/* SPDX-License-Identifier: BSD-3-Clause

*

* Copyright(c) 2022-2025 Intel Corporation.

*

* Author: Shriram Shastry <malladi.sastry@linux.intel.com>

* Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>

* Pasca, Bogdan <bogdan.pasca@intel.com>

*/

#ifndef __SOFM_EXP_FCN_H__

#define __SOFM_EXP_FCN_H__

#include <stdint.h>

#if defined(__XCC__)

/* HiFi */

#include <xtensa/config/core-isa.h>

#if XCHAL_HAVE_HIFI5 == 1

#define SOFM_EXPONENTIAL_HIFI5 1

#elif XCHAL_HAVE_HIFI4 == 1

#define SOFM_EXPONENTIAL_HIFI4 1

#elif XCHAL_HAVE_HIFI3 == 1

#define SOFM_EXPONENTIAL_HIFI3 1

#endif

#else

/* !XCC */

#define EXPONENTIAL_GENERIC 1

#endif

/* Q5.27 int32(round(log((2^31 - 1)/2^20) * 2^27)) */

#define SOFM_EXP_FIXED_INPUT_MAX 1023359037

/* Q8.24 int32(round((log((2^31 - 1)/2^20) * 20 / log(10)) * 2^24)) */

#define SOFM_DB2LIN_INPUT_MAX 1111097957

/**

* Calculates exponent function exp(x) = e^x with accurate and efficient technique that

* includes range reduction operations, approximation with Taylor series, and reconstruction

* operations to compensate the range reductions.

* @param x The input argument as Q4.28 from -8 to +8

* @return The calculated e^x value as Q13.19 from 3.3546e-04 to 2981.0

*/

int32_t sofm_exp_approx(int32_t x);

/**

* Calculated exponent function exp(x) = e^x by using sofm_exp_approx(). The input range for

* large arguments is internally reduced to -8 to +8 with rule exp(x) = exp(x/2) * exp(x/2)

* and reconstructed back. This function is essentially a wrapper for compatibility with

* existing usage of exp() function and Q-format choice. Note that the return value saturates

* to INT32_MAX with input arguments larger than 7.6246.

* @param x The input argument as Q5.27 from -16 to +16

* @return The calculated e^x value as Q12.20

*/

int32_t sofm_exp_fixed(int32_t x);

/**

* Converts a decibels value to liner amplitude lin = 10^(db/20) value with optimized

* equation exp(db * log(10)/20). Note that due to range limitation of sofm_exp_fixed()

* the output saturates to maximum with about +66 dB input.

* @param db Decibels value in Q8.24 format, from -128 to +66.226

* @return Linear value in Q12.20 format, from 3.9811e-07 to 2048

*/

int32_t sofm_db2lin_fixed(int32_t db);

#endif /* __SOFM_EXP_FCN_H__ */