From 1a219839034e9b11a4771fb84c90d4a2667365ce Mon Sep 17 00:00:00 2001
From: Roland Stigge <stigge@antcom.de>
Date: Sat, 16 Feb 2019 23:37:21 +0100
Subject: Added IFFT + AutoCorrelation

---
 fft.h | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

(limited to 'fft.h')

diff --git a/fft.h b/fft.h
index f2b7038..8c1e161 100644
--- a/fft.h
+++ b/fft.h
@@ -3,10 +3,12 @@
 #pragma once
 
 #include <complex>
+#include <memory>
 #include <vector>
 
 namespace RIT {
 
+// Fast Fourier Transform
 class FFT {
 private:
 	int mSize;
@@ -17,18 +19,42 @@ private:
 
 public:
 	FFT(int size, bool halfOnly = false);
-	std::vector<std::complex<double>> operator()(const std::vector<std::complex<double>> &v);
+	std::vector<std::complex<double>> operator()(const std::vector<std::complex<double>> &v) const;
 
 	FFT& SetHalfOnly(bool enable);
 
 private:
-	int bitreverse(int i);
+	int bitreverse(int i) const;
 
-	void reorder(const std::vector<std::complex<double>>& src, std::vector<std::complex<double>>& dst);
-	void fft_recursive(std::vector<std::complex<double>>::iterator X, int N);
-	void fft_half(std::vector<std::complex<double>>::iterator X, int N);
+	void reorder(const std::vector<std::complex<double>>& src, std::vector<std::complex<double>>& dst) const;
+	void fft_recursive(std::vector<std::complex<double>>::iterator X, int N) const;
+	void fft_half(std::vector<std::complex<double>>::iterator X, int N) const;
 }; // class FFT
 
+// Inverse FFT
+class IFFT {
+public:
+	IFFT(int size);
+	IFFT(std::shared_ptr<FFT> fft);
+	~IFFT();
+	std::vector<std::complex<double>> operator()(const std::vector<std::complex<double>> &v) const;
+
+private:
+	struct Impl;
+	std::unique_ptr<Impl> mImpl;
+}; // class IFFT
+
+class AutoCorrelation {
+public:
+	AutoCorrelation(int size);
+	~AutoCorrelation();
+	std::vector<std::complex<double>> operator()(const std::vector<std::complex<double>> &v) const;
+
+private:
+	struct Impl;
+	std::unique_ptr<Impl> mImpl;
+}; // class AutoCorrelation
+
 std::vector<double> magnitudes(std::vector<std::complex<double>>& v);
 
 } // namespace RIT
-- 
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