Initial community commit

Src/external_dependencies/openmpt-trunk/soundlib/TinyFFT.h

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+/*
+ * TinyFFT.h
+ * ---------
+ * Purpose: A simple FFT implementation for power-of-two FFTs
+ * Notes  : This is a C++ adaption of Ryuhei Mori's BSD 2-clause licensed TinyFFT
+ *          available from https://github.com/ryuhei-mori/tinyfft
+ * Authors: Ryuhei Mori
+ *          OpenMPT Devs
+ * The OpenMPT source code is released under the BSD license. Read LICENSE for more details.
+ */
+
+
+#pragma once
+
+#include "openmpt/all/BuildSettings.hpp"
+#include <complex>
+
+OPENMPT_NAMESPACE_BEGIN
+
+class TinyFFT
+{
+	static constexpr std::complex<double> I{0.0, 1.0};
+	std::vector<std::complex<double>> w;  // Pre-computed twiddle factors
+	const uint32 k; // log2 of FFT size
+
+	void GenerateTwiddleFactors(uint32 i, uint32 b, std::complex<double> z);
+
+public:
+	TinyFFT(const uint32 fftSize);
+
+	uint32 Size() const noexcept;
+
+	// Computes in-place FFT of size 2^k of A, result is in bit-reversed order.
+	void FFT(std::vector<std::complex<double>> &A) const;
+
+	// Computes in-place IFFT of size 2^k of A, input is expected to be in bit-reversed order.
+	void IFFT(std::vector<std::complex<double>> &A) const;
+
+	static void Normalize(std::vector<std::complex<double>> &data);
+};
+
+OPENMPT_NAMESPACE_END