1 | /* -*- mode: c++; c-basic-offset: 4; indent-tabs-mode: nil -*- */ |
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2 | /* CircularFifo.h |
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3 | * Not any company's property but Public-Domain |
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4 | * Do with source-code as you will. No requirement to keep this |
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5 | * header if need to use it/change it/ or do whatever with it |
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6 | * |
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7 | * Note that there is No guarantee that this code will work |
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8 | * and I take no responsibility for this code and any problems you |
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9 | * might get if using it. The code is highly platform dependent! |
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10 | * |
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11 | * Code & platform dependent issues with it was originally |
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12 | * published at http://www.kjellkod.cc/threadsafecircularqueue |
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13 | * 2009-11-02 |
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14 | * @author Kjell Hedström, hedstrom@kjellkod.cc */ |
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15 | |
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16 | #ifndef CIRCULARFIFO_H_ |
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17 | #define CIRCULARFIFO_H_ |
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18 | |
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19 | /** Circular Fifo (a.k.a. Circular Buffer) |
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20 | * Thread safe for one reader, and one writer */ |
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21 | template<typename Element, unsigned int Size> |
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22 | class CircularFifo { |
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23 | public: |
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24 | enum {Capacity = Size+1}; |
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25 | |
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26 | CircularFifo() : tail(0), head(0){} |
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27 | virtual ~CircularFifo() {} |
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28 | |
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29 | bool push(Element& item_); |
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30 | bool pop(Element& item_); |
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31 | bool isEmpty() const; |
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32 | bool isFull() const; |
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33 | |
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34 | // INSOO |
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35 | bool push(); |
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36 | int tailIndex(); |
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37 | bool pop(); |
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38 | bool top(Element&); |
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39 | |
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40 | public: |
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41 | volatile unsigned int tail; // input index |
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42 | Element array[Capacity]; |
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43 | volatile unsigned int head; // output index |
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44 | |
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45 | unsigned int increment(unsigned int idx_) const; |
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46 | }; |
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47 | |
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48 | |
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49 | |
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50 | |
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51 | /** Producer only: Adds item to the circular queue. |
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52 | * If queue is full at 'push' operation no update/overwrite |
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53 | * will happen, it is up to the caller to handle this case |
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54 | * |
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55 | * \param item_ copy by reference the input item |
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56 | * \return whether operation was successful or not */ |
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57 | template<typename Element, unsigned int Size> |
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58 | bool CircularFifo<Element, Size>::push(Element& item_) |
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59 | { |
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60 | int nextTail = increment(tail); |
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61 | if(((unsigned int) nextTail) != head) |
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62 | { |
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63 | array[tail] = item_; |
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64 | tail = nextTail; |
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65 | return true; |
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66 | } |
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67 | |
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68 | // queue was full |
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69 | return false; |
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70 | } |
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71 | |
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72 | template<typename Element, unsigned int Size> |
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73 | bool CircularFifo<Element, Size>::top(Element& data) |
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74 | { |
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75 | if(head == tail) |
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76 | return false; // empty queue |
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77 | |
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78 | data = array[head]; |
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79 | head = increment(head); |
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80 | return true; |
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81 | } |
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82 | |
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83 | |
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84 | /** Consumer only: Removes and returns item from the queue |
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85 | * If queue is empty at 'pop' operation no retrieve will happen |
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86 | * It is up to the caller to handle this case |
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87 | * |
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88 | * \param item_ return by reference the wanted item |
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89 | * \return whether operation was successful or not */ |
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90 | template<typename Element, unsigned int Size> |
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91 | bool CircularFifo<Element, Size>::pop(Element& item_) |
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92 | { |
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93 | if(head == tail) |
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94 | return false; // empty queue |
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95 | |
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96 | item_ = array[head]; |
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97 | head = increment(head); |
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98 | return true; |
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99 | } |
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100 | |
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101 | /** Consumer only: Removes and returns item from the queue |
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102 | * If queue is empty at 'pop' operation no retrieve will happen |
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103 | * It is up to the caller to handle this case |
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104 | * |
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105 | * \return whether operation was successful or not */ |
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106 | template<typename Element, unsigned int Size> |
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107 | bool CircularFifo<Element, Size>::pop() |
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108 | { |
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109 | if(head == tail) |
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110 | return false; // empty queue |
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111 | head = increment(head); |
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112 | return true; |
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113 | } |
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114 | |
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115 | /** Useful for testinng and Consumer check of status |
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116 | * Remember that the 'empty' status can change quickly |
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117 | * as the Procuder adds more items. |
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118 | * |
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119 | * \return true if circular buffer is empty */ |
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120 | template<typename Element, unsigned int Size> |
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121 | bool CircularFifo<Element, Size>::isEmpty() const |
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122 | { |
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123 | return (head == tail); |
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124 | } |
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125 | |
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126 | /** Useful for testing and Producer check of status |
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127 | * Remember that the 'full' status can change quickly |
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128 | * as the Consumer catches up. |
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129 | * |
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130 | * \return true if circular buffer is full. */ |
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131 | template<typename Element, unsigned int Size> |
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132 | bool CircularFifo<Element, Size>::isFull() const |
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133 | { |
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134 | int tailCheck = (tail+1) % Capacity; |
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135 | return (((unsigned int) tailCheck) == head); |
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136 | } |
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137 | |
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138 | /** Increment helper function for index of the circular queue |
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139 | * index is inremented or wrapped |
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140 | * |
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141 | * \param idx_ the index to the incremented/wrapped |
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142 | * \return new value for the index */ |
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143 | template<typename Element, unsigned int Size> |
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144 | unsigned int CircularFifo<Element, Size>::increment(unsigned int idx_) const |
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145 | { |
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146 | // increment or wrap |
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147 | // ================= |
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148 | // index++; |
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149 | // if(index == array.lenght) -> index = 0; |
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150 | // |
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151 | //or as written below: |
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152 | // index = (index+1) % array.length |
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153 | idx_ = (idx_+1) % Capacity; |
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154 | return idx_; |
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155 | } |
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156 | |
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157 | template<typename Element, unsigned int Size> |
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158 | int CircularFifo<Element, Size>::tailIndex() |
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159 | { |
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160 | int nextTail = increment(tail); |
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161 | if(((unsigned int)nextTail) != head) |
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162 | { |
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163 | return tail; |
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164 | } |
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165 | |
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166 | return -1; |
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167 | } |
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168 | |
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169 | |
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170 | template<typename Element, unsigned int Size> |
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171 | bool CircularFifo<Element, Size>::push() |
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172 | { |
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173 | int nextTail = increment(tail); |
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174 | if(((unsigned int)nextTail) != head) |
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175 | { |
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176 | tail = nextTail; |
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177 | return true; |
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178 | } |
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179 | |
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180 | return false; |
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181 | } |
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182 | |
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183 | #endif /* CIRCULARFIFO_H_ */ |
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