first re-commit.

pigpio-master/EXAMPLES/CPP/IR_RECEIVER/ir_hasher.cpp

@@ -0,0 +1,91 @@
+#include <pigpio.h>
+
+#include "ir_hasher.hpp"
+
+void Hasher::_hash(int old_val, int new_val)
+{
+   int val;
+
+   if      (new_val < (old_val * 0.60)) val = 13;
+   else if (old_val < (new_val * 0.60)) val = 23;
+   else                                 val = 2;
+
+   hash_val ^= val;
+   hash_val *= 16777619; /* FNV_PRIME_32 */
+}
+
+void Hasher::_callback(int gpio, int level, uint32_t tick)
+{
+   if (level != PI_TIMEOUT)
+   {
+      if (in_code == 0)
+      {
+         in_code = 1;
+
+         gpioSetWatchdog(mygpio, mytimeout);
+
+         hash_val = 2166136261U; /* FNV_BASIS_32 */
+
+         edges = 1;
+
+         t1 = 0;
+         t2 = 0;
+         t3 = 0;
+         t4 = tick;
+      }
+      else
+      {
+         edges++;
+
+         t1 = t2;
+         t2 = t3;
+         t3 = t4;
+         t4 = tick;
+
+         if (edges > 3) _hash(t2-t1, t4-t3);
+      }
+   }
+   else
+   {
+      if (in_code)
+      {
+         in_code = 0;
+
+         gpioSetWatchdog(mygpio, 0);
+
+         if (edges > 12) /* Anything less is probably noise. */
+         {
+            (mycallback)(hash_val);
+         }
+      }
+   }
+}
+
+void Hasher::_callbackExt(int gpio, int level, uint32_t tick, void *user)
+{
+   /*
+      Need a static callback to link with C.
+   */
+
+   Hasher *mySelf = (Hasher *) user;
+
+   mySelf->_callback(gpio, level, tick); /* Call the instance callback. */
+}
+
+Hasher::Hasher(int gpio, HasherCB_t callback, int timeout)
+{
+   /*
+      Initialises an IR remote hasher on a gpio.  A gap of timeout
+      milliseconds indicates the end of the remote key press.
+   */
+   mygpio     = gpio;
+   mycallback = callback;
+   mytimeout  = timeout;
+
+   in_code = 0;
+
+   gpioSetMode(gpio, PI_INPUT);
+
+   gpioSetAlertFuncEx(gpio, _callbackExt, (void *)this);
+}
+