https://github.com/akkartik/mu/blob/master/subx/070new-stream.subx

      1 # Helper to allocate a stream on the heap.
      2
      3 == code
      4 #   instruction                     effective address                                                   register    displacement    immediate
      5 # . op          subop               mod             rm32          base        index         scale       r32
      6 # . 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
      7
      8 new-stream:  # ad : (address allocation-descriptor), length : int, elemsize : int -> address/EAX
      9     # . prolog
     10     55/push-EBP
     11     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
     12     # . save registers
     13     52/push-EDX
     14     # n = elemsize * length + 12 (for read, write and length)
     15     # . EAX = elemsize
     16     8b/copy                         1/mod/*+disp8   5/rm32/EBP    .           .             .           0/r32/EAX   0x10/disp8      .                 # copy *(EBP+16) to EAX
     17     # . EAX *= length
     18     31/xor                          3/mod/direct    2/rm32/EDX    .           .             .           2/r32/EDX   .               .                 # clear EDX
     19     f7          4/subop/multiply    1/mod/*+disp8   5/rm32/EBP    .           .                                     0xc/disp8       .                 # multiply *(EBP+12) into EAX
     20     # . if overflow abort
     21     81          7/subop/compare     3/mod/direct    2/rm32/EDX    .           .             .           .           .               0/imm32           # compare EDX
     22     75/jump-if-not-equal  $new-stream:abort/disp8
     23     # . EDX = elemsize*length
     24     89/copy                         3/mod/direct    2/rm32/EDX    .           .             .           0/r32/EAX   .               .                 # copy EAX to EDX
     25     # . EAX += 12
     26     05/add-to-EAX  0xc/imm32
     27     # allocate(ad, n)
     28     # . . push args
     29     50/push-EAX
     30     ff          6/subop/push        1/mod/*+disp8   5/rm32/EBP    .           .             .           .           8/disp8         .                 # push *(EBP+8)
     31     # . . call
     32     e8/call  allocate/disp32
     33     # . . discard args
     34     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
     35     # EAX->length = elemsize*length
     36     89/copy                         1/mod/*+disp8   0/rm32/EAX    .           .             .           2/r32/EDX   8/disp8         .                 # copy EDX to *(EAX+8)
     37     # clear-stream(EAX)
     38     # . . push args
     39     50/push-EAX
     40     # . . call
     41     e8/call  clear-stream/disp32
     42     # . . discard args
     43     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
     44 $new-stream:end:
     45     # . restore registers
     46     5a/pop-to-EDX
     47     # . epilog
     48     89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
     49     5d/pop-to-EBP
     50     c3/return
     51
     52 $new-stream:abort:
     53     # . _write(2/stderr, error)
     54     # . . push args
     55     68/push  "new-stream: size too large"/imm32
     56     68/push  2/imm32/stderr
     57     # . . call
     58     e8/call  _write/disp32
     59     # . . discard args
     60     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
     61     # . syscall(exit, 1)
     62     bb/copy-to-EBX  1/imm32
     63     b8/copy-to-EAX  1/imm32/exit
     64     cd/syscall  0x80/imm8
     65     # never gets here
     66
     67 test-new-stream:
     68     # . prolog
     69     55/push-EBP
     70     89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
     71     # var ad/ECX : (address allocation-descriptor) = allocate-region(Heap, 512)
     72     # . EAX = allocate-region(Heap, 512)
     73     # . . push args
     74     68/push  0x200/imm32
     75     68/push  Heap/imm32
     76     # . . call
     77     e8/call  allocate-region/disp32
     78     # . . discard args
     79     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
     80     # . ECX = EAX
     81     89/copy                         3/mod/direct    1/rm32/ECX    .           .             .           0/r32/EAX   .               .                 # copy EAX to ECX
     82     # var start/EDX = ad->curr
     83     8b/copy                         0/mod/indirect  1/rm32/ECX    .           .             .           2/r32/EDX   .               .                 # copy *ECX to EDX
     84     # EAX = new-stream(ad, 3, 2)
     85     # . . push args
     86     68/push  2/imm32
     87     68/push  3/imm32
     88     51/push-ECX
     89     # . . call
     90     e8/call  new-stream/disp32
     91     # . . discard args
     92     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
     93     # check-ints-equal(EAX, EDX, msg)
     94     # . . push args
     95     68/push  "F - test-new-stream: returns current pointer of allocation descriptor"/imm32
     96     52/push-EDX
     97     50/push-EAX
     98     # . . call
     99     e8/call  check-ints-equal/disp32
    100     # . . discard args
    101     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
    102     # check-ints-equal(EAX->length, 6, msg)
    103     # . . push args
    104     68/push  "F - test-new-stream: sets length correctly"/imm32
    105     68/push  6/imm32
    106     ff          6/subop/push        1/mod/*+disp8   0/rm32/EAX    .           .             .           .           .               8/disp8           # push *(EAX+8)
    107     # . . call
    108     e8/call  check-ints-equal/disp32
    109     # . . discard args
    110     81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
    111     # the rest is delegated to clear-stream() so we won't bother checking it
    112     # . epilog
    113     89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
    114     5d/pop-to-EBP
    115     c3/return
    116
    117 # . . vim:nowrap:textwidth=0