InfoMagic Source Code 1993 July/THE_SOURCE_CODE_CD_ROM.iso/gnu/nihcl-3.0/lib/Semaphore.c

C/C++ Source or Header | 1990-05-19 | 4.1 KB | 205 lines

/* Semaphore.c -- implementation of Semaphore

    THIS SOFTWARE FITS THE DESCRIPTION IN THE U.S. COPYRIGHT ACT OF A
    "UNITED STATES GOVERNMENT WORK".  IT WAS WRITTEN AS A PART OF THE
    AUTHOR'S OFFICIAL DUTIES AS A GOVERNMENT EMPLOYEE.  THIS MEANS IT
    CANNOT BE COPYRIGHTED.  THIS SOFTWARE IS FREELY AVAILABLE TO THE
    PUBLIC FOR USE WITHOUT A COPYRIGHT NOTICE, AND THERE ARE NO
    RESTRICTIONS ON ITS USE, NOW OR SUBSEQUENTLY.

Author:
    K. E. Gorlen
    Bg. 12A, Rm. 2033
    Computer Systems Laboratory
    Division of Computer Research and Technology
    National Institutes of Health
    Bethesda, Maryland 20892
    Phone: [phone]
    uucp: uunet!nih-csl!kgorlen
    Internet: [e-mail]
    December, 1985

Function:

Objects of class Semaphore are used to synchronize Processes.

$Log:    Semaphore.c,v $
 * Revision 3.0  90/05/20  00:21:08  kgorlen
 * Release for 1st edition.
 *
*/

#include "Semaphore.h"
#include "Process.h"
#include "Scheduler.h"
#include "nihclIO.h"

#define    THIS    Semaphore
#define    BASE    Object
#define BASE_CLASSES BASE::desc()
#define MEMBER_CLASSES LinkedList::desc()
#define VIRTUAL_BASE_CLASSES Object::desc()

DEFINE_CLASS(Semaphore,1,"$Header: /afs/alw.nih.gov/unix/sun4_40c/usr/local/src/nihcl-3.0/share/lib/RCS/Semaphore.c,v 3.0 90/05/20 00:21:08 kgorlen Rel $",NULL,NULL);

extern const int NIHCL_ASTBLK,NIHCL_DLSEMWAIT,NIHCL_CPSEMWAIT,NIHCL_STSEMWAIT;

Semaphore::Semaphore(int initialCount)    { count = initialCount; }

#ifndef BUG_TOOBIG
// yacc stack overflow

Semaphore::Semaphore(const Semaphore& s) : waitList(s.waitList)
{
    count = s.count;
}

#endif

void Semaphore::signal(unsigned n)
{
    if (n == 0) return;
    AST_DISABLE;
        register Process* next;
        while (count<0 && n>0) {
            next = Process::castdown(waitList.removeFirst());
            if (next->state() != Process::TERMINATED) {
                next->resume();
                n--;
            }
            count++;
        }
        count += n;
    AST_ENABLE;
}

void Semaphore::wait()
{
    AST_DISABLE;
        if (--count < 0) {
            if (Scheduler::astActive()) setError(NIHCL_ASTBLK,DEFAULT,this,className(),"wait");
            Scheduler::activeProcess().suspend();
            waitList.addLast(Scheduler::activeProcess());
        }
    AST_ENABLE;
    if (count < 0) Scheduler::schedule();
}

Semaphore::~Semaphore()
{
    if (count<0) setError(NIHCL_DLSEMWAIT,DEFAULT,-count,this,className());
}

Object* Semaphore::copy() const    { return deepCopy(); }

void Semaphore::deepenShallowCopy()
{
    if (count < 0) setError(NIHCL_CPSEMWAIT,DEFAULT,-count,this,className());
}

unsigned Semaphore::hash() const    { return (unsigned)this; }

bool Semaphore::isEqual(const Object& ob) const    { return isSame(ob); }

void Semaphore::dumpOn(ostream& strm) const
{
    strm << className() << "[count: " << count << '\n';
    DO(waitList,Process,p) p->dumpOn(strm); OD
    strm << "]\n";
}

void Semaphore::printOn(ostream& strm) const
{
    strm << "count: " << count;
    if (count < 0) strm << "  waitList:";
    DO(waitList,Process,p) strm << ' ' << *p; OD
}

bool Semaphore::includes(const Process& p) const
{
    AST_DISABLE;
    bool i = waitList.includes(p);
    AST_ENABLE;
    return i;
}

Process* Semaphore::remove(Process& p)
{
    AST_DISABLE;
    if (count < 0 && waitList.includes(p)) {
        waitList.remove(p);
        ++count;
        AST_ENABLE;
        return &p;
    }
    else {
        AST_ENABLE;
        return 0;
    }
}

Process* Semaphore::removeFirst()
{
    AST_DISABLE;
    if (count < 0) {
        Process* p = Process::castdown(waitList.removeFirst());
        ++count;
        AST_ENABLE;
        return p;
    }
    else {
        AST_ENABLE;
        return 0;
    }
}

Process* Semaphore::removeLast()
{
    AST_DISABLE;
    if (count < 0) {
        Process* p = Process::castdown(waitList.removeLast());
        ++count;
        AST_ENABLE;
        return p;
    }
    else {
        AST_ENABLE;
        return 0;
    }
}

int Semaphore::value() const    { return count; }

Semaphore::Semaphore(OIOin& strm)
    : BASE(strm)
{
    strm >> count;
}

void Semaphore::storer(OIOout& strm) const
{
    if (count < 0) setError(NIHCL_STSEMWAIT,DEFAULT,-count,this,className());
    BASE::storer(strm);
    strm << count;
}

Semaphore::Semaphore(OIOifd& fd)
    : BASE(fd)
{
    fd >> count;
}

void Semaphore::storer(OIOofd& fd) const
{
    if ( count < 0 )
        setError(NIHCL_STSEMWAIT,DEFAULT,-count,this,className());
    BASE::storer(fd);
    fd << count;
}

int Semaphore::compare(const Object&) const
{
    shouldNotImplement("compare");
    return 0;
}