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Semaphore Class Reference

#include <synch.h>

List of all members.

Public Methods

 Semaphore (char *debugName, int initialValue)
 ~Semaphore ()
char * getName ()
void P ()
void V ()

Private Attributes

char * name
int value
List * queue

Constructor & Destructor Documentation

Semaphore::Semaphore (  char *    debugName,
int    initialValue
) 
 

Definition at line 36 of file synch.cc.

References name, queue, and value. 

00037 {
00038     name = debugName;
00039     value = initialValue;
00040     queue = new List;
00041 }

Semaphore::~Semaphore (    ) 
 

Definition at line 49 of file synch.cc.

References queue. 

00050 {
00051     delete queue;
00052 }

Member Function Documentation

char* Semaphore::getName (    )  [inline]
 

Definition at line 43 of file synch.h.

References name. 

00043 { return name;}                 // debugging assist

void Semaphore::P (    ) 
 

Definition at line 65 of file synch.cc.

References List::Append, IntOff, IntStatus, queue, and value.

Referenced by ConsoleTest, PostOffice::PostalDelivery, SynchConsole::ReadLine, SynchDisk::ReadSector, PostOffice::Send, SynchConsole::WriteLine, and SynchDisk::WriteSector. 

00066 {
00067     IntStatus oldLevel = interrupt->SetLevel(IntOff);   // disable interrupts
00068     
00069     while (value == 0) {                        // semaphore not available
00070         queue->Append((void *)currentThread);   // so go to sleep
00071         currentThread->Sleep();
00072     } 
00073     value--;                                    // semaphore available, 
00074                                                 // consume its value
00075     
00076     (void) interrupt->SetLevel(oldLevel);       // re-enable interrupts
00077 }

void Semaphore::V (    ) 
 

Definition at line 88 of file synch.cc.

References IntOff, IntStatus, NULL, queue, List::Remove, and value.

Referenced by PostOffice::IncomingPacket, PostOffice::PacketSent, SynchConsole::ReadAvail, ReadAvail, SynchDisk::RequestDone, SynchConsole::WriteDone, and WriteDone. 

00089 {
00090     Thread *thread;
00091     IntStatus oldLevel = interrupt->SetLevel(IntOff);
00092 
00093     thread = (Thread *)queue->Remove();
00094     if (thread != NULL)    // make thread ready, consuming the V immediately
00095         scheduler->ReadyToRun(thread);
00096     value++;
00097     (void) interrupt->SetLevel(oldLevel);
00098 }

Member Data Documentation

char* Semaphore::name [private]
 

Definition at line 49 of file synch.h.

Referenced by getName, and Semaphore.

List* Semaphore::queue [private]
 

Definition at line 51 of file synch.h.

Referenced by P, Semaphore, V, and ~Semaphore.

int Semaphore::value [private]
 

Definition at line 50 of file synch.h.

Referenced by P, Semaphore, and V.

The documentation for this class was generated from the following files:
Generated on Mon Feb 10 09:54:58 2003 for nachos by doxygen1.2.14 written by Dimitri van Heesch, © 1997-2002
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