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- ; *** Requirements ***
- ; lib/util
- ; *** Code ***
-
- ; Parse the hex char at A and extract it's 0-15 numerical value. Put the result
- ; in A.
- ;
- ; On success, the carry flag is reset. On error, it is set.
- parseHex:
- ; First, let's see if we have an easy 0-9 case
-
- add a, 0xc6 ; maps '0'-'9' onto 0xf6-0xff
- sub 0xf6 ; maps to 0-9 and carries if not a digit
- ret nc
-
- and 0xdf ; converts lowercase to uppercase
- add a, 0xe9 ; map 0x11-x017 onto 0xFA - 0xFF
- sub 0xfa ; map onto 0-6
- ret c
- ; we have an A-F digit
- add a, 10 ; C is clear, map back to 0xA-0xF
- ret
-
-
- ; Parses 2 characters of the string pointed to by HL and returns the numerical
- ; value in A. If the second character is a "special" character (<0x21) we don't
- ; error out: the result will be the one from the first char only.
- ; HL is set to point to the last char of the pair.
- ;
- ; On success, the carry flag is reset. On error, it is set.
- parseHexPair:
- push bc
-
- ld a, (hl)
- call parseHex
- jr c, .end ; error? goto end, keeping the C flag on
- rla \ rla \ rla \ rla ; let's push this in MSB
- ld b, a
- inc hl
- ld a, (hl)
- cp 0x21
- jr c, .single ; special char? single digit
- call parseHex
- jr c, .end ; error?
- or b ; join left-shifted + new. we're done!
- ; C flag was set on parseHex and is necessarily clear at this point
- jr .end
-
- .single:
- ; If we have a single digit, our result is already stored in B, but
- ; we have to right-shift it back.
- ld a, b
- and 0xf0
- rra \ rra \ rra \ rra
- dec hl
-
- .end:
- pop bc
- ret
-
- ; Parse the decimal char at A and extract it's 0-9 numerical value. Put the
- ; result in A.
- ;
- ; On success, the carry flag is reset. On error, it is set.
- ; Also, zero flag set if '0'
- ; parseDecimalDigit has been replaced with the following code inline:
- ; add a, 0xff-'9' ; maps '0'-'9' onto 0xf6-0xff
- ; sub 0xff-9 ; maps to 0-9 and carries if not a digit
-
- ; Parse string at (HL) as a decimal value and return value in IX under the
- ; same conditions as parseLiteral.
- ; Sets Z on success, unset on error.
- ; To parse successfully, all characters following HL must be digits and those
- ; digits must form a number that fits in 16 bits. To end the number, both \0
- ; and whitespaces (0x20 and 0x09) are accepted. There must be at least one
- ; digit in the string.
-
- parseDecimal:
- push hl
-
- ld a, (hl)
- 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 ; not a digit on first char? error
- exx ; preserve bc, hl, de
- ld h, 0
- ld l, a ; load first digit in without multiplying
- ld b, 3 ; Carries can only occur for decimals >=5 in length
-
- .loop:
- exx
- inc hl
- 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, .end
-
- add hl, hl ; x2
- ld d, h
- ld e, l ; de is x2
- add hl, hl ; x4
- add hl, hl ; x8
- add hl, de ; x10
- ld d, 0
- ld e, a
- add hl, de
- jr c, .end ; if hl was 0x1999, it may carry here
- djnz .loop
-
-
- inc b ; so loop only executes once more
- ; only numbers >0x1999 can carry when multiplied by 10.
- ld de, 0xE666
- ex de, hl
- add hl, de
- ex de, hl
- jr nc, .loop ; if it doesn't carry, it's small enough
-
- exx
- inc hl
- ld a, (hl)
- exx
- add a, 0xd0 ; the next line expects a null to be mapped to 0xd0
- .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
- push hl \ pop ix
- exx ; restore original de and bc
- pop hl
- ret z
- ; A is not 0? Ok, but if it's a space, we're happy too.
- jp isWS
- .error:
- pop hl
- jp unsetZ
-
- ; Parse string at (HL) as a hexadecimal value and return value in IX under the
- ; same conditions as parseLiteral.
- parseHexadecimal:
- call hasHexPrefix
- ret nz
- push hl
- push de
- ld d, 0
- inc hl ; get rid of "0x"
- inc hl
- call strlen
- cp 3
- jr c, .single
- cp 4
- jr c, .doubleShort ; 0x123
- cp 5
- jr c, .double ; 0x1234
- ; too long, error
- jr .error
- .double:
- call parseHexPair
- jr c, .error
- inc hl ; now HL is on first char of next pair
- ld d, a
- jr .single
- .doubleShort:
- ld a, (hl)
- call parseHex
- jr c, .error
- inc hl ; now HL is on first char of next pair
- ld d, a
- .single:
- call parseHexPair
- jr c, .error
- ld e, a
- cp a ; ensure Z
- jr .end
- .error:
- call unsetZ
- .end:
- push de \ pop ix
- pop de
- pop hl
- ret
-
- ; Sets Z if (HL) has a '0x' prefix.
- hasHexPrefix:
- ld a, (hl)
- cp '0'
- ret nz
- push hl
- inc hl
- ld a, (hl)
- cp 'x'
- pop hl
- ret
-
- ; Parse string at (HL) as a binary value (0b010101) and return value in IX.
- ; High IX byte is always clear.
- ; Sets Z on success.
- parseBinaryLiteral:
- call hasBinPrefix
- ret nz
- push bc
- push hl
- push de
- ld d, 0
- inc hl ; get rid of "0b"
- inc hl
- call strlen
- or a
- jr z, .error ; empty, error
- cp 9
- jr nc, .error ; >= 9, too long
- ; We have a string of 8 or less chars. What we'll do is that for each
- ; char, we rotate left and set the LSB according to whether we have '0'
- ; or '1'. Error out on anything else. C is our stored result.
- ld b, a ; we loop for "strlen" times
- ld c, 0 ; our stored result
- .loop:
- rlc c
- ld a, (hl)
- inc hl
- cp '0'
- jr z, .nobit ; no bit to set
- cp '1'
- jr nz, .error ; not 0 or 1
- ; We have a bit to set
- inc c
- .nobit:
- djnz .loop
- ld e, c
- cp a ; ensure Z
- jr .end
- .error:
- call unsetZ
- .end:
- push de \ pop ix
- pop de
- pop hl
- pop bc
- ret
-
- ; Sets Z if (HL) has a '0b' prefix.
- hasBinPrefix:
- ld a, (hl)
- cp '0'
- ret nz
- push hl
- inc hl
- ld a, (hl)
- cp 'b'
- pop hl
- ret
-
- ; Parse string at (HL) and, if it is a char literal, sets Z and return
- ; corresponding value in IX. High IX byte is always clear.
- ;
- ; A valid char literal starts with ', ends with ' and has one character in the
- ; middle. No escape sequence are accepted, but ''' will return the apostrophe
- ; character.
- parseCharLiteral:
- ld a, 0x27 ; apostrophe (') char
- cp (hl)
- ret nz
-
- push hl
- push de
- inc hl
- inc hl
- cp (hl)
- jr nz, .end ; not ending with an apostrophe
- inc hl
- ld a, (hl)
- or a ; cp 0
- jr nz, .end ; string has to end there
- ; Valid char, good
- ld d, a ; A is zero, take advantage of that
- dec hl
- dec hl
- ld a, (hl)
- ld e, a
- cp a ; ensure Z
- .end:
- push de \ pop ix
- pop de
- pop hl
- ret
-
- ; Parses the string at (HL) and returns the 16-bit value in IX. The string
- ; can be a decimal literal (1234), a hexadecimal literal (0x1234) or a char
- ; literal ('X').
- ;
- ; As soon as the number doesn't fit 16-bit any more, parsing stops and the
- ; number is invalid. If the number is valid, Z is set, otherwise, unset.
- parseLiteral:
- call parseCharLiteral
- ret z
- call parseHexadecimal
- ret z
- call parseBinaryLiteral
- ret z
- jp parseDecimal
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