diff options
Diffstat (limited to 'linux/202write-int.subx')
| -rw-r--r-- | linux/202write-int.subx | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/linux/202write-int.subx b/linux/202write-int.subx new file mode 100644 index 00000000..97e681c7 --- /dev/null +++ b/linux/202write-int.subx @@ -0,0 +1,121 @@ +# write-int: add (the binary representation of) a single int to a stream + +== 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 + +write-int: # out: (addr stream byte), 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 + 57/push-edi + # edi = out + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 8/disp8 . # copy *(ebp+8) to edi + # ecx = out->write + 8b/copy 0/mod/indirect 7/rm32/edi . . . 1/r32/ecx . . # copy *edi to ecx + # if (out->write >= out->size) abort + 3b/compare 1/mod/*+disp8 7/rm32/edi . . . 1/r32/ecx 8/disp8 . # compare ecx with *(edi+8) + 7d/jump-if->= $write-int:abort/disp8 +$write-int:to-stream: + # out->data[out->write] = n + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 0xc/disp8 . # copy *(ebp+12) to eax + 89/copy 1/mod/*+disp8 4/rm32/sib 7/base/edi 1/index/ecx . 0/r32/eax 0xc/disp8 . # copy eax to *(edi+ecx+12) + # out->write += 4 + 81 0/subop/add 0/mod/indirect 7/rm32/edi . . . . . 4/imm32 # add to *edi +$write-int:end: + # . restore registers + 5f/pop-to-edi + 59/pop-to-ecx + 58/pop-to-eax + # . epilogue + 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp + 5d/pop-to-ebp + c3/return + +$write-int:abort: + # . _write(2/stderr, error) + # . . push args + 68/push "write-int: out of space\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 + e8/call syscall_exit/disp32 + # never gets here + +test-write-int-single: + # - check that write-int writes to first int of 'stream' + # setup + # . clear-stream(_test-stream) + # . . push args + 68/push _test-stream/imm32 + # . . call + e8/call clear-stream/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # write-int(_test-stream, "abcd") + # . . push args + 68/push 0x64636261/imm32 + 68/push _test-stream/imm32 + # . . call + e8/call write-int/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # check-stream-equal(_test-stream, "abcd", msg) + # . . push args + 68/push "F - test-write-int-single"/imm32 + 68/push "abcd"/imm32 + 68/push _test-stream/imm32 + # . . call + e8/call check-stream-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + # . end + c3/return + +test-write-byte-buffered-multiple: + # - check that write-int correctly appends multiple writes + # setup + # . clear-stream(_test-stream) + # . . push args + 68/push _test-stream/imm32 + # . . call + e8/call clear-stream/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # write-int(_test-stream, "abcd") + # . . push args + 68/push 0x64636261/imm32 + 68/push _test-stream/imm32 + # . . call + e8/call write-int/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # write-int(_test-stream, "efgh") + # . . push args + 68/push 0x68676665/imm32 + 68/push _test-stream/imm32 + # . . call + e8/call write-int/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # check-stream-equal(_test-stream, "abcdefgh", msg) + # . . push args + 68/push "F - test-write-byte-buffered-multiple"/imm32 + 68/push "abcdefgh"/imm32 + 68/push _test-stream/imm32 + # . . call + e8/call check-stream-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + # . end + c3/return + +# . . vim:nowrap:textwidth=0 |