The optional iofunc_mount_t (mount) structure

The members of the mount structure, specifically the conf and flags members, modify the behavior of some of the iofunc layer functions.

If you need to modify any members of the mount structure, use iofunc_mount_init() to initialize it.

For example, your program saves files to a file system. You can use iofunc_mount_init() and iofunc_mount_set_time() to set a timestamp resolution for open files that matches the resolution the file system uses (a POSIX requirement).

The iofunc_mount_t structure is optional and contains at least the following:

typedef struct _iofunc_mount {
    uint32_t            flags;
    uint32_t            conf;
    dev_t               dev;
    int32_t             blocksize;
    iofunc_funcs_t      *funcs;
    void                *power;
    
    size_t              size;
    uint32_t            ext_flags;
    uint32_t            timeres;
    uint64_t            reserved[4];    
} iofunc_mount_t;

The variables are:

flags

Contains one relevant bit (manifest constant IOFUNC_MOUNT_32BIT), which indicates that the offsets used by this resource manager are 32-bit (as opposed to the extended 64-bit offsets). The user-modifiable mount flags are defined as IOFUNC_MOUNT_FLAGS_PRIVATE (see <sys/iofunc.h>).

conf

Contains several bits:

IOFUNC_PC_CHOWN_RESTRICTED

Causes the default handler for the _IO_CHOWN message to behave in a manner defined by POSIX as “chown-restricted”.

IOFUNC_PC_NO_TRUNC

Has no effect on the iofunc layer libraries, but is returned by the iofunc layer's default _IO_PATHCONF handler.

IOFUNC_PC_SYNC_IO

Indicates that the filesystem supports synchronous I/O operations. If this bit isn't set, the following may occur:

• The default iofunc layer _IO_OPEN handler, iofunc_open_default(), fails if the client specifies O_DSYNC, O_RSYNC, or O_SYNC.
• The iofunc_sync_verify() function returns EINVAL.
• Attempts to set O_DSYNC, O_RSYNC, or O_SYNC with fcntl() or the DCMD_ALL_SETFLAGS devctl() command fail.

IOFUNC_PC_LINK_DIR

Controls whether or not root is allowed to link and unlink directories.

IOFUNC_PC_ACL

Indicates whether or not the resource manager supports access control lists. For more information about ACLs, see Working with Access Control Lists (ACLs) in the QNX Neutrino Programmer's Guide.

IOFUNC_PC_EXT

Set automatically when iofunc_mount_init() is called to set the iofunc_mount_t structure.

Note that the options mentioned above for the conf member are returned by the iofunc layer _IO_PATHCONF default handler.

dev

Contains the device number for the filesystem. This number is returned to the client's stat() function in the struct stat st_dev member.

blocksize

Contains the block size of the device. On filesystem types of resource managers, this indicates the native blocksize of the disk, e.g., 512 bytes.

funcs

Contains the following structure:

struct _iofunc_funcs {
   unsigned     nfuncs;
   IOFUNC_OCB_T *(*ocb_calloc) (resmgr_context_t *ctp,
                                IOFUNC_ATTR_T *attr);
   void         (*ocb_free) (IOFUNC_OCB_T *ocb);
   int          (*attr_lock)(IOFUNC_ATTR_T *attr);
   int          (*attr_unlock)(IOFUNC_ATTR_T *attr);
   int          (*attr_trylock)(IOFUNC_ATTR_T *attr);

};

where:

nfuncs

Indicates the number of functions present in the structure; you should fill it with the manifest constant _IOFUNC_NFUNCS.

ocb_calloc() and ocb_free()

Allows you to override the OCBs on a per-mountpoint basis (see “Extending the OCB and attribute structures” in the Extending the POSIX-Layer Data Structures chapter). If these members are NULL, then the default library versions (iofunc_ocb_calloc() and iofunc_ocb_free()) are used. You must specify either both or neither of these functions; they operate as a matched pair.

attr_lock(), attr_unlock() and attr_trylock()

Allows you to create customized versions of the functions that lock, unlock, and attempt to lock the attribute structure.

power

Reserved for future use.

size

Contains the size of the iofunc_mount_t function. Set by iofunc_mount_init().

ext_flags

Extends the range of possible flags values.

timeres

Contains the timestamp resolution for iofunc functions and structures. Set by iofunc_mount_set_time().

reserved

Reserved for future use.