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diff --git a/webrtc/modules/audio_processing/utility/pffft_wrapper.h b/webrtc/modules/audio_processing/utility/pffft_wrapper.h
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+/*
+ *  Copyright (c) 2019 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef MODULES_AUDIO_PROCESSING_UTILITY_PFFFT_WRAPPER_H_
+#define MODULES_AUDIO_PROCESSING_UTILITY_PFFFT_WRAPPER_H_
+
+#include <memory>
+
+#include "api/array_view.h"
+
+// Forward declaration.
+struct PFFFT_Setup;
+
+namespace webrtc {
+
+// Pretty-Fast Fast Fourier Transform (PFFFT) wrapper class.
+// Not thread safe.
+class Pffft {
+ public:
+  enum class FftType { kReal, kComplex };
+
+  // 1D floating point buffer used as input/output data type for the FFT ops.
+  // It must be constructed using Pffft::CreateBuffer().
+  class FloatBuffer {
+   public:
+    FloatBuffer(const FloatBuffer&) = delete;
+    FloatBuffer& operator=(const FloatBuffer&) = delete;
+    ~FloatBuffer();
+
+    rtc::ArrayView<const float> GetConstView() const;
+    rtc::ArrayView<float> GetView();
+
+   private:
+    friend class Pffft;
+    FloatBuffer(size_t fft_size, FftType fft_type);
+    const float* const_data() const { return data_; }
+    float* data() { return data_; }
+    size_t size() const { return size_; }
+
+    const size_t size_;
+    float* const data_;
+  };
+
+  // TODO(https://crbug.com/webrtc/9577): Consider adding a factory and making
+  // the ctor private.
+  // static std::unique_ptr<Pffft> Create(size_t fft_size,
+  // FftType fft_type); Ctor. |fft_size| must be a supported size (see
+  // Pffft::IsValidFftSize()). If not supported, the code will crash.
+  Pffft(size_t fft_size, FftType fft_type);
+  Pffft(const Pffft&) = delete;
+  Pffft& operator=(const Pffft&) = delete;
+  ~Pffft();
+
+  // Returns true if the FFT size is supported.
+  static bool IsValidFftSize(size_t fft_size, FftType fft_type);
+
+  // Returns true if SIMD code optimizations are being used.
+  static bool IsSimdEnabled();
+
+  // Creates a buffer of the right size.
+  std::unique_ptr<FloatBuffer> CreateBuffer() const;
+
+  // TODO(https://crbug.com/webrtc/9577): Overload with rtc::ArrayView args.
+  // Computes the forward fast Fourier transform.
+  void ForwardTransform(const FloatBuffer& in, FloatBuffer* out, bool ordered);
+  // Computes the backward fast Fourier transform.
+  void BackwardTransform(const FloatBuffer& in, FloatBuffer* out, bool ordered);
+
+  // Multiplies the frequency components of |fft_x| and |fft_y| and accumulates
+  // them into |out|. The arrays must have been obtained with
+  // ForwardTransform(..., /*ordered=*/false) - i.e., |fft_x| and |fft_y| must
+  // not be ordered.
+  void FrequencyDomainConvolve(const FloatBuffer& fft_x,
+                               const FloatBuffer& fft_y,
+                               FloatBuffer* out,
+                               float scaling = 1.f);
+
+ private:
+  const size_t fft_size_;
+  const FftType fft_type_;
+  PFFFT_Setup* pffft_status_;
+  float* const scratch_buffer_;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_AUDIO_PROCESSING_UTILITY_PFFFT_WRAPPER_H_