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/read.s

@@ -0,0 +1,50 @@
+;
+; Karri Kaksonen, 2010
+;
+; This function reads count bytes from the place where the address counter is.
+; Use lseek to place the address counter where you want to read from.
+;
+; The file descriptor is ignored in this implementation. The read operation
+; reads bytes from a raw cart and does not understand the concept of files.
+; So if you read over the end of file you get data from the next file.
+;
+; The count-parameter can be positive (Atari style) or negative (BLL style).
+; In any case the read routine will work correctly.
+;
+; int __fastcall__ read(int fd,void *buf,int count)
+;
+	.importzp	_FileDestPtr
+	.import		lynxread0
+	.import		pushax,ldaxysp,ldax0sp,incsp6
+	.export		_read
+
+.segment	"CODE"
+
+.proc	_read: near
+
+.segment	"CODE"
+
+	jsr     pushax
+	ldy     #$03
+	jsr     ldaxysp
+	sta     _FileDestPtr
+	stx     _FileDestPtr+1
+	jsr     ldax0sp
+	phx			; The BLL kit uses negative counts
+	plx			; while the basic Lynx uses positive
+	bmi	@1		; make all counts negative
+	eor	#$FF
+	pha
+	txa
+	eor	#$FF
+	bra	@2
+@1:	pha
+	txa
+@2:	tay
+	plx
+	jsr     lynxread0
+	jsr     ldax0sp
+	jmp     incsp6
+
+.endproc
+