biterror.c

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/***************************************************************************
 *   biterror.c  - Software Radio channel simulation module
 *                           -------------------
 *   begin                :  Oct 17th, 2002
 *   authors              :  Roman Hofer
 *   emails               :  [e-mail]
 ***************************************************************************/

/***************************************************************************
 *                                Changes
 *                                -------
 * date - name - description
 * Oct.17th, 2002  - Creation of class - 
 * 04/03/05 - ineiti - adjusted documentation
 *
 **************************************************************************/

/***************************************************************************
 *                                                                         *
 *   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; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/


/**
 * A simple channel simulation which can be used in a test
 * Simply inverts some bits with a predefined probability
 */

#include <stdlib.h>
#include "spc.h"

#define DBG_LVL 0

typedef struct {
  // Bit Error Rate
  double ber; // 0.01
}
config_t;

typedef struct {
}
stats_t;

typedef struct {
  double ber;
}
private_t;

/*
 * The initialisation function, or constructor,
 * is called the first time this module is instantiated.
 */

int spc_init( swr_sdb_t *context ) {
  // Definition of variables - don't touch if you're not an expert
  config_t *config;
  stats_t *stats;
  context->private_data = swr_malloc( sizeof( private_t ) );

  swr_sdb_get_config_struct( context->id, (void**)&config );
  swr_sdb_get_stats_struct( context->id, (void**)&stats );

  config->ber = 0.01;

  // Definition - don't touch
  swr_sdb_free_config_struct( context->id, (void**)&config );
  swr_sdb_free_stats_struct( context->id, (void**)&stats );

  return 0;
}



int spc_configure_inputs( swr_sdb_t *context ) {
  // Definition of variables - don't touch
  config_t *config;
  swr_sdb_get_config_struct( context->id, (void**)&config );

  size_in(0) = size_out(0);

  // Definition - don't touch
  swr_sdb_free_config_struct( context->id, (void**)&config );
  return 0;
}

/*
 * This is called when the input-sizes change
 * It configures the outputs
 */
int spc_configure_outputs( swr_sdb_t *context ) {
  // Definition of variables - don't touch
  config_t *config;
  swr_sdb_get_config_struct( context->id, (void**)&config );

  size_out( 0 ) = size_in(0);

  // Definition - don't touch
  swr_sdb_free_config_struct( context->id, (void**)&config );
  return 0;
}

/*
 * Every time modules from the outside change the value of a configuration parameter,
 * this function is called.
 */

int spc_reconfig( swr_sdb_t *context ) {
  // Definition of variables - don't touch
  config_t *config;
  swr_sdb_get_config_struct( context->id, (void**)&config );

  private->ber = config->ber;

  // Definition - don't touch
  swr_sdb_free_config_struct( context->id, (void**)&config );
  return(0);
}


/*
 * This is function that impements the `main method' of the class
 * Every class has got just ONE method/working-mode.
 */
int spc_pdata( swr_sdb_t *context ) {
  // Definition of variables - don't touch
  int n;
  U8 *out;
  U8 *in;

  PR_DBG( 4, "rnd: in spc_pdata\n");

  out = buffer_out(0);
  in = buffer_in(0);

  // This for-loop
  // inverts a few bits
  for (n=0;n<size_in(0);n++) {
    U8 invertPattern=0x00;
    int i;
    for (i=0;i<8;i++) {
      if ( ((double)random())/RAND_MAX < private->ber ) {
        invertPattern += 1 << i;
      }
    }

    //invert these bits...
    out[n]=in[n]^invertPattern;
    if (invertPattern!=0) {
      PR_DBG( 4, "Modifying Byte #%d: Inverting Bits: %x. %x-->%x\n",
              n,invertPattern,in[n],out[n]);
    }
  }

  return(0);
}


int spc_custom_msg( swr_sdb_t *context, swr_usr_msg_t* msg_data, swr_msgq ret ) {
  spc_pdata( context );
  return 0;
}


/*
 * This is the `destructor'.
 */
int spc_finalize( swr_sdb_t *context ) {
  swr_free( private );
  MOD_DEC_USE_COUNT;
  return(0);
}


/*
 * This function is called upon "insmod" and is used to register the
 * different parts of the module to the SPM.
 */
swr_spc_id_t cdb_id;
int spc_module_init(void) {
  swr_spc_desc_t *desc;

  // Get a description-part from SPM
  // Give the following parameters:
  // Input-ports, output-ports, config-params, stat-params
  desc = swr_spc_get_new_desc( 1, 1, 1, 0 );
  if ( !desc ) {
    PR_DBG( 0, "Can't initialise the module. This is BAD!\n" );
    return -1;
  }

  // Define the different parts of config and stats
  UM_CONFIG_DOUBLE( "ber" );
  UM_INPUT( SIG_U8, 0 );
  UM_OUTPUT( SIG_U8, 0 );

  // Initialise the callback-functions. NULL for not-used functions
  desc->fn_init         = spc_init;
  desc->fn_reconfigure  = spc_reconfig;
  desc->fn_process_data = spc_pdata;
  desc->fn_finalize     = spc_finalize;
  desc->fn_custom_msg   = spc_custom_msg;
  desc->fn_configure_inputs  = spc_configure_inputs;
  desc->fn_configure_outputs = spc_configure_outputs;



  // And register the module in the SPM
  cdb_id = swr_cdb_register_spc( &desc, "biterror" );
  if ( cdb_id == SWR_SPM_INVALID_ID ) {
    swr_spc_free_desc( desc );
    PR_DBG( 0, "Couldn't register the module!\n" );
    return 1;
  }
  PR_DBG( 4, "Ready to generate random iid equiprobable u8\n");
  return 0;
}


/*
 * This is called upon rmmod
 */
void spc_module_exit( void ) {
  PR_DBG( 2, "Freeing id: %i\n", cdb_id );
  if ( swr_cdb_unregister_spc( cdb_id ) < 0 ) {
    PR_DBG( 0, "Still in use somewhere\n" );
  }
}

// Do not touch!
module_init( spc_module_init );
module_exit( spc_module_exit );