audio_prep/util.h

/*
 * Copyright 2022 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef AUDIO_PREP_UTIL_H_
#define AUDIO_PREP_UTIL_H_

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

// Evenly linear spaced array
void linspace(float* x, float start, float end, int n);

// Calculate the dot product of two vectors
float dot_product(float* v, float* u, int n);

/*---------------------------------------------------------------------------
 * FUNCTION NAME: rfft
 *
 * PURPOSE:       Real valued, in-place split-radix FFT
 *
 * INPUT:
 *   x            Pointer to input and output array
 *   m            2^m = n is the Length of FFT
 *
 * OUTPUT         Output order
 *                  Re(0), Re(1), ..., Re(n/2), Im(N/2-1), ..., Im(1)
 *
 * RETURN VALUE
 *   none
 *
 *---------------------------------------------------------------------------*/
void rfft(float* x, int m);

#endif  // AUDIO_PREP_UTIL_H_