millfork/include/encconv.mfk

#if ENCODING_SAME

#if ARCH_6502
inline byte __byte_identity(byte a) { ? rts }
#elseif ARCH_I80
#pragma zilog_syntax
inline byte __byte_identity(byte a) { ? ret }
#else
inline byte __byte_identity(byte a) = a
#endif

alias from_screencode = __byte_identity
alias to_screencode = __byte_identity

#else

alias from_screencode = __from_screencode
alias to_screencode = __to_screencode

#endif


// conversions for particular encoding pairs:

#if ARCH_6502

asm byte petscii_to_petscr(byte a) {
    cmp #$20
    bcc __petscii_to_petscr_ddRev
    cmp #$60
    bcc __petscii_to_petscr_dd1
    cmp #$80
    bcc __petscii_to_petscr_dd2
    cmp #$a0
    bcc __petscii_to_petscr_dd3
    cmp #$c0
    bcc __petscii_to_petscr_dd4
    cmp #$ff
    bcc __petscii_to_petscr_ddRev
    lda #$5e
    rts
__petscii_to_petscr_dd2:
    and #$5f
    rts
__petscii_to_petscr_dd3:
    ora #$40
    rts
__petscii_to_petscr_dd4:
    eor #$c0
    rts
__petscii_to_petscr_dd1:
    and #$3f
    rts
__petscii_to_petscr_ddRev:
    eor #$80
    rts
}

asm byte petscr_to_petscii(byte a) {
    cmp #$20
    bcs __petscr_to_petscii_40
    ora #$40
    rts
__petscr_to_petscii_40:
    cmp #$40
    bcs __petscr_to_petscii_60
    rts
__petscr_to_petscii_60:
    cmp #$60
    bcs __petscr_to_petscii_80
    eor #$80
    rts
__petscr_to_petscii_80:
    cmp #$80
    bcs __petscr_to_petscii_a0
    eor #$c0
    rts
__petscr_to_petscii_a0:
    cmp #$a0
    bcs __petscr_to_petscii_c0
    eor #$80
    rts
__petscr_to_petscii_c0:
    eor #$40
    rts
}

asm byte atascii_to_atasciiscr(byte a) {
    and #$7f
    cmp #$20
    bcs __atascii_to_atasciiscr_60
    ora #$40
    rts
__atascii_to_atasciiscr_60:
    cmp #$60
    bcs __atascii_to_atasciiscr_end
    sec
    sbc #$20
__atascii_to_atasciiscr_end:
    rts
}


asm byte atasciiscr_to_atascii(byte a) {
    and #$7f
    cmp #$40
    bcs __atascii_to_atasciiscr_60
    clc
    adc #$20
    rts
__atascii_to_atasciiscr_60:
    cmp #$60
    bcs __atascii_to_atasciiscr_end
    and #$1f
__atascii_to_atasciiscr_end:
    rts
}

#endif