source: buchla-68k/orig/DOC/FILESYS.TXT@ fa38804

filesys.c -- file system support functions
Version 11 -- 1987-06-03 -- D.N. Lynx Crowe

These functions support a {MS,GEM}DOS-like file system.
Subdirectories are not supported in this version.

Variables:
----------

        struct  bpb     *_thebpb;
        struct  dirent  _thedir[MAXDIRNT];
        struct  dirent  *_dptr;

        short   _thefat[MAXFAT * WDPSEC];

        int     _fatin, _dirin, _bpbin;
        long    _berrno;

Functions:
----------

        ClusMap(fcp)
        SnapFCB(fcp)

        _cl2lsn(bpp, clnum)
        _deadio(fcp)
        _dsrch(de)
        _fmake(fcp)
        _fsize(fcp)
        _ftrnc(dp)
        _getfat(bufad, bpp, nfat)
        _gtcl12(fat, cl)
        _inifcb(fcp, name,ext, mode)
        _nsic(fcp, bpp, fp)
        _opfcb(fcp)
        _ptcl12(fat, cl, val)
        _rdfat(bufad, bpp)
        _rdroot(buf, bpp)
        _rdsec(fcp, buf, ns)
        _seek(fcp)
        _sksec(fcp, sec)


_cl2lsn(bpp, clnum)

        Returns the logical sector number for cluster 'clnum' using the BPB
        pointed to by 'bpp'.

        int
        _cl2lsn(bpp, clnum)
        struct bpb *bpp;
        int clnum;


_ptcl12(fat, cl, val)

        Puts 'val' into cluster 'cl' in the FAT at 'fat'.

        putlc12(fat, cl, val)
        register char *fat;
        int cl, val;

_gtcl12(fat, cl)

        Returns the 12 bit cluster entry 'cl' from the FAT pointed to by 'fat'.

        int
        _gtcl12(fat, cl)
        register char *fat;
        int cl;


_getfat(bufad, bpp, nfat)

        Gets the FAT 'nfat' into the buffer pointed to by 'bufad' using
        the BPB pointed to by 'bpp'.

        int
        _getfat(bufad, bpp, nfat)
        int *bufad, nfat;
        register struct bpb *bpp;

_rdfat(bufad, bpp)

        Reads the FAT into the buffer pointed to by 'bufad'using the BPB
        pointed to by 'bpp'.

        int
        _rdfat(bufad, bpp)
        int *bufad;
        struct bpb *bpp;

_rdroot(buf, bpp)

        Reads the root directory into the buffer pointed to by 'buf'
        using the BPB pointed to by 'bpp'.

        int
        _rdroot(buf, bpp)
        int *buf;
        register struct bpb *bpp;

_nsic(fcp, bpp, fp)

        Gets the next sector in the file controlled by the FCB at 'fcp',
        using the BPB pointed to by 'bpp' and the FAT pointed to by 'fp'.
        Returns:  0 if successful, -1 on error, or 1 on EOF;

        int
        _nsic(fcp, bpp, fp)
        register struct fcb *fcp;
        struct bpb *bpp;
        char *fp;

_dsrch(de)

        Searches for the directory entry pointed to by 'de' in
        the current directory.

        struct dirent *
        _dsrch(de)
        register struct dirent *de;


_deadio(fcp)

        Marks the FCB pointed to by 'fcp' as 'in error'.

        _deadio(fcp)
        register struct fcb *fcp;

_seek(fcp)

        Seeks to to logical sector number in FCB pointed to by 'fcp'
        Returns:  -1 = error, 0 = OK, 1 = EOF.

        int
        _seek(fcp)
        register struct fcb *fcp;

_ftrnc(dp)

        Truncates the file pointed to by directory entry 'dp'.

        int
        _ftrnc(dp)
        struct dirent *dp;

_fmake(fcp)

        Makes a new file from the FCB pointed to by 'fcp'.

        int
        _fmake(fcp)
        struct fcb *fcp;

_opfcb(fcp)

        Opens the FCB pointed to by 'fcp'.  Returns 0 if opened successfully,
        -1 if an error occurred, with the error code in errno.

        int
        _opfcb(fcp)
        register struct fcb *fcp;

_inifcb(fcp, name,ext, mode)

        Initializes the FCB pointed to by 'fcp' for the file named 'name'.'ext'
        in mode 'mode'.  Returns 0 if ok, -1 if not.

        int
        _inifcb(fcp, name, ext, mode)
        register struct fcb *fcp;
        char *name, *ext;
        int mode;


_sksec(fcp, sec)

        Seeks the FCB pointed to by 'fcp' to sector 'sec'.
        Returns: -1 = error, 0 = OK, 1 = EOF

        int
        _sksec(fcp, sec)
        struct fcb *fcp;
        long sec;

_fsize(fcp)

        Returns the size, in sectors, of the file associated with
        the FCB pointed to by 'fcp', or -1 if the FCB isn't open.

        int
        _fsize(fcp)
        struct fcb *fcp;

_rdsec(fcp, buf, ns)

        Reads 'ns' sectors into the buffer at 'buf' from the file associated
        with the FCB pointed to b 'fcp'.  Returns 0 if OK, -1 if not.

        int
        _rdsec(fcp, buf, ns)
        struct fcb *fcp;
        char *buf;
        long ns;

ClusMap(fcp)

        Prints a map of the clusters for the file associated with
        the FCB pointed to by 'fcp'.  Ignored if file isn't open.
        Returns 0 if map was printed, -1 otherwise.

        int
        ClusMap(fcp)
        struct fcb *fcp;

SnapFCB(fcp)

        Prints the contents of an FCB pointed to by 'fcp'.  Only included
        in test versions of 'filesys.c' where TESTER is defined non-zero.

        SnapFCB(fcp)
        struct fcb *fcp;