CheckFile

Synopsis

error = CheckFile(filename, buffer)
 D0                  A0       A1

C Prototype

LONG CheckFile(STRPTR filename, STRPTR errorstring);

Description

Allows checking the status of a file. The file is opened in MODE_OLDFILE; if everything is fine, it returns NULL as the result. Otherwise, it returns the error code from dos.library/IoErr().

In addition to returning the error code, CheckFile() can also provide an associated error text by calling dos.library/Fault(). This is done by providing a buffer, which will be filled with the text of the associated error. However, you should always refer to the return error code to determine whether an error actually occurred.

The buffer pointer must be at least 80 characters long. The string will be NULL-terminated. The buffer pointer is not mandatory; if left as zero, it has no effect, and it will be the task’s responsibility to display the error as text.

The error text is linked to the system LOCALE, so the error string is in the language chosen in the system preferences.

Inputs

• filename — Pointer to a string containing the path and name of the file to check.
• buffer — OPTIONAL parameter. Address of a buffer, minimum 80 characters, that will contain the string describing the error in the system language.

Result

• error — NULL if no error occurred. Otherwise, an error code is returned via dos.library/IoErr().

See Also

dos.library/IoErr(), dos.library/Fault(), dos.library/PrintFault()

Implementation

The original 68020 assembly implementation:

; (02-Mar-1995) --- error = CheckFile(filename,buffer) (a0/a1)
_LVOCheckFile
        movem.l d2-d6/a6,-(sp)
        move.l  a1,d6                    ; Save Buffer
        move.l  ab_DosBase(a6),a6
        move.l  a0,d1
        lea     MODE_OLDFILE.W,A0
        move.l  a0,d2
        jsr     _LVOOpen(a6)
        tst.l   d0
        bne.s   CK_CLO
        jsr     _LVOIoErr(a6)
        move.l  d0,d5
CKGOERR move.l  d6,d3                    ; output buffer
        beq.s   CK_NTX
        move.l  d5,d1                    ; Error code
        moveq   #0,d2                    ; header buffer null
        moveq   #80,d4
        jsr     _LVOFault(a6)
        move.l  d5,d0
CK_NTX  movem.l (sp)+,d2-d6/a6
        rts
CK_CLO  move.l  d0,d1
        jsr     _LVOClose(a6)
        moveq   #0,d0
        movem.l (sp)+,d2-d6/a6
        rts