106 lines
2.5 KiB
C
106 lines
2.5 KiB
C
/*
|
|
* Copyright (c) 2011 The WebM project authors. All Rights Reserved.
|
|
*
|
|
* Use of this source code is governed by a BSD-style license
|
|
* that can be found in the LICENSE file in the root of the source
|
|
* tree. An additional intellectual property rights grant can be found
|
|
* in the file PATENTS. All contributing project authors may
|
|
* be found in the AUTHORS file in the root of the source tree.
|
|
*/
|
|
#include "vpx_config.h"
|
|
#define RTCD_C
|
|
#include "vpx_rtcd.h"
|
|
|
|
#if CONFIG_MULTITHREAD && defined(_WIN32)
|
|
#include <windows.h>
|
|
#include <stdlib.h>
|
|
static void once(void (*func)(void))
|
|
{
|
|
static CRITICAL_SECTION *lock;
|
|
static LONG waiters;
|
|
static int done;
|
|
void *lock_ptr = &lock;
|
|
|
|
/* If the initialization is complete, return early. This isn't just an
|
|
* optimization, it prevents races on the destruction of the global
|
|
* lock.
|
|
*/
|
|
if(done)
|
|
return;
|
|
|
|
InterlockedIncrement(&waiters);
|
|
|
|
/* Get a lock. We create one and try to make it the one-true-lock,
|
|
* throwing it away if we lost the race.
|
|
*/
|
|
|
|
{
|
|
/* Scope to protect access to new_lock */
|
|
CRITICAL_SECTION *new_lock = malloc(sizeof(CRITICAL_SECTION));
|
|
InitializeCriticalSection(new_lock);
|
|
if (InterlockedCompareExchangePointer(lock_ptr, new_lock, NULL) != NULL)
|
|
{
|
|
DeleteCriticalSection(new_lock);
|
|
free(new_lock);
|
|
}
|
|
}
|
|
|
|
/* At this point, we have a lock that can be synchronized on. We don't
|
|
* care which thread actually performed the allocation.
|
|
*/
|
|
|
|
EnterCriticalSection(lock);
|
|
|
|
if (!done)
|
|
{
|
|
func();
|
|
done = 1;
|
|
}
|
|
|
|
LeaveCriticalSection(lock);
|
|
|
|
/* Last one out should free resources. The destructed objects are
|
|
* protected by checking if(done) above.
|
|
*/
|
|
if(!InterlockedDecrement(&waiters))
|
|
{
|
|
DeleteCriticalSection(lock);
|
|
free(lock);
|
|
lock = NULL;
|
|
}
|
|
}
|
|
|
|
|
|
#elif CONFIG_MULTITHREAD && HAVE_PTHREAD_H
|
|
#include <pthread.h>
|
|
static void once(void (*func)(void))
|
|
{
|
|
static pthread_once_t lock = PTHREAD_ONCE_INIT;
|
|
pthread_once(&lock, func);
|
|
}
|
|
|
|
|
|
#else
|
|
/* No-op version that performs no synchronization. vpx_rtcd() is idempotent,
|
|
* so as long as your platform provides atomic loads/stores of pointers
|
|
* no synchronization is strictly necessary.
|
|
*/
|
|
|
|
static void once(void (*func)(void))
|
|
{
|
|
static int done;
|
|
|
|
if(!done)
|
|
{
|
|
func();
|
|
done = 1;
|
|
}
|
|
}
|
|
#endif
|
|
|
|
|
|
void vpx_rtcd()
|
|
{
|
|
once(setup_rtcd_internal);
|
|
}
|