cc65/libsrc/apple2/cpeekc.s

;
; 2020-07-12, Oliver Schmidt
;
; char cpeekc (void);
;

        .export         _cpeekc

        .include        "apple2.inc"

_cpeekc:
        ldy     CH
        .ifdef  __APPLE2ENH__
        bit     RD80VID         ; In 80 column mode?
        bpl     peek            ; No, just go ahead
        tya
        lsr                     ; Div by 2
        tay
        bcs     peek            ; Odd cols are in main memory
        bit     HISCR           ; Assume SET80COL
        .endif
peek:   lda     (BASL),Y        ; Get character
        .ifdef  __APPLE2ENH__
        bit     LOWSCR          ; Doesn't hurt in 40 column mode
        .endif
        eor     #$80            ; Invert high bit
        ldx     #$00
        rts
Implemented some CONIO peek functions. Please refer to https://github.com/cc65/cc65/pull/532 for background info. I wrote in https://sourceforge.net/p/cc65/mailman/message/35873183/ === cputs() wraps to the next line if the strings is too long to fit in the current line. I don't know if it's worth the effort to allow cpeeks() to continue reading from the next line. I'd like to discuss this aspect with the actual implementers. === This is still as unclear today as it was when I wrote the above. Therefore this change just doesn't add cpeeks() at all. Since https://github.com/cc65/cc65/commit/f8c6c58373426551eed096dcfab4eab137fc0430 the Apple II CONIO implementation doesn't "need" revers() anymore - meaning that (nearly) every possible value can be placed in VRAM with a straight cputc() (without the need for a previous revers(1)). The implementation of cpeekc() leverages that cputc() ability by always returning the value that can be fed into cputc() without a previous revers(1). Accordingly, cpeekrevers() always returns 0. So after the sequence revers(1); cputc(x); a cpeekc() will return a value different from x! However, I don't see this behavior braking the cpeekc() contract. I see the cpeekc() contract being defined by the sequence textcolor(cpeekcolor()); revers(cpeekrevers()); cputc(cpeekc()); placing the very same value in VRAM that there was before. And that contract is fulfilled. 2020-07-12 20:19:38 +00:00			`;`
			`; 2020-07-12, Oliver Schmidt`
			`;`
			`; char cpeekc (void);`
			`;`

			`.export _cpeekc`

			`.include "apple2.inc"`

			`_cpeekc:`
			`ldy CH`
			`.ifdef __APPLE2ENH__`
			`bit RD80VID ; In 80 column mode?`
			`bpl peek ; No, just go ahead`
			`tya`
			`lsr ; Div by 2`
			`tay`
			`bcs peek ; Odd cols are in main memory`
			`bit HISCR ; Assume SET80COL`
			`.endif`
			`peek: lda (BASL),Y ; Get character`
			`.ifdef __APPLE2ENH__`
			`bit LOWSCR ; Doesn't hurt in 40 column mode`
			`.endif`
			`eor #$80 ; Invert high bit`
			`ldx #$00`
			`rts`