# write-byte-buffered: add a single byte to a buffered-file. # flush: write out any buffered writes to disk. # # TODO: Come up with a way to signal failure to write to disk. This is hard # since the failure may impact previous calls that were buffered. == data # The buffered file for standard output. Stdout: # file descriptor or (address stream) 1/imm32 # standard output # current write index 0/imm32 # current read index 0/imm32 # length 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. == 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 lower byte of 'n' to 'f'. write-byte-buffered: # f : (address buffered-file), n : int -> # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # . save registers 51/push-ecx 57/push-edi # edi = f 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 8/disp8 . # copy *(ebp+8) to edi # ecx = f->write 8b/copy 1/mod/*+disp8 7/rm32/edi . . . 1/r32/ecx 4/disp8 . # copy *(edi+4) to ecx # if (f->write >= f->length) flush and clear f's stream 3b/compare 1/mod/*+disp8 7/rm32/edi . . . 1/r32/ecx 0xc/disp8 . # compare ecx with *(edi+12) 7c/jump-if-lesser $write-byte-buffered:to-stream/disp8 # . 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 ecx 31/xor 3/mod/direct 1/rm32/ecx . . . 1/r32/ecx . . # clear ecx $write-byte-buffered:to-stream: # write to stream # f->data[f->write] = LSB(n) 31/xor 3/mod/direct 0/rm32/eax . . . 0/r32/eax . . # clear eax 8a/copy-byte 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/AL 0xc/disp8 . # copy byte at *(ebp+12) to AL 88/copy-byte 1/mod/*+disp8 4/rm32/sib 7/base/edi 1/index/ecx . 0/r32/AL 0x10/disp8 . # copy AL to *(edi+ecx+16) # ++f->write ff 0/subop/increment 1/mod/*+disp8 7/rm32/edi . . . . 4/disp8 . # increment *(edi+4) $write-byte-buffered:end: # . restore registers 5f/pop-to-edi 59/pop-to-ecx # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return flush: # f : (address buffered-file) -> # . 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 # eax = f 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/eax 8/disp8 . # copy *(ebp+8) to eax # write-stream(f->fd, data = f+4) # . . push args 8d/copy-address 1/mod/*+disp8 0/rm32/eax . . . 1/r32/ecx 4/disp8 . # copy eax+4 to ecx 51/push-ecx ff 6/subop/push 0/mod/indirect 0/rm32/eax . . . . . . # push *eax # . . call e8/call write-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp $flush:end: # . restore registers 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-byte-buffered-single: # - check that write-byte-buffered writes to first byte of '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-byte-buffered(_test-buffered-file, 'A') # . . push args 68/push 0x41/imm32 68/push _test-buffered-file/imm32 # . . call e8/call write-byte-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, "A", msg) # . . push args 68/push "F - test-write-byte-buffered-single"/imm32 68/push "A"/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-flushes: # - check that write-byte-buffered correctly flushes buffered data # 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 # fill up the buffer for _test-buffered-file # . write(_test-buffered-file+4, "abcdef") # . . push args 68/push "abcdef"/imm32 b8/copy-to-eax _test-buffered-file/imm32 05/add-to-eax 4/imm32 50/push-eax # . . call e8/call write/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # write-byte-buffered(_test-buffered-file, 'g') # . . push args 68/push 0x67/imm32 68/push _test-buffered-file/imm32 # . . call e8/call write-byte-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, "abcdefg", msg) # . . push args 68/push "F - test-write-byte-buffered-multiple-flushes"/imm32 68/push "abcdefg"/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 # - variant without buffering # Write lower byte of 'n' to 'f'. append-byte: # f : (address stream), n : int -> # . prologue 55/push-ebp 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp # . save registers 51/push-ecx 57/push-edi # edi = f 8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 8/disp8 . # copy *(ebp+8) to edi # ecx = f->write 8b/copy 0/mod/indirect 7/rm32/edi . . . 1/r32/ecx . . # copy *edi to ecx # if (f->write >= f->length) abort 3b/compare 1/mod/*+disp8 7/rm32/edi . . . 1/r32/ecx 8/disp8 . # compare ecx with *(edi+8) 7d/jump-if-greater-or-equal $append-byte:abort/disp8 $append-byte:to-stream: # write to stream # f->data[f->write] = LSB(n) 31/xor 3/mod/direct 0/rm32/eax . . . 0/r32/eax . . # clear eax 8a/copy-byte 1/mod/*+disp8 5/rm32/ebp . . . 0/r32/AL 0xc/disp8 . # copy byte at *(ebp+12) to AL 88/copy-byte 1/mod/*+disp8 4/rm32/sib 7/base/edi 1/index/ecx . 0/r32/AL 0xc/disp8 . # copy AL to *(edi+ecx+12) # ++f->write ff 0/subop/increment 0/mod/indirect 7/rm32/edi . . . . . . # increment *edi $append-byte:end: # . restore registers 5f/pop-to-edi 59/pop-to-ecx # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return $append-byte:abort: # . _write(2/stderr, error) # . . push args 68/push "append-byte: 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 b8/copy-to-eax 1/imm32/exit cd/syscall 0x80/imm8 # never gets here test-append-byte-single: # - check that append-byte writes to first byte of '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 # append-byte(_test-stream, 'A') # . . push args 68/push 0x41/imm32 68/push _test-stream/imm32 # . . call e8/call append-byte/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # check-stream-equal(_test-stream, "A", msg) # . . push args 68/push "F - test-append-byte-single"/imm32 68/push "A"/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 == data _test-output-stream: # current write index 0/imm32 # current read index 0/imm32 # length 0x200/imm32 # 512 bytes # data (32 lines x 16 bytes/line) 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 # a test buffered file for _test-output-stream _test-output-buffered-file: # file descriptor or (address stream) _test-output-stream/imm32 # current write index 0/imm32 # current read index 0/imm32 # length 6/imm32 # data 00 00 00 00 00 00 # 6 bytes _test-error-stream: # current write index 0/imm32 # current read index 0/imm32 # line 0x80/imm32 # 128 bytes # data (8 lines x 16 bytes/line) 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 # a test buffered file for _test-error-stream _test-error-buffered-file: # file descriptor or (address stream) _test-error-stream/imm32 # current write index 0/imm32 # current read index 0/imm32 # length 6/imm32 # data 00 00 00 00 00 00 # 6 bytes # . . vim:nowrap:textwidth=0