From 4a7aad06d95701cf232198093ce396dcdbb53e5b Mon Sep 17 00:00:00 2001 From: Martin Sustrik Date: Thu, 16 Feb 2012 10:01:47 +0900 Subject: ZeroMQ renamed to Crossroads Signed-off-by: Martin Sustrik --- doc/xs_poll.txt | 129 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 129 insertions(+) create mode 100644 doc/xs_poll.txt (limited to 'doc/xs_poll.txt') diff --git a/doc/xs_poll.txt b/doc/xs_poll.txt new file mode 100644 index 0000000..37f7dc5 --- /dev/null +++ b/doc/xs_poll.txt @@ -0,0 +1,129 @@ +xs_poll(3) +========== + + +NAME +---- +xs_poll - input/output multiplexing + + +SYNOPSIS +-------- + +*int xs_poll (xs_pollitem_t '*items', int 'nitems', long 'timeout');* + + +DESCRIPTION +----------- +The _xs_poll()_ function provides a mechanism for applications to multiplex +input/output events in a level-triggered fashion over a set of sockets. Each +member of the array pointed to by the 'items' argument is a *xs_pollitem_t* +structure. The 'nitems' argument specifies the number of items in the 'items' +array. The *xs_pollitem_t* structure is defined as follows: + +["literal", subs="quotes"] +typedef struct +{ + void '*socket'; + int 'fd'; + short 'events'; + short 'revents'; +} xs_pollitem_t; + +For each *xs_pollitem_t* item, _xs_poll()_ shall examine either the Crossroads +socket referenced by 'socket' *or* the standard socket specified by the file +descriptor 'fd', for the event(s) specified in 'events'. If both 'socket' and +'fd' are set in a single *xs_pollitem_t*, the Crossroads socket referenced by +'socket' shall take precedence and the value of 'fd' shall be ignored. + +For each *xs_pollitem_t* item, _xs_poll()_ shall first clear the 'revents' +member, and then indicate any requested events that have occurred by setting the +bit corresponding to the event condition in the 'revents' member. + +If none of the requested events have occurred on any *xs_pollitem_t* item, +_xs_poll()_ shall wait 'timeout' milliseconds for an event to occur on +any of the requested items. If the value of 'timeout' is `0`, _xs_poll()_ +shall return immediately. If the value of 'timeout' is `-1`, _xs_poll()_ shall +block indefinitely until a requested event has occurred on at least one +*xs_pollitem_t*. + +The 'events' and 'revents' members of *xs_pollitem_t* are bit masks constructed +by OR'ing a combination of the following event flags: + +*XS_POLLIN*:: +For Crossroads sockets, at least one message may be received from the 'socket' +without blocking. For standard sockets this is equivalent to the 'POLLIN' flag +of the _poll()_ system call and generally means that at least one byte of data +may be read from 'fd' without blocking. + +*XS_POLLOUT*:: +For Crossroads sockets, at least one message may be sent to the 'socket' without +blocking. For standard sockets this is equivalent to the 'POLLOUT' flag of the +_poll()_ system call and generally means that at least one byte of data may be +written to 'fd' without blocking. + +*XS_POLLERR*:: +For standard sockets, this flag is passed through _xs_poll()_ to the +underlying _poll()_ system call and generally means that some sort of error +condition is present on the socket specified by 'fd'. For Crossroads sockets +this flag has no effect if set in 'events', and shall never be returned in +'revents' by _xs_poll()_. + +NOTE: The _xs_poll()_ function may be implemented or emulated using operating +system interfaces other than _poll()_, and as such may be subject to the limits +of those interfaces in ways not defined in this documentation. + + +RETURN VALUE +------------ +Upon successful completion, the _xs_poll()_ function shall return the number +of *xs_pollitem_t* structures with events signaled in 'revents' or `0` if no +events have been signaled. Upon failure, _xs_poll()_ shall return `-1` and set +'errno' to one of the values defined below. + + +ERRORS +------ +*ETERM*:: +At least one of the members of the 'items' array refers to a 'socket' whose +associated 'context' was terminated. +*EFAULT*:: +The provided 'items' was not valid (NULL). +*EINTR*:: +The operation was interrupted by delivery of a signal before any events were +available. + + +EXAMPLE +------- +.Polling indefinitely for input events on both a Crossroads socket and a standard socket. +---- +xs_pollitem_t items [2]; +/* First item refers to Crossroads socket 'socket' */ +items[0].socket = socket; +items[0].events = XS_POLLIN; +/* Second item refers to standard socket 'fd' */ +items[1].socket = NULL; +items[1].fd = fd; +items[1].events = XS_POLLIN; +/* Poll for events indefinitely */ +int rc = xs_poll (items, 2, -1); +assert (rc >= 0); +/* Returned events will be stored in items[].revents */ +---- + + +SEE ALSO +-------- +linkxs:xs_socket[3] +linkxs:xs_send[3] +linkxs:xs_recv[3] +linkxs:xs[7] + +Your operating system documentation for the _poll()_ system call. + + +AUTHORS +------- +The Crossroads documentation was written by Martin Sustrik +and Martin Lucina . -- cgit v1.2.3