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Diffstat (limited to 'subx/061read-byte.subx')
| -rw-r--r-- | subx/061read-byte.subx | 293 |
1 files changed, 0 insertions, 293 deletions
diff --git a/subx/061read-byte.subx b/subx/061read-byte.subx deleted file mode 100644 index 99e2babe..00000000 --- a/subx/061read-byte.subx +++ /dev/null @@ -1,293 +0,0 @@ -# read-byte-buffered: one higher-level abstraction atop 'read'. -# -# There are many situations where 'read' is a lot to manage, and we need -# to abstract some details away. One of them is when we want to read a file -# character by character. In this situation we follow C's FILE data structure, -# which manages the underlying file descriptor together with the buffer it -# reads into. We call our version 'buffered-file'. Should be useful with other -# primitives as well, in later layers. - -== data - -# The buffered file for standard input. Also illustrates the layout for -# buffered-file. -Stdin: - # file descriptor or (address stream) - 0/imm32 # standard input - # 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 - -# return next byte value in EAX, with top 3 bytes cleared. -# On reaching end of file, return 0xffffffff (Eof). -read-byte-buffered: # f : (address buffered-file) -> byte-or-Eof/EAX - # . prolog - 55/push-EBP - 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP - # . save registers - 51/push-ECX - 56/push-ESI - # ESI = f - 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 6/r32/ESI 8/disp8 . # copy *(EBP+8) to ESI - # ECX = f->read - 8b/copy 1/mod/*+disp8 6/rm32/ESI . . . 1/r32/ECX 8/disp8 . # copy *(ESI+8) to ECX - # if (f->read >= f->write) populate stream from file - 3b/compare 1/mod/*+disp8 6/rm32/ESI . . . 1/r32/ECX 4/disp8 . # compare ECX with *(ESI+4) - 7c/jump-if-lesser $read-byte-buffered:from-stream/disp8 - # . clear-stream(stream = f+4) - # . . push args - 8d/copy-address 1/mod/*+disp8 6/rm32/ESI . . . 0/r32/EAX 4/disp8 . # copy ESI+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->read must now be 0; update its cache at ECX - 31/xor 3/mod/direct 1/rm32/ECX . . . 1/r32/ECX . . # clear ECX - # . EAX = read(f->fd, stream = f+4) - # . . push args - 50/push-EAX - ff 6/subop/push 0/mod/indirect 6/rm32/ESI . . . . . . # push *ESI - # . . call - e8/call read/disp32 - # . . discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP - # if (EAX == 0) return 0xffffffff - 3d/compare-EAX-and 0/imm32 - 75/jump-if-not-equal $read-byte-buffered:from-stream/disp8 - b8/copy-to-EAX 0xffffffff/imm32/Eof - eb/jump $read-byte-buffered:end/disp8 -$read-byte-buffered:from-stream: - # read byte from stream - # AL = f->data[f->read] - 31/xor 3/mod/direct 0/rm32/EAX . . . 0/r32/EAX . . # clear EAX - 8a/copy-byte 1/mod/*+disp8 4/rm32/sib 6/base/ESI 1/index/ECX . 0/r32/AL 0x10/disp8 . # copy byte at *(ESI+ECX+16) to AL - # ++f->read - ff 0/subop/increment 1/mod/*+disp8 6/rm32/ESI . . . . 8/disp8 . # increment *(ESI+8) -$read-byte-buffered:end: - # . restore registers - 5e/pop-to-ESI - 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 - -# - tests - -test-read-byte-buffered-single: - # - check that read-byte-buffered returns 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(_test-stream, "Ab") - # . . push args - 68/push "Ab"/imm32 - 68/push _test-stream/imm32 - # . . call - e8/call write/disp32 - # . . discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP - # read-byte-buffered(_test-buffered-file) - # . . push args - 68/push _test-buffered-file/imm32 - # . . call - e8/call read-byte-buffered/disp32 - # . . discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP - # check-ints-equal(EAX, 'A', msg) - # . . push args - 68/push "F - test-read-byte-buffered-single"/imm32 - 68/push 0x41/imm32 - 50/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 - # . end - c3/return - -test-read-byte-buffered-multiple: - # - call read-byte-buffered twice, check that second call returns second byte - # 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(_test-stream, "Ab") - # . . push args - 68/push "Ab"/imm32 - 68/push _test-stream/imm32 - # . . call - e8/call write/disp32 - # . . discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP - # read-byte-buffered(_test-buffered-file) - # . . push args - 68/push _test-buffered-file/imm32 - # . . call - e8/call read-byte-buffered/disp32 - # . . discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP - # read-byte-buffered(_test-buffered-file) - # . . push args - 68/push _test-buffered-file/imm32 - # . . call - e8/call read-byte-buffered/disp32 - # . . discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP - # check-ints-equal(EAX, 'b', msg) - # . . push args - 68/push "F - test-read-byte-buffered-multiple"/imm32 - 68/push 0x62/imm32 - 50/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 - # . end - c3/return - -test-read-byte-buffered-end-of-file: - # - call read-byte-buffered on an empty 'file', check that it returns Eof - # 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 - # read-byte-buffered(_test-buffered-file) - # . . push args - 68/push _test-buffered-file/imm32 - # . . call - e8/call read-byte-buffered/disp32 - # . . discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP - # check-ints-equal(EAX, 0xffffffff, msg) - # . . push args - 68/push "F - test-read-byte-buffered-end-of-file"/imm32 - 68/push 0xffffffff/imm32/Eof - 50/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 - # . end - c3/return - -test-read-byte-buffered-refills-buffer: - # - consume buffered-file's buffer, check that next read-byte-buffered still works - # 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(_test-stream, "Abcdefgh") - # . . push args - 68/push "Abcdefgh"/imm32 - 68/push _test-stream/imm32 - # . . call - e8/call write/disp32 - # . . discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP - # pretend buffer is full - # . _test-buffered-file->read = 6 # >= _test-buffered-file->length - b8/copy-to-EAX _test-buffered-file/imm32 - c7 0/subop/copy 1/mod/*+disp8 0/rm32/EAX . . . . 8/disp8 6/imm32 # copy to *(EAX+8) - # read-byte-buffered(_test-buffered-file) - # . . push args - 68/push _test-buffered-file/imm32 - # . . call - e8/call read-byte-buffered/disp32 - # . . discard args - 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP - # check-ints-equal(EAX, 'A', msg) - # . . push args - 68/push "F - test-read-byte-buffered-refills-buffer"/imm32 - 68/push 0x41/imm32 - 50/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 - # . end - c3/return - -== data - -# a test buffered file for _test-stream -_test-buffered-file: - # file descriptor or (address stream) - _test-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 |