1 # Repeatedly read 32-bit numbers from /dev/random, print them to stdout.
 2 #
 3 # To run:
 4 #   $ ./subx translate 0*.subx apps/random.subx -o apps/random
 5 #   $ ./subx run apps/random
 6 
 7 == code 0x09000000
 8 #   instruction                     effective address                                                   register    displacement    immediate
 9 # . op          subop               mod             rm32          base        index         scale       r32
10 # . 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
11 
12 Entry:
13     # stream/esi = syscall(open, "/dev/null", O_RDONLY, 0)  # we can't use 'fd' because it looks like a hex byte
14     bb/copy-to-ebx  Filename/imm32
15     b9/copy-to-ecx  0/imm32/rdonly
16     ba/copy-to-edx  0x180/imm32/fixed-perms
17     b8/copy-to-eax  5/imm32/open
18     cd/syscall  0x80/imm8
19     # . stream = eax
20     89/copy                         3/mod/direct    6/rm32/esi    .           .             .           0/r32/eax   .               .                 # copy eax to esi
21 
22 $loop:
23 
24     # syscall(read, Stream, N, 4)
25     89/copy                         3/mod/direct    3/rm32/ebx    .           .             .           6/r32/esi   .               .                 # copy esi to ebx
26     b9/copy-to-ecx  N/imm32
27     ba/copy-to-edx  4/imm32/size
28     b8/copy-to-eax  3/imm32/read
29     cd/syscall  0x80/imm8
30 
31     # print-int32-buffered(Stdout, *N)
32     # . . push args
33     ff          6/subop/push        0/mod/indirect  5/rm32/.disp32            .             .           .           N/disp32                          # push *N
34     68/push  Stdout/imm32
35     # . . call
36     e8/call  print-int32-buffered/disp32
37 
38     # write-buffered(Stdout, Newline)
39     # . . push args
40     68/push  Newline/imm32
41     68/push  Stdout/imm32
42     # . . call
43     e8/call  write-buffered/disp32
44     # . . discard args
45     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
46 
47     eb/jump  $loop/disp8
48 
49     # syscall(exit, 0)
50     bb/copy-to-ebx  0/imm32
51     b8/copy-to-eax  1/imm32/exit
52     cd/syscall  0x80/imm8
53 
54 == data 0x0a000000
55 
56 N:
57     0/imm32
58 Filename:
59     2f 64 65 76 2f 72 61 6e 64 6f 6d 00
60 #   /  d  e  v  /  r  a  n  d  o  m  null
61 
62 # . . vim:nowrap:textwidth=0