Me@0: /*
Me@0:  *  Copyright 2009 OpenSourceCodeStewardshipFoundation.org
Me@0:  *  Licensed under GNU General Public License version 2
Me@0:  *
Me@0:  * NOTE: this version of SRSW correct as of April 25, 2010
Me@0:  *
Me@0:  * Author: seanhalle@yahoo.com
Me@0:  */
Me@0: 
Me@0: 
Me@0: #include <stdio.h>
Me@0: #include <string.h>
Me@0: #include <errno.h>
Me@0: #include <stdlib.h>
Me@0: 
Me@0: #include "PrivateQueue.h"
Me@0: 
Me@0: 
Me@0: 
Me@0: //===========================================================================
Me@0: 
Me@0: /*This kind of queue is private to a single core at a time -- has no
Me@0:  * synchronizations 
Me@0:  */
Me@0: 
Me@0: PrivQueueStruc* makePrivQ()
Me@0:  {
Me@0:    PrivQueueStruc* retQ;
Me@0:    retQ = (PrivQueueStruc *) malloc( sizeof( PrivQueueStruc ) );
Me@0: 
Me@0:    retQ->startOfData = malloc( 1024 * sizeof(void *) );
Me@0:    
Me@0:    retQ->extractPos = &(retQ->startOfData[0]); //side by side == empty
Me@0:    retQ->insertPos  = &(retQ->startOfData[1]); // so start pos's have to be
Me@0:    retQ->endOfData  = &(retQ->startOfData[1023]);
Me@0: 
Me@0:    return retQ;
Me@0:  }
Me@0: 
Me@0: PrivQueueStruc* make_larger_PrivQ( PrivQueueStruc *Q )
Me@0:  { int    oldSize, newSize;
Me@0:    void **oldStartOfData;
Me@0: 
Me@0:    oldSize           = Q->endOfData - Q->startOfData;
Me@0:    newSize           = 2 * oldSize;
Me@0:    Q->startOfData = malloc( newSize * sizeof(void *) );
Me@0:    memcpy(Q->startOfData, oldStartOfData, oldSize * sizeof(void *));
Me@0:    free(oldStartOfData);
Me@0:    
Me@0:    Q->extractPos  = &(Q->startOfData[0]); //side by side == empty
Me@0:    Q->insertPos   = &(Q->startOfData[1]); // so start pos's have to be
Me@0:    Q->endOfData   = &(Q->startOfData[newSize - 1]);
Me@0: 
Me@0:    return Q;
Me@0:  }
Me@0: 
Me@0: 
Me@0: /*Returns NULL when queue is empty
Me@0:  */
Me@0: void* readPrivQ( PrivQueueStruc* Q )
Me@0:  { void *out    = 0;
Me@0:    int  startOfData = Q->startOfData;
Me@0:    int  endOfData   = Q->endOfData;
Me@0: 
Me@0:    volatile int insertPos  = Q->insertPos;
Me@0:    volatile int extractPos = Q->extractPos;
Me@0: 
Me@0:       //if not empty -- extract just below insert when empty
Me@0:    if( insertPos - extractPos != 1 &&
Me@0:        !(extractPos == endOfData && insertPos == startOfData))
Me@0:     {    //move before read
Me@0:       if( extractPos == endOfData ) //write new pos exactly once, correctly
Me@0:        { Q->extractPos = startOfData; //can't overrun then fix it 'cause
Me@0:        }                              // other thread might read bad pos
Me@0:       else
Me@0:        { Q->extractPos++;
Me@0:        }
Me@0:       out = *(Q->extractPos);
Me@0:       return out;
Me@0:     }
Me@0:       //Q is empty
Me@0:    return NULL;
Me@0:  }
Me@0: 
Me@0: /*Returns false when the queue was full.
Me@0:  * have option of calling make_larger_PrivQ to make more room, then try again
Me@0:  */
Me@0: bool8 writePrivQ( void * in, PrivQueueStruc* Q )
Me@0:  {
Me@0:    int  startOfData = Q->startOfData;
Me@0:    int  endOfData   = Q->endOfData;
Me@0:    
Me@0:    volatile int insertPos  = Q->insertPos;
Me@0:    volatile int extractPos = Q->extractPos;
Me@0: 
Me@0:    if( extractPos - insertPos != 1 &&
Me@0:        !(insertPos == endOfData && extractPos == startOfData))
Me@0:     { *(insertPos) = in;   //insert before move
Me@0:       if( insertPos == endOfData ) //write new pos exactly once, correctly
Me@0:        { Q->insertPos = startOfData;
Me@0:        }
Me@0:       else
Me@0:        { Q->insertPos++;
Me@0:        }
Me@0:       return TRUE;
Me@0:     }
Me@0:       //Q is full
Me@0:    return FALSE;
Me@0:  }
Me@0: