Lynx update including file routines that access a file system on a cartridge

by Karri Kaksonen.


git-svn-id: svn://svn.cc65.org/cc65/trunk@4892 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/lynx/lseek.s

@@ -0,0 +1,59 @@
+;
+; Karri Kaksonen, 2010
+;
+; This function is used to place the Lynx hardware to point to any byte in
+; the Lynx cart.
+;
+; This function supports all available block sizes (512, 1024 and 2048 bytes).
+; No other block sizes have been used afaik.
+;
+; Only SEEK_SET operation mode is implemented.
+;
+; off_t __fastcall__ lseek(int fd, off_t offset, int whence);
+
+	.importzp	sp, sreg, regsave, regbank, tmp1, ptr1, ptr2
+	.macpack	longbranch
+	.export		_lseek
+	.import		addysp, stax0sp, tosand0ax, pusheax, asreax2
+	.import		ldeaxysp, decsp2, pushax, incsp8
+	.import		tosandeax,decax1,tosdiveax,axlong,ldaxysp
+	.import		lynxskip0, lynxblock,tosasreax
+	.import		__BLOCKSIZE__
+	.importzp	_FileCurrBlock
+
+.segment	"CODE"
+
+.proc	_lseek: near
+
+.segment	"CODE"
+
+	jsr     pushax
+	ldy     #$05
+	jsr     ldeaxysp
+	jsr     pusheax
+	ldx     #$00
+	lda     #<(__BLOCKSIZE__/1024 + 9)
+	jsr     tosasreax
+	sta     _FileCurrBlock
+	jsr     lynxblock
+	ldy     #$05
+	jsr     ldeaxysp
+	jsr     pusheax
+	lda     #<(__BLOCKSIZE__-1)
+	ldx     #>(__BLOCKSIZE__-1)
+	jsr     decax1
+	jsr     axlong
+	jsr     tosandeax
+	eor	#$FF
+	pha
+	txa
+	eor	#$FF
+	tay
+	plx
+	jsr     lynxskip0
+	ldy     #$05
+	jsr     ldeaxysp
+	jmp     incsp8
+
+.endproc
+