# Helper to print an int32 in decimal. == 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 #? Entry: # run a single test, while debugging #? e8/call test-print-int32-decimal-negative/disp32 #? #? # syscall(exit, Num-test-failures) #? 8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/EBX Num-test-failures/disp32 # copy *Num-test-failures to EBX #? b8/copy-to-EAX 1/imm32/exit #? cd/syscall 0x80/imm8 print-int32-decimal: # out : (address stream), n : int32 # PSEUDOCODE # based on K&R itoa: https://en.wikibooks.org/wiki/C_Programming/stdlib.h/itoa # push SENTINAL # if n >= 0: # goto digit-encode # else: # n = -n # negative = true # while true: # push n % 10 + '0' # n = n / 10 # break if n == 0 # if negative: # push '-' # while true: # EAX = pop # break if EAX == SENTINAL # out->data[out->write++] = EAX # # . 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 53/push-EBX 57/push-EDI # negative = false bf/copy-to-EDI 0/imm32 # EDI = 0 # push sentinal for $append-loop 68/push-sentinel 0/imm32 # EAX = n 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 0/r32/EAX 0xc/disp8 . # EAX = *(EBP+12) # if n >= 0 jump to digit-encode 3d/compare-EAX-and 0/imm32 7d/jump-if-greater-eq $digit-encode:prelude/disp8 # else # n = -n f7 3/subop/negate 3/mod/direct 0/rm32/EAX # EAX = -EAX # negative = true bf/copy-to-EDI 1/imm32 # EDI = 1 $digit-encode:prelude: # EBX = n 8b/copy 3/mod/direct 0/rm32/EAX . . . 3/r32/EBX . . # EBX = EAX $digit-encode-loop: # EAX = EBX(n) 89/copy 3/mod/direct 0/rm32/EAX . . . 3/r32/EBX . . # EAX = EBX b9/copy-to-ECX 0xa/imm32 99/sign-extend-EAX-into-EDX # EDX:EAX(n) / ECX(10) # EDX, EAX = n % 10, n / 10 f7 7/subop/idiv 3/mod/direct 1/rm32/ECX . . . . . . # divide EDX:EAX by ECX, storing quotient in EAX and remainder in EDX 81 0/subop/add 3/mod/direct 2/rm32/EDX . . . . . 0x30/imm32 # EDX += '0' (0x30) # push n % 10 + '0' 52/push-EDX # EBX = n / 10 89/copy 3/mod/direct 3/rm32/EBX . . . 0/r32/EAX . . # EBX = EAX # loop if n / 10 > 0 3d/compare-EAX-and 0/imm32 7f/jump-if-greater $digit-encode-loop/disp8 # else: 8b/copy 3/mod/direct 7/rm32/EDI . . . 0/r32/EAX . . # EAX = EDX # . if !negative: goto append-loop 3d/compare-EAX-and 0/imm32 74/jump-if-equal $append-loop:prelude/disp8 # . else 68/push-negative 0x2d/imm32 # push '-' $append-loop:prelude: # EBX = &out 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 3/r32/EBX 8/disp8 . # copy *(EBP+8) to EBX $append-loop: # EAX = next_character 58/pop-to-EAX 3d/compare-EAX . . . . . . . 0/imm32 # EAX == 0 74/jump-if-equal $append-loop:break/disp8 # ECX = out->write 8b/copy 0/mod/indirect 3/rm32/EBX . . . 1/r32/ECX . . # ECX = *EBX # out->data[out->write] = next_character # . ECX = &out->data[out->write] 8d/copy-address 1/mod/*+disp8 4/rm32/sib 3/base/EBX 1/index/ECX . 1/r32/ECX 0xc/disp8 . # copy EBX+ECX+12 to ECX # . out->data[out->write] = EAX 89/copy 0/mod/indirect 1/rm32/ECX . . . 0/r32/ECX . . # *ECX = EAX # out->write++ ff 0/subop/increment 0/mod/indirect 3/rm32/EBX . . . . . . # (*EBX)++ eb/jump $append-loop/disp8 $append-loop:break: $print-int32-decimal:end: # . reclaim locals # . restore registers 57/pop-to-EDI 5b/pop-to-EBX 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 $print-int32-decimal:abort: # . _write(2/stderr, error) # . . push args 68/push "print-int32-decimal: 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-print-int32-decimal: # - check that a single-digit number converts correctly # 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 # print-int32-decimal(_test-stream, 9) # . . push args 68/push 9/imm32 68/push _test-stream/imm32 # . . call e8/call print-int32-decimal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP # check-stream-equal(_test-stream, "9", msg) # . . push args 68/push "F - test-print-int32-decimal"/imm32 68/push "9"/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 test-print-int32-decimal-zero: # - check that 0 converts correctly # 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 # print-int32-decimal(_test-stream, 0) # . . push args 68/push 0/imm32 68/push _test-stream/imm32 # . . call e8/call print-int32-decimal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP # check-stream-equal(_test-stream, "0", msg) # . . push args 68/push "F - test-print-int32-decimal-zero"/imm32 68/push "0"/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 test-print-int32-decimal-multiple-digits: # - check that a multi-digit number converts correctly # 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 # print-int32-decimal(_test-stream, 10) # . . push args 68/push 0xa/imm32 68/push _test-stream/imm32 # . . call e8/call print-int32-decimal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP # check-stream-equal(_test-stream, "10", msg) # . . push args 68/push "F - test-print-int32-decimal-multiple-digits"/imm32 68/push "10"/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 test-print-int32-decimal-negative: # - check that a negative single-digit number converts correctly # 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 # print-int32-decimal(_test-stream, -9) # . . push args 68/push -9/imm32 68/push _test-stream/imm32 # . . call e8/call print-int32-decimal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP #? # dump _test-stream {{{ #? # . write(2/stderr, "^") #? # . . push args #? 68/push "^"/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 #? # . write-stream(2/stderr, _test-stream) #? # . . push args #? 68/push _test-stream/imm32 #? 68/push 2/imm32/stderr #? # . . call #? e8/call write-stream/disp32 #? # . . discard args #? 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP #? # . write(2/stderr, "$\n") #? # . . push args #? 68/push "$\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 #? # }}} # check-stream-equal(_test-stream, "-9", msg) # . . push args 68/push "F - test-print-int32-decimal-negative"/imm32 68/push "-9"/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 test-print-int32-decimal-negative-multiple-digits: # - check that a multi-digit number converts correctly # 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 # print-int32-decimal(_test-stream, -10) # . . push args 68/push -0xa/imm32 68/push _test-stream/imm32 # . . call e8/call print-int32-decimal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP # check-stream-equal(_test-stream, "-10", msg) # . . push args 68/push "F - test-print-int32-decimal-negative-multiple-digits"/imm32 68/push "-10"/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