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/* -*- c++ -*- */
/*
* Copyright 2007 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3, or (at your option)
* any later version.
*
* GNU Radio is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
/*
* config.h is generated by configure. It contains the results
* of probing for features, options etc. It should be the first
* file included in your .cc file.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <cvsd_decode_bs.h>
#include <gr_io_signature.h>
#include <limits.h>
/*
* Create a new instance of cvsd_decode_bs and return
* a boost shared_ptr. This is effectively the public constructor.
*/
cvsd_decode_bs_sptr
cvsd_make_decode_bs (short min_step, short max_step, double step_decay,
double accum_decay, int K, int J,
short pos_accum_max, short neg_accum_max)
{
return cvsd_decode_bs_sptr (new cvsd_decode_bs (min_step, max_step,
step_decay, accum_decay, K, J,
pos_accum_max, neg_accum_max));
}
cvsd_decode_bs::cvsd_decode_bs (short min_step, short max_step, double step_decay,
double accum_decay, int K, int J,
short pos_accum_max, short neg_accum_max)
: gr_sync_interpolator ("cvsd_decode_bs",
gr_make_io_signature (1, 1, sizeof (unsigned char)),
gr_make_io_signature (1, 1, sizeof (short)),
8),
d_min_step (min_step), d_max_step(max_step), d_step_decay(step_decay),
d_accum_decay(accum_decay), d_K(K), d_J(J),
d_pos_accum_max(pos_accum_max), d_neg_accum_max(neg_accum_max),
d_accum(0),
d_loop_counter(1),
d_runner(0),
d_runner_mask(0),
d_stepsize(min_step)
{
assert(d_K <= 32);
assert(d_J <= d_K);
}
cvsd_decode_bs::~cvsd_decode_bs ()
{
// nothing else required in this example
}
unsigned char cvsd_decode_bs::cvsd_bitwise_sum (unsigned int input)
{
unsigned int temp=input;
unsigned char bits=0;
while(temp) {
temp=temp&(temp-1);
bits++;
}
return bits;
}
int cvsd_decode_bs::cvsd_round (double input)
{
double temp;
temp=input+0.5;
temp=floor(temp);
return (int)temp;
}
unsigned int cvsd_decode_bs::cvsd_pow (short radix, short power)
{
double d_radix = (double) radix;
int i_power = (int) power;
double output;
output=pow(d_radix,i_power);
return ( (unsigned int) cvsd_round(output));
}
int
cvsd_decode_bs::work (int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const unsigned char *in = (const unsigned char *) input_items[0];
short *out = (short *) output_items[0];
int i=0;
short output_short=0; // 2 bytes 0 .. 65,535
unsigned char bit_count=0; // 1 byte, 0 .. 255
unsigned int mask=0; // 4 bytes, 0 .. 4,294,967,295
unsigned char input_byte=0; // 1 bytes
unsigned char input_bit=0; // 1 byte, 0 .. 255
// Loop through each input data point
for(i = 0; i < noutput_items/8.0; i++) {
input_byte = in[i];
// Initiliaze bit counter
bit_count=0;
while(bit_count<8) {
// Compute the Appropriate Mask
mask=cvsd_pow(2,7-bit_count);
// Pull off the corresponding bit
input_bit = input_byte & mask;
// Update the bit counter
bit_count++;
// Update runner with the next input bit
// Runner is a shift-register; shift left, add on newest output bit
d_runner = (d_runner<<1) | ((unsigned int) input_bit);
// Run this only if you have >= J bits in your shift register
if (d_loop_counter>=d_J) {
// Update Step Size
d_runner_mask=(cvsd_pow(2,d_J)-1);
if ((cvsd_bitwise_sum(d_runner & d_runner_mask)>=d_J)||(cvsd_bitwise_sum((~d_runner) & d_runner_mask)>=d_J)) {
// Runs of 1s and 0s
d_stepsize = std::min( (short) (d_stepsize + d_min_step), d_max_step);
}
else {
// No runs of 1s and 0s
d_stepsize = std::max( (short) cvsd_round(d_stepsize*d_step_decay), d_min_step);
}
}
// Update Accum (i.e. the reference value)
if (input_bit) {
d_accum=d_accum+d_stepsize;
}
else {
d_accum=d_accum-d_stepsize;
}
// Multiply by Accum_Decay
d_accum=(cvsd_round(d_accum*d_accum_decay));
// Check for overflow
if (d_accum >=((int) d_pos_accum_max)) {
d_accum=(int)d_pos_accum_max;
}
else if (d_accum <=((int) d_neg_accum_max)) {
d_accum=(int)d_neg_accum_max;
}
// Find the output short to write to the file
output_short=((short) d_accum);
if (d_loop_counter <= d_K) {
d_loop_counter++;
}
*(out++) = output_short;
} // while ()
} // for()
return noutput_items;
}
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