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5143 - add a bounds check 

We'll just loudly abort the entire program if the output stream isn't large
enough to accept all the characters we want to print.
This commit is contained in:
Kartik Agaram 2019-05-04 14:57:04 -07:00
parent 37aa2bf3e8
commit 8591331a7f
1 changed files with 10 additions and 0 deletions
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10
subx/074print-int-decimal.subx
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@ -27,9 +27,11 @@ print-int32-decimal: # out : (address stream), n : int32
# push '-'
# w = out->write
# curr = &out->data[out->write]
# max = &out->data[out->length]
# while true
# pop into EAX
# if (EAX == sentinel) break
# if (curr >= max) abort
# *curr = AL
# ++curr
# ++w
@ -45,6 +47,7 @@ print-int32-decimal: # out : (address stream), n : int32
50/push-EAX
51/push-ECX
52/push-EDX
53/push-EBX
57/push-EDI
# ten/ECX = 10
b9/copy-to-ECX 0xa/imm32
@ -78,12 +81,18 @@ $print-int32-decimal:write:
8b/copy 0/mod/indirect 7/rm32/EDI . . . 2/r32/EDX . . # copy *EDI to EDX
# curr/ECX = &out->data[out->write]
8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 2/index/EDX . 1/r32/ECX 0xc/disp8 . # copy EBX+EDX+12 to ECX
# max/EBX = &out->data[out->length]
8b/copy 1/mod/*+disp8 7/rm32/EDI . . . 3/r32/EBX 8/disp8 . # copy *(EDI+8) to EBX
8d/copy-address 1/mod/*+disp8 4/rm32/sib 7/base/EDI 3/index/EBX . 3/r32/EBX 0xc/disp8 . # copy EDI+EBX+12 to EBX
$print-int32-decimal:write-loop:
# pop into EAX
58/pop-to-EAX
# if (EAX == sentinel) break
3d/compare-EAX-and 0/imm32/sentinel
74/jump-if-equal $print-int32-decimal:write-break/disp8
# if (curr >= max) abort
39/compare 3/mod/direct 1/rm32/ECX . . . 3/r32/EBX . . # compare ECX with EBX
7d/jump-if-greater-or-equal $print-int32-decimal:abort/disp8
# *curr = AL
88/copy-byte 0/mod/indirect 1/rm32/ECX . . . 0/r32/AL . . # copy AL to byte at *ECX
# ++curr
@ -97,6 +106,7 @@ $print-int32-decimal:write-break:
$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