modbus/mb_runtime.c
author Edouard Tisserant <edouard.tisserant@gmail.com>
Tue, 02 Mar 2021 09:28:44 +0100
changeset 2729 4e0cd7806776
parent 2723 cde2e410b874
child 3733 d1acf20e8e7c
permissions -rw-r--r--
IDE: Iec2CSettings: Log wasn't available in case of exception when launching iec2c.
/* File generated by Beremiz (PlugGenerate_C method of Modbus plugin) */

/*
 * Copyright (c) 2016 Mario de Sousa (msousa@fe.up.pt)
 *
 * This file is part of the Modbus library for Beremiz and matiec.
 *
 * This Modbus library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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 Lesser 
 * General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this Modbus library.  If not, see <http://www.gnu.org/licenses/>.
 *
 * This code is made available on the understanding that it will not be
 * used in safety-critical situations without a full and competent review.
 */


#include <stdio.h>
#include <string.h>  /* required for memcpy() */
#include <errno.h>
#include <time.h>
#include <signal.h>
#include <unistd.h>  /* required for pause() */
#include "mb_slave_and_master.h"
#include "MB_%(locstr)s.h"


#define MAX_MODBUS_ERROR_CODE 11
static const char *modbus_error_messages[MAX_MODBUS_ERROR_CODE+1] = {
    /* 0 */ "",                             /* un-used -> no error! */
    /* 1 */ "illegal/unsuported function",
    /* 2 */ "illegal data address",
    /* 3 */ "illegal data value",
    /* 4 */ "slave device failure",
    /* 5 */ "acknowledge -> slave intends to reply later",
    /* 6 */ "slave device busy",
    /* 7 */ "negative acknowledge",
    /* 8 */ "memory parity error",
    /* 9 */ "",                             /* undefined by Modbus */
    /* 10*/ "gateway path unavalilable",
    /* 11*/ "gateway target device failed to respond"
};    


/* Execute a modbus client transaction/request */
static int __execute_mb_request(int request_id){
	switch (client_requests[request_id].mb_function){
	
	case  1: /* read coils */
		return read_output_bits(client_requests[request_id].slave_id,
					client_requests[request_id].address,
					client_requests[request_id].count,
					client_requests[request_id].coms_buffer,
					(int) client_requests[request_id].count,
					client_nodes[client_requests[request_id].client_node_id].mb_nd,
					client_requests[request_id].retries,
					&(client_requests[request_id].mb_error_code),
					&(client_requests[request_id].resp_timeout),
					&(client_requests[request_id].coms_buf_mutex));

	case  2: /* read discrete inputs */
		return read_input_bits( client_requests[request_id].slave_id,
					client_requests[request_id].address,
					client_requests[request_id].count,
					client_requests[request_id].coms_buffer,
					(int) client_requests[request_id].count,
					client_nodes[client_requests[request_id].client_node_id].mb_nd,
					client_requests[request_id].retries,
					&(client_requests[request_id].mb_error_code),
					&(client_requests[request_id].resp_timeout),
					&(client_requests[request_id].coms_buf_mutex));

	case  3: /* read holding registers */
		return read_output_words(client_requests[request_id].slave_id,
					client_requests[request_id].address,
					client_requests[request_id].count,
					client_requests[request_id].coms_buffer,
					(int) client_requests[request_id].count,
					client_nodes[client_requests[request_id].client_node_id].mb_nd,
					client_requests[request_id].retries,
					&(client_requests[request_id].mb_error_code),
					&(client_requests[request_id].resp_timeout),
					&(client_requests[request_id].coms_buf_mutex));
	
	case  4: /* read input registers */
		return read_input_words(client_requests[request_id].slave_id,
					client_requests[request_id].address,
					client_requests[request_id].count,
					client_requests[request_id].coms_buffer,
					(int) client_requests[request_id].count,
					client_nodes[client_requests[request_id].client_node_id].mb_nd,
					client_requests[request_id].retries,
					&(client_requests[request_id].mb_error_code),
					&(client_requests[request_id].resp_timeout),
					&(client_requests[request_id].coms_buf_mutex));

	case  5: /* write single coil */
		return write_output_bit(client_requests[request_id].slave_id,
					client_requests[request_id].address,
					client_requests[request_id].coms_buffer[0],
					client_nodes[client_requests[request_id].client_node_id].mb_nd,
					client_requests[request_id].retries,
					&(client_requests[request_id].mb_error_code),
					&(client_requests[request_id].resp_timeout),
					&(client_requests[request_id].coms_buf_mutex));

	case  6: /* write single register */
		return write_output_word(client_requests[request_id].slave_id,
					client_requests[request_id].address,
					client_requests[request_id].coms_buffer[0],
					client_nodes[client_requests[request_id].client_node_id].mb_nd,
					client_requests[request_id].retries,
					&(client_requests[request_id].mb_error_code),
					&(client_requests[request_id].resp_timeout),
					&(client_requests[request_id].coms_buf_mutex));

	case  7: break; /* function not yet supported */
	case  8: break; /* function not yet supported */
	case  9: break; /* function not yet supported */
	case 10: break; /* function not yet supported */
	case 11: break; /* function not yet supported */
	case 12: break; /* function not yet supported */
	case 13: break; /* function not yet supported */
	case 14: break; /* function not yet supported */
	
	case 15: /* write multiple coils */
		return write_output_bits(client_requests[request_id].slave_id,
					 client_requests[request_id].address,
					 client_requests[request_id].count,
					 client_requests[request_id].coms_buffer,
					 client_nodes[client_requests[request_id].client_node_id].mb_nd,
					 client_requests[request_id].retries,
					 &(client_requests[request_id].mb_error_code),
					 &(client_requests[request_id].resp_timeout),
					 &(client_requests[request_id].coms_buf_mutex));

	case 16: /* write multiple registers */
		return write_output_words(client_requests[request_id].slave_id,
					client_requests[request_id].address,
					client_requests[request_id].count,
					client_requests[request_id].coms_buffer,
					client_nodes[client_requests[request_id].client_node_id].mb_nd,
					client_requests[request_id].retries,
					&(client_requests[request_id].mb_error_code),
					&(client_requests[request_id].resp_timeout),
					&(client_requests[request_id].coms_buf_mutex));
	
	default: break;  /* should never occur, if file generation is correct */
	}

	fprintf(stderr, "Modbus plugin: Modbus function %%d not supported\n", request_id); /* should never occur, if file generation is correct */
	return -1;
}



/* pack bits from unpacked_data to packed_data */
static inline int __pack_bits(u16 *unpacked_data, u16 start_addr, u16 bit_count,  u8  *packed_data) {
  u8 bit;
  u16 byte, coils_processed;

  if ((0 == bit_count) || (65535-start_addr < bit_count-1))
    return -ERR_ILLEGAL_DATA_ADDRESS; /* ERR_ILLEGAL_DATA_ADDRESS defined in mb_util.h */
  
  for( byte = 0, coils_processed = 0; coils_processed < bit_count; byte++) {
    packed_data[byte] = 0;
    for( bit = 0x01; (bit & 0xFF) && (coils_processed < bit_count); bit <<= 1, coils_processed++ ) {
      if(unpacked_data[start_addr + coils_processed])
            packed_data[byte] |=  bit; /*   set bit */
      else  packed_data[byte] &= ~bit; /* reset bit */
    }
  }
  return 0;
}


/* unpack bits from packed_data to unpacked_data */
static inline int __unpack_bits(u16 *unpacked_data, u16 start_addr, u16 bit_count,  u8  *packed_data) {
  u8  temp, bit;
  u16 byte, coils_processed;

  if ((0 == bit_count) || (65535-start_addr < bit_count-1))
    return -ERR_ILLEGAL_DATA_ADDRESS; /* ERR_ILLEGAL_DATA_ADDRESS defined in mb_util.h */
  
  for(byte = 0, coils_processed = 0; coils_processed < bit_count; byte++) {
    temp = packed_data[byte] ;
    for(bit = 0x01; (bit & 0xff) && (coils_processed < bit_count); bit <<= 1, coils_processed++) {
      unpacked_data[start_addr + coils_processed] = (temp & bit)?1:0;
    }
  }
  return 0;
}


static int __read_inbits   (void *mem_map, u16 start_addr, u16 bit_count, u8  *data_bytes) {
  int res = __pack_bits(((server_mem_t *)mem_map)->ro_bits, start_addr, bit_count, data_bytes);
  
  if (res >= 0) {
    /* update the flag and counter of Modbus requests we have processed. */
    ((server_mem_t *)mem_map)->flag_read_req_counter++;
    ((server_mem_t *)mem_map)->flag_read_req_flag = 1;
  }

  return res;
}

static int __read_outbits  (void *mem_map, u16 start_addr, u16 bit_count, u8  *data_bytes) {
  int res = __pack_bits(((server_mem_t *)mem_map)->rw_bits, start_addr, bit_count, data_bytes);
  
  if (res >= 0) {
    /* update the flag and counter of Modbus requests we have processed. */
    ((server_mem_t *)mem_map)->flag_read_req_counter++;
    ((server_mem_t *)mem_map)->flag_read_req_flag = 1;
  }

  return res;
}

static int __write_outbits (void *mem_map, u16 start_addr, u16 bit_count, u8  *data_bytes) {
  int res = __unpack_bits(((server_mem_t *)mem_map)->rw_bits, start_addr, bit_count, data_bytes);
  
  if (res >= 0) {
    /* update the flag and counter of Modbus requests we have processed. */
    ((server_mem_t *)mem_map)->flag_write_req_counter++;
    ((server_mem_t *)mem_map)->flag_write_req_flag = 1;
  }

  return res;
}




static int __read_inwords  (void *mem_map, u16 start_addr, u16 word_count, u16 *data_words) {

  if ((start_addr + word_count) > MEM_AREA_SIZE)
    return -ERR_ILLEGAL_DATA_ADDRESS; /* ERR_ILLEGAL_DATA_ADDRESS defined in mb_util.h */

  /* update the flag and counter of Modbus requests we have processed. */
  ((server_mem_t *)mem_map)->flag_read_req_counter++;
  ((server_mem_t *)mem_map)->flag_read_req_flag = 1;

  /* use memcpy() because loop with pointers (u16 *) caused alignment problems */
  memcpy(/* dest */ (void *)data_words,
         /* src  */ (void *)&(((server_mem_t *)mem_map)->ro_words[start_addr]),
         /* size */ word_count * 2);
  return 0;
}



static int __read_outwords (void *mem_map, u16 start_addr, u16 word_count, u16 *data_words) {

  if ((start_addr + word_count) > MEM_AREA_SIZE)
    return -ERR_ILLEGAL_DATA_ADDRESS; /* ERR_ILLEGAL_DATA_ADDRESS defined in mb_util.h */

  /* update the flag and counter of Modbus requests we have processed. */
  ((server_mem_t *)mem_map)->flag_read_req_counter++;
  ((server_mem_t *)mem_map)->flag_read_req_flag = 1;

  /* use memcpy() because loop with pointers (u16 *) caused alignment problems */
  memcpy(/* dest */ (void *)data_words,
         /* src  */ (void *)&(((server_mem_t *)mem_map)->rw_words[start_addr]),
         /* size */ word_count * 2);
  return 0;
}




static int __write_outwords(void *mem_map, u16 start_addr, u16 word_count, u16 *data_words) {

  if ((start_addr + word_count) > MEM_AREA_SIZE)
    return -ERR_ILLEGAL_DATA_ADDRESS; /* ERR_ILLEGAL_DATA_ADDRESS defined in mb_util.h */

  /* update the flag and counter of Modbus requests we have processed. */
  ((server_mem_t *)mem_map)->flag_write_req_counter++;
  ((server_mem_t *)mem_map)->flag_write_req_flag = 1;

  /* WARNING: The data returned in the data_words[] array is not guaranteed to be 16 bit aligned.
   *           It is not therefore safe to cast it to an u16 data type.
   *           The following code cannot be used. memcpy() is used instead.
   */
  /*
  for (count = 0; count < word_count ; count++)
    ((server_mem_t *)mem_map)->rw_words[count + start_addr] = data_words[count];
  */
  memcpy(/* dest */ (void *)&(((server_mem_t *)mem_map)->rw_words[start_addr]),
         /* src  */ (void *)data_words,
         /* size */ word_count * 2);
  return 0;
}




#include <pthread.h>

static void *__mb_server_thread(void *_server_node)  {
	server_node_t *server_node = _server_node;
	mb_slave_callback_t callbacks = { 
			&__read_inbits,
			&__read_outbits,
			&__write_outbits,
			&__read_inwords,
			&__read_outwords,
			&__write_outwords,
			(void *)&(server_node->mem_area)
			};  
	
	// Enable thread cancelation. Enabled is default, but set it anyway to be safe.
	pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);

	// mb_slave_run() should never return!
	mb_slave_run(server_node->mb_nd /* nd */, callbacks, server_node->slave_id);
	fprintf(stderr, "Modbus plugin: Modbus server for node %%s died unexpectedly!\n", server_node->location); /* should never occur */
	return NULL;
}


#define timespec_add(ts, sec, nsec) {		\
	ts.tv_sec  +=  sec;			\
	ts.tv_nsec += nsec;			\
	if (ts.tv_nsec >= 1000000000) {		\
		ts.tv_sec  ++;			\
		ts.tv_nsec -= 1000000000;	\
	}					\
}


static void *__mb_client_thread(void *_index)  {
	int client_node_id = (char *)_index - (char *)NULL; // Use pointer arithmetic (more portable than cast)

	// Enable thread cancelation. Enabled is default, but set it anyway to be safe.
	pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
	
    /* loop the communication with the client
     * 
         * When the client thread has difficulty communicating with remote client and/or server (network issues, for example),
         * then the communications get delayed and we will fall behind in the period. 
         * 
         * This is OK. Note that if the condition variable were to be signaled multiple times while the client thread is inside the same
         * Modbus transaction, then all those signals would be ignored.
         * However, and since we keep the mutex locked during the communication cycle, it is not possible to signal the condition variable
         * during that time (it is only possible while the thread is blocked during the call to pthread_cond_wait().
         * 
         * This means that when network issues eventually get resolved, we will NOT have a bunch of delayed activations to handle
         * in quick succession (which would goble up CPU time). 
         * 
         * Notice that the above property is valid whether the communication cycle is run with the mutex locked, or unlocked.
         * Since it makes it easier to implement the correct semantics for the other activation methods if the communication cycle
         * is run with the mutex locked, then that is what we do.
         * 
     * Note that during all the communication cycle we will keep locked the mutex 
     * (i.e. the mutex used together with the condition variable that will activate a new communication cycle)
     * 
     * Note that we never get to explicitly unlock this mutex. It will only be unlocked by the pthread_cond_wait()
     * call at the end of the cycle.
     */
    pthread_mutex_lock(&(client_nodes[client_node_id].mutex));

	while (1) {
		/*
		struct timespec cur_time;
		clock_gettime(CLOCK_MONOTONIC, &cur_time);
		fprintf(stderr, "Modbus client thread (%%d) - new cycle (%%ld:%%ld)!\n", client_node_id, cur_time.tv_sec, cur_time.tv_nsec);
		*/
		int req;
		for (req=0; req < NUMBER_OF_CLIENT_REQTS; req ++){
			/* just do the requests belonging to the client */
			if (client_requests[req].client_node_id != client_node_id)
				continue;
            
            /* only do the request if:
             *   - this request was explictly asked to be executed by the client program
             *  OR
             *   - the client thread was activated periodically
             *     (in which case we execute all the requests belonging to the client node)
             */
            if ((client_requests[req].flag_exec_req == 0) && (client_nodes[client_requests[req].client_node_id].periodic_act == 0))
                continue;
            
            /*
            fprintf(stderr, "Modbus client thread (%%d): RUNNING Modbus request %%d  (periodic = %%d  flag_exec_req = %%d)\n", 
                    client_node_id, req, client_nodes[client_requests[req].client_node_id].periodic_act, client_requests[req].flag_exec_req );
            */
            
			int res_tmp = __execute_mb_request(req);
			client_requests[req].tn_error_code = 0; // assume success
			switch (res_tmp) {
			  case PORT_FAILURE: {
				if (res_tmp != client_nodes[client_node_id].prev_error)
					fprintf(stderr, "Modbus plugin: Error connecting Modbus client %%s to remote server.\n", client_nodes[client_node_id].location);
				client_nodes[client_node_id].prev_error = res_tmp;
				client_requests[req].tn_error_code = 1; // error accessing IP network, or serial interface
				break;
			  }
			  case INVALID_FRAME: {
				if ((res_tmp != client_requests[req].prev_error) && (0 == client_nodes[client_node_id].prev_error))
					fprintf(stderr, "Modbus plugin: Modbus client request configured at location %%s was unsuccesful. Server/slave returned an invalid/corrupted frame.\n", client_requests[req].location);
				client_requests[req].prev_error = res_tmp;
				client_requests[req].tn_error_code = 2; // reply received from server was an invalid frame
				break;
			  }
			  case TIMEOUT: {
				if ((res_tmp != client_requests[req].prev_error) && (0 == client_nodes[client_node_id].prev_error))
					fprintf(stderr, "Modbus plugin: Modbus client request configured at location %%s timed out waiting for reply from server.\n", client_requests[req].location);
				client_requests[req].prev_error = res_tmp;
				client_requests[req].tn_error_code = 3; // server did not reply before timeout expired
				break;
			  }
			  case MODBUS_ERROR: {
				if (client_requests[req].prev_error != client_requests[req].mb_error_code) {
					fprintf(stderr, "Modbus plugin: Modbus client request configured at location %%s was unsuccesful. Server/slave returned error code 0x%%2x", client_requests[req].location, client_requests[req].mb_error_code);
					if (client_requests[req].mb_error_code <= MAX_MODBUS_ERROR_CODE ) {
						fprintf(stderr, "(%%s)", modbus_error_messages[client_requests[req].mb_error_code]);
						fprintf(stderr, ".\n");
					}
				}
				client_requests[req].prev_error = client_requests[req].mb_error_code;
				client_requests[req].tn_error_code = 4; // server returned a valid Modbus error frame
				break;
			  }
			  default: {
				if ((res_tmp >= 0) && (client_nodes[client_node_id].prev_error != 0)) {
					fprintf(stderr, "Modbus plugin: Modbus client %%s has reconnected to server/slave.\n", client_nodes[client_node_id].location);
				}
				if ((res_tmp >= 0) && (client_requests[req]        .prev_error != 0)) {
					fprintf(stderr, "Modbus plugin: Modbus client request configured at location %%s has succesfully resumed comunication.\n", client_requests[req].location);
				}
				client_nodes[client_node_id].prev_error = 0;
				client_requests[req]        .prev_error = 0;
				break;
			  }
			}

			/* Set the flag_tn_error_code and flag_mb_error_code that are mapped onto
             * located BYTE variables, so the user program
             * knows how the communication is going.
             */
            client_requests[req].flag_mb_error_code = client_requests[req].mb_error_code;
            client_requests[req].flag_tn_error_code = client_requests[req].tn_error_code;
            
            /* We have just finished excuting a client transcation request.
             * If the current cycle was activated by user request we reset the flag used to ask to run it
             */
            if (0 != client_requests[req].flag_exec_req) {
                client_requests[req].flag_exec_req     = 0;
                client_requests[req].flag_exec_started = 0;   
            }
            
            //fprintf(stderr, "Modbus plugin: RUNNING<---> of Modbus request %%d  (periodic = %%d  flag_exec_req = %%d)\n", 
            //        req, client_nodes[client_requests[req].client_node_id].periodic_act, client_requests[req].flag_exec_req );
        }

        // Wait for signal (from timer or explicit request from user program) before starting the next cycle
        {
            // No need to lock the mutex. Is is already locked just before the while(1) loop.
            // Read the comment there to understand why.
            // pthread_mutex_lock(&(client_nodes[client_node_id].mutex));
            
            /* the client thread has just finished a cycle, so all the flags used to signal an activation
             * and specify the activation source (periodic, user request, ...)
             * get reset here, before waiting for a new activation.
             */
            client_nodes[client_node_id].periodic_act = 0;            
            client_nodes[client_node_id].execute_req  = 0;
            
            while (client_nodes[client_node_id].execute_req == 0)
                pthread_cond_wait(&(client_nodes[client_node_id].condv),
                                &(client_nodes[client_node_id].mutex)); 
                            
            // We run the communication cycle with the mutex locked.
            // Read the comment just above the while(1) to understand why.
            // pthread_mutex_unlock(&(client_nodes[client_node_id].mutex));
        }
	}

	// humour the compiler.
	return NULL;
}





/* Thread that simply implements a periodic 'timer',
 *  i.e. periodically sends signal to the  thread running __mb_client_thread()
 * 
 * Note that we do not use a posix timer (timer_create() ) because there doesn't seem to be a way
 * of having the timer notify the thread that is portable across Xenomai and POSIX.
 * - SIGEV_THREAD    : not supported by Xenomai
 * - SIGEV_THREAD_ID : Linux specific (i.e. non POSIX)
 *                     Even so, I did not get it to work under Linux (issues with the header files)
 * - SIGEV_SIGNAL    : Will not work, as signal is sent to random thread in process!
 */
static void *__mb_client_timer_thread(void *_index) {
	int client_node_id = (char *)_index - (char *)NULL; // Use pointer arithmetic (more portable than cast)
	struct timespec next_cycle;

	int period_sec  =  client_nodes[client_node_id].comm_period / 1000;          /* comm_period is in ms */
	int period_nsec = (client_nodes[client_node_id].comm_period %%1000)*1000000; /* comm_period is in ms */

	// Enable thread cancelation. Enabled is default, but set it anyway to be safe.
	pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
    
    if (client_nodes[client_node_id].comm_period <= 0) {
        // No periodic activation required => nothing to do! 
        while (1) pause(); // wait to be canceled when program terminates (shutdown() is called)
        return NULL;  // not really necessary, just makes it easier to understand the code.
    }

	// get the current time
	clock_gettime(CLOCK_MONOTONIC, &next_cycle);

    while(1) {
        // Determine absolute time instant for starting the next cycle
        struct timespec prev_cycle, now;
        prev_cycle = next_cycle;
        timespec_add(next_cycle, period_sec, period_nsec);
                
        /* NOTE:
         * It is probably un-necessary to check for overflow of timer!
         * Even in 32 bit systems this will take at least 68 years since the computer booted
         * (remember, we are using CLOCK_MONOTONIC, which should start counting from 0
         * every time the system boots). On 64 bit systems, it will take over 
         * 10^11 years to overflow.
         */
        clock_gettime(CLOCK_MONOTONIC, &now);
        if (next_cycle.tv_sec < prev_cycle.tv_sec) {
           /* Timer overflow. See NOTE B above */
            next_cycle = now;
            timespec_add(next_cycle, period_sec, period_nsec);
        }
        
        while (0 != clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &next_cycle, NULL));
        
        /* signal the client node's condition variable on which the client node's thread should be waiting... */
        /* Since the communication cycle is run with the mutex locked, we use trylock() instead of lock() */
        if (pthread_mutex_trylock (&(client_nodes[client_node_id].mutex)) == 0) {
            client_nodes[client_node_id].execute_req  = 1; // tell the thread to execute
            client_nodes[client_node_id].periodic_act = 1; // tell the thread the activation was done by periodic timer   
            pthread_cond_signal (&(client_nodes[client_node_id].condv));
            pthread_mutex_unlock(&(client_nodes[client_node_id].mutex));
        } else {
            /* We never get to signal the thread for activation. But that is OK.
             * If it still in the communication cycle (during which the mutex is kept locked)
             * then that means that the communication cycle is falling behing in the periodic 
             * communication cycle, and we therefore need to skip a period.
             */
        }
    }

    return NULL; // humour the compiler -> will never be executed!
}


int __cleanup_%(locstr)s ();
int __init_%(locstr)s (int argc, char **argv){
	int index;

	for (index=0; index < NUMBER_OF_CLIENT_NODES;index++) {
		client_nodes[index].mb_nd = -1;
        /* see comment in mb_runtime.h to understad why we need to initialize these entries */
        switch (client_nodes[index].node_address.naf) {
            case naf_tcp:
                client_nodes[index].node_address.addr.tcp.host    = client_nodes[index].str1;
                client_nodes[index].node_address.addr.tcp.service = client_nodes[index].str2;
                break;
            case naf_rtu:
                client_nodes[index].node_address.addr.rtu.device  = client_nodes[index].str1;
                break;
        }
    }

	for (index=0; index < NUMBER_OF_SERVER_NODES;index++) {
		// mb_nd with negative numbers indicate how far it has been initialised (or not)
		//   -2  --> no modbus node created;  no thread  created
		//   -1  -->    modbus node created!; no thread  created
		//  >=0  -->    modbus node created!;    thread  created!
		server_nodes[index].mb_nd = -2; 
		server_nodes[index].mem_area.flag_write_req_flag    = 0; 
		server_nodes[index].mem_area.flag_write_req_counter = 0; 
		server_nodes[index].mem_area.flag_read_req_counter  = 0; 
		server_nodes[index].mem_area.flag_read_req_flag     = 0; 
        /* see comment in mb_runtime.h to understad why we need to initialize these entries */
        switch (server_nodes[index].node_address.naf) {
            case naf_tcp:
                server_nodes[index].node_address.addr.tcp.host    = server_nodes[index].str1;
                server_nodes[index].node_address.addr.tcp.service = server_nodes[index].str2;
                break;
            case naf_rtu:
                server_nodes[index].node_address.addr.rtu.device  = server_nodes[index].str1;
                break;
        }
	}

	/* modbus library init */
	/* Note that TOTAL_xxxNODE_COUNT are the nodes required by _ALL_ the instances of the modbus
	 *  extension currently in the user's project. This file (MB_xx.c) is handling only one instance,
	 *  but must initialize the library for all instances. Only the first call to mb_slave_and_master_init()
	 *  will result in memory being allocated. All subsequent calls (by other MB_xx,c files) will be ignored
	 *  by the mb_slave_and_master_init() funtion, as long as they are called with the same arguments.
	 */
	if (mb_slave_and_master_init(TOTAL_TCPNODE_COUNT, TOTAL_RTUNODE_COUNT, TOTAL_ASCNODE_COUNT) <0) {
		fprintf(stderr, "Modbus plugin: Error starting modbus library\n");
		// return imediately. Do NOT goto error_exit, as we did not get to
		//  start the modbus library!
		return -1;
	}
	
	/* init each client request */
	/* Must be done _before_ launching the client threads!! */
	for (index=0; index < NUMBER_OF_CLIENT_REQTS; index ++){
        /* make sure flags connected to user program MB transaction start request are all reset */
        client_requests[index].flag_exec_req     = 0;
        client_requests[index].flag_exec_started = 0;        
        /* init the mutex for each client request */
        /* Must be done _before_ launching the client threads!! */
		if (pthread_mutex_init(&(client_requests[index].coms_buf_mutex), NULL)) {
			fprintf(stderr, "Modbus plugin: Error initializing request for modbus client node %%s\n", client_nodes[client_requests[index].client_node_id].location);
			goto error_exit;
		}
	}

	/* init each client connection to remote modbus server, and launch thread */
	/* NOTE: All client_nodes[].init_state are initialised to 0 in the code 
	 *       generated by the modbus plugin 
	 */
	for (index=0; index < NUMBER_OF_CLIENT_NODES;index++){
		/* establish client connection */
		client_nodes[index].mb_nd = mb_master_connect (client_nodes[index].node_address);
		if (client_nodes[index].mb_nd < 0){
			fprintf(stderr, "Modbus plugin: Error creating modbus client node %%s\n", client_nodes[index].location);
			goto error_exit;
		}
		client_nodes[index].init_state = 1; // we have created the node 
		
		/* initialize the mutex variable that will be used by the thread handling the client node */
        bzero(&(client_nodes[index].mutex), sizeof(pthread_mutex_t));
        if (pthread_mutex_init(&(client_nodes[index].mutex), NULL) < 0) {
			fprintf(stderr, "Modbus plugin: Error creating mutex for modbus client node %%s\n", client_nodes[index].location);
			goto error_exit;                
        }
		client_nodes[index].init_state = 2; // we have created the mutex
		
		/* initialize the condition variable that will be used by the thread handling the client node */
        bzero(&(client_nodes[index].condv), sizeof(pthread_cond_t));
        if (pthread_cond_init(&(client_nodes[index].condv), NULL) < 0) {
			fprintf(stderr, "Modbus plugin: Error creating condition variable for modbus client node %%s\n", client_nodes[index].location);
			goto error_exit;                
        }
        client_nodes[index].execute_req = 0; //variable associated with condition variable
		client_nodes[index].init_state = 3; // we have created the condition variable
		
		/* launch a thread to handle this client node timer */
		{
			int res = 0;
			pthread_attr_t attr;
			res |= pthread_attr_init(&attr);
			res |= pthread_create(&(client_nodes[index].timer_thread_id), &attr, &__mb_client_timer_thread, (void *)((char *)NULL + index));
			if (res !=  0) {
				fprintf(stderr, "Modbus plugin: Error starting timer thread for modbus client node %%s\n", client_nodes[index].location);
				goto error_exit;
			}
		}
        client_nodes[index].init_state = 4; // we have created the timer

		/* launch a thread to handle this client node */
		{
			int res = 0;
			pthread_attr_t attr;
			res |= pthread_attr_init(&attr);
			res |= pthread_create(&(client_nodes[index].thread_id), &attr, &__mb_client_thread, (void *)((char *)NULL + index));
			if (res !=  0) {
				fprintf(stderr, "Modbus plugin: Error starting thread for modbus client node %%s\n", client_nodes[index].location);
				goto error_exit;
			}
		}
		client_nodes[index].init_state = 5; // we have created the thread
	}

	/* init each local server */
	/* NOTE: All server_nodes[].init_state are initialised to 0 in the code 
	 *       generated by the modbus plugin 
	 */
	for (index=0; index < NUMBER_OF_SERVER_NODES;index++){
		/* create the modbus server */
		server_nodes[index].mb_nd = mb_slave_new (server_nodes[index].node_address);
		if (server_nodes[index].mb_nd < 0){
			fprintf(stderr, "Modbus plugin: Error creating modbus server node %%s\n", server_nodes[index].location);
			goto error_exit;
		}
		server_nodes[index].init_state = 1; // we have created the node
		
		/* launch a thread to handle this server node */
		{
			int res = 0;
			pthread_attr_t attr;
			res |= pthread_attr_init(&attr);
			res |= pthread_create(&(server_nodes[index].thread_id), &attr, &__mb_server_thread, (void *)&(server_nodes[index]));
			if (res !=  0) {
				fprintf(stderr, "Modbus plugin: Error starting modbus server thread for node %%s\n", server_nodes[index].location);
				goto error_exit;
			}
		}
		server_nodes[index].init_state = 2; // we have created the node and thread
	}

	return 0;
	
error_exit:
	__cleanup_%(locstr)s ();
	return -1;
}





void __publish_%(locstr)s (){
	int index;

	for (index=0; index < NUMBER_OF_CLIENT_REQTS; index ++){
		/* synchronize the PLC and MB buffers only for the output requests */
		if (client_requests[index].req_type == req_output){
            
            // lock the mutex brefore copying the data
			if(pthread_mutex_trylock(&(client_requests[index].coms_buf_mutex)) == 0){
                
                // Check if user configured this MB request to be activated whenever the data to be written changes
                if (client_requests[index].write_on_change) {
                    // Let's check if the data did change...
                    // compare the data in plcv_buffer to coms_buffer
                    int res;
                    res = memcmp((void *)client_requests[index].coms_buffer /* buf 1 */,
                                 (void *)client_requests[index].plcv_buffer /* buf 2*/,
                                 REQ_BUF_SIZE * sizeof(u16) /* size in bytes */);
                    
                    // if data changed, activate execution request 
                    if (0 != res)
                        client_requests[index].flag_exec_req = 1;
                }
                
                // copy from plcv_buffer to coms_buffer
                memcpy((void *)client_requests[index].coms_buffer /* destination */,
                       (void *)client_requests[index].plcv_buffer /* source */,
                       REQ_BUF_SIZE * sizeof(u16) /* size in bytes */);
                pthread_mutex_unlock(&(client_requests[index].coms_buf_mutex));
            }
		}
        /* if the user program set the execution request flag, then activate the thread
         *  that handles this Modbus client transaction so it gets a chance to be executed
         *  (but don't activate the thread if it has already been activated!)
         * 
         * NOTE that we do this, for both the IN and OUT mapped location, under this
         *  __publish_() function. The scan cycle of the PLC works as follows:
         *   - call __retrieve_()
         *   - execute user programs
         *   - call __publish_()
         *   - insert <delay> until time to start next periodic/cyclic scan cycle
         * 
         *  In an attempt to be able to run the MB transactions during the <delay>
         *  interval in which not much is going on, we handle the user program
         *  requests to execute a specific MB transaction in this __publish_()
         *  function.
         */
        if ((client_requests[index].flag_exec_req != 0) && (0 == client_requests[index].flag_exec_started)) {
            int client_node_id = client_requests[index].client_node_id;
            
             /* We TRY to signal the client thread.
              * We do this because this function can be called at the end of the PLC scan cycle
              * and we don't want it to block at that time.
              */
             if (pthread_mutex_trylock(&(client_nodes[client_node_id].mutex)) == 0) {
                 client_nodes[client_node_id].execute_req = 1; // tell the thread to execute
                 pthread_cond_signal (&(client_nodes[client_node_id].condv));
                 pthread_mutex_unlock(&(client_nodes[client_node_id].mutex));
                 /* - upon success, set flag_exec_started
                  * - both flags (flag_exec_req and flag_exec_started) will be reset
                  *   once the transaction has completed.
                  */
                 client_requests[index].flag_exec_started = 1;    
             } else {
                 /* The mutex is locked => the client thread is currently executing MB transactions.
                  * We will try to activate it in the next PLC cycle...
                  * For now, do nothing.
                  */
             }
        }                    
    }
}





void __retrieve_%(locstr)s (){
	int index;

	for (index=0; index < NUMBER_OF_CLIENT_REQTS; index ++){
		/*just do the input requests */
		if (client_requests[index].req_type == req_input){
			if(pthread_mutex_trylock(&(client_requests[index].coms_buf_mutex)) == 0){
                // copy from coms_buffer to plcv_buffer
                memcpy((void *)client_requests[index].plcv_buffer /* destination */,
                       (void *)client_requests[index].coms_buffer /* source */,
                       REQ_BUF_SIZE * sizeof(u16) /* size in bytes */);
                pthread_mutex_unlock(&(client_requests[index].coms_buf_mutex));
            }
		}
	}
}





int __cleanup_%(locstr)s (){
	int index, close;
	int res = 0;

	/* kill thread and close connections of each modbus client node */
	for (index=0; index < NUMBER_OF_CLIENT_NODES; index++) {
		close = 0;
		if (client_nodes[index].init_state >= 5) {
			// thread was launched, so we try to cancel it!
			close  = pthread_cancel(client_nodes[index].thread_id);
			close |= pthread_join  (client_nodes[index].thread_id, NULL);
			if (close < 0)
				fprintf(stderr, "Modbus plugin: Error closing thread for modbus client node %%s\n", client_nodes[index].location);
		}
		res |= close;

		close = 0;
		if (client_nodes[index].init_state >= 4) {
			// timer thread was launched, so we try to cancel it!
			close  = pthread_cancel(client_nodes[index].timer_thread_id);
			close |= pthread_join  (client_nodes[index].timer_thread_id, NULL);
			if (close < 0)
				fprintf(stderr, "Modbus plugin: Error closing timer thread for modbus client node %%s\n", client_nodes[index].location);

		}
		res |= close;

		close = 0;
		if (client_nodes[index].init_state >= 3) {
			// condition variable was created, so we try to destroy it!
			close  = pthread_cond_destroy(&(client_nodes[index].condv));
			if (close < 0)
				fprintf(stderr, "Modbus plugin: Error destroying condition variable for modbus client node %%s\n", client_nodes[index].location);
		}
		res |= close;

		close = 0;
		if (client_nodes[index].init_state >= 2) {
			// mutex was created, so we try to destroy it!
			close  = pthread_mutex_destroy(&(client_nodes[index].mutex));
			if (close < 0)
				fprintf(stderr, "Modbus plugin: Error destroying mutex for modbus client node %%s\n", client_nodes[index].location);
		}
		res |= close;

		close = 0;
		if (client_nodes[index].init_state >= 1) {
			// modbus client node was created, so we try to close it!
			close = mb_master_close (client_nodes[index].mb_nd);
			if (close < 0){
				fprintf(stderr, "Modbus plugin: Error closing modbus client node %%s\n", client_nodes[index].location);
				// We try to shut down as much as possible, so we do not return noW!
			}
			client_nodes[index].mb_nd = -1;
		}
		res |= close;
		client_nodes[index].init_state = 0;
	}
	
//fprintf(stderr, "Modbus plugin: __cleanup_%%s()  5  close=%%d   res=%%d\n", client_nodes[index].location, close, res);
	/* kill thread and close connections of each modbus server node */
	for (index=0; index < NUMBER_OF_SERVER_NODES; index++) {
		close = 0;
		if (server_nodes[index].init_state >= 2) {
			// thread was launched, so we try to cancel it!
			close  = pthread_cancel(server_nodes[index].thread_id);
			close |= pthread_join  (server_nodes[index].thread_id, NULL);
			if (close < 0)
				fprintf(stderr, "Modbus plugin: Error closing thread for modbus server %%s\n", server_nodes[index].location);
		}
		res |= close;

		close = 0;
		if (server_nodes[index].init_state >= 1) {
			// modbus server node was created, so we try to close it!
			close = mb_slave_close (server_nodes[index].mb_nd);
			if (close < 0) {
				fprintf(stderr, "Modbus plugin: Error closing node for modbus server %%s (%%d)\n", server_nodes[index].location, server_nodes[index].mb_nd);
				// We try to shut down as much as possible, so we do not return noW!
			}
			server_nodes[index].mb_nd = -1;
		}
		res |= close;
		server_nodes[index].init_state = 0;
	}

	/* destroy the mutex of each client request */
	for (index=0; index < NUMBER_OF_CLIENT_REQTS; index ++) {
		if (pthread_mutex_destroy(&(client_requests[index].coms_buf_mutex))) {
			fprintf(stderr, "Modbus plugin: Error destroying request for modbus client node %%s\n", client_nodes[client_requests[index].client_node_id].location);
			// We try to shut down as much as possible, so we do not return noW!
			res |= -1;
		}
	}

	/* modbus library close */
	//fprintf(stderr, "Shutting down modbus library...\n");
	if (mb_slave_and_master_done()<0) {
		fprintf(stderr, "Modbus plugin: Error shutting down modbus library\n");
		res |= -1;
	}

	return res;
}





/**********************************************/
/** Functions for Beremiz web interface.     **/
/**********************************************/

/*
 * Beremiz has a program to run on the PLC (Beremiz_service.py)
 * to handle downloading of compiled programs, start/stop of PLC, etc.
 * (see runtime/PLCObject.py for start/stop, loading, ...)
 * 
 * This service also includes a web server to access PLC state (start/stop)
 * and to change some basic confiuration parameters.
 * (see runtime/NevowServer.py for the web server)
 * 
 * The web server allows for extensions, where additional configuration
 * parameters may be changed on the running/downloaded PLC.
 * Modbus plugin also comes with an extension to the web server, through
 * which the basic Modbus plugin configuration parameters may be changed
 * 
 * These parameters are changed _after_ the code (.so file) is loaded into 
 * memmory. These changes may be applied before (or after) the code starts
 * running (i.e. before or after __init_() ets called)! 
 * 
 * The following functions are never called from other C code. They are 
 * called instead from the python code in runtime/Modbus_config.py, that
 * implements the web server extension for configuring Modbus parameters.
 */


/* The number of Cient nodes (i.e. the number of entries in the client_nodes array)
 * The number of Server nodes (i.e. the numb. of entries in the server_nodes array)
 * 
 * These variables are also used by the Modbus web config code to determine 
 * whether the current loaded PLC includes the Modbus plugin
 * (so it should make the Modbus parameter web interface visible to the user).
 */
const int __modbus_plugin_client_node_count = NUMBER_OF_CLIENT_NODES;
const int __modbus_plugin_server_node_count = NUMBER_OF_SERVER_NODES;
const int __modbus_plugin_param_string_size = MODBUS_PARAM_STRING_SIZE;



/* NOTE: We could have the python code in runtime/Modbus_config.py
 *       directly access the server_node_t and client_node_t structures,
 *       however this would create a tight coupling between these two
 *       disjoint pieces of code.
 *       Any change to the server_node_t or client_node_t structures would
 *       require the python code to be changed accordingly. I have therefore 
 *       opted to create get/set functions, one for each parameter.
 * 
 *       We also convert the enumerated constants naf_ascii, etc...
 *       (from node_addr_family_t in modbus/mb_addr.h)
 *       into strings so as to decouple the python code that will be calling
 *       these functions from the Modbus library code definitions.
 */
const char *addr_type_str[] = {
        [naf_ascii] = "ascii",
        [naf_rtu  ] = "rtu",
        [naf_tcp  ] = "tcp"    
};


#define __safe_strcnpy(str_dest, str_orig, max_size) {  \
    strncpy(str_dest, str_orig, max_size);              \
    str_dest[max_size - 1] = '\0';                      \
}


/* NOTE: The host, port and device parameters are strings that may be changed 
 *       (by calling the following functions) after loading the compiled code 
 *       (.so file) into memory, but before the code starts running
 *       (i.e. before __init_() gets called).
 *       This means that the host, port and device parameters may be changed
 *       _before_ they get mapped onto the str1 and str2 variables by __init_(),
 *       which is why the following functions must access the str1 and str2 
 *       parameters directly.
 */
const char *       __modbus_get_ClientNode_config_name(int nodeid)  {return client_nodes[nodeid].config_name;                    }
const char *       __modbus_get_ClientNode_host       (int nodeid)  {return client_nodes[nodeid].str1;                           }
const char *       __modbus_get_ClientNode_port       (int nodeid)  {return client_nodes[nodeid].str2;                           }
const char *       __modbus_get_ClientNode_device     (int nodeid)  {return client_nodes[nodeid].str1;                           }
int                __modbus_get_ClientNode_baud       (int nodeid)  {return client_nodes[nodeid].node_address.addr.rtu.baud;     }
int                __modbus_get_ClientNode_parity     (int nodeid)  {return client_nodes[nodeid].node_address.addr.rtu.parity;   }
int                __modbus_get_ClientNode_stop_bits  (int nodeid)  {return client_nodes[nodeid].node_address.addr.rtu.stop_bits;}
u64                __modbus_get_ClientNode_comm_period(int nodeid)  {return client_nodes[nodeid].comm_period;                    }
const char *       __modbus_get_ClientNode_addr_type  (int nodeid)  {return addr_type_str[client_nodes[nodeid].node_address.naf];}
                                                                                                                        
const char *       __modbus_get_ServerNode_config_name(int nodeid)  {return server_nodes[nodeid].config_name;                    }
const char *       __modbus_get_ServerNode_host       (int nodeid)  {char*x=server_nodes[nodeid].str1; return (x[0]=='\0'?"#ANY#":x); }
const char *       __modbus_get_ServerNode_port       (int nodeid)  {return server_nodes[nodeid].str2;                           }
const char *       __modbus_get_ServerNode_device     (int nodeid)  {return server_nodes[nodeid].str1;                           }
int                __modbus_get_ServerNode_baud       (int nodeid)  {return server_nodes[nodeid].node_address.addr.rtu.baud;     }
int                __modbus_get_ServerNode_parity     (int nodeid)  {return server_nodes[nodeid].node_address.addr.rtu.parity;   }
int                __modbus_get_ServerNode_stop_bits  (int nodeid)  {return server_nodes[nodeid].node_address.addr.rtu.stop_bits;}
u8                 __modbus_get_ServerNode_slave_id   (int nodeid)  {return server_nodes[nodeid].slave_id;                       }
const char *       __modbus_get_ServerNode_addr_type  (int nodeid)  {return addr_type_str[server_nodes[nodeid].node_address.naf];}


void __modbus_set_ClientNode_host       (int nodeid, const char * value)  {__safe_strcnpy(client_nodes[nodeid].str1, value, MODBUS_PARAM_STRING_SIZE);}
void __modbus_set_ClientNode_port       (int nodeid, const char * value)  {__safe_strcnpy(client_nodes[nodeid].str2, value, MODBUS_PARAM_STRING_SIZE);}
void __modbus_set_ClientNode_device     (int nodeid, const char * value)  {__safe_strcnpy(client_nodes[nodeid].str1, value, MODBUS_PARAM_STRING_SIZE);}
void __modbus_set_ClientNode_baud       (int nodeid, int          value)  {client_nodes[nodeid].node_address.addr.rtu.baud      = value;}
void __modbus_set_ClientNode_parity     (int nodeid, int          value)  {client_nodes[nodeid].node_address.addr.rtu.parity    = value;}
void __modbus_set_ClientNode_stop_bits  (int nodeid, int          value)  {client_nodes[nodeid].node_address.addr.rtu.stop_bits = value;}
void __modbus_set_ClientNode_comm_period(int nodeid, u64          value)  {client_nodes[nodeid].comm_period                     = value;}
                                                                                                                        

void __modbus_set_ServerNode_host       (int nodeid, const char * value)  {if (strcmp(value,"#ANY#")==0) value = "";
                                                                           __safe_strcnpy(server_nodes[nodeid].str1, value, MODBUS_PARAM_STRING_SIZE);}
void __modbus_set_ServerNode_port       (int nodeid, const char * value)  {__safe_strcnpy(server_nodes[nodeid].str2, value, MODBUS_PARAM_STRING_SIZE);}
void __modbus_set_ServerNode_device     (int nodeid, const char * value)  {__safe_strcnpy(server_nodes[nodeid].str1, value, MODBUS_PARAM_STRING_SIZE);}
void __modbus_set_ServerNode_baud       (int nodeid, int          value)  {server_nodes[nodeid].node_address.addr.rtu.baud      = value;}
void __modbus_set_ServerNode_parity     (int nodeid, int          value)  {server_nodes[nodeid].node_address.addr.rtu.parity    = value;}
void __modbus_set_ServerNode_stop_bits  (int nodeid, int          value)  {server_nodes[nodeid].node_address.addr.rtu.stop_bits = value;}
void __modbus_set_ServerNode_slave_id   (int nodeid, u8           value)  {server_nodes[nodeid].slave_id                        = value;}