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== 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
# read bytes from 'f' until (and including) a newline and store them into 's'
# 's' fails to grow if and only if no data found
# just abort if 's' is too small
read-line-buffered: # f : (address buffered-file), s : (address stream byte) -> <void>
# pseudocode:
# while true
# if (s->write >= s->length) abort
# if (f->read >= f->write) populate stream from file
# if (f->write == 0) break
# AL = f->data[f->read]
# s->data[s->write] = AL
# ++f->read
# ++s->write
# if (AL == '\n') break
# . 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
56/push-ESI
57/push-EDI
# 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
# EDI = s
8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 7/r32/EDI 0xc/disp8 . # copy *(EBP+12) to EDI
# EDX = s->write
8b/copy 0/mod/indirect 7/rm32/EDI . . . 2/r32/EDX . . # copy *EDI to EDX
$read-line-buffered:loop:
# if (s->write >= s->length) abort
3b/compare 1/mod/*+disp8 7/rm32/EDI . . . 2/r32/EDX 8/disp8 . # compare EDX with *(EDI+8)
7d/jump-if-greater-or-equal $read-line-buffered:abort/disp8
# 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-line-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 (f->write == 0) break
# since f->read was initially 0, EAX is the same as f->write
# . if (EAX == 0) return true
3d/compare-EAX-and 0/imm32
74/jump-if-equal $read-line-buffered:end/disp8
$read-line-buffered: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
# s->data[s->write] = AL
88/copy-byte 1/mod/*+disp8 4/rm32/sib 7/base/EDI 2/index/EDX . 0/r32/AL 0xc/disp8 . # copy AL to *(EDI+EDX+12)
# ++f->read
41/increment-ECX
# ++s->write
42/increment-EDX
# if (AL == '\n') return
3d/compare-EAX-and 0xa/imm32
75/jump-if-not-equal $read-line-buffered:loop/disp8
$read-line-buffered:end:
# save f->read
89/copy 1/mod/*+disp8 6/rm32/ESI . . . 1/r32/ECX 8/disp8 . # copy ECX to *(ESI+8)
# save s->write
89/copy 0/mod/indirect 7/rm32/EDI . . . 2/r32/EDX . . # copy EDX to *EDI
# . restore registers
5f/pop-to-EDI
5e/pop-to-ESI
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
$read-line-buffered:abort:
# . _write(2/stderr, error)
# . . push args
68/push "read-line-buffered: line too long\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-read-line-buffered:
# - check that read-line-buffered stops at a newline
# 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
# . clear-stream(_test-tmp-stream)
# . . push args
68/push _test-tmp-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
# write(_test-stream, "ab\ncd")
# . . push args
68/push "ab\ncd"/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 a line from _test-stream (buffered by _test-buffered-file) into _test-tmp-stream
# . EAX = read-line-buffered(_test-buffered-file, _test-tmp-stream)
# . . push args
68/push _test-tmp-stream/imm32
68/push _test-buffered-file/imm32
# . . call
e8/call read-line-buffered/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# check-next-stream-line-equal(_test-tmp-stream, "ab", msg)
# . . push args
68/push "F - test-read-line-buffered"/imm32
68/push "ab"/imm32
68/push _test-tmp-stream/imm32
# . . call
e8/call check-next-stream-line-equal/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP
# end
c3/return
test-read-line-buffered-reads-final-line-until-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
# . clear-stream(_test-tmp-stream)
# . . push args
68/push _test-tmp-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
# write(_test-stream, "cd")
# . . push args
68/push "cd"/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 a line from _test-stream (buffered by _test-buffered-file) into _test-tmp-stream
# . EAX = read-line-buffered(_test-buffered-file, _test-tmp-stream)
# . . push args
68/push _test-tmp-stream/imm32
68/push _test-buffered-file/imm32
# . . call
e8/call read-line-buffered/disp32
# . . discard args
81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP
# check-stream-equal(_test-tmp-stream, "cd", msg)
# . . push args
68/push "F - test-read-line-buffered-reads-final-line-until-Eof"/imm32
68/push "cd"/imm32
68/push _test-tmp-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
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