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/projects/cubeos/src_current/kernel/seminl.h

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/*  src_experimental/kernel/seminl.h
    CubeOS Version 0.4.90 experimental
    Copyright (C) 1999,2000 Holger Kenn

    CubeOS is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or any later version.

    CubeOS 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
    Library General Public License for more details.

*/  
#ifndef _SEMINL_H
#define _SEMINL_H

#ifdef MULTI_SEM

typedef struct sem_s {
        int init; 
        int c;    
        int task; 
        } sem_t;



static inline void sem_post(sem_t x)
{
        if (!x.init) return;
        disable();
        x.c++;
        if (x.task!=NO_TASK)
        {
                wakeup(x.task); // this resets the task state, 
                                                // but we're still in disable()d state!
                x.task=_KERN_ptable[x.task].next;
        }
        enable();
}


#define sem_signal(x) sem_post(x) 


static inline void sem_wait(sem_t x)
{
        if (!x.init) return;
        disable();      
        x.c--;
        if (x.c<0){
                // put ourself to sleep
                if (x.task == NO_TASK)
                {
                        _KERN_ptable[getpid()].next=NO_TASK;
                } 
                else
                {
                        _KERN_ptable[getpid()].next=x.task;
                }
                x.task=getpid();
                enable();
                KERN_suspend(getpid());
        } 
        else 
        {
                enable(); // the semaphore was free
        }
}

#define sem_trywait(x) (x.c<0) 
#define sem_getvalue(x,i) (*i=x.c) 


static inline int sem_init(sem_t x,int i,int v)
{
        if (x.init) return (-1);
        disable();
        x.c=v;
        x.task=NO_TASK;
        x.init=1;
        enable();
        return (0);
}

static inline int sem_destroy(sem_t x)
{
        if (!x.init) return (-1);
        disable();
        while(x.task!=NO_TASK)
                {
                        wakeup(x.task); // this resets the task state, 
                                                        // but we're still in disable()d state!
                        x.task=_KERN_ptable[x.task].next;
                }
        enable();
        return(0);
}
#endif // of ifdef MULTI_SEM
#endif // of ifndef _SEMINL_H

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