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/*
* Copyright © 2012 Keith Packard <keithp@keithp.com>
*
* This program 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; version 2 of the License.
*
* This program 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 this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
#include <ao_fec.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#ifndef RANDOM_MAX
#define RANDOM_MAX 0x7fffffff
#endif
static double
rand_real(void) {
return (double) random() / (double) RANDOM_MAX;
}
static double
gaussian_random(double mean, double dev)
{
static int save_x_valid = 0;
static double save_x;
double x;
if (save_x_valid)
{
x = save_x;
save_x_valid = 0;
}
else
{
double w;
double normal_x1, normal_x2;
do {
normal_x1 = 2 * rand_real () - 1;
normal_x2 = 2 * rand_real () - 1;
w = normal_x1*normal_x1 + normal_x2*normal_x2;
} while (w >= 1 || w < 1E-30);
w = sqrt(log(w)*(-2./w));
/*
* normal_x1 and normal_x2 are independent normally
* distributed variates
*/
x = normal_x1 * w;
/* save normal_x2 for next call */
save_x = normal_x2 * w;
save_x_valid = 1;
}
return x * dev + mean;
}
#define PREPARE_LEN(input_len) ((input_len) + AO_FEC_PREPARE_EXTRA)
#define ENCODE_LEN(input_len) (PREPARE_LEN(input_len) * 2)
#define INTERLEAVE_LEN(input_len) ENCODE_LEN(input_len)
static int
ao_encode(uint8_t *input, int input_len, uint8_t *output)
{
uint8_t prepare[PREPARE_LEN(input_len)];
uint8_t encode[ENCODE_LEN(input_len)];
uint8_t interleave[INTERLEAVE_LEN(input_len)];
uint8_t prepare_len;
uint8_t encode_len;
uint8_t interleave_len;
ao_fec_dump_bytes(input, input_len, "Input");
prepare_len = ao_fec_prepare(input, input_len, prepare);
ao_fec_dump_bytes(prepare, prepare_len, "Prepare");
encode_len = ao_fec_encode(prepare, prepare_len, encode);
ao_fec_dump_bytes(encode, encode_len, "Encode");
interleave_len = ao_fec_interleave(encode, encode_len, output);
ao_fec_dump_bytes(output, interleave_len, "Interleave");
return interleave_len;
}
#define RADIO_LEN(input_len) (INTERLEAVE_LEN(input_len) * 8)
static int
ao_radio(uint8_t *bits, int bits_len, uint8_t *bytes)
{
uint8_t b, *bytes_orig = bytes;
uint8_t interleave[bits_len];
int i, bit;
ao_fec_interleave(bits, bits_len, interleave);
ao_fec_dump_bytes(interleave, bits_len, "De-interleave");
for (i = 0; i < bits_len; i++) {
b = interleave[i];
for (bit = 7; bit >= 0; bit--)
*bytes++ = ((b >> bit) & 1) * 0xff;
}
ao_fec_dump_bytes(bytes_orig, bits_len * 8, "Bytes");
return bits_len * 8;
}
static int
ao_fuzz (uint8_t *in, int in_len, uint8_t *out, double dev)
{
int i;
int errors = 0;
for (i = 0; i < in_len; i++) {
double error = gaussian_random(0, dev);
uint8_t byte = in[i];
if (error > 0) {
if (error > 0xff)
error = 0xff;
if (error >= 0x80)
errors++;
if (byte < 0x80)
byte += error;
else
byte -= error;
}
out[i] = byte;
}
printf ("Introduced %d errors\n", errors);
ao_fec_dump_bytes(out, in_len, "Fuzz");
return in_len;
}
static int
ao_decode(uint8_t *bytes, int bytes_len, uint8_t *bits)
{
int bits_len;
bits_len = ao_fec_decode(bytes, bytes_len, bits);
ao_fec_dump_bytes(bits, bits_len, "Decode");
}
int
main(int argc, char **argv)
{
uint8_t original[4] = { 3, 1, 2, 3 };
uint8_t encode[INTERLEAVE_LEN(sizeof(original))];
int encode_len;
uint8_t transmit[RADIO_LEN(sizeof(original))];
int transmit_len;
uint8_t receive[RADIO_LEN(sizeof(original))];
int receive_len;
uint8_t decode[INTERLEAVE_LEN(sizeof(original))];
int decode_len;
encode_len = ao_encode(original, sizeof(original), encode);
transmit_len = ao_radio(encode, encode_len, transmit);
/* apply gaussian noise to test viterbi code against errors */
receive_len = ao_fuzz(transmit, transmit_len, receive, 0x80);
decode_len = ao_decode(receive, receive_len, decode);
}
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