include/library/triplebuffer.hpp

   1 #ifndef _library_triplebuffer__hpp__included__
   2 #define _library_triplebuffer__hpp__included__
   3
   4 #include <stdexcept>
   5 #include "threads.hpp"
   6
   7 namespace triplebuffer
   8 {
   9 /**
  10  * Triple-buffering logic.
  11  */
  12 class logic
  13 {
  14 public:
  15 /**
  16  * Create a new triple buffer.
  17  */
  18         logic() throw();
  19 /**
  20  * Get read pointer and increment read count by 1.
  21  *
  22  * Return value: Read pointer (0-2).
  23  *
  24  * Note: If read count is zero, last complete buffer is returned. Otherwise the same buffer as last call is returned.
  25  */
  26         unsigned get_read() throw();
  27 /**
  28  * Put read pointer and decrement read count by 1.
  29  *
  30  * Throws std::logic_error: If read count is 0.
  31  */
  32         void put_read() throw(std::logic_error);
  33 /**
  34  * Get write pointer and increment write count by 1.
  35  *
  36  * Return value: Write pointer (0-2).
  37  *
  38  * Note: If write count is nonzero before call, the returned buffer is the same as last time.
  39  */
  40         unsigned get_write() throw();
  41 /**
  42  * Put write pointer and decrement write count by 1. If write count hits 0, the buffer is marked as last complete
  43  * buffer.
  44  *
  45  * Throws std::logic_error: If write count is 0.
  46  */
  47         void put_write() throw(std::logic_error);
  48 private:
  49         threads::lock lock;
  50         unsigned last_complete;         //Number of last completed buffer
  51         unsigned current_read;          //Number of current read buffer (only valid if count_read > 0).
  52         unsigned current_write;         //Number of current write buffer (only valid if count_write > 0).
  53         unsigned count_read;            //Number of readers.
  54         unsigned count_write;           //Number of writers.
  55 };
  56
  57 /**
  58  * Triple buffer with objects.
  59  */
  60 template<typename T>
  61 class triplebuffer
  62 {
  63 public:
  64 /**
  65  * Create a new triple buffer.
  66  *
  67  * Parameter A: Object #1.
  68  * Parameter B: Object #2.
  69  * Parameter C: Object #3.
  70  */
  71         triplebuffer(T& A, T& B, T& C) throw()
  72         {
  73                 objs[0] = &A;
  74                 objs[1] = &B;
  75                 objs[2] = &C;
  76         }
  77 /**
  78  * Get read pointer and increment read count by 1.
  79  *
  80  * Return value: Read pointer.
  81  *
  82  * Note: If read count is zero, last complete buffer is returned. Otherwise the same buffer as last call is returned.
  83  */
  84         T& get_read() throw() { return *objs[l.get_read()]; }
  85 /**
  86  * Put read pointer and decrement read count by 1.
  87  *
  88  * Throws std::logic_error: If read count is 0.
  89  */
  90         void put_read() throw(std::logic_error) { l.put_read(); }
  91 /**
  92  * Get write pointer and increment write count by 1.
  93  *
  94  * Return value: Write pointer.
  95  *
  96  * Note: If write count is nonzero before call, the returned buffer is the same as last time.
  97  */
  98         T& get_write() throw() { return *objs[l.get_write()]; }
  99 /**
 100  * Put write pointer and decrement write count by 1. If write count hits 0, the buffer is marked as last complete
 101  * buffer.
 102  *
 103  * Throws std::logic_error: If write count is 0.
 104  */
 105         void put_write() throw(std::logic_error) { l.put_write(); }
 106 private:
 107         T* objs[3];
 108         logic l;
 109 };
 110 }
 111
 112 #endif