Implement IIRFilter node for WebAudio.

third_party/WebKit/Source/modules/webaudio/IIRProcessor.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef IIRProcessor_h
+#define IIRProcessor_h
+
+#include "modules/webaudio/AudioNode.h"
+#include "platform/audio/AudioDSPKernel.h"
+#include "platform/audio/AudioDSPKernelProcessor.h"
+#include "platform/audio/IIRFilter.h"
+
+namespace blink {
+
+class IIRDSPKernel;
+
+class IIRProcessor final : public AudioDSPKernelProcessor {
+public:
+    IIRProcessor(float sampleRate, size_t numberOfChannels,
+        const Vector<double>& feedforwardCoef, const Vector<double>& feedbackCoef);
+    ~IIRProcessor() override;
+
+    PassOwnPtr<AudioDSPKernel> createKernel() override;
+
+    void process(const AudioBus* source, AudioBus* destination, size_t framesToProcess) override;
+
+    // Get the magnitude and phase response of the filter at the given
+    // set of frequencies (in Hz). The phase response is in radians.
+    void getFrequencyResponse(int nFrequencies, const float* frequencyHz, float* magResponse, float* phaseResponse);
+
+    AudioDoubleArray* feedback() { return &m_feedback; }
+    AudioDoubleArray* feedforward() { return &m_feedforward; }
+
+private:
+    // The feedback and feedforward filter coefficients for the IIR filter.
+    AudioDoubleArray m_feedback;
+    AudioDoubleArray m_feedforward;
+    // This holds the IIR kernel for computing the frequency response.
+    OwnPtr<IIRDSPKernel> m_responseKernel;
+};
+
+} // namespace blink
+
+#endif // IIRProcessor_h