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| #pragma disable-camelcase ||<tablewidth="100%" style="color: #FF0000;" :> DRAFT|| |
#pragma camelcase off |
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| Use this function to create a semaphore, initialized with value, returns NULL on failure. <<Color2(green,Should this description stop at semaphore and the remaining info be moved below?)>> |
Use this function to create a semaphore. |
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| ||'''initial_value'''||^the starting value for the semaphore^|| | ||'''initial_value'''||the starting value of the semaphore|| |
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| Returns ^the current semaphore value for the resource^ on success, or NULL on failure; call [[SDL_GetError]]() for more information. <<Color2(green,-OR- does it return a positive value when the resource is available and 0 when it is in use?)>> |
Returns a new semaphore or NULL on failure; call [[SDL_GetError]]() for more information. |
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| ## Begin Semaphore Example Typical use of semaphores: |
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| You can add your code example here | SDL_atomic_t done; SDL_sem *sem; SDL_AtomicSet(&done, 0); sem = SDL_CreateSemaphore(0); . . Thread A: while (!SDL_AtomicGet(&done)) { add_data_to_queue(); SDL_SemPost(sem); } Thread B: while (!SDL_AtomicGet(&done)) { SDL_SemWait(sem); if (data_available()) { get_data_from_queue(); } } . . SDL_AtomicSet(&done, 1); SDL_SemPost(sem); wait_for_threads(); SDL_DestroySemaphore(sem); |
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| ## End Semaphore Example | |
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| ''You can add useful comments here'' | This function creates a new semaphore and initializes it with the value '''initial_value'''. Each wait operation on the semaphore will atomically decrement the semaphore value and potentially block if the semaphore value is 0. Each post operation will atomically increment the semaphore value and wake waiting threads and allow them to retry the wait operation. |
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| .[[SDL_DestroySemaphore]] ??? | .[[SDL_DestroySemaphore]] .[[SDL_SemPost]] .[[SDL_SemTryWait]] .[[SDL_SemValue]] .[[SDL_SemWait]] .[[SDL_SemWaitTimeout]] |
SDL_CreateSemaphore
Use this function to create a semaphore.
Contents
Syntax
SDL_sem* SDL_CreateSemaphore(Uint32 initial_value)
Function Parameters
initial_value |
the starting value of the semaphore |
Return Value
Returns a new semaphore or NULL on failure; call SDL_GetError() for more information.
Code Examples
Typical use of semaphores:
SDL_atomic_t done;
SDL_sem *sem;
SDL_AtomicSet(&done, 0);
sem = SDL_CreateSemaphore(0);
.
.
Thread A:
while (!SDL_AtomicGet(&done)) {
add_data_to_queue();
SDL_SemPost(sem);
}
Thread B:
while (!SDL_AtomicGet(&done)) {
SDL_SemWait(sem);
if (data_available()) {
get_data_from_queue();
}
}
.
.
SDL_AtomicSet(&done, 1);
SDL_SemPost(sem);
wait_for_threads();
SDL_DestroySemaphore(sem);
Remarks
This function creates a new semaphore and initializes it with the value initial_value. Each wait operation on the semaphore will atomically decrement the semaphore value and potentially block if the semaphore value is 0. Each post operation will atomically increment the semaphore value and wake waiting threads and allow them to retry the wait operation.
