128 lines
3.1 KiB
C++
128 lines
3.1 KiB
C++
#ifndef _library_triplebuffer__hpp__included__
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#define _library_triplebuffer__hpp__included__
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#include <functional>
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#include <stdexcept>
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#include "threads.hpp"
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namespace triplebuffer
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{
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/**
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* Triple-buffering logic.
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*/
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class logic
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{
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public:
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/**
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* Create a new triple buffer.
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*/
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logic() throw();
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/**
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* Get read pointer and increment read count by 1.
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*
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* Return value: Read pointer (0-2).
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*
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* Note: If read count is zero, last complete buffer is returned. Otherwise the same buffer as last call is returned.
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*/
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unsigned get_read() throw();
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/**
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* Put read pointer and decrement read count by 1.
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*
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* Throws std::logic_error: If read count is 0.
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*/
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void put_read();
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/**
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* Get write pointer and increment write count by 1.
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*
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* Return value: Write pointer (0-2).
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*
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* Note: If write count is nonzero before call, the returned buffer is the same as last time.
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*/
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unsigned get_write() throw();
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/**
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* Put write pointer and decrement write count by 1. If write count hits 0, the buffer is marked as last complete
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* buffer.
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*
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* Throws std::logic_error: If write count is 0.
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*/
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void put_write();
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/**
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* Call specified function synchronously for last written buffer.
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*
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* The buffer number is passed to specified function.
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*/
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void read_last_write_synchronous(std::function<void(unsigned)> fn) throw();
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private:
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threads::lock lock;
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unsigned last_complete; //Number of last completed buffer
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unsigned current_read; //Number of current read buffer (only valid if count_read > 0).
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unsigned current_write; //Number of current write buffer (only valid if count_write > 0).
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unsigned count_read; //Number of readers.
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unsigned count_write; //Number of writers.
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};
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/**
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* Triple buffer with objects.
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*/
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template<typename T>
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class triplebuffer
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{
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public:
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/**
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* Create a new triple buffer.
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*
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* Parameter A: Object #1.
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* Parameter B: Object #2.
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* Parameter C: Object #3.
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*/
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triplebuffer(T& A, T& B, T& C) throw()
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{
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objs[0] = &A;
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objs[1] = &B;
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objs[2] = &C;
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}
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/**
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* Get read pointer and increment read count by 1.
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*
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* Return value: Read pointer.
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*
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* Note: If read count is zero, last complete buffer is returned. Otherwise the same buffer as last call is returned.
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*/
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T& get_read() throw() { return *objs[l.get_read()]; }
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/**
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* Put read pointer and decrement read count by 1.
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*
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* Throws std::logic_error: If read count is 0.
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*/
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void put_read() { l.put_read(); }
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/**
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* Get write pointer and increment write count by 1.
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*
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* Return value: Write pointer.
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*
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* Note: If write count is nonzero before call, the returned buffer is the same as last time.
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*/
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T& get_write() throw() { return *objs[l.get_write()]; }
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/**
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* Put write pointer and decrement write count by 1. If write count hits 0, the buffer is marked as last complete
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* buffer.
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*
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* Throws std::logic_error: If write count is 0.
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*/
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void put_write() { l.put_write(); }
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/**
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* Call specified function synchronously for last written buffer.
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*
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* The buffer itself is passed to the function.
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*/
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void read_last_write_synchronous(std::function<void(T&)> fn) throw()
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{
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l.read_last_write_synchronous([this,fn](unsigned x){ fn(*objs[x]); });
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}
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private:
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T* objs[3];
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logic l;
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};
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}
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#endif
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