lib/poll-loop.h

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2011 Nicira Networks.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 /* High-level wrapper around the "poll" system call.
  18  *
  19  * Intended usage is for the program's main loop to go about its business
  20  * servicing whatever events it needs to.  Then, when it runs out of immediate
  21  * tasks, it calls each subordinate module's "wait" function, which in turn
  22  * calls one (or more) of the functions poll_fd_wait(), poll_immediate_wake(),
  23  * and poll_timer_wait() to register to be awakened when the appropriate event
  24  * occurs.  Then the main loop calls poll_block(), which blocks until one of
  25  * the registered events happens. */
  26
  27 #ifndef POLL_LOOP_H
  28 #define POLL_LOOP_H 1
  29
  30 #include <poll.h>
  31 #include "util.h"
  32
  33 #ifdef  __cplusplus
  34 extern "C" {
  35 #endif
  36
  37 struct poll_waiter;
  38
  39 /* Schedule events to wake up the following poll_block().
  40  *
  41  * The poll_loop logs the 'where' argument to each function at "debug" level
  42  * when an event causes a wakeup.  Ordinarily, it is automatically filled in
  43  * with the location in the source of the call, and caller should therefore
  44  * omit it.  But, if the function you are implementing is very generic, so that
  45  * its location in the source would not be very helpful for debugging, you can
  46  * avoid the macro expansion and pass a different argument, e.g.:
  47  *      (poll_fd_wait)(fd, events, where);
  48  * See timer_wait() for an example.
  49  */
  50 struct poll_waiter *poll_fd_wait(int fd, short int events, const char *where);
  51 #define poll_fd_wait(fd, events) poll_fd_wait(fd, events, SOURCE_LOCATOR)
  52
  53 void poll_timer_wait(long long int msec, const char *where);
  54 #define poll_timer_wait(msec) poll_timer_wait(msec, SOURCE_LOCATOR)
  55
  56 void poll_timer_wait_until(long long int msec, const char *where);
  57 #define poll_timer_wait_until(msec) poll_timer_wait_until(msec, SOURCE_LOCATOR)
  58
  59 void poll_immediate_wake(const char *where);
  60 #define poll_immediate_wake() poll_immediate_wake(SOURCE_LOCATOR)
  61
  62 /* Wait until an event occurs. */
  63 void poll_block(void);
  64
  65 /* Cancel a file descriptor callback or event. */
  66 void poll_cancel(struct poll_waiter *);
  67
  68 #ifdef  __cplusplus
  69 }
  70 #endif
  71
  72 #endif /* poll-loop.h */