Access to external files.

• §1. API
• §2. Errors

§1. API. The 16-bit architecture does not allow for any external file I/O at all, so these functions essentially refuse to do anything. Note that FileIO_GetC returns end-of-file at all times, thus treating all files as if empty.

[ FileIO_Exists extf; rfalse; ];
[ FileIO_Ready extf; rfalse; ];
[ FileIO_GetC extf; return -1; ];
[ FileIO_PutTable extf tab;
    return FileIO_Error(extf, "external files cannot be used in the Z-machine");
];
[ FileIO_MarkReady extf status; FileIO_PutTable(extf); ];
[ FileIO_GetTable extf tab; FileIO_PutTable(extf); ];
[ FileIO_PrintContents extf; FileIO_PutTable(extf); ];
[ FileIO_PutContents extf; FileIO_PutTable(extf); ];

§2. Errors. This could be used for I/O errors of all kinds, but in fact we only need one: see above.

[ FileIO_Error extf err_text  struc;
    if ((extf < 1) || (extf > NO_EXTERNAL_FILES)) {
        print "^*** Error on unknown file: ", (string) err_text, " ***^";
    } else {
        struc = TableOfExternalFiles-->extf;
        print "^*** Error on file '",
            (string) struc-->AUXF_FILENAME, "': ",
            (string) err_text, " ***^";
    }
    IssueRTP("FileIOFailed", "Error handling external file.", BasicInformKitRTPs);
    return 0;
];