[2798] | 1 | /* -*- mode: c++; c-basic-offset: 4; indent-tabs-mode: nil -*- */ |
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[2096] | 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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