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Renamed .error, removed trailing whitespace, more verbose comments.

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Clanmaster21 2019-10-21 15:30:28 +01:00 committed by GitHub
parent 8093bef9cb
commit 7d43f7a760
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1 changed files with 11 additions and 8 deletions
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13
apps/lib/parse.asm
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@ -26,7 +26,7 @@ parseDecimal:
ld h, 0
ld l, a ; load first digit in without multiplying
ld b, 3 ; Carries can only occur for decimals >=5 in length
jr c, .error
jr c, .end
.loop:
exx
@ -34,9 +34,11 @@ parseDecimal:
ld a, (hl)
exx
; inline parseDecimalDigit
add a, 0xff-'9' ; maps '0'-'9' onto 0xf6-0xff
sub 0xff-9 ; maps to 0-9 and carries if not a digit
jr c, .error
jr c, .end
add hl, hl ; x2
ld d, h
@ -47,7 +49,7 @@ parseDecimal:
ld d, 0
ld e, a
add hl, de
jr c, .error ; if hl was 0x1999, it may carry here
jr c, .end ; if hl was 0x1999, it may carry here
djnz .loop
@ -64,10 +66,11 @@ parseDecimal:
ld a, (hl)
exx
add a, 0xd0 ; the next line expects a null to be mapped to 0xd0
.error:
.end:
; Because of the add and sub in parseDecimalDigit, null is mapped
; to 0x00+(0xff-'9')-(0xff-9)=-0x30=0xd0
sub 0xd0 ; if a is null, set Z
; a is checked for null before any errors
.end:
push hl \ pop ix
exx ; restore original de and bc
pop hl