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      1 /*
      2   Simple DirectMedia Layer
      3   Copyright (C) 1997-2014 Sam Lantinga <slouken (at) 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 
     22 #ifndef _SDL_thread_h
     23 #define _SDL_thread_h
     24 
     25 /**
     26  *  \file SDL_thread.h
     27  *
     28  *  Header for the SDL thread management routines.
     29  */
     30 
     31 #include "SDL_stdinc.h"
     32 #include "SDL_error.h"
     33 
     34 /* Thread synchronization primitives */
     35 #include "SDL_atomic.h"
     36 #include "SDL_mutex.h"
     37 
     38 #include "begin_code.h"
     39 /* Set up for C function definitions, even when using C++ */
     40 #ifdef __cplusplus
     41 extern "C" {
     42 #endif
     43 
     44 /* The SDL thread structure, defined in SDL_thread.c */
     45 struct SDL_Thread;
     46 typedef struct SDL_Thread SDL_Thread;
     47 
     48 /* The SDL thread ID */
     49 typedef unsigned long SDL_threadID;
     50 
     51 /* Thread local storage ID, 0 is the invalid ID */
     52 typedef unsigned int SDL_TLSID;
     53 
     54 /**
     55  *  The SDL thread priority.
     56  *
     57  *  \note On many systems you require special privileges to set high priority.
     58  */
     59 typedef enum {
     60     SDL_THREAD_PRIORITY_LOW,
     61     SDL_THREAD_PRIORITY_NORMAL,
     62     SDL_THREAD_PRIORITY_HIGH
     63 } SDL_ThreadPriority;
     64 
     65 /**
     66  *  The function passed to SDL_CreateThread().
     67  *  It is passed a void* user context parameter and returns an int.
     68  */
     69 typedef int (SDLCALL * SDL_ThreadFunction) (void *data);
     70 
     71 #if defined(__WIN32__) && !defined(HAVE_LIBC)
     72 /**
     73  *  \file SDL_thread.h
     74  *
     75  *  We compile SDL into a DLL. This means, that it's the DLL which
     76  *  creates a new thread for the calling process with the SDL_CreateThread()
     77  *  API. There is a problem with this, that only the RTL of the SDL.DLL will
     78  *  be initialized for those threads, and not the RTL of the calling
     79  *  application!
     80  *
     81  *  To solve this, we make a little hack here.
     82  *
     83  *  We'll always use the caller's _beginthread() and _endthread() APIs to
     84  *  start a new thread. This way, if it's the SDL.DLL which uses this API,
     85  *  then the RTL of SDL.DLL will be used to create the new thread, and if it's
     86  *  the application, then the RTL of the application will be used.
     87  *
     88  *  So, in short:
     89  *  Always use the _beginthread() and _endthread() of the calling runtime
     90  *  library!
     91  */
     92 #define SDL_PASSED_BEGINTHREAD_ENDTHREAD
     93 #include <process.h>            /* This has _beginthread() and _endthread() defined! */
     94 
     95 typedef uintptr_t(__cdecl * pfnSDL_CurrentBeginThread) (void *, unsigned,
     96                                                         unsigned (__stdcall *
     97                                                                   func) (void
     98                                                                          *),
     99                                                         void *arg, unsigned,
    100                                                         unsigned *threadID);
    101 typedef void (__cdecl * pfnSDL_CurrentEndThread) (unsigned code);
    102 
    103 /**
    104  *  Create a thread.
    105  */
    106 extern DECLSPEC SDL_Thread *SDLCALL
    107 SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data,
    108                  pfnSDL_CurrentBeginThread pfnBeginThread,
    109                  pfnSDL_CurrentEndThread pfnEndThread);
    110 
    111 /**
    112  *  Create a thread.
    113  */
    114 #if defined(SDL_CreateThread) && SDL_DYNAMIC_API
    115 #undef SDL_CreateThread
    116 #define SDL_CreateThread(fn, name, data) SDL_CreateThread_REAL(fn, name, data, (pfnSDL_CurrentBeginThread)_beginthreadex, (pfnSDL_CurrentEndThread)_endthreadex)
    117 #else
    118 #define SDL_CreateThread(fn, name, data) SDL_CreateThread(fn, name, data, (pfnSDL_CurrentBeginThread)_beginthreadex, (pfnSDL_CurrentEndThread)_endthreadex)
    119 #endif
    120 
    121 #else
    122 
    123 /**
    124  *  Create a thread.
    125  *
    126  *   Thread naming is a little complicated: Most systems have very small
    127  *    limits for the string length (Haiku has 32 bytes, Linux currently has 16,
    128  *    Visual C++ 6.0 has nine!), and possibly other arbitrary rules. You'll
    129  *    have to see what happens with your system's debugger. The name should be
    130  *    UTF-8 (but using the naming limits of C identifiers is a better bet).
    131  *   There are no requirements for thread naming conventions, so long as the
    132  *    string is null-terminated UTF-8, but these guidelines are helpful in
    133  *    choosing a name:
    134  *
    135  *    http://stackoverflow.com/questions/149932/naming-conventions-for-threads
    136  *
    137  *   If a system imposes requirements, SDL will try to munge the string for
    138  *    it (truncate, etc), but the original string contents will be available
    139  *    from SDL_GetThreadName().
    140  */
    141 extern DECLSPEC SDL_Thread *SDLCALL
    142 SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data);
    143 
    144 #endif
    145 
    146 /**
    147  * Get the thread name, as it was specified in SDL_CreateThread().
    148  *  This function returns a pointer to a UTF-8 string that names the
    149  *  specified thread, or NULL if it doesn't have a name. This is internal
    150  *  memory, not to be free()'d by the caller, and remains valid until the
    151  *  specified thread is cleaned up by SDL_WaitThread().
    152  */
    153 extern DECLSPEC const char *SDLCALL SDL_GetThreadName(SDL_Thread *thread);
    154 
    155 /**
    156  *  Get the thread identifier for the current thread.
    157  */
    158 extern DECLSPEC SDL_threadID SDLCALL SDL_ThreadID(void);
    159 
    160 /**
    161  *  Get the thread identifier for the specified thread.
    162  *
    163  *  Equivalent to SDL_ThreadID() if the specified thread is NULL.
    164  */
    165 extern DECLSPEC SDL_threadID SDLCALL SDL_GetThreadID(SDL_Thread * thread);
    166 
    167 /**
    168  *  Set the priority for the current thread
    169  */
    170 extern DECLSPEC int SDLCALL SDL_SetThreadPriority(SDL_ThreadPriority priority);
    171 
    172 /**
    173  *  Wait for a thread to finish. Threads that haven't been detached will
    174  *  remain (as a "zombie") until this function cleans them up. Not doing so
    175  *  is a resource leak.
    176  *
    177  *  Once a thread has been cleaned up through this function, the SDL_Thread
    178  *  that references it becomes invalid and should not be referenced again.
    179  *  As such, only one thread may call SDL_WaitThread() on another.
    180  *
    181  *  The return code for the thread function is placed in the area
    182  *  pointed to by \c status, if \c status is not NULL.
    183  *
    184  *  You may not wait on a thread that has been used in a call to
    185  *  SDL_DetachThread(). Use either that function or this one, but not
    186  *  both, or behavior is undefined.
    187  *
    188  *  It is safe to pass NULL to this function; it is a no-op.
    189  */
    190 extern DECLSPEC void SDLCALL SDL_WaitThread(SDL_Thread * thread, int *status);
    191 
    192 /**
    193  *  A thread may be "detached" to signify that it should not remain until
    194  *  another thread has called SDL_WaitThread() on it. Detaching a thread
    195  *  is useful for long-running threads that nothing needs to synchronize
    196  *  with or further manage. When a detached thread is done, it simply
    197  *  goes away.
    198  *
    199  *  There is no way to recover the return code of a detached thread. If you
    200  *  need this, don't detach the thread and instead use SDL_WaitThread().
    201  *
    202  *  Once a thread is detached, you should usually assume the SDL_Thread isn't
    203  *  safe to reference again, as it will become invalid immediately upon
    204  *  the detached thread's exit, instead of remaining until someone has called
    205  *  SDL_WaitThread() to finally clean it up. As such, don't detach the same
    206  *  thread more than once.
    207  *
    208  *  If a thread has already exited when passed to SDL_DetachThread(), it will
    209  *  stop waiting for a call to SDL_WaitThread() and clean up immediately.
    210  *  It is not safe to detach a thread that might be used with SDL_WaitThread().
    211  *
    212  *  You may not call SDL_WaitThread() on a thread that has been detached.
    213  *  Use either that function or this one, but not both, or behavior is
    214  *  undefined.
    215  *
    216  *  It is safe to pass NULL to this function; it is a no-op.
    217  */
    218 extern DECLSPEC void SDLCALL SDL_DetachThread(SDL_Thread * thread);
    219 
    220 /**
    221  *  \brief Create an identifier that is globally visible to all threads but refers to data that is thread-specific.
    222  *
    223  *  \return The newly created thread local storage identifier, or 0 on error
    224  *
    225  *  \code
    226  *  static SDL_SpinLock tls_lock;
    227  *  static SDL_TLSID thread_local_storage;
    228  *
    229  *  void SetMyThreadData(void *value)
    230  *  {
    231  *      if (!thread_local_storage) {
    232  *          SDL_AtomicLock(&tls_lock);
    233  *          if (!thread_local_storage) {
    234  *              thread_local_storage = SDL_TLSCreate();
    235  *          }
    236  *          SDL_AtomicUnLock(&tls_lock);
    237  *      }
    238  *      SDL_TLSSet(thread_local_storage, value);
    239  *  }
    240  *
    241  *  void *GetMyThreadData(void)
    242  *  {
    243  *      return SDL_TLSGet(thread_local_storage);
    244  *  }
    245  *  \endcode
    246  *
    247  *  \sa SDL_TLSGet()
    248  *  \sa SDL_TLSSet()
    249  */
    250 extern DECLSPEC SDL_TLSID SDLCALL SDL_TLSCreate(void);
    251 
    252 /**
    253  *  \brief Get the value associated with a thread local storage ID for the current thread.
    254  *
    255  *  \param id The thread local storage ID
    256  *
    257  *  \return The value associated with the ID for the current thread, or NULL if no value has been set.
    258  *
    259  *  \sa SDL_TLSCreate()
    260  *  \sa SDL_TLSSet()
    261  */
    262 extern DECLSPEC void * SDLCALL SDL_TLSGet(SDL_TLSID id);
    263 
    264 /**
    265  *  \brief Set the value associated with a thread local storage ID for the current thread.
    266  *
    267  *  \param id The thread local storage ID
    268  *  \param value The value to associate with the ID for the current thread
    269  *  \param destructor A function called when the thread exits, to free the value.
    270  *
    271  *  \return 0 on success, -1 on error
    272  *
    273  *  \sa SDL_TLSCreate()
    274  *  \sa SDL_TLSGet()
    275  */
    276 extern DECLSPEC int SDLCALL SDL_TLSSet(SDL_TLSID id, const void *value, void (*destructor)(void*));
    277 
    278 
    279 /* Ends C function definitions when using C++ */
    280 #ifdef __cplusplus
    281 }
    282 #endif
    283 #include "close_code.h"
    284 
    285 #endif /* _SDL_thread_h */
    286 
    287 /* vi: set ts=4 sw=4 expandtab: */
    288