exercise: reimplement print-int-decimal

1 files changed, 1 insertions, 97 deletions

diff --git a/subx/074print-int-decimal.subx b/subx/074print-int-decimal.subx
index 86015a00..cce8e21e 100644
--- a/subx/074print-int-decimal.subx
+++ b/subx/074print-int-decimal.subx
@@ -13,109 +13,13 @@
 #?     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:
+    # . reclaim locals
     # . 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