# 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/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 # works by generating characters from lowest to highest and pushing them # to the stack, before popping them one by one into the stream # # pseudocode: # copy ESP to EBX # EAX = n # while true # if (EAX == 0) break # sign-extend EAX into EDX # EAX, EDX = EAX/10, EAX%10 # push EDX # if n < 0 # push '-' - 0x30 = -3 # w/EAX = out->write # max/ECX = out->length # curr/EDI = out->data[out->write] # while true # if (ESP == EBX) break # if (curr >= max) abort # pop into EDX # EDX += '0' # convert decimal digit to ascii # *curr = DL # ++curr # ++w # out->write = w # # . 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 # copy ESP to EBX 89/copy 3/mod/direct 3/rm32/EBX . . . 4/r32/ESP . . # copy ESP to EBX # ten/ECX = 10 b9/copy-to-ECX 0xa/imm32 # EAX = |n| 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 0/r32/EAX 0xc/disp8 . # copy *(EBP+12) to EAX 3d/compare-EAX-with 0/imm32 7d/jump-if-greater-or-equal $print-int32-decimal:read-loop/disp8 $print-int32-decimal:negative: f7 3/subop/negate 3/mod/direct 0/rm32/EAX . . . . . . # negate EAX $print-int32-decimal:read-loop: # if (EAX == 0) break 3d/compare-EAX-and 0/imm32 74/jump-if-equal $print-int32-decimal:read-break/disp8 # sign-extend 99/sign-extend-EAX-into-EDX # EAX, EDX = divide-with-remainder EAX/ten, EAX%ten f7 7/subop/divide-by 3/mod/direct 1/rm32/ECX . . . . . . # divide EDX:EAX by ECX, storing quotient in EAX and remainder in EDX # push EDX 52/push-EDX eb/jump $print-int32-decimal:read-loop/disp8 $print-int32-decimal:read-break: # if (n < 0) push('-') 81 7/subop/compare 1/mod/*+disp8 5/rm32/EBP . . . . 0xc/disp8 0/imm32 # compare *(EBP+12) 7d/jump-if-greater-or-equal $print-int32-decimal:write/disp8 $print-int32-decimal:push-negative: 68/push -3/imm32/dash-minus-zero # fall through $print-int32-decimal:write: # EDI = out 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 7/r32/EDI 8/disp8 . # copy *(EBP+8) to EDI # max/ECX = &out->data[out->length] 8b/copy 1/mod/*+disp8 7/rm32/EDI . . . 1/r32/ECX 8/disp8 . # copy *(EDI+8) to ECX 8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 1/index/ECX . 1/r32/ECX 0xc/disp8 . # copy EDI+ECX+12 to ECX # w/EAX = out->write 8b/copy 0/mod/indirect 7/rm32/EDI . . . 0/r32/EAX . . # copy *EDI to EAX # curr/EDI = &out->data[out->write] 8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 0/index/EAX . 7/r32/EDI 0xc/disp8 . # copy EDI+EAX+12 to EDI $print-int32-decimal:write-loop: # if (ESP == EBX) break 39/compare 3/mod/direct 4/rm32/ESP . . . 3/r32/EBX . . # compare ESP and EBX 74/jump-if-equal $print-int32-decimal:write-break/disp8 # if (curr >= max) abort 39/compare 3/mod/direct 7/rm32/EDI . . . 1/r32/ECX . . # compare EDI and ECX 7d/jump-if-greater-or-equal $print-int32-decimal:abort/disp8 # pop into EDX 5a/pop-into-EDX # EDX += '0' 81 0/subop/add 3/mod/direct 2/rm32/EDX . . . . . 0x30/imm32/zero # add to EDX $print-int32-decimal:write-char: # *curr = DL 88/copy-byte 0/mod/indirect 7/rm32/EDI . . . 2/r32/DL . . # copy DL to byte at *ECX # ++curr 47/increment-EDI # ++w 40/increment-EAX eb/jump $print-int32-decimal:write-loop/disp8 $print-int32-decimal:write-break: # out->write = w 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 7/r32/EDI 8/disp8 . # copy *(EBP+8) to EDI 89/copy 0/mod/indirect 7/rm32/EDI . . . 0/r32/EAX . . # copy EAX to *EDI $print-int32-decimal:end: # . restore registers 5f/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-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