On filesystems

Some PalmOS thigns will not work on DGOS. Specifically I am talking about SlotDrivers and FsLibs. Why? Specifically because:

• In DGOS, for efficiency reasons, the driver model is differet from PalmOS
• Drivers are in kernel space in DGOS, so they can make very quick system calls, and admitting any PalmOS code into kernel space is a bad idea because it was never written to be even thread safe
• Porting an existing driver to DGOS is not hard

Filesystems are created as a kernel module, and register themselves with the DGOS kernel using the vfsRegisterFs() function, which takes, as a parameter, a pointer to a VfsFS structure. This structure is a table of function pointers and an FS name.

The module provides this, and from then on, until it is unregistered using vfsUnregisterFs(), it can be used to mount and format filesystems.

Here it is in details:

#define VFS_OPEN_MODE_READ                  1
#define VFS_OPEN_MODE_RW                    2
#define VFS_OPEN_MODE_EXCLUSIVE             4

#define VFS_SEEK_SET                        0
#define VFS_SEEK_CUR                        1
#define VFS_SEEK_END                        2

#define FILE_ATTR_HIDDEN                    0x00000001
#define FILE_ATTR_SYSTEM                    0x00000002
#define FILE_ATTR_READONLY                  0x00000004
#define FILE_ATTR_ARCHIVE                   0x00000008

#define VFS_FS_NAME_SZ                      16

typedef Err (*VfsVolInitFn)        (void** fsData);
typedef Err (*VfsVolDeinitFn)      (void* fsData);

typedef Err (*VfsFsMountFn)        (void* fsData,UInt32 blkDev);
typedef Err (*VfsFsUnmountFn)      (void* fsData);
typedef Err (*VfsFsSizesFn)        (void* fsData,UInt64* free,UInt64* used,UInt64* total);    //in bytes
typedef Err (*VfsFsInfoFn)         (void* fsData,VfsFsInfo* info);
typedef Err (*VfsFsCreate)         (void* fsData,UInt32 blkDev);
typedef Err (*VfsFsGetLabel)       (void* fsData,wchar_t* label,UInt32* size /* in / out */);
typedef Err (*VfsFsSetLabel)       (void* fsData,const wchar_t* label);

typedef Err (*VfsFileCreateFn)     (void* fsData,const wchar_t* path);
typedef Err (*VfsFileDeleteFn)     (void* fsData,const wchar_t* path);
typedef Err (*VfsFileRenameFn)     (void* fsData,const wchar_t* oldPath,const wchar_t* newPath);        //MUST handle moving files too, not just renaming

typedef Err (*VfsFileOpenFn)       (void* fsData,const wchar_t* path,UInt32 mode,void** openFileData);
typedef Err (*VfsFileCloseFn)      (void* fsData,void* openFileData);
typedef Err (*VfsFileReadFn)       (void* fsData,void* openFileData,void* buf,UInt32 bytes,UInt32* done);
typedef Err (*VfsFileWriteFn)      (void* fsData,void* openFileData,const void* buf,UInt32 bytes,UInt32* done);
typedef Err (*VfsFileSeekFn)       (void* fsData,void* openFileData,UInt32 whence,Int32 offset);
typedef Err (*VfsFileTellFn)       (void* fsData,void* openFileData,UInt32* position);
typedef Err (*VfsFileGetAttrFn)    (void* fsData,void* openFileData,UInt32* attr);
typedef Err (*VfsFileSetAttrFn)    (void* fsData,void* openFileData,UInt32 attr);
typedef Err (*VfsFileGetDateFn)    (void* fsData,void* openFileData,UInt32* create,UInt32* mod,UInt32* access);    //null to not get
typedef Err (*VfsFileSetDateFn)    (void* fsData,void* openFileData,UInt32* create,UInt32* mod,UInt32* access);    //null to not set
typedef Err (*VfsFileGetSizeFn)    (void* fsData,void* openFileData,UInt32* sz);
typedef Err (*VfsFileSetSizeFn)    (void* fsData,void* openFileData,UInt32 sz);

typedef Err (*VfsDirCreateFn)      (void* fsData,const wchar_t* path);
typedef Err (*VfsDirDeleteFn)      (void* fsData,const wchar_t* path);
typedef Err (*VfsDirOpenFn)        (void* fsData,const wchar_t* path,void** openDirData);
typedef Err (*VfsDirCloseFn)       (void* fsData,void* openDirData);
typedef Err (*VfsDirEnumeFn)       (void* fsData,void* openDirData,UInt32* iterator,VfsDirEntry* entry);

typedef struct{
    
    wchar_t                 fsName[VFS_FS_NAME_SZ];
    
    //vol ops
    VfsVolInitFn            volInit;
    VfsVolDeinitFn          volDeinit;
    
    //FS ops
    VfsFsMountFn            fsMount;
    VfsFsUnmountFn          fsUnmount;
    VfsFsSizesFn            fsSizes;        //used,free,total
    VfsFsInfoFn             fsInfo;
    VfsFsCreate             fsCreate;       //format a disk
    VfsFsGetLabel           fsGetLabel;
    VfsFsSetLabel           fsSetLabel;
    
    //ops on unopened files
    VfsFileCreateFn         fileCreate;
    VfsFileDeleteFn         fileDelete;
    VfsFileRenameFn         fileRename;
    
    //ops on opened files
    VfsFileOpenFn           fileOpen;
    VfsFileCloseFn          fileClose;
    VfsFileReadFn           fileRead;
    VfsFileWriteFn          fileWrite;
    VfsFileSeekFn           fileSeek;
    VfsFileTellFn           fileTell;
    VfsFileGetAttrFn        fileGetAttr;
    VfsFileSetAttrFn        fileSetAttr;
    VfsFileGetDateFn        fileGetDates;
    VfsFileSetDateFn        fileSetDates;
    VfsFileGetSizeFn        fileGetSize;
    VfsFileSetSizeFn        fileSetSize;    //resize
    
    //ops on unopened dirs
    VfsDirCreateFn          dirCreate;
    VfsDirDeleteFn          dirDelete;
    
    //open on open dirs
    VfsDirOpenFn            dirOpen;
    VfsDirCloseFn           dirClose;
    VfsDirEnumeFn           dirEnumerate;
    
}VfsFS;