s3fs-fuse/src/psemaphore.h

/*
 * s3fs - FUSE-based file system backed by Amazon S3
 *
 * Copyright(C) 2007 Randy Rizun <rrizun@gmail.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

#ifndef S3FS_SEMAPHORE_H_
#define S3FS_SEMAPHORE_H_

//-------------------------------------------------------------------
// Class Semaphore
//-------------------------------------------------------------------
// portability wrapper for sem_t since macOS does not implement it
#ifdef __APPLE__

#include <dispatch/dispatch.h>

class Semaphore
{
    public:
        explicit Semaphore(int value) : value(value), sem(dispatch_semaphore_create(value)) {}
        ~Semaphore()
        {
            // macOS cannot destroy a semaphore with posts less than the initializer
            for(int i = 0; i < get_value(); ++i){
                post();
            }
            dispatch_release(sem);
        }
        void wait() { dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER); }
        bool try_wait()
        {
            if(0 == dispatch_semaphore_wait(sem, DISPATCH_TIME_NOW)){
                return true;
            }else{
                return false;
            }
        }
        void post() { dispatch_semaphore_signal(sem); }
        int get_value() const { return value; }

    private:
        const int value;
        dispatch_semaphore_t sem;
};

#else

#include <errno.h>
#include <semaphore.h>

class Semaphore
{
    public:
        explicit Semaphore(int value) : value(value) { sem_init(&mutex, 0, value); }
        ~Semaphore() { sem_destroy(&mutex); }
        void wait()
        {
            int r;
            do {
                r = sem_wait(&mutex);
            } while (r == -1 && errno == EINTR);
        }
        bool try_wait()
        {
            int result;
            do{
                result = sem_trywait(&mutex);
            }while(result == -1 && errno == EINTR);

            return (0 == result);
        }
        void post() { sem_post(&mutex); }
        int get_value() const { return value; }

    private:
        const int value;
        sem_t mutex;
};

#endif

#endif // S3FS_SEMAPHORE_H_

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