iofunc_fdinfo_default()

Default handler for _IO_FDINFO messages

Synopsis:

#include <sys/iomgr.h>

int iofunc_fdinfo_default( resmgr_context_t * ctp, 
                  io_fdinfo_t * msg, 
                  iofunc_ocb_t * ocb );

Arguments:

ctp

A pointer to a resmgr_context_t structure that the resource-manager library uses to pass context information between functions.

msg

A pointer to the io_fdinfo_t structure that contains the message that the resource manager received; see below.

ocb

A pointer to the iofunc_ocb_t structure for the Open Control Block that was created when the client opened the resource.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The iofunc_fdinfo_default() function provides the default handler for the client's iofdinfo() call, which is received as an _IO_FDINFO message by the resource manager.

You can place this function directly into the io_funcs table passed to resmgr_attach(), at the fdinfo position, or you can call iofunc_func_init() to initialize all of the functions to their default values.

The iofunc_fdinfo_default() function calls iofunc_fdinfo() and resmgr_pathname() to do the actual work.

io_fdinfo_t structure

The io_fdinfo_t structure holds the _IO_FDINFO message received by the resource manager:

struct _io_fdinfo {
    uint16_t                    type;
    uint16_t                    combine_len;
    uint32_t                    flags;
    int32_t                     path_len;
    uint32_t                    reserved;
};

struct _io_fdinfo_reply {
    uint32_t                    zero[2];
    struct _fdinfo              info;
/*  char                        path[path_len + 1];  */
};

typedef union {
    struct _io_fdinfo           i;
    struct _io_fdinfo_reply     o;
} io_fdinfo_t;

The I/O message structures are unions of an input message (coming to the resource manager) and an output or reply message (going back to the client).

The i member is a structure of type _io_fdinfo that contains the following members:

type

_IO_FDINFO.

combine_len

If the message is a combine message, _IO_COMBINE_FLAG is set in this member. For more information, see Combine Messages chapter of Writing a Resource Manager.

flags

Specify _FDINFO_FLAG_LOCALPATH to return only the local path info (i.e. exclude the network path info).

path_len

The size of the path reply buffers that follow the reply.

The o member is a structure of type _io_fdinfo_reply that contains the following members:

info

A _fdinfo structure that's defined (in <sys/iomgr.h>) as:

struct _fdinfo {
    uint32_t     mode;   /* File mode */
    uint32_t     ioflag; /* Current io flags */
    uint64_t     offset; /* Current seek position */
    uint64_t     size;   /* Current size of file */
    uint32_t     flags;  /* _FDINFO_* */
    uint16_t     sflag;  /* Share flags */
    uint16_t     count;  /* File use count */
    uint16_t     rcount; /* File reader count */
    uint16_t     wcount; /* File writer count */
    uint16_t     rlocks; /* Number of read locks */
    uint16_t     wlocks; /* Number of write locks */
    uint32_t     zero[6];
};
  

The commented-out declaration for path indicates that path_len + 1 bytes of data immediately follow the _io_fdinfo_reply structure.

Returns:

-1

Success; the resource manager library should return a one-part IOV to the client.

EMSGSIZE

Insufficient space is available in the server's buffer to receive the entire message.

Classification:

QNX Neutrino

See also:

iofdinfo(), iofunc_fdinfo_default(), iofunc_func_init(), iofunc_ocb_t, resmgr_attach(), resmgr_context_t, resmgr_io_funcs_t, _RESMGR_NPARTS(), resmgr_pathname()

Writing a Resource Manager

Resource Managers chapter of Getting Started with QNX Neutrino