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      1 /* -*- mode: C; c-file-style: "gnu" -*- */
      2 /* dbus-threads.h  D-Bus threads handling
      3  *
      4  * Copyright (C) 2002  Red Hat Inc.
      5  *
      6  * Licensed under the Academic Free License version 2.1
      7  *
      8  * This program is free software; you can redistribute it and/or modify
      9  * it under the terms of the GNU General Public License as published by
     10  * the Free Software Foundation; either version 2 of the License, or
     11  * (at your option) any later version.
     12  *
     13  * This program is distributed in the hope that it will be useful,
     14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
     15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     16  * GNU General Public License for more details.
     17  *
     18  * You should have received a copy of the GNU General Public License
     19  * along with this program; if not, write to the Free Software
     20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
     21  *
     22  */
     23 #if !defined (DBUS_INSIDE_DBUS_H) && !defined (DBUS_COMPILATION)
     24 #error "Only <dbus/dbus.h> can be included directly, this file may disappear or change contents."
     25 #endif
     26 
     27 #ifndef DBUS_THREADS_H
     28 #define DBUS_THREADS_H
     29 
     30 #include <dbus/dbus-macros.h>
     31 #include <dbus/dbus-types.h>
     32 
     33 DBUS_BEGIN_DECLS
     34 
     35 /**
     36  * @addtogroup DBusThreads
     37  * @{
     38  */
     39 
     40 /** An opaque mutex type provided by the #DBusThreadFunctions implementation installed by dbus_threads_init(). */
     41 typedef struct DBusMutex DBusMutex;
     42 /** An opaque condition variable type provided by the #DBusThreadFunctions implementation installed by dbus_threads_init(). */
     43 typedef struct DBusCondVar DBusCondVar;
     44 
     45 /** Deprecated, provide DBusRecursiveMutexNewFunction instead. */
     46 typedef DBusMutex*  (* DBusMutexNewFunction)    (void);
     47 /** Deprecated, provide DBusRecursiveMutexFreeFunction instead. */
     48 typedef void        (* DBusMutexFreeFunction)   (DBusMutex *mutex);
     49 /** Deprecated, provide DBusRecursiveMutexLockFunction instead. Return value is lock success, but gets ignored in practice. */
     50 typedef dbus_bool_t (* DBusMutexLockFunction)   (DBusMutex *mutex);
     51 /** Deprecated, provide DBusRecursiveMutexUnlockFunction instead. Return value is unlock success, but gets ignored in practice. */
     52 typedef dbus_bool_t (* DBusMutexUnlockFunction) (DBusMutex *mutex);
     53 
     54 /** Creates a new recursively-lockable mutex, or returns #NULL if not
     55  * enough memory.  Can only fail due to lack of memory.  Found in
     56  * #DBusThreadFunctions. Do not just use PTHREAD_MUTEX_RECURSIVE for
     57  * this, because it does not save/restore the recursion count when
     58  * waiting on a condition. libdbus requires the Java-style behavior
     59  * where the mutex is fully unlocked to wait on a condition.
     60  */
     61 typedef DBusMutex*  (* DBusRecursiveMutexNewFunction)    (void);
     62 /** Frees a recursively-lockable mutex.  Found in #DBusThreadFunctions.
     63  */
     64 typedef void        (* DBusRecursiveMutexFreeFunction)   (DBusMutex *mutex);
     65 /** Locks a recursively-lockable mutex.  Found in #DBusThreadFunctions.
     66  * Can only fail due to lack of memory.
     67  */
     68 typedef void        (* DBusRecursiveMutexLockFunction)   (DBusMutex *mutex);
     69 /** Unlocks a recursively-lockable mutex.  Found in #DBusThreadFunctions.
     70  * Can only fail due to lack of memory.
     71  */
     72 typedef void        (* DBusRecursiveMutexUnlockFunction) (DBusMutex *mutex);
     73 
     74 /** Creates a new condition variable.  Found in #DBusThreadFunctions.
     75  * Can only fail (returning #NULL) due to lack of memory.
     76  */
     77 typedef DBusCondVar*  (* DBusCondVarNewFunction)         (void);
     78 /** Frees a condition variable.  Found in #DBusThreadFunctions.
     79  */
     80 typedef void          (* DBusCondVarFreeFunction)        (DBusCondVar *cond);
     81 
     82 /** Waits on a condition variable.  Found in
     83  * #DBusThreadFunctions. Must work with either a recursive or
     84  * nonrecursive mutex, whichever the thread implementation
     85  * provides. Note that PTHREAD_MUTEX_RECURSIVE does not work with
     86  * condition variables (does not save/restore the recursion count) so
     87  * don't try using simply pthread_cond_wait() and a
     88  * PTHREAD_MUTEX_RECURSIVE to implement this, it won't work right.
     89  *
     90  * Has no error conditions. Must succeed if it returns.
     91  */
     92 typedef void          (* DBusCondVarWaitFunction)        (DBusCondVar *cond,
     93 							  DBusMutex   *mutex);
     94 
     95 /** Waits on a condition variable with a timeout.  Found in
     96  *  #DBusThreadFunctions. Returns #TRUE if the wait did not
     97  *  time out, and #FALSE if it did.
     98  *
     99  * Has no error conditions. Must succeed if it returns.
    100  */
    101 typedef dbus_bool_t   (* DBusCondVarWaitTimeoutFunction) (DBusCondVar *cond,
    102 							  DBusMutex   *mutex,
    103 							  int          timeout_milliseconds);
    104 /** Wakes one waiting thread on a condition variable.  Found in #DBusThreadFunctions.
    105  *
    106  * Has no error conditions. Must succeed if it returns.
    107  */
    108 typedef void          (* DBusCondVarWakeOneFunction) (DBusCondVar *cond);
    109 
    110 /** Wakes all waiting threads on a condition variable.  Found in #DBusThreadFunctions.
    111  *
    112  * Has no error conditions. Must succeed if it returns.
    113  */
    114 typedef void          (* DBusCondVarWakeAllFunction) (DBusCondVar *cond);
    115 
    116 /**
    117  * Flags indicating which functions are present in #DBusThreadFunctions. Used to allow
    118  * the library to detect older callers of dbus_threads_init() if new possible functions
    119  * are added to #DBusThreadFunctions.
    120  */
    121 typedef enum
    122 {
    123   DBUS_THREAD_FUNCTIONS_MUTEX_NEW_MASK      = 1 << 0,
    124   DBUS_THREAD_FUNCTIONS_MUTEX_FREE_MASK     = 1 << 1,
    125   DBUS_THREAD_FUNCTIONS_MUTEX_LOCK_MASK     = 1 << 2,
    126   DBUS_THREAD_FUNCTIONS_MUTEX_UNLOCK_MASK   = 1 << 3,
    127   DBUS_THREAD_FUNCTIONS_CONDVAR_NEW_MASK    = 1 << 4,
    128   DBUS_THREAD_FUNCTIONS_CONDVAR_FREE_MASK   = 1 << 5,
    129   DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_MASK   = 1 << 6,
    130   DBUS_THREAD_FUNCTIONS_CONDVAR_WAIT_TIMEOUT_MASK   = 1 << 7,
    131   DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ONE_MASK = 1 << 8,
    132   DBUS_THREAD_FUNCTIONS_CONDVAR_WAKE_ALL_MASK = 1 << 9,
    133   DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_NEW_MASK    = 1 << 10,
    134   DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_FREE_MASK   = 1 << 11,
    135   DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_LOCK_MASK   = 1 << 12,
    136   DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_UNLOCK_MASK = 1 << 13,
    137   DBUS_THREAD_FUNCTIONS_ALL_MASK     = (1 << 14) - 1
    138 } DBusThreadFunctionsMask;
    139 
    140 /**
    141  * Functions that must be implemented to make the D-Bus library
    142  * thread-aware. The recursive mutex functions should be specified
    143  * rather than the old, deprecated nonrecursive ones.
    144  *
    145  * The condition variable functions have to work with recursive
    146  * mutexes if you provide those, or with nonrecursive mutexes if you
    147  * provide those.
    148  *
    149  * If implementing threads using pthreads, be aware that
    150  * PTHREAD_MUTEX_RECURSIVE is broken in combination with condition
    151  * variables. libdbus relies on the Java-style behavior that when
    152  * waiting on a condition, the recursion count is saved and restored,
    153  * and the mutex is completely unlocked, not just decremented one
    154  * level of recursion.
    155  *
    156  * Thus with pthreads you probably have to roll your own emulated
    157  * recursive mutexes, you can't use PTHREAD_MUTEX_RECURSIVE. This is
    158  * what dbus_threads_init_default() does on platforms that use
    159  * pthreads.
    160  */
    161 typedef struct
    162 {
    163   unsigned int mask; /**< Mask indicating which functions are present. */
    164 
    165   DBusMutexNewFunction mutex_new; /**< Function to create a mutex; optional and deprecated. */
    166   DBusMutexFreeFunction mutex_free; /**< Function to free a mutex; optional and deprecated. */
    167   DBusMutexLockFunction mutex_lock; /**< Function to lock a mutex; optional and deprecated. */
    168   DBusMutexUnlockFunction mutex_unlock; /**< Function to unlock a mutex; optional and deprecated. */
    169 
    170   DBusCondVarNewFunction condvar_new; /**< Function to create a condition variable */
    171   DBusCondVarFreeFunction condvar_free; /**< Function to free a condition variable */
    172   DBusCondVarWaitFunction condvar_wait; /**< Function to wait on a condition */
    173   DBusCondVarWaitTimeoutFunction condvar_wait_timeout; /**< Function to wait on a condition with a timeout */
    174   DBusCondVarWakeOneFunction condvar_wake_one; /**< Function to wake one thread waiting on the condition */
    175   DBusCondVarWakeAllFunction condvar_wake_all; /**< Function to wake all threads waiting on the condition */
    176 
    177   DBusRecursiveMutexNewFunction recursive_mutex_new; /**< Function to create a recursive mutex */
    178   DBusRecursiveMutexFreeFunction recursive_mutex_free; /**< Function to free a recursive mutex */
    179   DBusRecursiveMutexLockFunction recursive_mutex_lock; /**< Function to lock a recursive mutex */
    180   DBusRecursiveMutexUnlockFunction recursive_mutex_unlock; /**< Function to unlock a recursive mutex */
    181 
    182   void (* padding1) (void); /**< Reserved for future expansion */
    183   void (* padding2) (void); /**< Reserved for future expansion */
    184   void (* padding3) (void); /**< Reserved for future expansion */
    185   void (* padding4) (void); /**< Reserved for future expansion */
    186 
    187 } DBusThreadFunctions;
    188 
    189 dbus_bool_t  dbus_threads_init         (const DBusThreadFunctions *functions);
    190 dbus_bool_t  dbus_threads_init_default (void);
    191 
    192 /** @} */
    193 
    194 DBUS_END_DECLS
    195 
    196 #endif /* DBUS_THREADS_H */
    197