    68/push  "F - test-trace-second-scan-starts-where-first-left-off"/imm32
    68/push  0/imm32
    b8/copy-to-eax  _test-trace-stream/imm32
    ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         .                 # push *(eax+4)
    # . . call
    e8/call check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # pop into *Trace-stream
    8f          0/subop/pop         0/mod/indirect  5/rm32/.disp32            .             .           .           Trace-stream/disp32               # pop into *Trace-stream
    # . end
    c3/return

next-line-matches?:  # t : (address stream), line : (address string) -> result/eax : boolean
    # pseudocode:
    #   while true:
    #     if (currl >= maxl) break
    #     if (currt >= maxt) return false
    #     if (*currt != *currl) return false
    #     ++currt
    #     ++currl
    #   return *currt == '\n'
    #
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    51/push-ecx
    52/push-edx
    53/push-ebx
    56/push-esi
    57/push-edi
    # edx = line
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         2/r32/edx   0xc/disp8       .                 # copy *(ebp+12) to edx
    # currl/esi = line->data
    # . esi = line/edx->data
    8d/copy-address                 1/mod/*+disp8   2/rm32/edx    .           .             .           6/r32/esi   4/disp8         .                 # copy edx+4 to esi
    # maxl/ecx = line->data + line->size
    # . eax = line/edx->size
    8b/copy                         0/mod/indirect  2/rm32/edx    .           .                         0/r32/eax   .               .                 # copy *edx to eax
    # . maxl/ecx = line->data/esi + line->size/eax
    8d/copy-address                 0/mod/indirect  4/rm32/sib    6/base/esi  0/index/eax   .           1/r32/ecx   .               .                 # copy edx+eax to ecx
    # edi = t
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         7/r32/edi   8/disp8         .                 # copy *(ebp+8) to edi
    # ebx = t->data
    8d/copy-address                 1/mod/*+disp8   7/rm32/edi    .           .             .           3/r32/ebx   0xc/disp8       .                 # copy edi+12 to ebx
    # maxt/edx = t->data + t->write
    # . eax = t->write
    8b/copy                         0/mod/indirect  7/rm32/edi    .           .                         0/r32/eax   .               .                 # copy *edi to eax
    # . maxt/edx = t->data/ebx + t->write/eax
    8d/copy-address                 0/mod/indirect  4/rm32/sib    3/base/ebx  0/index/eax   .           2/r32/edx   .               .                 # copy ebx+eax to edx
    # currt/edi = t->data + t->read
    # . eax = t/edi->read
    8b/copy                         1/mod/*+disp8   7/rm32/edi    .           .                         0/r32/eax   4/disp8         .                 # copy *(edi+4) to eax
    # . currt/edi = t->data/ebx + t->read/eax
    8d/copy-address                 0/mod/indirect  4/rm32/sib    3/base/ebx  0/index/eax   .           7/r32/edi   .               .                 # copy ebx+eax to edi
$next-line-matches?:loop:
    # if (currl/esi >= maxl/ecx) break
    39/compare                      3/mod/direct    6/rm32/esi    .           .             .           1/r32/ecx   .               .                 # compare esi and ecx
    73/jump-if-greater-or-equal-unsigned  $next-line-matches?:break/disp8
    # if (currt/edi >= maxt/edx) return false
    # . eax = false
    b8/copy-to-eax  0/imm32/false
    39/compare                      3/mod/direct    7/rm32/edi    .           .             .           2/r32/edx   .               .                 # compare edi and edx
    73/jump-if-greater-or-equal-unsigned  $next-line-matches?:end/disp8
    # if (*currt/edi != *currl/esi) return false
    31/xor                          3/mod/direct    0/rm32/eax    .           .             .           0/r32/eax   .               .                 # clear eax
    31/xor                          3/mod/direct    3/rm32/eax    .           .             .           3/r32/eax   .               .                 # clear ebx
    # . eax = (char) *currt/edi
    8a/copy-byte                    0/mod/indirect  7/rm32/edi    .           .                         0/r32/eax   .               .                 # copy *edi to eax
    # . ebx = (char) *currl/esi
    8a/copy-byte                    0/mod/indirect  6/rm32/esi    .           .                         3/r32/ebx   .               .                 # copy *esi to ebx
    # . eax >= ebx
    39/compare                      3/mod/direct    0/rm32/eax    .           .             .           3/r32/ebx   .               .                 # compare eax and ebx
    # . eax = false
    b8/copy-to-eax  0/imm32/false
    75/jump-if-not-equal  $next-line-matches?:end/disp8
    # ++currt/edi
    47/increment-edi
    # ++currl/esi
    46/increment-esi
    eb/jump  $next-line-matches?:loop/disp8
$next-line-matches?:break:
    # return *currt == '\n'
    31/xor                          3/mod/direct    0/rm32/eax    .           .             .           0/r32/eax   .               .                 # clear eax
    # . eax = (char) *currt
    8a/copy-byte                    0/mod/indirect  7/rm32/edi    .           .                         0/r32/eax   .               .                 # copy *edi to eax
    3d/compare-eax-and  0xa/imm32/newline
    # . eax = false
    b8/copy-to-eax  1/imm32/true
    74/jump-if-equal  $next-line-matches?:end/disp8
    b8/copy-to-eax  0/imm32/true
$next-line-matches?:end:
    # . restore registers
    5f/pop-to-edi
    5e/pop-to-esi
    5b/pop-to-ebx
    5a/pop-to-edx
    59/pop-to-ecx
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

test-next-line-matches?-no-match-1:
    # next line of "ABABA" does not match "blah blah"
    # . eax = next-line-matches?(_test-stream-line-ABABA, "blah blah")
    # . . push args
    68/push  "blah blah"/imm32
    68/push  _test-stream-line-ABABA/imm32
    # . . call
    e8/call  next-line-matches?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # . check-ints-equal(eax, 0, msg)
    # . . push args
    68/push  "F - test-next-line-matches?-no-match-1"/imm32
    68/push  0/imm32
    50/push-eax
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    c3/return

test-next-line-matches?-no-match-2:
    # next line of "ABABA" does not match ""
    # . eax = next-line-matches?(_test-stream-line-ABABA, "")
    # . . push args
    68/push  ""/imm32
    68/push  _test-stream-line-ABABA/imm32
    # . . call
    e8/call  next-line-matches?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # . check-ints-equal(eax, 0, msg)
    # . . push args
    68/push  "F - test-next-line-matches?-no-match-2"/imm32
    68/push  0/imm32
    50/push-eax
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    c3/return

test-next-line-matches?-no-match-3:
    # next line of "ABABA" does not match  "AA"
    # . eax = next-line-matches?(_test-stream-line-ABABA, "AA")
    # . . push args
    68/push  "AA"/imm32
    68/push  _test-stream-line-ABABA/imm32
    # . . call
    e8/call  next-line-matches?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # . check-ints-equal(eax, 0, msg)
    # . . push args
    68/push  "F - test-next-line-matches?-no-match-3"/imm32
    68/push  0/imm32
    50/push-eax
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    c3/return

test-next-line-matches?-match:
    # next line of "ABABA" matches "ABABA"
    # . eax = next-line-matches?(_test-stream-line-ABABA, "ABABA")
    # . . push args
    68/push  "ABABA"/imm32
    68/push  _test-stream-line-ABABA/imm32
    # . . call
    e8/call  next-line-matches?/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # . check-ints-equal(eax, 1, msg)
    # . . push args
    68/push  "F - test-next-line-matches?-match"/imm32
    68/push  1/imm32
    50/push-eax
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    c3/return

# move t->read to _after_ next newline
skip-next-line:  # t : (address stream)
    # pseudocode:
    #   max = t->data + t->write
    #   i = t->read
    #   curr = t->data + t->read
    #   while true
    #     if (curr >= max) break
    #     ++i
    #     if (*curr == '\n') break
    #     ++curr
    #   t->read = i
    #
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    50/push-eax
    51/push-ecx
    52/push-edx
    53/push-ebx
    # ecx = t
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         1/r32/ecx   8/disp8         .                 # copy *(ebp+8) to ecx
    # edx = t/ecx->data
    8d/copy-address                 1/mod/*+disp8   1/rm32/ecx    .           .             .           2/r32/edx   0xc/disp8       .                 # copy ecx+12 to edx
    # eax = t/ecx->write
    8b/copy                         0/mod/indirect  1/rm32/ecx    .           .             .           0/r32/eax   .               .                 # copy *ecx to eax
    # max/ebx = t->data/edx + t->write/eax
    8d/copy-address                 0/mod/indirect  4/rm32/sib    2/base/edx  0/index/eax   .           3/r32/ebx   .               .                 # copy edx+eax to ebx
    # eax = t/ecx->read
    8b/copy                         1/mod/*+disp8   1/rm32/ecx    .           .             .           0/r32/eax   4/disp8         .                 # copy *(ecx+4) to edx
    # curr/ecx = t->data/edx + t->read/eax
    8d/copy-address                 0/mod/indirect  4/rm32/sib    2/base/edx  0/index/eax   .           1/r32/ecx   .               .                 # copy edx+eax to ecx
    # i/edx = eax
    89/copy                         3/mod/direct    2/rm32/edx    .           .             .           0/r32/eax   .               .                 # copy eax to edx
$skip-next-line:loop:
    # if (curr/ecx >= max/ebx) break
    39/compare                      3/mod/direct    1/rm32/ecx    .           .             .           3/r32/ebx   .               .                 # compare ecx and ebx
    73/jump-if-greater-or-equal-unsigned  $skip-next-line:end/disp8
    # ++i/edx
    42/increment-edx
    # if (*curr/ecx == '\n') break
    31/xor                          3/mod/direct    0/rm32/eax    .           .             .           0/r32/eax   .               .                 # clear eax
    8a/copy-byte                    0/mod/indirect  1/rm32/ecx    .           .             .           0/r32/eax   .               .                 # copy *ecx to eax
    3d/compare-eax-and  0a/imm32/newline
    74/jump-if-equal  $skip-next-line:end/disp8
    # ++curr/ecx
    41/increment-ecx
    # loop
    eb/jump  $skip-next-line:loop/disp8
$skip-next-line:end:
    # ecx = t
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         1/r32/ecx   8/disp8         .                 # copy *(ebp+8) to ecx
    # t/ecx->read = i/edx
    89/copy                         1/mod/*+disp8   1/rm32/ecx    .           .             .           2/r32/edx   4/disp8         .                 # copy edx to *(ecx+4)
    # . restore registers
    5b/pop-to-ebx
    5a/pop-to-edx
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

test-skip-next-line-empty:
    # skipping next line in empty stream leaves read pointer at 0
    # . skip-next-line(_test-stream-empty)
    # . . push args
    68/push  _test-stream-empty/imm32
    # . . call
    e8/call  skip-next-line/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . check-ints-equal(_test-stream-empty->read, 0, msg)
    # . . push args
    68/push  "F - test-skip-next-line-empty"/imm32
    68/push  0/imm32
    b8/copy-to-eax  _test-stream-empty/imm32
    8b/copy                         1/mod/*+disp8   0/rm32/eax    .           .             .           0/r32/eax   4/disp8         .                 # copy *(eax+4) to eax
    50/push-eax
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    c3/return

test-skip-next-line-filled:
    # skipping next line increments read pointer by length of line + 1 (for newline)
    # . skip-next-line(_test-stream-filled)
    # . . push args
    68/push  _test-stream-filled/imm32
    # . . call
    e8/call  skip-next-line/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . check-ints-equal(_test-stream-filled->read, 5, msg)
    # . . push args
    68/push  "F - test-skip-next-line-filled"/imm32
    68/push  5/imm32
    b8/copy-to-eax  _test-stream-filled/imm32
    8b/copy                         1/mod/*+disp8   0/rm32/eax    .           .             .           0/r32/eax   4/disp8         .                 # copy *(eax+4) to eax
    50/push-eax
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    c3/return

clear-trace-stream:
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    50/push-eax
    51/push-ecx
    # eax = *Trace-stream
    8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           0/r32/eax   Trace-stream/disp32               # copy *Trace-stream to eax
    # ecx = t->length
    8b/copy                         1/mod/*+disp8   0/rm32/eax    .           .             .           1/r32/ecx   8/disp8         .                 # copy *(eax+8) to ecx
    # ecx = &t->data[t->length]
    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    0/base/eax  1/index/ecx   .           1/r32/ecx   0xc/disp8       .                 # copy eax+ecx+12 to ecx
    # t->write = 0
    c7          0/subop/copy        0/mod/direct    0/rm32/eax    .           .             .           .           .               0/imm32           # copy to *eax
    # t->read = 0
    c7          0/subop/copy        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         0/imm32           # copy to *(eax+4)
    # eax = t->data
    81          0/subop/add         3/mod/direct    0/rm32/eax    .           .             .           .           .               0xc/imm32         # add to eax
$clear-trace-stream:loop:
    # if (eax >= ecx) break
    39/compare                      3/mod/direct    0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # compare eax with ecx
    73/jump-if-greater-or-equal-unsigned  $clear-trace-stream:end/disp8
    # *eax = 0
    c7          0/subop/copy        0/mod/direct    0/rm32/eax    .           .             .           .           .               0/imm32           # copy to *eax
    # eax += 4
    81          0/subop/add         3/mod/direct    0/rm32/eax    .           .             .           .           .               4/imm32           # add to eax
    eb/jump  $clear-trace-stream:loop/disp8
$clear-trace-stream:end:
    # . restore registers
    59/pop-to-ecx
    58/pop-to-eax
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

# - helpers

# 3-argument variant of _append
_append-3:  # out : address, outend : address, s : (array byte) -> num_bytes_appended/eax
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    51/push-ecx
    # eax = _append-4(out, outend, &s->data[0], &s->data[s->length])
    # . . push &s->data[s->length]
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         0/r32/eax   0x10/disp8      .                 # copy *(ebp+16) to eax
    8b/copy                         0/mod/indirect  0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # copy *eax to ecx
    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
    51/push-ecx
    # . . push &s->data[0]
    8d/copy-address                 1/mod/*+disp8   0/rm32/eax    .           .             .           1/r32/ecx   4/disp8         .                 # copy eax+4 to ecx
    51/push-ecx
    # . . push outend
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
    # . . push out
    ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           8/disp8         .                 # push *(ebp+8)
    # . . call
    e8/call  _append-4/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0x10/imm32        # add to esp
$_append-3:end:
    # . restore registers
    59/pop-to-ecx
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

# 4-argument variant of _append
_append-4:  # out : address, outend : address, in : address, inend : address -> num_bytes_appended/eax
    # . prologue
    55/push-ebp
    89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
    # . save registers
    51/push-ecx
    52/push-edx
    53/push-ebx
    56/push-esi
    57/push-edi
    # eax/num_bytes_appended = 0
    b8/copy-to-eax  0/imm32
    # edi = out
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           7/r32/edi   8/disp8         .                 # copy *(ebp+8) to edi
    # edx = outend
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           2/r32/edx   0xc/disp8       .                 # copy *(ebp+12) to edx
    # esi = in
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           6/r32/esi   0x10/disp8      .                 # copy *(ebp+16) to esi
    # ecx = inend
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           1/r32/ecx   0x14/disp8      .                 # copy *(ebp+20) to ecx
$_append-4:loop:
    # if (in >= inend) break
    39/compare                      3/mod/direct    6/rm32/esi    .           .             .           1/r32/ecx   .               .                 # compare esi with ecx
    73/jump-if-greater-or-equal-unsigned  $_append-4:end/disp8
    # if (out >= outend) abort  # just to catch test failures fast
    39/compare                      3/mod/direct    7/rm32/edi    .           .             .           2/r32/edx   .               .                 # compare edi with edx
    73/jump-if-greater-or-equal-unsigned  $_append-4:abort/disp8
    # *out = *in
    8a/copy-byte                    0/mod/indirect  6/rm32/esi    .           .             .           3/r32/BL    .               .                 # copy byte at *esi to BL
    88/copy-byte                    0/mod/indirect  7/rm32/edi    .           .             .           3/r32/BL    .               .                 # copy byte at BL to *edi
    # ++num_bytes_appended
    40/increment-eax
    # ++in
    46/increment-esi
    # ++out
    47/increment-edi
    eb/jump  $_append-4:loop/disp8
$_append-4:end:
    # . restore registers
    5f/pop-to-edi
    5e/pop-to-esi
    5b/pop-to-ebx
    5a/pop-to-edx
    59/pop-to-ecx
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

$_append-4:abort:
    # . _write(2/stderr, error)
    # . . push args
    68/push  "stream overflow\n"/imm32
    68/push  2/imm32/stderr
    # . . call
    e8/call  _write/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # . syscall(exit, 1)
    bb/copy-to-ebx  1/imm32
    b8/copy-to-eax  1/imm32/exit
    cd/syscall  0x80/imm8
    # never gets here

== data

_test-stream-line-ABABA:
    # write
    8/imm32
    # read
    0/imm32
    # length
    8/imm32
    # data
    41 42 41 42 41 0a 00 00  # 8 bytes

_test-stream-empty:
    # write
    0/imm32
    # read
    0/imm32
    # length
    8/imm32
    # data
    00 00 00 00 00 00 00 00  # 8 bytes

_test-stream-filled:
    # write
    8/imm32
    # read
    0/imm32
    # length
    8/imm32
    # data
    41 41 41 41 0a 41 41 41  # 8 bytes

# . . vim:nowrap:textwidth=0