Mu - 057write.subx

1 # write: like _write, but also support in-memory streams in addition to file 2 # descriptors. 3 # 4 # Our first dependency-injected and testable primitive. We can pass it either 5 # a file descriptor or an address to a stream. If a file descriptor is passed 6 # in, we _write to it using the right syscall. If a 'fake file descriptor' or 7 # stream is passed in, we append to the stream. This lets us redirect output 8 # in tests and check it later. 9 # 10 # We assume our data segment will never begin at an address shorter than 11 # 0x08000000, so any smaller arguments are assumed to be real file descriptors. 12 # 13 # A stream looks like this: 14 # read: int # index at which to read next 15 # write: int # index at which writes go 16 # data: (array byte) # prefixed by size as usual 17 18 == code 19 # instruction effective address register displacement immediate 20 # . op subop mod rm32 base index scale r32 21 # . 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 22 23 # TODO: come up with a way to signal when a write to disk fails 24 write: # f: fd or (addr stream byte), s: (addr array byte) 25 # . prologue 26 55/push-ebp 27 89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp 28 # if (f < 0x08000000) _write(f, s) and return # f can't be a user-mode address, so treat it as a kernel file descriptor 29 81 7/subop/compare 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 0x08000000/imm32 # compare *(ebp+8) 30 73/jump-if-addr>= $write:fake/disp8 31 # . . push args 32 ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0xc/disp8 . # push *(ebp+12) 33 ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 8/disp8 . # push *(ebp+8) 34 # . . call 35 e8/call _write/disp32 36 # . . discard args 37 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp 38 eb/jump $write:end/disp8 39 $write:fake: 40 # otherwise, treat 'f' as a stream to append to 41 # . save registers 42 50/push-eax 43 51/push-ecx 44 52/push-edx 45 53/push-ebx 46 # ecx = f 47 8b/copy 1/mod/*+disp8 5/rm32/ebp . . 1/r32/ecx 8/disp8 . # copy *(ebp+8) to ecx 48 # edx = f->write 49 8b/copy 0/mod/indirect 1/rm32/ecx . . . 2/r32/edx . . # copy *ecx to edx 50 # ebx = f->size 51 8b/copy 1/mod/*+disp8 1/rm32/ecx . . . 3/r32/ebx 8/disp8 . # copy *(ecx+8) to ebx 52 # eax = _append-3(&f->data[f->write], &f->data[f->size], s) 53 # . . push s 54 ff 6/subop/push 1/mod/*+disp8 5/rm32/ebp . . . . 0xc/disp8 . # push *(ebp+12) 55 # . . push &f->data[f->size] 56 8d/copy-address 1/mod/*+disp8 4/rm32/sib 1/base/ecx 3/index/ebx . 3/r32/ebx 0xc/disp8 . # copy ecx+ebx+12 to ebx 57 53/push-ebx 58 # . . push &f->data[f->write] 59 8d/copy-address 1/mod/*+disp8 4/rm32/sib 1/base/ecx 2/index/edx . 3/r32/ebx 0xc/disp8 . # copy ecx+edx+12 to ebx 60 53/push-ebx 61 # . . call 62 e8/call _append-3/disp32 63 # . . discard args 64 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp 65 # f->write += eax 66 01/add 0/mod/indirect 1/rm32/ecx . . . 0/r32/eax . . # add eax to *ecx 67 # . restore registers 68 5b/pop-to-ebx 69 5a/pop-to-edx 70 59/pop-to-ecx 71 58/pop-to-eax 72 $write:end: 73 # . epilogue 74 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 75 5d/pop-to-ebp 76 c3/return 77 78 test-write-single: 79 # clear-stream(_test-stream) 80 # . . push args 81 68/push _test-stream/imm32 82 # . . call 83 e8/call clear-stream/disp32 84 # . . discard args 85 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp 86 # write(_test-stream, "Ab") 87 # . . push args 88 68/push "Ab"/imm32 89 68/push _test-stream/imm32 90 # . . call 91 e8/call write/disp32 92 # . . discard args 93 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp 94 # check-ints-equal(*_test-stream->data, 41/A 62/b 00 00, msg) 95 # . . push args 96 68/push "F - test-write-single"/imm32 97 68/push 0x006241/imm32/Ab 98 # . . push *_test-stream->data 99 b8/copy-to-eax _test-stream/imm32 100 ff 6/subop/push 1/mod/*+disp8 0/rm32/eax . . . . 0xc/disp8 . # push *(eax+12) 101 # . . call 102 e8/call check-ints-equal/disp32 103 # . . discard args 104 81 0/subop/add 3/mod/direct 4/rm32/esp . pre { line-height: 125%; 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;;; Finite State Machine Interpreter (FSM)

to game :which
fsm thing word "mach :which
end

to fsm :machine
cleartext
setcursor [0 3]
localmake "start startpart :machine
localmake "moves movepart :machine
localmake "accept acceptpart :machine
fsm1 :start
end

to fsm1 :here
ifelse memberp :here :accept [accept] [reject]
fsm1 (fsmnext :here readchar)
end

to fsmnext :here :input
blank
if memberp :input (list char 13 char 10) ~
   [print ifelse memberp :here :accept ["| ACCEPT|] ["| REJECT|]
    output :start]
type :input
catch "error [output last find [fsmtest :here :input ?] :moves]
output -1
end

to fsmtest :here :input :move
output and (equalp :here arrowtail :move) ~
           (memberp :input arrowtext :move)
end

;; Display machine state

to accept
display "accept
end

to reject
display "reject
end

to blank
display "|      |
end

to display :text
localmake "oldpos cursor
setcursor [15 1]
type :text
setcursor :oldpos
end

;; Data abstraction for machines

to startpart :machine
output first :machine
end

to movepart :machine
output first bf :machine
end

to acceptpart :machine
output last :machine
end

to make.machine :start :moves :accept
output (list :start :moves :accept)
end

;; Data abstraction for arrows

to arrowtail :arrow
output first :arrow
end

to arrowtext :arrow
output first butfirst :arrow
end

to arrowhead :arrow
output last :arrow
end

to make.arrow :tai