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| author | Kartik Agaram <vc@akkartik.com> | 2019-05-02 23:44:43 -0700 |
|---|---|---|
| committer | Kartik Agaram <vc@akkartik.com> | 2019-05-02 23:48:52 -0700 |
| commit | d134a83b7454911285101dee8d14b9a41671d850 (patch) | |
| tree | 8a2a01164bf73f001fac05d8979996477c011ebf /subx/064write-byte.subx | |
| parent | f2cd405d04cd904bf1ed4d5ddf4916234c0509f5 (diff) | |
| download | mu-d134a83b7454911285101dee8d14b9a41671d850.tar.gz | |
new primitives: append-byte, append-byte-hex
These are variants of write-byte-buffered and print-byte-buffered respectively that operate on in-memory `stream`s rather than `buffered-file`s. They don't operate on files, so we'll avoid using the prefix 'write-'.
Diffstat (limited to 'subx/064write-byte.subx')
| -rw-r--r-- | subx/064write-byte.subx | 81 |
1 files changed, 79 insertions, 2 deletions
diff --git a/subx/064write-byte.subx b/subx/064write-byte.subx index a432171d..606cc7d3 100644 --- a/subx/064write-byte.subx +++ b/subx/064write-byte.subx @@ -103,8 +103,6 @@ $flush:end: 5d/pop-to-EBP c3/return -# - tests - test-write-byte-buffered-single: # - check that write-byte-buffered writes to first byte of 'file' # setup @@ -208,4 +206,83 @@ test-write-byte-buffered-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 |