diff options
| -rw-r--r-- | subx/074print-int-decimal.subx | 182 |
1 files changed, 97 insertions, 85 deletions
diff --git a/subx/074print-int-decimal.subx b/subx/074print-int-decimal.subx index 86015a00..e5dbaa30 100644 --- a/subx/074print-int-decimal.subx +++ b/subx/074print-int-decimal.subx @@ -6,38 +6,32 @@ # . 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 +#? 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 - # 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 '-' - '0' = -3 - # max/ECX = &out->data[out->length] - # w/EAX = out->write - # 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 + # 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 @@ -48,70 +42,88 @@ print-int32-decimal: # out : (address stream), n : int32 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 + + # 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 - 74/jump-if-equal $print-int32-decimal:read-break/disp8 - # sign-extend + 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 - # 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 + # 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 - 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 + + # 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 - 5f/pop-to-EDI + 57/pop-to-EDI 5b/pop-to-EBX 5a/pop-to-EDX 59/pop-to-ECX |