SDL_thread.h File Reference

#include "SDL_stdinc.h"
#include "SDL_error.h"
#include "SDL_atomic.h"
#include "SDL_mutex.h"
#include "begin_code.h"
#include "close_code.h"

Go to the source code of this file.

Typedefs
typedef struct SDL_Thread	SDL_Thread
typedef unsigned long	SDL_threadID
typedef unsigned int	SDL_TLSID
typedef int(SDLCALL *	SDL_ThreadFunction) (void *data)

Enumerations
enum	SDL_ThreadPriority { SDL_THREAD_PRIORITY_LOW, SDL_THREAD_PRIORITY_NORMAL, SDL_THREAD_PRIORITY_HIGH, SDL_THREAD_PRIORITY_TIME_CRITICAL }

Functions
DECLSPEC SDL_Thread *SDLCALL	SDL_CreateThread (SDL_ThreadFunction fn, const char *name, void *data)
DECLSPEC SDL_Thread *SDLCALL	SDL_CreateThreadWithStackSize (SDL_ThreadFunction fn, const char *name, const size_t stacksize, void *data)
DECLSPEC const char *SDLCALL	SDL_GetThreadName (SDL_Thread *thread)
DECLSPEC SDL_threadID SDLCALL	SDL_ThreadID (void)
DECLSPEC SDL_threadID SDLCALL	SDL_GetThreadID (SDL_Thread *thread)
DECLSPEC int SDLCALL	SDL_SetThreadPriority (SDL_ThreadPriority priority)
DECLSPEC void SDLCALL	SDL_WaitThread (SDL_Thread *thread, int *status)
DECLSPEC void SDLCALL	SDL_DetachThread (SDL_Thread *thread)
DECLSPEC SDL_TLSID SDLCALL	SDL_TLSCreate (void)
	Create an identifier that is globally visible to all threads but refers to data that is thread-specific. More...
DECLSPEC void *SDLCALL	SDL_TLSGet (SDL_TLSID id)
	Get the value associated with a thread local storage ID for the current thread. More...
DECLSPEC int SDLCALL	SDL_TLSSet (SDL_TLSID id, const void *value, void(SDLCALL *destructor)(void *))
	Set the value associated with a thread local storage ID for the current thread. More...

Detailed Description

Header for the SDL thread management routines.

Definition in file SDL_thread.h.

Typedef Documentation

SDL_Thread

typedef struct SDL_Thread SDL_Thread

Definition at line 46 of file SDL_thread.h.

SDL_ThreadFunction

typedef int(SDLCALL * SDL_ThreadFunction) (void *data)

The function passed to SDL_CreateThread(). It is passed a void* user context parameter and returns an int.

Definition at line 70 of file SDL_thread.h.

SDL_threadID

typedef unsigned long SDL_threadID

Definition at line 49 of file SDL_thread.h.

SDL_TLSID

typedef unsigned int SDL_TLSID

Definition at line 52 of file SDL_thread.h.

Enumeration Type Documentation

SDL_ThreadPriority

enum SDL_ThreadPriority

The SDL thread priority.

Note

On many systems you require special privileges to set high or time critical priority.

Enumerator
SDL_THREAD_PRIORITY_LOW
SDL_THREAD_PRIORITY_NORMAL
SDL_THREAD_PRIORITY_HIGH
SDL_THREAD_PRIORITY_TIME_CRITICAL

Definition at line 59 of file SDL_thread.h.

             {
    SDL_THREAD_PRIORITY_LOW,
    SDL_THREAD_PRIORITY_NORMAL,
    SDL_THREAD_PRIORITY_HIGH,
    SDL_THREAD_PRIORITY_TIME_CRITICAL
} SDL_ThreadPriority;

Function Documentation

SDL_CreateThread()

DECLSPEC SDL_Thread* SDLCALL SDL_CreateThread	(	SDL_ThreadFunction	fn,
		const char *	name,
		void *	data
	)

Create a thread with a default stack size.

This is equivalent to calling: SDL_CreateThreadWithStackSize(fn, name, 0, data);

SDL_CreateThreadWithStackSize()

DECLSPEC SDL_Thread* SDLCALL SDL_CreateThreadWithStackSize	(	SDL_ThreadFunction	fn,
		const char *	name,
		const size_t	stacksize,
		void *	data
	)

Create a thread.

Thread naming is a little complicated: Most systems have very small limits for the string length (Haiku has 32 bytes, Linux currently has 16, Visual C++ 6.0 has nine!), and possibly other arbitrary rules. You'll have to see what happens with your system's debugger. The name should be UTF-8 (but using the naming limits of C identifiers is a better bet). There are no requirements for thread naming conventions, so long as the string is null-terminated UTF-8, but these guidelines are helpful in choosing a name:

http://stackoverflow.com/questions/149932/naming-conventions-for-threads

If a system imposes requirements, SDL will try to munge the string for it (truncate, etc), but the original string contents will be available from SDL_GetThreadName().

The size (in bytes) of the new stack can be specified. Zero means "use the system default" which might be wildly different between platforms (x86 Linux generally defaults to eight megabytes, an embedded device might be a few kilobytes instead).

In SDL 2.1, stacksize will be folded into the original SDL_CreateThread function.

SDL_DetachThread()

DECLSPEC void SDLCALL SDL_DetachThread

(

SDL_Thread *

thread

)

A thread may be "detached" to signify that it should not remain until another thread has called SDL_WaitThread() on it. Detaching a thread is useful for long-running threads that nothing needs to synchronize with or further manage. When a detached thread is done, it simply goes away.

There is no way to recover the return code of a detached thread. If you need this, don't detach the thread and instead use SDL_WaitThread().

Once a thread is detached, you should usually assume the SDL_Thread isn't safe to reference again, as it will become invalid immediately upon the detached thread's exit, instead of remaining until someone has called SDL_WaitThread() to finally clean it up. As such, don't detach the same thread more than once.

If a thread has already exited when passed to SDL_DetachThread(), it will stop waiting for a call to SDL_WaitThread() and clean up immediately. It is not safe to detach a thread that might be used with SDL_WaitThread().

You may not call SDL_WaitThread() on a thread that has been detached. Use either that function or this one, but not both, or behavior is undefined.

It is safe to pass NULL to this function; it is a no-op.

SDL_GetThreadID()

DECLSPEC SDL_threadID SDLCALL SDL_GetThreadID

(

SDL_Thread *

thread

)

Get the thread identifier for the specified thread.

Equivalent to SDL_ThreadID() if the specified thread is NULL.

SDL_GetThreadName()

DECLSPEC const char* SDLCALL SDL_GetThreadName

(

SDL_Thread *

thread

)

Get the thread name, as it was specified in SDL_CreateThread(). This function returns a pointer to a UTF-8 string that names the specified thread, or NULL if it doesn't have a name. This is internal memory, not to be free()'d by the caller, and remains valid until the specified thread is cleaned up by SDL_WaitThread().

SDL_SetThreadPriority()

DECLSPEC int SDLCALL SDL_SetThreadPriority

(

SDL_ThreadPriority

priority

)

Set the priority for the current thread

SDL_ThreadID()

DECLSPEC SDL_threadID SDLCALL SDL_ThreadID

(

void

)

Get the thread identifier for the current thread.

SDL_TLSCreate()

DECLSPEC SDL_TLSID SDLCALL SDL_TLSCreate

(

void

)

Create an identifier that is globally visible to all threads but refers to data that is thread-specific.

Returns

The newly created thread local storage identifier, or 0 on error

static SDL_SpinLock tls_lock;
static SDL_TLSID thread_local_storage;

void SetMyThreadData(void *value)
{
    if (!thread_local_storage) {
        SDL_AtomicLock(&tls_lock);
        if (!thread_local_storage) {
            thread_local_storage = SDL_TLSCreate();
        }
        SDL_AtomicUnlock(&tls_lock);
    }
    SDL_TLSSet(thread_local_storage, value, 0);
}

void *GetMyThreadData(void)
{
    return SDL_TLSGet(thread_local_storage);
}

See also

SDL_TLSGet()

SDL_TLSSet()

SDL_TLSGet()

DECLSPEC void* SDLCALL SDL_TLSGet

(

SDL_TLSID

id

)

Get the value associated with a thread local storage ID for the current thread.

Parameters

id	The thread local storage ID

Returns

The value associated with the ID for the current thread, or NULL if no value has been set.

See also

SDL_TLSCreate()

SDL_TLSSet()

SDL_TLSSet()

DECLSPEC int SDLCALL SDL_TLSSet	(	SDL_TLSID	id,
		const void *	value,
		void(SDLCALL *destructor)(void *)
	)

Set the value associated with a thread local storage ID for the current thread.

Parameters

id	The thread local storage ID
value	The value to associate with the ID for the current thread
destructor	A function called when the thread exits, to free the value.

Returns

0 on success, -1 on error

See also

SDL_TLSCreate()

SDL_TLSGet()

SDL_WaitThread()

DECLSPEC void SDLCALL SDL_WaitThread	(	SDL_Thread *	thread,
		int *	status
	)

Wait for a thread to finish. Threads that haven't been detached will remain (as a "zombie") until this function cleans them up. Not doing so is a resource leak.

Once a thread has been cleaned up through this function, the SDL_Thread that references it becomes invalid and should not be referenced again. As such, only one thread may call SDL_WaitThread() on another.

The return code for the thread function is placed in the area pointed to by status, if status is not NULL.

You may not wait on a thread that has been used in a call to SDL_DetachThread(). Use either that function or this one, but not both, or behavior is undefined.

It is safe to pass NULL to this function; it is a no-op.