/*
 * Copyright (c) 2007 - 2015 Joseph Gaeddert
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

//
// Design raised-cosine filter
//

#include <math.h>
#include <stdio.h>
#include <stdlib.h>

#include "liquid.internal.h"

// Design Nyquist raised-cosine filter
//  _k      : samples/symbol
//  _m      : symbol delay
//  _beta   : rolloff factor (0 < beta <= 1)
//  _dt     : fractional sample delay
//  _h      : output coefficient buffer (length: 2*k*m+1)
void liquid_firdes_rcos(unsigned int _k,
                        unsigned int _m,
                        float _beta,
                        float _dt,
                        float * _h)
{
    if ( _k < 1 ) {
        fprintf(stderr,"error: liquid_firdes_rcos(): k must be greater than 0\n");
        exit(1);
    } else if ( _m < 1 ) {
        fprintf(stderr,"error: liquid_firdes_rcos(): m must be greater than 0\n");
        exit(1);
    } else if ( (_beta < 0.0f) || (_beta > 1.0f) ) {
        fprintf(stderr,"error: liquid_firdes_rcos(): beta must be in [0,1]\n");
        exit(1);
    } else;

    unsigned int n;
    float z, t1, t2, t3;

    float nf, kf, mf;

    unsigned int h_len = 2*_k*_m + 1;

    // Calculate filter coefficients
    for (n=0; n<h_len; n++) {
        nf = (float) n;
        kf = (float) _k;
        mf = (float) _m;

        z = (nf+_dt)/kf-mf;
        t1 = cosf(_beta*M_PI*z);
        t2 = sincf(z);
        t3 = 1 - 4.0f*_beta*_beta*z*z;

        // check for special condition where 4*_beta^2*z^2 equals 1
        if ( fabsf(t3) < 1e-3f )
            _h[n] = sinf(M_PI/(2.0*_beta))*_beta*0.5f;
        else
            _h[n] = t1*t2/t3;
    }
}

