DataSpy.cc

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#include <DataSpy.hh>
 
int DataSpy::Open( int id ) {
 
    if( id < 0 || id >= MAX_ID ) {
        perror ("dataSpyOpen - id number out of range");
        return -1;
    }
 
#if( defined SOLARIS || defined POSIX )
 
    // create a file mapped object (MASTER) or obtain ID of existing object
    //sprintf( object_name, "SHM_%d", shmkey+id );
    snprintf( object_name, sizeof(object_name), "SHM_%d", shmkey+id );
 
    shmid[id] = shm_open( object_name, O_RDONLY, (mode_t)0 );
    if( shmid[id] == -1 ) {
        perror("shm_open");
        exit(1);
    }
 
#else
 
    shmid[id] = shmget(shmkey+id, 0, SHM_R);
    if (shmid[id] == -1) {perror("shmget"); return -1;}
 
#endif
 
#if( defined SOLARIS || defined POSIX )
 
    // attach the memory segment
    shm_bufferarea[id] = mmap((void *) NULL, (size_t) SHMSIZE, PROT_READ, MAP_SHARED, shmid[id], (off_t) 0);
    if( shm_bufferarea[id] == (void *) MAP_FAILED ) {
        perror("mmap");
        exit(1);
    }
 
    close( shmid[id] );
 
#else
 
    shm_bufferarea[id] = shmat( shmid[id], (void *) 0, SHM_RDONLY );
    if( shm_bufferarea[id] == (void *) -1 ) {
        perror("shmat");
        exit(1);
    }
 
#endif
 
    std::cout << "DataSpy Shared buffer area " << id << " (/SHM_" << shmkey+id << ") located at " << (unsigned long)shm_bufferarea[id] << std::endl;
 
    baseaddress = (BUFFER_HEADER *) shm_bufferarea[id];
 
    number_of_buffers[id] = baseaddress->buffer_number;
    buffers_offset[id] = baseaddress->buffer_offset;
 
    // Flush all old buffers by setting current index ...
    next_index[id] = baseaddress->buffer_next;
    current_age[id] = baseaddress->buffer_currentage;
 
    std::cout << "DataSpy Current age " << current_age[id] << " index " << next_index[id] << std::endl;
 
    return 0;
 
}
 
int DataSpy::Close( int id ) {
 
    if( id < 0 || id >= MAX_ID ) {
 
        perror( "DataSpy::Close - id number out of range" );
        return -1;
 
    }
 
#if (defined SOLARIS || defined POSIX)
 
    // detach the memory segment
    (void)munmap(shm_bufferarea[id], (size_t) SHMSIZE);
 
#else
 
    (void)shmdt(shm_bufferarea[id]);
 
#endif
 
    std::cout << "DataSpy Shared buffer area " << id << " located at " << (unsigned long)shm_bufferarea[id] << " detached" << std::endl;
 
    return 0;
 
}
 
int DataSpy::ReadWithSeq( int id, char *data, unsigned int length, int *seq ) {
    
    int *bufferaddress;
    unsigned int len;
    int *ptr;
    
    
    if( id < 0 || id >= MAX_ID ) {
        perror( "DataSpy::Read - id number out of range" );
        return -1;
    }
    
    len = 0;
    baseaddress = (BUFFER_HEADER *) shm_bufferarea[id];
    
retry:
    
    if( baseaddress->buffer_age[next_index[id]] != 0 ) {
        
        if( baseaddress->buffer_age[next_index[id]] >= current_age[id] ) {
            
            current_age[id] = baseaddress->buffer_age[next_index[id]];
            
            len = baseaddress->buffer_length;
            if( !len ) len = MAX_BUFFER_SIZE;
            
            bufferaddress = (int *) ((char *)shm_bufferarea[id] + buffers_offset[id] + (len * next_index[id]));
            
            if( length < len ) len = length;
            
            if( verbose )
                printf( "DataSpy::Read id %d: Age %lld Index %d Buffer length %d\n",
                       id, current_age[id], next_index[id], len );
            
            // copy data from shared memory to user buffer
            ptr = (int*)data;
            for( unsigned int i = 0; i < (len >> 2); i++ )
                ptr[i] = bufferaddress[i];
            *seq = (int)current_age[id];
            
            // check if the entry could have changed while copying (can happen) and if so retry
            if( current_age[id] != baseaddress->buffer_age[next_index[id]] ) {
                
                if( verbose ) {
                    std::cout << "DataSpy::Read id " << id << ": Copied oldage " << current_age[id];
                    std::cout << "newage " << baseaddress->buffer_age[next_index[id]] << std::endl;
                }
                
                goto retry;
                
            }
            
            next_index[id] = (1+next_index[id]) & (number_of_buffers[id] -1);
            
        }
        
    }
    
    else {
        
        if( verbose )
            std::cout << "DataSpy::Read - id " << id << " has no data" << std::endl;
        
    }
    
    if( verbose )
        std::cout << "DataSpy::Read - id " << id << " length " << len << std::endl;
    
    return len;                      /* return actual length of data block */
    
}
int DataSpy::Read( int id, char *data, unsigned int length ) {
 
    int seq;
 
    return ReadWithSeq( id, data, length, &seq );
 
}
/*****************************************************************************/