;
; Oliver Schmidt, 30.12.2004
;
; File descriptor management for the POSIX I/O routines
;

        .include	"errno.inc"
        .include	"fcntl.inc"
        .include	"filedes.inc"

getfd:
        ; Check for handle >= 256
        cpx	#$00
        bne	error

        ; Check for handle >= MAX_FDS
        cmp	#MAX_FDS
        bcs	error

        ; Convert handle to fdtab slot
        .assert .sizeof(FD) = 4, error
        asl
        asl

        ; Check for fdtab slot in use
        tay
        lda	fdtab + FD::REF_NUM,y
        beq	error

        ; Return success
        clc
        rts

        ; Load errno code and return error
error:  lda	#EINVAL
        sec
        rts

        .data

fdtab:  .assert .sizeof(FD) = 4, error

        .byte	$80		; STDIN_FILENO ::REF_NUM
        .byte	O_RDONLY	; STDIN_FILENO ::FLAGS
        .addr	$0000		; STDIN_FILENO ::BUFFER

        .byte	$80		; STDOUT_FILENO::REF_NUM
        .byte	O_WRONLY	; STDOUT_FILENO::FLAGS
        .addr	$0000		; STDOUT_FILENO::BUFFER

        .byte	$80		; STDERR_FILENO::REF_NUM
        .byte	O_WRONLY	; STDERR_FILENO::FLAGS
        .addr	$0000		; STDERR_FILENO::BUFFER

        .res	(MAX_FDS - 3) * .sizeof(FD)
