BBC BASIC Programmers' Reference

Unicode filenames

by Richard Russell, October 2016

Although BBC BASIC for Windows includes limited support for Unicode (UTF-8) strings, this support does not extend to directory and file names. Even if you explicitly select UTF-8 as the character set in a VDU 23,22 command, all the native statements and functions that require a path or a directory name still expect to receive them as ANSI strings. This is obviously a limitation if you want to access files or directories whose names include non-ASCII characters.

To solve this problem I have listed below a number of replacement routines that can be used instead of the native equivalents. No replacement for OPENOUT is listed; it will normally be easier to create the file initially with an ASCII name and then to use PROCrenameUTF8 to change the name to the required Unicode form.

OPENIN:

        DEF FNopeninUTF8(utf8$)
        LOCAL A%, R%, S%, W%
        DIM A% LOCAL 260, W% LOCAL 521, S% LOCAL 521
        SYS "MultiByteToWideChar", &FDE9, 0, utf8$, -1, W%, 260
        SYS "GetShortPathNameW", W%, S%, 260 TO R%
        IF R% = 0 THEN = 0
        SYS "WideCharToMultiByte", 0, 0, S%, -1, A%, 260, 0, 0
        = OPENIN($$A%)

OPENUP:

        DEF FNopenupUTF8(utf8$)
        LOCAL A%, R%, S%, W%
        DIM A% LOCAL 260, W% LOCAL 521, S% LOCAL 521
        SYS "MultiByteToWideChar", &FDE9, 0, utf8$, -1, W%, 260
        SYS "GetShortPathNameW", W%, S%, 260 TO R%
        IF R% = 0 THEN = 0
        SYS "WideCharToMultiByte", 0, 0, S%, -1, A%, 260, 0, 0
        = OPENUP($$A%)

DELETE/ERASE:

        DEF PROCdeleteUTF8(utf8$)
        LOCAL W%
        DIM W% LOCAL 521
        SYS "MultiByteToWideChar", &FDE9, 0, utf8$, -1, W%, 260
        SYS "DeleteFileW", W%
        ENDPROC

*RENAME:

        DEF PROCrenameUTF8(old$, new$)
        LOCAL O%, N%
        DIM O% LOCAL 521, N% LOCAL 521
        SYS "MultiByteToWideChar", &FDE9, 0, old$, -1, O%, 260
        SYS "MultiByteToWideChar", &FDE9, 0, new$, -1, N%, 260
        SYS "MoveFileW", O%, N%
        ENDPROC

*MKDIR:

        DEF PROCmkdirUTF8(utf8$)
        LOCAL W%
        DIM W% LOCAL 521
        SYS "MultiByteToWideChar", &FDE9, 0, utf8$, -1, W%, 260
        SYS "CreateDirectoryW", W%, 0
        ENDPROC

*CHDIR:

        DEF PROCchdirUTF8(utf8$)
        LOCAL W%
        DIM W% LOCAL 521
        SYS "MultiByteToWideChar", &FDE9, 0, utf8$, -1, W%, 260
        SYS "SetCurrentDirectoryW", W%
        ENDPROC

*RMDIR:

        DEF PROCrmdirUTF8(utf8$)
        LOCAL W%
        DIM W% LOCAL 521
        SYS "MultiByteToWideChar", &FDE9, 0, utf8$, -1, W%, 260
        SYS "RemoveDirectoryW", W%
        ENDPROC

Note that none of these routines generates an error if, for example, the specified file does not exist. If you require this functionality you can easily check the value returned from the relevant API function to check whether it was successful or not (generally a non-zero returned value will signify success and zero will signify failure).

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