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I accidentally pushed an optimisation I pushed to another branch

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Clanmaster21 2019-10-17 21:00:41 +01:00 committed by GitHub
parent 6c0052578e
commit 85cf733279
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1 changed files with 19 additions and 9 deletions
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kernel/parse.asm
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@ -11,16 +11,26 @@
; On success, the carry flag is reset. On error, it is set. ; On success, the carry flag is reset. On error, it is set.
parseHex: parseHex:
; First, let's see if we have an easy 0-9 case ; First, let's see if we have an easy 0-9 case
cp '0'
add a, 0xc6 ; maps '0'-'9' onto 0xf6-0xff jr c, .error ; if < '0', we have a problem
sub 0xf6 ; maps to 0-9 and carries if not a digit cp '9'+1
ret nc jr nc, .alpha ; if >= '9'+1, we might have alpha
; We are in the 0-9 range
sub '0' ; C is clear
ret
and 0xdf ; converts lowercase to uppercase .alpha:
add a, 0xe9 ; map 0x11-x017 onto 0xFA - 0xFF call upcase
sub 0xfa ; map onto 0-6 cp 'A'
ret c jr c, .error ; if < 'A', we have a problem
add a, 10 ; C is clear, map back to 0xA-0xF cp 'F'+1
jr nc, .error ; if >= 'F', we have a problem
; We have alpha.
sub 'A'-10 ; C is clear
ret
.error:
scf
ret ret
; Parses 2 characters of the string pointed to by HL and returns the numerical ; Parses 2 characters of the string pointed to by HL and returns the numerical