1 #   instruction                     effective address                                                   register    displacement    immediate
 2 # . op          subop               mod             rm32          base        index         scale       r32
 3 # . 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
 4 
 5 write:  # f: (addr stream byte), s: (addr array byte)
 6     # . prologue
 7     55/push-ebp
 8     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
 9     # if (s == 0) return
10     81          7/subop/compare     1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       0/imm32           # compare *(ebp+12)
11     74/jump-if-=  $write:end/disp8
12     # TODO: write to file
13     # otherwise, treat 'f' as a stream to append to
14     # . save registers
15     50/push-eax
16     51/push-ecx
17     52/push-edx
18     53/push-ebx
19     # ecx = f
20     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         1/r32/ecx   8/disp8         .                 # copy *(ebp+8) to ecx
21     # edx = f->write
22     8b/copy                         0/mod/indirect  1/rm32/ecx    .           .             .           2/r32/edx   .               .                 # copy *ecx to edx
23     # ebx = f->size
24     8b/copy                         1/mod/*+disp8   1/rm32/ecx    .           .             .           3/r32/ebx   8/disp8         .                 # copy *(ecx+8) to ebx
25     # eax = _append-3(&f->data[f->write], &f->data[f->size], s)
26     # . . push s
27     ff          6/subop/push        1/mod/*+disp8   5/rm32/ebp    .           .             .           .           0xc/disp8       .                 # push *(ebp+12)
28     # . . push &f->data[f->size]
29     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    1/base/ecx  3/index/ebx   .           3/r32/ebx   0xc/disp8       .                 # copy ecx+ebx+12 to ebx
30     53/push-ebx
31     # . . push &f->data[f->write]
32     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    1/base/ecx  2/index/edx   .           3/r32/ebx   0xc/disp8       .                 # copy ecx+edx+12 to ebx
33     53/push-ebx
34     # . . call
35     e8/call  _append-3/disp32
36     # . . discard args
37     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
38     # f->write += eax
39     01/add                          0/mod/indirect  1/rm32/ecx    .           .             .           0/r32/eax   .               .                 # add eax to *ecx
40     # . restore registers
41     5b/pop-to-ebx
42     5a/pop-to-edx
43     59/pop-to-ecx
44     58/pop-to-eax
45 $write:end:
46     # . epilogue
47     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
48     5d/pop-to-ebp
49     c3/return
50 
51 # TODO: bring in tests once we have check-ints-equal
52 
53 # . . vim:nowrap:textwidth=0