ack keeper

void * acknowledgment_keeper( void * _block ){

    signal( SIGUSR1, erase );


    int     ret,            len = sizeof( struct sockaddr_in );

    char    *id,            *seq_num;


    char    *buffer = malloc( sizeof( char ) * MAXLINE );

    block   *myblock = ( block * ) _block;

    worker  *w_tmp = ( myblock -> workers );

    sw_slot *sw_tmp;

    printf("\n ACKNOWLEDGMENT KEEPER RUNNING FOR BLOCK MATCHED TO FILE : %s\n ", myblock -> filename ); fflush(stdout);

    do {

        /*  Receive a packet (acknowledgments) from related block's socket.  */

        struct sockaddr_in     client_address;

        memset( buffer, 0, sizeof( buffer ) );

        ret = recvfrom( myblock -> server_sock_desc, (char *) buffer, MAXLINE , MSG_WAITALL, ( struct sockaddr *) &client_address, &len);
        if (ret <= 0) {
            printf("\n ACK KEEPER EXITS...");
            pthread_exit( NULL );
        }

        printf("\n ACK received : ");

        /*  Parse the packet to keep separated the identifier and sequence number fields.  */

        id = strtok( buffer, "/" );
        if (ret == -1)      Error_("Error in function sprintf (acknowledgment_demultiplexer).", 1);

        seq_num = strtok( NULL, "/" ) ;
        if (ret == -1)      Error_("Error in function sprintf (acknowledgment_demultiplexer).", 1);


        /*  Find the block's worker with identifier as specified on ACK. */

        while ( ( w_tmp -> identifier ) != atoi(id) ) {

            w_tmp = ( w_tmp -> next );

        }


        /*  Once the worker is found, find the worker's window's slot with sequence number as specified on ACK  */

        sw_tmp = ( w_tmp -> sliding_window_slot_ );

        while ( ( sw_tmp -> sequence_number ) != atoi(seq_num) ) {

            sw_tmp = ( sw_tmp -> next );

        }


        {
            pthread_mutex_lock( &( w_tmp -> s_window_mutex) );

            /*  THIS IS A CRITICAL SECTION FOR ACCESS ON THE SLIDING WINDOW (shared by ack-keeper thread and the relative worker).
                Update worker window's slot's status from SENT to ACKED.
                If the slot is the first of the sliding window, forward a SIGUSR2 signal to worker-thread to get the window sliding on. */

            if ( ( sw_tmp -> status ) != SENT )  {
                printf("\n Error in acknowledgemnt keeper : unexpected window status = %d", sw_tmp ->status);
            }

            sw_tmp -> status = ACKED;

            printf(" %d", sw_tmp -> sequence_number );                  fflush(stdout);

            //current_timestamp( sw_tmp -> acked_timestamp );

            if ( ( sw_tmp -> is_first ) == '1' )    {
                pthread_kill( ( w_tmp -> tid ), SIGUSR2 );
                printf("\n SIGNAL THE WORKER TO SLIDE ON.");            fflush(stdout);
            }

            pthread_mutex_unlock( &( w_tmp -> s_window_mutex) );

        }


    } while ( myblock -> eraser != '1');

    pthread_exit( NULL );

}