release/src/router/dnscrypt/src/libevent/include/event2/thread.h

   1 /*
   2  * Copyright (c) 2008-2012 Niels Provos and Nick Mathewson
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  * 3. The name of the author may not be used to endorse or promote products
  13  *    derived from this software without specific prior written permission.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26 #ifndef _EVENT2_THREAD_H_
  27 #define _EVENT2_THREAD_H_
  28
  29 /** @file event2/thread.h
  30
  31   Functions for multi-threaded applications using Libevent.
  32
  33   When using a multi-threaded application in which multiple threads
  34   add and delete events from a single event base, Libevent needs to
  35   lock its data structures.
  36
  37   Like the memory-management function hooks, all of the threading functions
  38   _must_ be set up before an event_base is created if you want the base to
  39   use them.
  40
  41   Most programs will either be using Windows threads or Posix threads.  You
  42   can configure Libevent to use one of these event_use_windows_threads() or
  43   event_use_pthreads() respectively.  If you're using another threading
  44   library, you'll need to configure threading functions manually using
  45   evthread_set_lock_callbacks() and evthread_set_condition_callbacks().
  46
  47  */
  48
  49 #ifdef __cplusplus
  50 extern "C" {
  51 #endif
  52
  53 #include <event2/event-config.h>
  54
  55 /**
  56    @name Flags passed to lock functions
  57
  58    @{
  59 */
  60 /** A flag passed to a locking callback when the lock was allocated as a
  61  * read-write lock, and we want to acquire or release the lock for writing. */
  62 #define EVTHREAD_WRITE  0x04
  63 /** A flag passed to a locking callback when the lock was allocated as a
  64  * read-write lock, and we want to acquire or release the lock for reading. */
  65 #define EVTHREAD_READ   0x08
  66 /** A flag passed to a locking callback when we don't want to block waiting
  67  * for the lock; if we can't get the lock immediately, we will instead
  68  * return nonzero from the locking callback. */
  69 #define EVTHREAD_TRY    0x10
  70 /**@}*/
  71
  72 #if !defined(_EVENT_DISABLE_THREAD_SUPPORT) || defined(_EVENT_IN_DOXYGEN)
  73
  74 #define EVTHREAD_LOCK_API_VERSION 1
  75
  76 /**
  77    @name Types of locks
  78
  79    @{*/
  80 /** A recursive lock is one that can be acquired multiple times at once by the
  81  * same thread.  No other process can allocate the lock until the thread that
  82  * has been holding it has unlocked it as many times as it locked it. */
  83 #define EVTHREAD_LOCKTYPE_RECURSIVE 1
  84 /* A read-write lock is one that allows multiple simultaneous readers, but
  85  * where any one writer excludes all other writers and readers. */
  86 #define EVTHREAD_LOCKTYPE_READWRITE 2
  87 /**@}*/
  88
  89 /** This structure describes the interface a threading library uses for
  90  * locking.   It's used to tell evthread_set_lock_callbacks() how to use
  91  * locking on this platform.
  92  */
  93 struct evthread_lock_callbacks {
  94         /** The current version of the locking API.  Set this to
  95          * EVTHREAD_LOCK_API_VERSION */
  96         int lock_api_version;
  97         /** Which kinds of locks does this version of the locking API
  98          * support?  A bitfield of EVTHREAD_LOCKTYPE_RECURSIVE and
  99          * EVTHREAD_LOCKTYPE_READWRITE.
 100          *
 101          * (Note that RECURSIVE locks are currently mandatory, and
 102          * READWRITE locks are not currently used.)
 103          **/
 104         unsigned supported_locktypes;
 105         /** Function to allocate and initialize new lock of type 'locktype'.
 106          * Returns NULL on failure. */
 107         void *(*alloc)(unsigned locktype);
 108         /** Funtion to release all storage held in 'lock', which was created
 109          * with type 'locktype'. */
 110         void (*free)(void *lock, unsigned locktype);
 111         /** Acquire an already-allocated lock at 'lock' with mode 'mode'.
 112          * Returns 0 on success, and nonzero on failure. */
 113         int (*lock)(unsigned mode, void *lock);
 114         /** Release a lock at 'lock' using mode 'mode'.  Returns 0 on success,
 115          * and nonzero on failure. */
 116         int (*unlock)(unsigned mode, void *lock);
 117 };
 118
 119 /** Sets a group of functions that Libevent should use for locking.
 120  * For full information on the required callback API, see the
 121  * documentation for the individual members of evthread_lock_callbacks.
 122  *
 123  * Note that if you're using Windows or the Pthreads threading library, you
 124  * probably shouldn't call this function; instead, use
 125  * evthread_use_windows_threads() or evthread_use_posix_threads() if you can.
 126  */
 127 int evthread_set_lock_callbacks(const struct evthread_lock_callbacks *);
 128
 129 #define EVTHREAD_CONDITION_API_VERSION 1
 130
 131 struct timeval;
 132
 133 /** This structure describes the interface a threading library uses for
 134  * condition variables.  It's used to tell evthread_set_condition_callbacks
 135  * how to use locking on this platform.
 136  */
 137 struct evthread_condition_callbacks {
 138         /** The current version of the conditions API.  Set this to
 139          * EVTHREAD_CONDITION_API_VERSION */
 140         int condition_api_version;
 141         /** Function to allocate and initialize a new condition variable.
 142          * Returns the condition variable on success, and NULL on failure.
 143          * The 'condtype' argument will be 0 with this API version.
 144          */
 145         void *(*alloc_condition)(unsigned condtype);
 146         /** Function to free a condition variable. */
 147         void (*free_condition)(void *cond);
 148         /** Function to signal a condition variable.  If 'broadcast' is 1, all
 149          * threads waiting on 'cond' should be woken; otherwise, only on one
 150          * thread is worken.  Should return 0 on success, -1 on failure.
 151          * This function will only be called while holding the associated
 152          * lock for the condition.
 153          */
 154         int (*signal_condition)(void *cond, int broadcast);
 155         /** Function to wait for a condition variable.  The lock 'lock'
 156          * will be held when this function is called; should be released
 157          * while waiting for the condition to be come signalled, and
 158          * should be held again when this function returns.
 159          * If timeout is provided, it is interval of seconds to wait for
 160          * the event to become signalled; if it is NULL, the function
 161          * should wait indefinitely.
 162          *
 163          * The function should return -1 on error; 0 if the condition
 164          * was signalled, or 1 on a timeout. */
 165         int (*wait_condition)(void *cond, void *lock,
 166             const struct timeval *timeout);
 167 };
 168
 169 /** Sets a group of functions that Libevent should use for condition variables.
 170  * For full information on the required callback API, see the
 171  * documentation for the individual members of evthread_condition_callbacks.
 172  *
 173  * Note that if you're using Windows or the Pthreads threading library, you
 174  * probably shouldn't call this function; instead, use
 175  * evthread_use_windows_threads() or evthread_use_pthreads() if you can.
 176  */
 177 int evthread_set_condition_callbacks(
 178         const struct evthread_condition_callbacks *);
 179
 180 /**
 181    Sets the function for determining the thread id.
 182
 183    @param base the event base for which to set the id function
 184    @param id_fn the identify function Libevent should invoke to
 185      determine the identity of a thread.
 186 */
 187 void evthread_set_id_callback(
 188     unsigned long (*id_fn)(void));
 189
 190 #if (defined(WIN32) && !defined(_EVENT_DISABLE_THREAD_SUPPORT)) || defined(_EVENT_IN_DOXYGEN)
 191 /** Sets up Libevent for use with Windows builtin locking and thread ID
 192     functions.  Unavailable if Libevent is not built for Windows.
 193
 194     @return 0 on success, -1 on failure. */
 195 int evthread_use_windows_threads(void);
 196 /**
 197    Defined if Libevent was built with support for evthread_use_windows_threads()
 198 */
 199 #define EVTHREAD_USE_WINDOWS_THREADS_IMPLEMENTED 1
 200 #endif
 201
 202 #if defined(_EVENT_HAVE_PTHREADS) || defined(_EVENT_IN_DOXYGEN)
 203 /** Sets up Libevent for use with Pthreads locking and thread ID functions.
 204     Unavailable if Libevent is not build for use with pthreads.  Requires
 205     libraries to link against Libevent_pthreads as well as Libevent.
 206
 207     @return 0 on success, -1 on failure. */
 208 int evthread_use_pthreads(void);
 209 /** Defined if Libevent was built with support for evthread_use_pthreads() */
 210 #define EVTHREAD_USE_PTHREADS_IMPLEMENTED 1
 211
 212 #endif
 213
 214 /** Enable debugging wrappers around the current lock callbacks.  If Libevent
 215  * makes one of several common locking errors, exit with an assertion failure.
 216  *
 217  * If you're going to call this function, you must do so before any locks are
 218  * allocated.
 219  **/
 220 void evthread_enable_lock_debuging(void);
 221
 222 #endif /* _EVENT_DISABLE_THREAD_SUPPORT */
 223
 224 struct event_base;
 225 /** Make sure it's safe to tell an event base to wake up from another thread
 226     or a signal handler.
 227
 228     @return 0 on success, -1 on failure.
 229  */
 230 int evthread_make_base_notifiable(struct event_base *base);
 231
 232 #ifdef __cplusplus
 233 }
 234 #endif
 235
 236 #endif /* _EVENT2_THREAD_H_ */