// Copyright 2018-2019 Espressif Systems (Shanghai) PTE LTD
//
// 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.

#include "dsps_sqrt.h"
#include <math.h>


inline float dsps_sqrtf_f32_ansi(float f)
{
    const int result = 0x1fbb4000 + (*(int*)&f >> 1);
    return *(float*)&result;   
}

esp_err_t dsps_sqrt_f32_ansi(const float *input, float *output, int len)
{
    if (NULL == input) return ESP_ERR_DSP_PARAM_OUTOFRANGE;
    if (NULL == output) return ESP_ERR_DSP_PARAM_OUTOFRANGE;

    for (int i = 0 ; i < len ; i++) {
        output[i] = dsps_sqrtf_f32_ansi(input[i]);
    }
    return ESP_OK;
}

float dsps_inverted_sqrtf_f32_ansi(float data )
{	
	const float x2 = data * 0.5F;
	const float threehalfs = 1.5F;

	union {
		float f;
		uint32_t i;
	} conv = {data}; // member 'f' set to value of 'data'.
	conv.i  = 0x5f3759df - ( conv.i >> 1 );
	conv.f  *= ( threehalfs - ( x2 * conv.f * conv.f ) );
	return conv.f;
}

