diff options
Diffstat (limited to 'subx/066write-buffered.subx')
-rw-r--r-- | subx/066write-buffered.subx | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/subx/066write-buffered.subx b/subx/066write-buffered.subx new file mode 100644 index 00000000..343aa364 --- /dev/null +++ b/subx/066write-buffered.subx @@ -0,0 +1,218 @@ +# 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 + +#? Entry: # run a single test, while debugging +#? e8/call test-write-buffered/disp32 +#? e8/call test-write-buffered-with-intermediate-flush/disp32 +#? # syscall(exit, Num-test-failures) +#? 8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/EBX Num-test-failures/disp32 # copy *Num-test-failures to EBX +#? b8/copy-to-EAX 1/imm32/exit +#? cd/syscall 0x80/imm8 + +write-buffered: # f : (address buffered-file), msg : (address array byte) -> <void> + # pseudocode: + # in = msg->data + # inend = &msg->data[msg->length] + # while (in < inend) + # if f->write >= f->length + # flush(f) + # clear-stream(f) + # c = *in + # f->data[f->write] = c + # ++f->write + # ++in + # + # registers: + # in: ESI + # inend: ECX + # f: EDI + # f->length: EDX + # f->write: EBX (cached; need to keep in sync) + # c: EAX + # + # . prolog + 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 + # in/ESI = msg->data + 8d/copy-address 1/mod/*+disp8 0/rm32/EAX . . . 6/r32/ESI 4/disp8 . # copy EAX+4 to ESI + # inend/ECX = &msg->data[msg->length] + 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->length + 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 + 7d/jump-if-greater-or-equal $write-buffered:loop-end/disp8 + # if (f->write >= f->length) flush and clear f's stream + 39/compare 3/mod/direct 3/rm32/EBX . . . 2/r32/EDX . . # compare EBX with EDX + 7c/jump-if-lesser $write-buffered:to-stream/disp8 + # . persist f->write + 89/copy 1/mod/*+disp8 7/rm32/EDI . . . 3/r32/EBX 4/disp8 . # copy EBX to *(EDI+4) + # . flush(f) + # . . push args + 57/push-EDI + # . . call + e8/call flush/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP + # . clear-stream(stream = f+4) + # . . push args + 8d/copy-address 1/mod/*+disp8 7/rm32/EDI . . . 0/r32/EAX 4/disp8 . # copy EDI+4 to EAX + 50/push-EAX + # . . call + e8/call clear-stream/disp32 + # . . discard args + 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP + # . f->write must now be 0; update its cache at EBX + 31/xor 3/mod/direct 3/rm32/EBX . . . 3/r32/EBX . . # clear EBX +$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 + # . epilog + 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+4) + # . . push args + b8/copy-to-EAX _test-buffered-file/imm32 + 05/add-to-EAX 4/imm32 + 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 + # 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+4) + # . . push args + b8/copy-to-EAX _test-buffered-file/imm32 + 05/add-to-EAX 4/imm32 + 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 + # _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 + +# . . vim:nowrap:textwidth=0 |