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/********************************************************************************
* *
* S e m a p h o r e C l a s s *
* *
*********************************************************************************
* Copyright (C) 2004,2022 by Jeroen van der Zijp. All Rights Reserved. *
*********************************************************************************
* This library is free software; you can redistribute it and/or modify *
* it under the terms of the GNU Lesser General Public License as published by *
* the Free Software Foundation; either version 3 of the License, or *
* (at your option) any later version. *
* *
* This library is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU Lesser General Public License for more details. *
* *
* You should have received a copy of the GNU Lesser General Public License *
* along with this program. If not, see <http://www.gnu.org/licenses/> *
********************************************************************************/
#include "xincs.h"
#include "fxver.h"
#include "fxdefs.h"
#include "FXSemaphore.h"
/*
Notes:
- Semaphore variable.
- Implementation using Condition and Mutex now used for MacOSX and Minix.
This may be less performant than a true semaphore, but its a nice and fully functional
fallback until full posix semaphore implementation is available.
- Increased reserved for pthread_mutex_t as up to 11 FXuval's in size on MacOSX,
worst case is on 32-bit versions.
- Keep in mind we can not do sizeof() in the header file, as we're trying to avoid
including system-headers from public accessible FOX header files. This is so
as to avoid "accidental" incorporation of declarations or unexpected macros,
that may clash.
- Also we want to avoid calls to memory allocators as that would incur a big
performance penalty; besides, a memory allocator may need to call locking
primitives since memory is a resource shared by all threads.
- The upshot is that the space allocated for the semaphore may be a bit more
than strictly necessary on some machines. It may actually be a good thing
as this increases the odds of these datastructures living in dedicated
cache-lines.
*/
using namespace FX;
namespace FX {
/*******************************************************************************/
// Initialize semaphore with given count
FXSemaphore::FXSemaphore(FXint count){
#if defined(WIN32)
FXASSERT_STATIC(sizeof(data)>=sizeof(HANDLE));
data[0]=(FXuval)CreateSemaphore(nullptr,count,0x7fffffff,nullptr);
#elif (defined(__APPLE__) || defined(__minix))
// If this fails on your machine, determine what value of
// sizeof(pthread_cond_t) and sizeof(pthread_mutex_t) is
// supposed to be and mail it to: jeroen@fox-toolkit.net!!
//FXTRACE((150,"sizeof(pthread_cond_t)=%d\n",sizeof(pthread_cond_t)));
//FXTRACE((150,"sizeof(pthread_mutex_t)=%d\n",sizeof(pthread_mutex_t)));
FXASSERT_STATIC(sizeof(FXuval)*9 >= sizeof(pthread_cond_t));
FXASSERT_STATIC(sizeof(FXuval)*11 >= sizeof(pthread_mutex_t));
data[0]=count;
pthread_cond_init((pthread_cond_t*)&data[1],nullptr);
pthread_mutex_init((pthread_mutex_t*)&data[10],nullptr);
#else
// If this fails on your machine, determine what value
// of sizeof(sem_t) is supposed to be on your
// machine and mail it to: jeroen@fox-toolkit.net!!
//FXTRACE((150,"sizeof(sem_t)=%d\n",sizeof(sem_t)));
FXASSERT_STATIC(sizeof(data)>=sizeof(sem_t));
sem_init((sem_t*)data,0,(unsigned int)count);
#endif
}
// Decrement semaphore, waiting if count is zero
void FXSemaphore::wait(){
#if defined(WIN32)
WaitForSingleObject((HANDLE)data[0],INFINITE);
#elif (defined(__APPLE__) || defined(__minix))
pthread_mutex_lock((pthread_mutex_t*)&data[10]);
while(data[0]==0){
pthread_cond_wait((pthread_cond_t*)&data[1],(pthread_mutex_t*)&data[10]);
}
data[0]-=1;
pthread_mutex_unlock((pthread_mutex_t*)&data[10]);
#else
sem_wait((sem_t*)data);
#endif
}
// Try decrement semaphore; return false if timed out
FXbool FXSemaphore::wait(FXTime nsec){
#if defined(WIN32)
if(0<nsec){
if(nsec<forever){
DWORD delay=(DWORD)(nsec/1000000);
return WaitForSingleObject((HANDLE)data[0],delay)==WAIT_OBJECT_0;
}
return WaitForSingleObject((HANDLE)data[0],INFINITE)==WAIT_OBJECT_0;
}
return WaitForSingleObject((HANDLE)data[0],0)==WAIT_OBJECT_0;
#elif (defined(__APPLE__) || defined(__minix))
pthread_mutex_lock((pthread_mutex_t*)&data[10]);
while(data[0]==0){
if(0<nsec){
if(nsec<forever){
#if (_POSIX_C_SOURCE >= 199309L)
struct timespec ts;
clock_gettime(CLOCK_REALTIME,&ts);
ts.tv_sec=ts.tv_sec+(ts.tv_nsec+nsec)/1000000000;
ts.tv_nsec=(ts.tv_nsec+nsec)%1000000000;
if(pthread_cond_timedwait((pthread_cond_t*)&data[1],(pthread_mutex_t*)&data[10],&ts)!=0) goto x;
#else
struct timespec ts;
struct timeval tv;
gettimeofday(&tv,nullptr);
tv.tv_usec*=1000;
ts.tv_sec=tv.tv_sec+(tv.tv_usec+nsec)/1000000000;
ts.tv_nsec=(tv.tv_usec+nsec)%1000000000;
if(pthread_cond_timedwait((pthread_cond_t*)&data[1],(pthread_mutex_t*)&data[10],&ts)!=0) goto x;
#endif
continue;
}
pthread_cond_wait((pthread_cond_t*)&data[1],(pthread_mutex_t*)&data[10]);
continue;
}
x: pthread_mutex_unlock((pthread_mutex_t*)&data[10]);
return false;
}
--data[0];
pthread_mutex_unlock((pthread_mutex_t*)&data[10]);
return true;
#else
if(0<nsec){
if(nsec<forever){
#if (_POSIX_C_SOURCE >= 199309L)
struct timespec ts;
clock_gettime(CLOCK_REALTIME,&ts);
ts.tv_sec=ts.tv_sec+(ts.tv_nsec+nsec)/1000000000;
ts.tv_nsec=(ts.tv_nsec+nsec)%1000000000;
return sem_timedwait((sem_t*)data,&ts)==0;
#else
struct timespec ts;
struct timeval tv;
gettimeofday(&tv,nullptr);
tv.tv_usec*=1000;
ts.tv_sec=tv.tv_sec+(tv.tv_usec+nsec)/1000000000;
ts.tv_nsec=(tv.tv_usec+nsec)%1000000000;
return sem_timedwait((sem_t*)data,&ts)==0;
#endif
}
return sem_wait((sem_t*)data)==0;
}
return sem_trywait((sem_t*)data)==0;
#endif
}
// Try decrement semaphore; and return false if count was zero
FXbool FXSemaphore::trywait(){
#if defined(WIN32)
return WaitForSingleObject((HANDLE)data[0],0)==WAIT_OBJECT_0;
#elif (defined(__APPLE__) || defined(__minix))
pthread_mutex_lock((pthread_mutex_t*)&data[10]);
if(data[0]==0){
pthread_mutex_unlock((pthread_mutex_t*)&data[10]);
return false;
}
data[0]-=1;
pthread_mutex_unlock((pthread_mutex_t*)&data[10]);
return true;
#else
return sem_trywait((sem_t*)data)==0;
#endif
}
// Increment semaphore
void FXSemaphore::post(){
#if defined(WIN32)
ReleaseSemaphore((HANDLE)data[0],1,nullptr);
#elif (defined(__APPLE__) || defined(__minix))
pthread_mutex_lock((pthread_mutex_t*)&data[10]);
data[0]+=1;
pthread_cond_signal((pthread_cond_t*)&data[1]);
pthread_mutex_unlock((pthread_mutex_t*)&data[10]);
#else
sem_post((sem_t*)data);
#endif
}
// Delete semaphore
FXSemaphore::~FXSemaphore(){
#if defined(WIN32)
CloseHandle((HANDLE)data[0]);
#elif (defined(__APPLE__) || defined(__minix))
pthread_mutex_destroy((pthread_mutex_t*)&data[10]);
pthread_cond_destroy((pthread_cond_t*)&data[1]);
#else
sem_destroy((sem_t*)data);
#endif
}
}
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