srv_poll (UNIX only)

Description

Check for I/O events on file descriptors for a set of open streams.

Syntax

CS_INT srv_poll(fdsp, nfds, waitflag)

SRV_POLLFD         *fdsp;
CS_INT                   nfds;
CS_INT                 waitflag;

Parameters

fdsp: A pointer to an array of SRV_POLLFD structures with one element for each open file descriptor of interest. The SRV_POLLFD structure has the following members:

CS_INT srv_fd; /* File descriptor. */

CS_INT srv_events; /* Relevant events. */

CS_INT srv_revents; /* Returned events. */

nfds: The number of elements in the *fdsp array.

waitflag: A CS_INT value that indicates whether the thread should be suspended until a file descriptor is available for the desired operation. If set to SRV_M_WAIT, the thread is suspended and will wake when any file descriptor represented in the *fdsp array is available for the specified operation. If the flag is set to SRV_M_NOWAIT, srv_poll will perform a single check and return to the caller. A return status greater than zero indicates that a file descriptor was available for the desired operation.

Returns

**Table 3-82: Return values (srv_poll)**
Returns	To indicate
An integer	The number of &ready file descriptors.
-1	The routine failed.
0	No file descriptors are &ready.

Examples

Example 1

#include   <ospublic.h>

/*

** Local Prototype

*/

CS_RETCODE      ex_srv_pollPROTOTYPE((

struct pollfd   *fdp,

CS_INT          nfds

));

/*

** EX_SRV_POLL

**

**   This routine demonstrates how to use srv_poll to poll

**   application-specific file descriptors.

**

** Arguments:

**         fdp - The address of the file descriptor array.

**         nfds - The number of file descriptors to poll.

**

** Returns

**

**    CS_SUCCEED    If the data address is returned.

**    CS_FAIL       If the call to srv_poll failed.

**

*/

CS_RETCODE      ex_srv_poll(fdp, nfds)

struct pollfd   *fdp;

CS_INT          nfds;

/*

      ** Initialization.

*/

      lp = (CS_VOID *)NULL;

/*

      ** Calls srv_poll to check if any of these file

      ** descriptors are active; ask to sleep until at

      ** least one of them is.

*/

      if( srv_poll(fdp, nfds, SRV_M_WAIT) == (CS_INT)-1 )

          return CS_FAIL;

/*

      ** All done.

*/

      return CS_SUCCEED;

Usage

An application can use srv_poll to poll the file descriptor or to suspend a thread until there is I/O to be performed.

Table 3-83 summarizes legal values for srv_events and srv_revents:

**Table 3-83: Values for srv_events and revents (srv_poll)**
Value	Description
SRV_POLLIN	Normal read event.
SRV_POLLPRI	Priority event received.
SRV_POLLOUT	File descriptor is writable.
SRV_POLLERR	Error occurred on file descriptor.
SRV_POLLHUP	A hang up occurred on the file descriptor. This value is valid in returned events only.
SRV_POLLNVAL	Invalid file descriptor specified in SRV_POLLFD.

srv_poll is available on all UNIX platforms.

If an application uses srv_poll on a UNIX platform that supports the native poll(2) system call, the application must include <sys/poll.h> before ospublic.h.