View source for OpenIGTLink/Tutorial/igtlutil

[[OpenIGTLink/Library/Tutorial | &lt;&lt; OpenIGTLink Tutorial Home]]
<div class="floatright">__TOC__</div>


=Serializing Open IGT Link message for linear transform data=

To generate a transform message using the igtlutil library, first we include following header files:

  #include "igtl_util.h"
  #include "igtl_header.h"
  #include "igtl_transform.h"

Then, prepare a transform:
  /********** pack data body **********/
  igtl_float32 transform[12];
  
  transform[0] = tx;
  transform[1] = ty;
  transform[2] = tz;
  transform[3] = sx;
  transform[4] = sy;
  transform[5] = sz;
  transform[6] = nx;
  transform[7] = ny;
  transform[8] = nz;
  transform[9] = px;
  transform[10] = py;
  transform[11] = pz;
  
  igtl_transform_convert_byte_order(transform);  /* convert endian if necessary */

Once the transform data has been prepared, we create a general header:
  
  /********** general header **********/  
  igtl_header header;
  igtl_uint64 crc = crc64(0, 0, 0LL);          /* initial crc */
  header.version   = IGTL_HEADER_VERSION;
  header.timestamp = 0;
  header.body_size = IGTL_TRANSFORM_SIZE;
  header.crc       = crc64((unsigned char*)transform, IGTL_TRANSFORM_SIZE, crc);
  
  strncpy(header.name, "TRANSFORM", 12);       /* Device Type: should be "TRANSFORM" */
  strncpy(header.device_name, "Tracker", 20);    /* Device name */
  
  igtl_header_convert_byte_order(&header);   /* convert endian if necessary */

Now it's time to send the serialized data. Since igtlutil library doesn't have a socket implementation, we need to some socket libraries or API, available in the environment we are working on. In case of BSD socket, call:

  send(sock, (void*) &header, IGTL_HEADER_SIZE, 0);
  send(sock, (void*) transform, IGTL_TRANSFORM_SIZE, 0);

after establishing the connection.

=Deserializing Open IGT Link message for linear transform data=
<br>

First of all, we receive the header data from the sender. It may look like the following code,
in case of using BSD socket API:

  igtl_header header;
  int n;
  
  n = recv(sock, header, IGTL_HEADER_SIZE);
  if (n != IGTL_HEADER_SIZE)
    {
      /*** do something for error handling ***/
    }  

Then convert byte order of each element:

  igtl_header_convert_byte_order(&header);

Now the header is ready to be read. Header fields e.g. header version, size, CRC etc. can be access as members of igtl_header structure.

The following code shows how to detect which type of message is in the body part.

  char deviceType[13];
  deviceType[12] = 0;
  memcpy((void*)deviceType, header.name, 12);
  
  if (strcmp(deviceType, "TRANSFORM") == 0)
    {
      /*** code to read TRANSFORM data ***/
    }
  else if (strcmp(deviceType, "IMAGE") == 0)
    {
      /*** code to read IMAGE data ***/
    }
  
    /*** .... other types ...  ***/
  
  else
    {
      /*** Unknown type: read the rest of the message and discard it. ***/
    }