static int mongo_message_send( mongo *conn, mongo_message *mm ) {
    mongo_header head; /* little endian */
    int res;
    bson_little_endian32( &head.len, &mm->head.len );
    bson_little_endian32( &head.id, &mm->head.id );
    bson_little_endian32( &head.responseTo, &mm->head.responseTo );
    bson_little_endian32( &head.op, &mm->head.op );

    res = mongo_env_write_socket( conn, &head, sizeof( head ) );
    if( res != MONGO_OK ) {
        bson_free( mm );
        return res;
    }

    res = mongo_env_write_socket( conn, &mm->data, mm->head.len - sizeof( head ) );
    if( res != MONGO_OK ) {
        bson_free( mm );
        return res;
    }

    bson_free( mm );
    return MONGO_OK;
}
static int mongo_message_send( mongo *conn, mongo_message *mm ) {
    mongo_header head;  
    int res;
    bson_little_endian32( &head.len, &mm->head.len );
    bson_little_endian32( &head.id, &mm->head.id );
    bson_little_endian32( &head.responseTo, &mm->head.responseTo );
    bson_little_endian32( &head.op, &mm->head.op );

    res = mongo_env_write_socket( conn, &head, sizeof( head ) );
    if( res != MONGO_OK ) {
        bson_free( mm );
        return res;
    }

    res = mongo_env_write_socket( conn, &mm->data, mm->head.len - sizeof( head ) );
    if( res != MONGO_OK ) {
        bson_free( mm );
        return res;
    }

    bson_free( mm );
    return MONGO_OK;
}