mirror of https://github.com/encounter/SDL.git
Add SDL_sem implementation using Atomics and WaitOnAddress API.
Keep Semaphore Kernel Object impl for Windows 7 and older - choose at runtime
v2: - Fix mixed int/LONG types
- Reorder definitions
- Add missing include
v3: - Use `GetModuleHandle()` to load the API Set
This commit is contained in:
Joel Linn
parent
2b040cebbe
commit
d0b8295c0d
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@ -1210,6 +1210,22 @@ extern "C" {
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*/
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#define SDL_HINT_WINDOWS_FORCE_MUTEX_CRITICAL_SECTIONS "SDL_WINDOWS_FORCE_MUTEX_CRITICAL_SECTIONS"
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/**
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* \brief Force SDL to use Kernel Semaphores on Windows.
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* Kernel Semaphores are inter-process and require a context
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* switch on every interaction. On Windows 8 and newer, the
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* WaitOnAddress API is available. Using that and atomics to
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* implement semaphores increases performance.
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* SDL will fall back to Kernel Objects on older OS versions
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* or if forced to by this hint.
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*
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* This variable can be set to the following values:
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* "0" - Use Atomics and WaitOnAddress API when available. If not, fall back to Kernel Objects. (default)
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* "1" - Force the use of Kernel Objects in all cases.
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*
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*/
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#define SDL_HINT_WINDOWS_FORCE_SEMAPHORE_KERNEL "SDL_WINDOWS_FORCE_SEMAPHORE_KERNEL"
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/**
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* \brief Tell SDL which Dispmanx layer to use on a Raspberry PI
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*
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@ -22,27 +22,239 @@
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#if SDL_THREAD_WINDOWS
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/* Semaphore functions using the Win32 API */
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/**
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* Semaphore functions using the Win32 API
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* There are two implementations available based on:
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* - Kernel Semaphores. Available on all OS versions. (kern)
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* Heavy-weight inter-process kernel objects.
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* - Atomics and WaitOnAddress API. (atom)
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* Faster due to significantly less context switches.
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* Requires Windows 8 or newer.
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* which are chosen at runtime.
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*/
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#include "../../core/windows/SDL_windows.h"
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#include "SDL_hints.h"
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#include "SDL_thread.h"
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#include "SDL_timer.h"
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struct SDL_semaphore
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typedef SDL_sem * (*pfnSDL_CreateSemaphore)(Uint32);
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typedef void (*pfnSDL_DestroySemaphore)(SDL_sem *);
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typedef int (*pfnSDL_SemWaitTimeout)(SDL_sem *, Uint32);
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typedef int (*pfnSDL_SemTryWait)(SDL_sem *);
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typedef int (*pfnSDL_SemWait)(SDL_sem *);
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typedef Uint32 (*pfnSDL_SemValue)(SDL_sem *);
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typedef int (*pfnSDL_SemPost)(SDL_sem *);
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typedef struct SDL_semaphore_impl_t
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{
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pfnSDL_CreateSemaphore Create;
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pfnSDL_DestroySemaphore Destroy;
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pfnSDL_SemWaitTimeout WaitTimeout;
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pfnSDL_SemTryWait TryWait;
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pfnSDL_SemWait Wait;
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pfnSDL_SemValue Value;
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pfnSDL_SemPost Post;
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} SDL_sem_impl_t;
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/* Implementation will be chosen at runtime based on available Kernel features */
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static SDL_sem_impl_t SDL_sem_impl_active = {0};
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/**
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* Atomic + WaitOnAddress implementation
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*/
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typedef BOOL(WINAPI *pfnWaitOnAddress)(volatile VOID*, PVOID, SIZE_T, DWORD);
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typedef VOID(WINAPI *pfnWakeByAddressSingle)(PVOID);
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static pfnWaitOnAddress pWaitOnAddress = NULL;
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static pfnWakeByAddressSingle pWakeByAddressSingle = NULL;
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typedef struct SDL_semaphore_atom
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{
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HANDLE id;
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LONG count;
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} SDL_sem_atom;
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static SDL_sem *
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SDL_CreateSemaphore_atom(Uint32 initial_value)
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{
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SDL_sem_atom *sem;
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sem = (SDL_sem_atom *) SDL_malloc(sizeof(*sem));
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if (sem) {
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sem->count = initial_value;
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} else {
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SDL_OutOfMemory();
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}
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return (SDL_sem *)sem;
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}
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static void
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SDL_DestroySemaphore_atom(SDL_sem * sem)
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{
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if (sem) {
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SDL_free(sem);
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}
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}
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static int
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SDL_SemTryWait_atom(SDL_sem * _sem)
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{
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SDL_sem_atom *sem = (SDL_sem_atom *)_sem;
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LONG count;
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if (!sem) {
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return SDL_SetError("Passed a NULL sem");
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}
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count = sem->count;
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if (count == 0) {
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return SDL_MUTEX_TIMEDOUT;
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}
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if (InterlockedCompareExchange(&sem->count, count - 1, count) == count) {
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return 0;
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}
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return SDL_MUTEX_TIMEDOUT;
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}
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static int
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SDL_SemWait_atom(SDL_sem * _sem)
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{
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SDL_sem_atom *sem = (SDL_sem_atom *)_sem;
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LONG count;
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if (!sem) {
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return SDL_SetError("Passed a NULL sem");
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}
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for (;;) {
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count = sem->count;
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while (count == 0) {
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if (pWaitOnAddress(&sem->count, &count, sizeof(sem->count), INFINITE) == FALSE) {
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return SDL_SetError("WaitOnAddress() failed");
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}
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count = sem->count;
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}
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if (InterlockedCompareExchange(&sem->count, count - 1, count) == count) {
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return 0;
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}
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}
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}
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static int
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SDL_SemWaitTimeout_atom(SDL_sem * _sem, Uint32 timeout)
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{
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SDL_sem_atom *sem = (SDL_sem_atom *)_sem;
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LONG count;
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Uint32 now;
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Uint32 deadline;
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DWORD timeout_eff;
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if (timeout == SDL_MUTEX_MAXWAIT) {
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return SDL_SemWait_atom(_sem);
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}
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if (!sem) {
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return SDL_SetError("Passed a NULL sem");
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}
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/**
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* WaitOnAddress is subject to spurious and stolen wakeups so we
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* need to recalculate the effective timeout before every wait
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*/
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now = SDL_GetTicks();
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deadline = now + (DWORD) timeout;
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for (;;) {
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count = sem->count;
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/* If no semaphore is available we need to wait */
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while (count == 0) {
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now = SDL_GetTicks();
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if (deadline > now) {
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timeout_eff = deadline - now;
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} else {
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return SDL_MUTEX_TIMEDOUT;
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}
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if (pWaitOnAddress(&sem->count, &count, sizeof(count), timeout_eff) == FALSE) {
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if (GetLastError() == ERROR_TIMEOUT) {
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return SDL_MUTEX_TIMEDOUT;
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}
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return SDL_SetError("WaitOnAddress() failed");
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}
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count = sem->count;
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}
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/* Actually the semaphore is only consumed if this succeeds */
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/* If it doesn't we need to do everything again */
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if (InterlockedCompareExchange(&sem->count, count - 1, count) == count) {
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return 0;
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}
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}
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}
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static Uint32
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SDL_SemValue_atom(SDL_sem * _sem)
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{
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SDL_sem_atom *sem = (SDL_sem_atom *)_sem;
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if (!sem) {
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SDL_SetError("Passed a NULL sem");
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return 0;
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}
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return (Uint32)sem->count;
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}
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static int
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SDL_SemPost_atom(SDL_sem * _sem)
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{
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SDL_sem_atom *sem = (SDL_sem_atom *)_sem;
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if (!sem) {
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return SDL_SetError("Passed a NULL sem");
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}
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InterlockedIncrement(&sem->count);
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pWakeByAddressSingle(&sem->count);
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return 0;
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}
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static const SDL_sem_impl_t SDL_sem_impl_atom =
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{
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&SDL_CreateSemaphore_atom,
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&SDL_DestroySemaphore_atom,
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&SDL_SemWaitTimeout_atom,
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&SDL_SemTryWait_atom,
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&SDL_SemWait_atom,
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&SDL_SemValue_atom,
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&SDL_SemPost_atom,
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};
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/* Create a semaphore */
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SDL_sem *
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SDL_CreateSemaphore(Uint32 initial_value)
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/**
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* Fallback Semaphore implementation using Kernel Semaphores
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*/
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typedef struct SDL_semaphore_kern
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{
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SDL_sem *sem;
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HANDLE id;
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LONG count;
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} SDL_sem_kern;
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/* Create a semaphore */
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static SDL_sem *
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SDL_CreateSemaphore_kern(Uint32 initial_value)
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{
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SDL_sem_kern *sem;
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/* Allocate sem memory */
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sem = (SDL_sem *) SDL_malloc(sizeof(*sem));
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sem = (SDL_sem_kern *) SDL_malloc(sizeof(*sem));
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if (sem) {
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/* Create the semaphore, with max value 32K */
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#if __WINRT__
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@ -59,13 +271,14 @@ SDL_CreateSemaphore(Uint32 initial_value)
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} else {
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SDL_OutOfMemory();
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}
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return (sem);
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return (SDL_sem *)sem;
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}
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/* Free the semaphore */
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void
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SDL_DestroySemaphore(SDL_sem * sem)
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static void
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SDL_DestroySemaphore_kern(SDL_sem * _sem)
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{
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SDL_sem_kern *sem = (SDL_sem_kern *)_sem;
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if (sem) {
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if (sem->id) {
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CloseHandle(sem->id);
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@ -75,9 +288,10 @@ SDL_DestroySemaphore(SDL_sem * sem)
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}
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}
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int
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SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
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static int
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SDL_SemWaitTimeout_kern(SDL_sem * _sem, Uint32 timeout)
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{
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SDL_sem_kern *sem = (SDL_sem_kern *)_sem;
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int retval;
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DWORD dwMilliseconds;
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@ -105,22 +319,23 @@ SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
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return retval;
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}
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int
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SDL_SemTryWait(SDL_sem * sem)
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static int
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SDL_SemTryWait_kern(SDL_sem * sem)
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{
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return SDL_SemWaitTimeout(sem, 0);
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return SDL_SemWaitTimeout_kern(sem, 0);
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}
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int
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SDL_SemWait(SDL_sem * sem)
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static int
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SDL_SemWait_kern(SDL_sem * sem)
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{
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return SDL_SemWaitTimeout(sem, SDL_MUTEX_MAXWAIT);
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return SDL_SemWaitTimeout_kern(sem, SDL_MUTEX_MAXWAIT);
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}
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/* Returns the current count of the semaphore */
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Uint32
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SDL_SemValue(SDL_sem * sem)
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static Uint32
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SDL_SemValue_kern(SDL_sem * _sem)
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{
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SDL_sem_kern *sem = (SDL_sem_kern *)_sem;
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if (!sem) {
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SDL_SetError("Passed a NULL sem");
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return 0;
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@ -128,9 +343,10 @@ SDL_SemValue(SDL_sem * sem)
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return (Uint32)sem->count;
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}
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int
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SDL_SemPost(SDL_sem * sem)
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static int
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SDL_SemPost_kern(SDL_sem * _sem)
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{
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SDL_sem_kern *sem = (SDL_sem_kern *)_sem;
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if (!sem) {
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return SDL_SetError("Passed a NULL sem");
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}
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@ -147,6 +363,90 @@ SDL_SemPost(SDL_sem * sem)
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return 0;
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}
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static const SDL_sem_impl_t SDL_sem_impl_kern =
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{
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&SDL_CreateSemaphore_kern,
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&SDL_DestroySemaphore_kern,
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&SDL_SemWaitTimeout_kern,
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&SDL_SemTryWait_kern,
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&SDL_SemWait_kern,
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&SDL_SemValue_kern,
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&SDL_SemPost_kern,
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};
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/**
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* Runtime selection and redirection
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*/
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SDL_sem *
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SDL_CreateSemaphore(Uint32 initial_value)
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{
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if (SDL_sem_impl_active.Create == NULL) {
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/* Default to fallback implementation */
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const SDL_sem_impl_t * impl = &SDL_sem_impl_kern;
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if (!SDL_GetHintBoolean(SDL_HINT_WINDOWS_FORCE_SEMAPHORE_KERNEL, SDL_FALSE)) {
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/* We already statically link to features from this Api
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* Set (e.g. WaitForSingleObject). Dynamically loading
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* API Sets is not explicitly documented but according to
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* Microsoft our specific use case is legal and correct:
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* https://github.com/microsoft/STL/pull/593#issuecomment-655799859
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*/
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HMODULE synch120 = GetModuleHandleW(L"api-ms-win-core-synch-l1-2-0.dll");
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if (synch120) {
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/* Try to load required functions provided by Win 8 or newer */
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pWaitOnAddress = (pfnWaitOnAddress) GetProcAddress(synch120, "WaitOnAddress");
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pWakeByAddressSingle = (pfnWakeByAddressSingle) GetProcAddress(synch120, "WakeByAddressSingle");
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if(pWaitOnAddress && pWakeByAddressSingle) {
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impl = &SDL_sem_impl_atom;
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}
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}
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}
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/* Copy instead of using pointer to save one level of indirection */
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SDL_memcpy(&SDL_sem_impl_active, impl, sizeof(SDL_sem_impl_active));
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}
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return SDL_sem_impl_active.Create(initial_value);
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}
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void
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SDL_DestroySemaphore(SDL_sem * sem)
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{
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SDL_sem_impl_active.Destroy(sem);
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}
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int
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SDL_SemWaitTimeout(SDL_sem * sem, Uint32 timeout)
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{
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return SDL_sem_impl_active.WaitTimeout(sem, timeout);
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}
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int
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SDL_SemTryWait(SDL_sem * sem)
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{
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return SDL_sem_impl_active.TryWait(sem);
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}
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int
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SDL_SemWait(SDL_sem * sem)
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{
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return SDL_sem_impl_active.Wait(sem);
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}
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Uint32
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SDL_SemValue(SDL_sem * sem)
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{
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return SDL_sem_impl_active.Value(sem);
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}
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int
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SDL_SemPost(SDL_sem * sem)
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{
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return SDL_sem_impl_active.Post(sem);
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}
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#endif /* SDL_THREAD_WINDOWS */
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/* vi: set ts=4 sw=4 expandtab: */
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Reference in New Issue