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1 /*
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2 * Copyright 2009 OpenSourceCodeStewardshipFoundation.org
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3 * Licensed under GNU General Public License version 2
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4 *
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5 * NOTE: this version of SRSW correct as of April 25, 2010
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6 *
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7 * Author: seanhalle@yahoo.com
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8 */
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9
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10
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11 #include <stdio.h>
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12 #include <string.h>
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13 #include <errno.h>
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14 #include <stdlib.h>
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15
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16 #include "PrivateQueue.h"
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17
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18
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19
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20 //===========================================================================
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21
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22 /*This kind of queue is private to a single core at a time -- has no
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23 * synchronizations
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24 */
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25
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26 PrivQueueStruc* makePrivQ()
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27 {
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28 PrivQueueStruc* retQ;
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29 retQ = (PrivQueueStruc *) malloc( sizeof( PrivQueueStruc ) );
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30
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31 retQ->startOfData = malloc( 1024 * sizeof(void *) );
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32
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33 retQ->extractPos = &(retQ->startOfData[0]); //side by side == empty
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34 retQ->insertPos = &(retQ->startOfData[1]); // so start pos's have to be
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35 retQ->endOfData = &(retQ->startOfData[1023]);
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36
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37 return retQ;
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38 }
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39
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40 PrivQueueStruc* make_larger_PrivQ( PrivQueueStruc *Q )
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41 { int oldSize, newSize;
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42 void **oldStartOfData;
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43
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44 oldSize = Q->endOfData - Q->startOfData;
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45 newSize = 2 * oldSize;
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46 Q->startOfData = malloc( newSize * sizeof(void *) );
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47 memcpy(Q->startOfData, oldStartOfData, oldSize * sizeof(void *));
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48 free(oldStartOfData);
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49
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50 Q->extractPos = &(Q->startOfData[0]); //side by side == empty
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51 Q->insertPos = &(Q->startOfData[1]); // so start pos's have to be
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52 Q->endOfData = &(Q->startOfData[newSize - 1]);
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53
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54 return Q;
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55 }
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56
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57
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58 /*Returns NULL when queue is empty
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59 */
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60 void* readPrivQ( PrivQueueStruc* Q )
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61 { void *out = 0;
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62 int startOfData = Q->startOfData;
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63 int endOfData = Q->endOfData;
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64
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65 volatile int insertPos = Q->insertPos;
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66 volatile int extractPos = Q->extractPos;
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67
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68 //if not empty -- extract just below insert when empty
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69 if( insertPos - extractPos != 1 &&
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70 !(extractPos == endOfData && insertPos == startOfData))
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71 { //move before read
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72 if( extractPos == endOfData ) //write new pos exactly once, correctly
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73 { Q->extractPos = startOfData; //can't overrun then fix it 'cause
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74 } // other thread might read bad pos
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75 else
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76 { Q->extractPos++;
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77 }
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78 out = *(Q->extractPos);
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79 return out;
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80 }
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81 //Q is empty
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82 return NULL;
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83 }
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84
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85 /*Returns false when the queue was full.
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86 * have option of calling make_larger_PrivQ to make more room, then try again
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87 */
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88 bool8 writePrivQ( void * in, PrivQueueStruc* Q )
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89 {
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90 int startOfData = Q->startOfData;
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91 int endOfData = Q->endOfData;
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92
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93 volatile int insertPos = Q->insertPos;
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94 volatile int extractPos = Q->extractPos;
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95
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96 if( extractPos - insertPos != 1 &&
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97 !(insertPos == endOfData && extractPos == startOfData))
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98 { *(insertPos) = in; //insert before move
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99 if( insertPos == endOfData ) //write new pos exactly once, correctly
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100 { Q->insertPos = startOfData;
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101 }
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102 else
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103 { Q->insertPos++;
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104 }
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105 return TRUE;
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106 }
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107 //Q is full
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108 return FALSE;
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109 }
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110
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