Finally: Commodore file I/O

git-svn-id: svn://svn.cc65.org/cc65/trunk@1531 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/cbm/open.s

@@ -0,0 +1,168 @@
+;
+; Ullrich von Bassewitz, 16.11.2002
+;
+; int open (const char* name, int flags, ...);	/* May take a mode argument */
+;
+
+        .export         _open
+
+        .import         addysp, popax
+        .import         scratch, fnparse, fncomplete, fnset
+        .import         getdiskerror
+        .import         __errno, __oserror
+        .import         fnunit
+        .importzp       sp, tmp2, tmp3
+
+        .include        "errno.inc"
+        .include        "fcntl.inc"
+        .include        "cbm.inc"
+        .include        "filedes.inc"
+
+
+;--------------------------------------------------------------------------
+; initstdout: Open the stdout and stderr file descriptors for the screen.
+
+.proc   _open
+
+	cpy	#4     	   	; correct # of arguments (bytes)?
+	beq	parmok 	   	; parameter count ok
+	tya	       	   	; parm count < 4 shouldn't be needed to be...
+       	sec    	       	       	; ...checked (it generates a c compiler warning)
+	sbc	#4
+	tay
+	jsr	addysp	   	; fix stack, throw away unused parameters
+
+; Parameters ok. Pop the flags and save them into tmp3
+
+parmok: jsr     popax           ; Get flags
+        sta     tmp3
+
+; Get the filename from stack and parse it. Bail out if is not ok
+
+        jsr     popax           ; Get name
+        jsr     fnparse         ; Parse it
+        cmp     #0
+        bne     error           ; Bail out if problem with name
+
+; Get a free file handle and remember it in tmp2
+
+        jsr     freefd
+        bcs     nofile
+        stx     tmp2
+
+; Check the flags. We cannot have:
+;
+;  - both, read and write flags set
+;  - the append flag set
+;
+
+        lda     tmp3
+        and     #O_RDWR
+        beq     invflags        ; Neither read nor write
+        cmp     #O_RDWR
+        beq     invflags        ; Jump if both set
+        cmp     #O_RDONLY
+        beq     doread
+
+; Write bit is set. We cannot open a file for writing without creating it,
+; so check for the O_CREAT bit.
+
+        lda     tmp3
+        and     #O_CREAT
+        beq     invflags
+
+; If O_TRUNC is set, scratch the file, but ignore any errors
+
+        lda     tmp3
+        and     #O_TRUNC
+        beq     notrunc
+        jsr     scratch
+
+; Complete the the file name
+
+notrunc:
+        lda     #'w'
+        jsr     fncomplete
+
+; Setup the real open flags
+
+        lda     #LFN_WRITE
+        bne     common
+
+; Read bit is set. Add an 'r' to the name
+
+doread: lda     #'r'
+        jsr     fncomplete
+        lda     #LFN_READ
+
+; Common read/write code. Flags in A, handle in tmp2
+
+common: sta     tmp3
+        jsr     fnset           ; Set the file name
+
+        lda     tmp2
+        clc
+        adc     #LFN_OFFS
+        ldx     fnunit
+        tay                     ; Use the LFN also as SA
+        jsr     SETLFS          ; Set the file params
+
+        jsr     OPEN
+        bcs     error
+
+; Read the error channel
+
+        ldx     fnunit
+        jsr     getdiskerror
+        cmp     #0
+        beq     isopen          ; Branch if no error
+
+; We had an error, close the file
+
+        pha
+        lda     tmp2
+        clc
+        adc     #LFN_OFFS
+        jsr     CLOSE
+        pla
+        bne     error           ; Branch always
+
+; File is open. Mark it as open in the table
+
+isopen: ldx     tmp2
+        lda     tmp3
+        sta     fdtab,x
+        lda     fnunit
+        sta     unittab,x       ; Remember
+
+; Done. Return the handle in a/x
+
+        txa                     ; Handle
+        ldx     #0
+        rts
+
+; Error entry: No more file handles
+
+nofile: lda     #1              ; Too many open files
+
+; Error entry. Error code is in A.
+
+error:  sta     __oserror
+errout: lda     #$FF
+        tax                     ; Return -1
+        rts
+
+; Error entry: Invalid flag parameter
+
+invflags:
+        lda     #EINVAL
+        sta     __errno
+        lda     #0
+        sta     __errno+1
+        beq     errout
+
+
+
+.endproc
+
+