; ; utility.s ; General utilities for 6502 ; ; Created by Quinn Dunki on 8/15/14. ; Copyright (c) 2014 One Girl, One Laptop Productions. All rights reserved. ; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; delayShort ; Sleeps for ~1/30th second ; delayShort: SAVE_AXY ldy #$06 ; Loop a bit delayShortOuter: ldx #$ff delayShortInner: nop nop nop nop nop nop nop dex bne delayShortInner dey bne delayShortOuter RESTORE_AXY rts .if 0 ;;;;;;;;;;;;;;;;;;;;;;; ; scanHexDigit ; Scans a 4 bit hex value from an ASCII character ; A: ASCII character ; Out A: Hex value ; scanHexDigit: cmp #'a' bcs scanHexDigitLowCase cmp #'A' bcs scanHexDigitLetter sec sbc #'0' jmp scanHexDigitDone scanHexDigitLowCase: sec sbc #32 scanHexDigitLetter: sec sbc #55 scanHexDigitDone: rts ;;;;;;;;;;;;;;;;;;;;;;; ; scanHex8 ; Scans an 8 bit hex value from a string ; PARAM0: Pointer to string (LSB) ; PARAM1: Pointer to string (MSB) ; Y: Offset into string ; Out A: 8-bit hex value ; Y: One past what we scanned ; Side effects: Clobbers S0 ; scanHex8: lda (PARAM0),y jsr scanHexDigit asl asl asl asl sta SCRATCH0 ; Stash first digit for later iny lda (PARAM0),y jsr scanHexDigit ora SCRATCH0 iny ; Be nice and advance Y to end rts .endif ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; WGStrLen ; Finds the length of a null-terminated string ; PARAM0: String pointer, LSB ; PARAM1: String pointer, MSB ; Return: A: String length, not including null ; WGStrLen: phy ldy #0 WGStrLen_loop: lda (PARAM0),y beq WGStrLen_done iny bra WGStrLen_loop WGStrLen_done: tya ply rts ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; WGStoreStr ; Finds room in our block allocator and copies the given string. ; A: Terminator character ; PARAM0: String pointer, LSB ; PARAM1: String pointer, MSB ; Return: PARAM0: Stored string, LSB ; PARAM1: Stored string, MSB ; Side Effects: Clobbers SA ; WGStoreStr: sta WG_SCRATCHA SAVE_AXY ldx #0 ldy #0 WGStoreStr_findEmptyLoop: lda WG_STRINGS,x beq WGStoreStr_copy txa clc adc #16 ; String blocks are 16 bytes wide bcs WGStoreStr_noRoom tax bra WGStoreStr_findEmptyLoop WGStoreStr_noRoom: lda #0 sta PARAM0 sta PARAM1 bra WGStoreStr_done WGStoreStr_copy: phx ; Remember the start of our string WGStoreStr_copyLoop: lda (PARAM0),y cmp WG_SCRATCHA beq WGStoreStr_terminate sta WG_STRINGS,x inx iny cpy #15 ; Clip string to maximum block size bne WGStoreStr_copyLoop WGStoreStr_terminate: lda #0 ; Terminate the stored string sta WG_STRINGS,x pla ; Return pointer to the start of the block clc adc #WG_STRINGS sta PARAM1 WGStoreStr_done: RESTORE_AXY rts