116 lines
2.2 KiB
C++
116 lines
2.2 KiB
C++
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#ifndef _FIFO_QUEUE_H_
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#define _FIFO_QUEUE_H_
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// a simple lockless thread-safe,
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// single reader, single writer queue
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#include "common/atomic.h"
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namespace Common
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{
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template <typename T>
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class FifoQueue
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{
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public:
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FifoQueue() : m_size(0)
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{
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m_write_ptr = m_read_ptr = new ElementPtr();
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}
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~FifoQueue()
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{
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// this will empty out the whole queue
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delete m_read_ptr;
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}
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u32 Size() const
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{
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return m_size;
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}
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bool Empty() const
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{
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//return (m_read_ptr == m_write_ptr);
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return (0 == m_size);
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}
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T& Front() const
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{
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return *m_read_ptr->current;
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}
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template <typename Arg>
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void Push(Arg&& t)
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{
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// create the element, add it to the queue
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m_write_ptr->current = new T(std::forward<Arg>(t));
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// set the next pointer to a new element ptr
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// then advance the write pointer
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m_write_ptr = m_write_ptr->next = new ElementPtr();
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Common::AtomicIncrement(m_size);
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}
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void Pop()
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{
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Common::AtomicDecrement(m_size);
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ElementPtr *const tmpptr = m_read_ptr;
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// advance the read pointer
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m_read_ptr = m_read_ptr->next;
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// set the next element to NULL to stop the recursive deletion
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tmpptr->next = NULL;
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delete tmpptr; // this also deletes the element
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}
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bool Pop(T& t)
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{
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if (Empty())
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return false;
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t = std::move(Front());
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Pop();
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return true;
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}
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// not thread-safe
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void Clear()
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{
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m_size = 0;
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delete m_read_ptr;
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m_write_ptr = m_read_ptr = new ElementPtr();
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}
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private:
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// stores a pointer to element
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// and a pointer to the next ElementPtr
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class ElementPtr
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{
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public:
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ElementPtr() : current(NULL), next(NULL) {}
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~ElementPtr()
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{
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if (current)
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{
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delete current;
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// recusion ftw
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if (next)
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delete next;
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}
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}
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T *volatile current;
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ElementPtr *volatile next;
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};
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ElementPtr *volatile m_write_ptr;
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ElementPtr *volatile m_read_ptr;
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volatile u32 m_size;
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};
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}
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#endif
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