diff options
Diffstat (limited to 'subx/064write-byte.subx')
| -rw-r--r-- | subx/064write-byte.subx | 111 |
1 files changed, 94 insertions, 17 deletions
diff --git a/subx/064write-byte.subx b/subx/064write-byte.subx index 9f97c336..606cc7d3 100644 --- a/subx/064write-byte.subx +++ b/subx/064write-byte.subx @@ -1,4 +1,4 @@ -# write-byte: write a single byte to a buffered-file. The write may be buffered. +# 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 @@ -28,7 +28,7 @@ Stdout: # . 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: # f : (address buffered-file), n : int -> <void> +write-byte-buffered: # f : (address buffered-file), n : int -> <void> # . prolog 55/push-EBP 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP @@ -41,7 +41,7 @@ write-byte: # f : (address buffered-file), n : int -> <void> 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:to-stream/disp8 + 7c/jump-if-lesser $write-byte-buffered:to-stream/disp8 # . flush(f) # . . push args 57/push-EDI @@ -59,7 +59,7 @@ write-byte: # f : (address buffered-file), n : int -> <void> 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP # . f->write must now be 0; update its cache at ECX 31/xor 3/mod/direct 1/rm32/ECX . . . 1/r32/ECX . . # clear ECX -$write-byte:to-stream: +$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 @@ -67,7 +67,7 @@ $write-byte:to-stream: 88/copy-byte 1/mod/*+disp8 4/rm32/sib 7/base/EDI 1/index/ECX . 0/r32/AL 0x10/disp8 . # copy AL to *(EDI+ECX+16) # ++f->write ff 0/subop/increment 1/mod/*+disp8 7/rm32/EDI . . . . 4/disp8 . # increment *(EDI+4) -$write-byte:end: +$write-byte-buffered:end: # . restore registers 5f/pop-to-EDI 59/pop-to-ECX @@ -103,10 +103,8 @@ $flush:end: 5d/pop-to-EBP c3/return -# - tests - -test-write-byte-single: - # - check that write-byte writes to first byte of 'file' +test-write-byte-buffered-single: + # - check that write-byte-buffered writes to first byte of 'file' # setup # . clear-stream(_test-stream) # . . push args @@ -124,12 +122,12 @@ test-write-byte-single: e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP - # write-byte(_test-buffered-file, 'A') + # write-byte-buffered(_test-buffered-file, 'A') # . . push args 68/push 0x41/imm32 68/push _test-buffered-file/imm32 # . . call - e8/call write-byte/disp32 + 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) @@ -141,7 +139,7 @@ test-write-byte-single: 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-single"/imm32 + 68/push "F - test-write-byte-buffered-single"/imm32 68/push "A"/imm32 68/push _test-stream/imm32 # . . call @@ -151,8 +149,8 @@ test-write-byte-single: # . end c3/return -test-write-byte-multiple-flushes: - # - check that write-byte correctly flushes buffered data +test-write-byte-buffered-multiple-flushes: + # - check that write-byte-buffered correctly flushes buffered data # setup # . clear-stream(_test-stream) # . . push args @@ -181,12 +179,12 @@ test-write-byte-multiple-flushes: e8/call write/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP - # write-byte(_test-buffered-file, 'g') + # write-byte-buffered(_test-buffered-file, 'g') # . . push args 68/push 0x67/imm32 68/push _test-buffered-file/imm32 # . . call - e8/call write-byte/disp32 + 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) @@ -198,7 +196,7 @@ test-write-byte-multiple-flushes: 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP # check-stream-equal(_test-stream, "abcdef", msg) # . . push args - 68/push "F - test-write-byte-multiple-flushes: 1"/imm32 + 68/push "F - test-write-byte-buffered-multiple-flushes: 1"/imm32 68/push "abcdefg"/imm32 68/push _test-stream/imm32 # . . call @@ -208,4 +206,83 @@ test-write-byte-multiple-flushes: # . end c3/return +# - variant without buffering + +# Write lower byte of 'n' to 'f'. +append-byte: # f : (address stream), n : int -> <void> + # . prolog + 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 +$append-byte:end: + # . restore registers + 5f/pop-to-EDI + 59/pop-to-ECX + # . epilog + 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP + 5d/pop-to-EBP + c3/return + +$append-byte:abort: + # . _write(2/stderr, error) + # . . push args + 68/push "append-byte: out of space"/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 + # . . vim:nowrap:textwidth=0 |