From aa45dcbd178e5b7fe85a5df2b11eb41e5168bc7f Mon Sep 17 00:00:00 2001
From: f4exb <f4exb06@gmail.com>
Date: Mon, 10 Oct 2016 02:08:48 +0200
Subject: [PATCH] Add an interpolate method to the Interpolator class

---
 sdrbase/dsp/interpolator.h | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/sdrbase/dsp/interpolator.h b/sdrbase/dsp/interpolator.h
index cdd7055ef..1ce9da83d 100644
--- a/sdrbase/dsp/interpolator.h
+++ b/sdrbase/dsp/interpolator.h
@@ -35,6 +35,24 @@ public:
 		return true;
 	}
 
+	// interpolation works nearly the same way
+	bool interpolate(Real *distance, const Complex& next, Complex* result)
+	{
+        *distance -= 1.0;
+
+        if (*distance < 1.0) // use sample
+        {
+            advanceFilter(next);
+            doInterpolate((int) floor(*distance * (Real)m_phaseSteps), result);
+            return true;  // need new input sample and increment distance
+        }
+        else // use zero
+        {
+            advanceFilter();
+            doInterpolate((int) floor(*distance * (Real)m_phaseSteps), result);
+            return false; // input sample was not used and do not increment distance
+        }
+	}
 
 private:
 	float* m_taps;
@@ -56,6 +74,15 @@ private:
 		m_samples[m_ptr] = next;
 	}
 
+    void advanceFilter()
+    {
+        m_ptr--;
+        if(m_ptr < 0)
+            m_ptr = m_nTaps - 1;
+        m_samples[m_ptr].real(0.0);
+        m_samples[m_ptr].imag(0.0);
+    }
+
 	void doInterpolate(int phase, Complex* result)
 	{
 		if (phase < 0)