diff options
Diffstat (limited to 'linux/116write-buffered.subx')
| -rw-r--r-- | linux/116write-buffered.subx | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/linux/116write-buffered.subx b/linux/116write-buffered.subx new file mode 100644 index 00000000..19df446e --- /dev/null +++ b/linux/116write-buffered.subx @@ -0,0 +1,226 @@ +# write-buffered: like 'write', but for a buffered-file + +== 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-buffered: # f: (addr buffered-file), msg: (addr array byte) + # pseudocode: + # in = msg->data + # inend = &msg->data[msg->size] + # while (in < inend) + # if f->write >= f->size + # flush(f) + # clear-stream(f) + # c = *in + # f->data[f->write] = c + # ++f->write + # ++in + # + # registers: + # in: esi + # inend: ecx + # f: edi + # f->size: edx + # f->write: ebx (cached; need to keep in sync) + # c: eax + # + # . 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 + # eax = msg + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . 0/r32/eax 0xc/disp8 . # copy *(ebp+12) to eax + # var in/esi: (addr byte) = msg->data + 8d/copy-address 1/mod/*+disp8 0/rm32/eax . . . 6/r32/esi 4/disp8 . # copy eax+4 to esi + # var inend/ecx: (addr byte) = &msg->data[msg->size] + 8b/copy 0/mod/indirect 0/rm32/eax . . . 1/r32/ecx . . # copy *eax to ecx + 8d/copy-address 0/mod/indirect 4/rm32/sib 6/base/esi 1/index/ecx . 1/r32/ecx . . # copy esi+ecx to ecx + # edi = f + 8b/copy 1/mod/*+disp8 5/rm32/ebp . . 7/r32/edi 8/disp8 . # copy *(ebp+8) to edi + # edx = f->size + 8b/copy 1/mod/*+disp8 7/rm32/edi . . . 2/r32/edx 0xc/disp8 . # copy *(edi+12) to edx + # ebx = f->write + 8b/copy 1/mod/*+disp8 7/rm32/edi . . . 3/r32/ebx 4/disp8 . # copy *(edi+4) to ebx +$write-buffered:loop: + # if (in >= inend) break + 39/compare 3/mod/direct 6/rm32/esi . . . 1/r32/ecx . . # compare esi with ecx + 73/jump-if-addr>= $write-buffered:loop-end/disp8 + # if (f->write >= f->size) flush and clear f's stream + 39/compare 3/mod/direct 3/rm32/ebx . . . 2/r32/edx . . # compare ebx with edx + 7c/jump-if-< $write-buffered:to-stream/disp8 + # . persist f->write + 89/copy 1/mod/*+disp8 7/rm32/edi . . . 3/r32/ebx 4/disp8 . # copy ebx to *(edi+4) + # . flush(f) + # . . push args + 57/push-edi + # . . call + e8/call flush/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # . clear-stream(stream = f+4) + # . . push args + 8d/copy-address 1/mod/*+disp8 7/rm32/edi . . . 0/r32/eax 4/disp8 . # copy edi+4 to eax + 50/push-eax + # . . call + e8/call clear-stream/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # . f->write must now be 0; update its cache at ebx + 31/xor 3/mod/direct 3/rm32/ebx . . . 3/r32/ebx . . # clear ebx +$write-buffered:to-stream: + # write to stream + # f->data[f->write] = *in + # . AL = *in + 31/xor 3/mod/direct 0/rm32/eax . . . 0/r32/eax . . # clear eax + 8a/copy-byte 0/mod/indirect 6/rm32/esi . . . 0/r32/AL . . # copy byte at *esi to AL + # . f->data[f->write] = AL + 88/copy-byte 1/mod/*+disp8 4/rm32/sib 7/base/edi 3/index/ebx . 0/r32/AL 0x10/disp8 . # copy AL to *(edi+ebx+16) + # ++f->write + 43/increment-ebx + # ++in + 46/increment-esi + eb/jump $write-buffered:loop/disp8 +$write-buffered:loop-end: + # persist necessary variables from registers + 89/copy 1/mod/*+disp8 7/rm32/edi . . . 3/r32/ebx 4/disp8 . # copy ebx to *(edi+4) +$write-buffered:end: + # . restore registers + 5f/pop-to-edi + 5e/pop-to-esi + 5b/pop-to-ebx + 5a/pop-to-edx + 59/pop-to-ecx + 58/pop-to-eax + # . epilogue + 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp + 5d/pop-to-ebp + c3/return + +test-write-buffered: + # - check that write-buffered writes to the file + # setup + # . clear-stream(_test-stream) + # . . push args + 68/push _test-stream/imm32 + # . . call + e8/call clear-stream/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # . clear-stream($_test-buffered-file->buffer) + # . . push args + 68/push $_test-buffered-file->buffer/imm32 + # . . call + e8/call clear-stream/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # write-buffered(_test-buffered-file, "Abc") + # . . push args + 68/push "Abc"/imm32 + 68/push _test-buffered-file/imm32 + # . . call + e8/call write-buffered/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # flush(_test-buffered-file) + # . . push args + 68/push _test-buffered-file/imm32 + # . . call + e8/call flush/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # check-stream-equal(_test-stream, "Abc", msg) + # . . push args + 68/push "F - test-write-buffered-single"/imm32 + 68/push "Abc"/imm32 + 68/push _test-stream/imm32 + # . . call + e8/call check-stream-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + # . end + c3/return + +test-write-buffered-with-intermediate-flush: + # - check that write-buffered flushes in the middle if its buffer fills up + # setup + # . clear-stream(_test-stream) + # . . push args + 68/push _test-stream/imm32 + # . . call + e8/call clear-stream/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # . clear-stream($_test-buffered-file->buffer) + # . . push args + 68/push $_test-buffered-file->buffer/imm32 + # . . call + e8/call clear-stream/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp + # _test-stream can hold 8 bytes, but _test-buffered-file can hold only 6. + # Try to write 7 bytes. + # . write-buffered(_test-buffered-file, "Abcdefg") + # . . push args + 68/push "Abcdefg"/imm32 + 68/push _test-buffered-file/imm32 + # . . call + e8/call write-buffered/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp + # don't flush + # 6 bytes should still have gotten to _test-stream + # . check-ints-equal(*_test-stream->write, 6, msg) + # . . push args + 68/push "F - test-write-buffered-with-intermediate-flush: flushed data"/imm32 + 68/push 6/imm32 + # . . push *_test-stream->write + b8/copy-to-eax _test-stream/imm32 + ff 6/subop/push 0/mod/indirect 0/rm32/eax . . . . . . # push *eax + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + # and 1 byte should still be in _test-buffered-file + # . check-ints-equal(*_test-buffered-file->write, 1, msg) + # . . push args + 68/push "F - test-write-buffered-with-intermediate-flush: unflushed bytes"/imm32 + 68/push 1/imm32 + # . . push *_test-buffered-file->write + b8/copy-to-eax _test-buffered-file/imm32 + ff 6/subop/push 1/mod/*+disp8 0/rm32/eax . . . . 4/disp8 . # push *(eax+4) + # . . call + e8/call check-ints-equal/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp + # . end + c3/return + +== data + +# The buffered file for standard error. +Stderr: # buffered-file + # file descriptor or (addr stream byte) + 2/imm32 # standard error +$Stderr->buffer: + # inlined fields for a stream + # current write index + 0/imm32 + # current read index + 0/imm32 + # size + 8/imm32 + # data + 00 00 00 00 00 00 00 00 # 8 bytes + +# TODO: 8 bytes is too small. We'll need to grow the buffer for efficiency. But +# I don't want to type in 1024 bytes here. + +# . . vim:nowrap:textwidth=0 |