src/thread/stdcpp/SDL_syscond.cpp
author Sam Lantinga <slouken@libsdl.org>
Thu, 13 Mar 2014 00:40:08 -0700
changeset 8615 097646deaef2
parent 8600 092802455aed
child 9619 b94b6d0bff0f
permissions -rw-r--r--
Fixed the copyright date on files contributed by David Ludwig
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2014 Sam Lantinga <slouken@libsdl.org>
     4 
     5   This software is provided 'as-is', without any express or implied
     6   warranty.  In no event will the authors be held liable for any damages
     7   arising from the use of this software.
     8 
     9   Permission is granted to anyone to use this software for any purpose,
    10   including commercial applications, and to alter it and redistribute it
    11   freely, subject to the following restrictions:
    12 
    13   1. The origin of this software must not be misrepresented; you must not
    14      claim that you wrote the original software. If you use this software
    15      in a product, an acknowledgment in the product documentation would be
    16      appreciated but is not required.
    17   2. Altered source versions must be plainly marked as such, and must not be
    18      misrepresented as being the original software.
    19   3. This notice may not be removed or altered from any source distribution.
    20 */
    21 #include "../../SDL_internal.h"
    22 
    23 extern "C" {
    24 #include "SDL_thread.h"
    25 }
    26 
    27 #include <chrono>
    28 #include <condition_variable>
    29 #include <ratio>
    30 #include <system_error>
    31 
    32 #include "SDL_sysmutex_c.h"
    33 
    34 struct SDL_cond
    35 {
    36     std::condition_variable_any cpp_cond;
    37 };
    38 
    39 /* Create a condition variable */
    40 extern "C"
    41 SDL_cond *
    42 SDL_CreateCond(void)
    43 {
    44     /* Allocate and initialize the condition variable */
    45     try {
    46         SDL_cond * cond = new SDL_cond;
    47         return cond;
    48     } catch (std::system_error & ex) {
    49         SDL_SetError("unable to create a C++ condition variable: code=%d; %s", ex.code(), ex.what());
    50         return NULL;
    51     } catch (std::bad_alloc &) {
    52         SDL_OutOfMemory();
    53         return NULL;
    54     }
    55 }
    56 
    57 /* Destroy a condition variable */
    58 extern "C"
    59 void
    60 SDL_DestroyCond(SDL_cond * cond)
    61 {
    62     if (cond) {
    63         delete cond;
    64     }
    65 }
    66 
    67 /* Restart one of the threads that are waiting on the condition variable */
    68 extern "C"
    69 int
    70 SDL_CondSignal(SDL_cond * cond)
    71 {
    72     if (!cond) {
    73         SDL_SetError("Passed a NULL condition variable");
    74         return -1;
    75     }
    76 
    77     cond->cpp_cond.notify_one();
    78     return 0;
    79 }
    80 
    81 /* Restart all threads that are waiting on the condition variable */
    82 extern "C"
    83 int
    84 SDL_CondBroadcast(SDL_cond * cond)
    85 {
    86     if (!cond) {
    87         SDL_SetError("Passed a NULL condition variable");
    88         return -1;
    89     }
    90 
    91     cond->cpp_cond.notify_all();
    92     return 0;
    93 }
    94 
    95 /* Wait on the condition variable for at most 'ms' milliseconds.
    96    The mutex must be locked before entering this function!
    97    The mutex is unlocked during the wait, and locked again after the wait.
    98 
    99 Typical use:
   100 
   101 Thread A:
   102     SDL_LockMutex(lock);
   103     while ( ! condition ) {
   104         SDL_CondWait(cond, lock);
   105     }
   106     SDL_UnlockMutex(lock);
   107 
   108 Thread B:
   109     SDL_LockMutex(lock);
   110     ...
   111     condition = true;
   112     ...
   113     SDL_CondSignal(cond);
   114     SDL_UnlockMutex(lock);
   115  */
   116 extern "C"
   117 int
   118 SDL_CondWaitTimeout(SDL_cond * cond, SDL_mutex * mutex, Uint32 ms)
   119 {
   120     if (!cond) {
   121         SDL_SetError("Passed a NULL condition variable");
   122         return -1;
   123     }
   124 
   125     if (!mutex) {
   126         SDL_SetError("Passed a NULL mutex variable");
   127         return -1;
   128     }
   129 
   130     try {
   131         std::unique_lock<std::recursive_mutex> cpp_lock(mutex->cpp_mutex, std::defer_lock_t());
   132         if (ms == SDL_MUTEX_MAXWAIT) {
   133             cond->cpp_cond.wait(
   134                 cpp_lock
   135                 );
   136             cpp_lock.release();
   137             return 0;
   138         } else {
   139             auto wait_result = cond->cpp_cond.wait_for(
   140                 cpp_lock,
   141                 std::chrono::duration<Uint32, std::milli>(ms)
   142                 );
   143             cpp_lock.release();
   144             if (wait_result == std::cv_status::timeout) {
   145                 return SDL_MUTEX_TIMEDOUT;
   146             } else {
   147                 return 0;
   148             }
   149         }
   150     } catch (std::system_error & ex) {
   151         SDL_SetError("unable to wait on a C++ condition variable: code=%d; %s", ex.code(), ex.what());
   152         return -1;
   153     }
   154 }
   155 
   156 /* Wait on the condition variable forever */
   157 extern "C"
   158 int
   159 SDL_CondWait(SDL_cond * cond, SDL_mutex * mutex)
   160 {
   161     return SDL_CondWaitTimeout(cond, mutex, SDL_MUTEX_MAXWAIT);
   162 }
   163 
   164 /* vi: set ts=4 sw=4 expandtab: */