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# 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 '-' - '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
    #
    # . 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