Chapter 5.7
zHL7 Class

Healthcare data is frequently passed between systems using a special format called hl7. If not used in the Healthcare Industry, then zWebitwill not need this class. When zWebit is used in a healthcare environment, the zHL7 class can be used for manipulating hl7 formatted data in C++ programs.

The zHl7 routines basically work by treating the entire transaction as one string of data, and applying seek and find or seek and update logic on the string. The zHl7 class is derived from the zString class.

The zHl7 class does not check for hl7 validity and is not as powerful as some other hl7 parsing tools available. However, it has proven adequate for zWebit, and it is extensible as well.

zWebit is not exclusive to the Healthcare industry alone. In fact, it can be utilized for other endeavors concerning data communication and data manipulation. zWebit is capable of using other classes and libraries for data manipulation.

For example, if SegCode = OBR, SegNo = 0 then this will process the first OBR record.

HL7 messages are typically sent from system to system with particular framing bytes. Although not all systems follow these rules, many systems frame the record as follows:

Data messages are stored in zWebit in an unframed manner. That is, the first byte and last bytes are removed from the transaction by the acquisition program before storing the data. The delivery program is responsible for correctly framing messages before delivering the data to its destination. The zHl7 class assumes unframed data is being processed. There are two methods, zString::FrameIt ( ) and zString::deFrameIt ( ), which can be used for handling the framing of the data. See the zString section for information regarding the frame characters.

/* zhl7 test program

   Copyright (c) 2000 HSC  GNU/GPL
      
*/

#include 
#include 

#include "../../base/zstring.cpp"
#include "../../base/zhl7.cpp"

using namespace std;

int main()
{
  zHl7 hl7;

  zString ws;   /* work string */
  char c;
  int rc;
  
  /* load the test data record in (one byte at a time) */

  ifstream infile( "testhl7.dat", ios::in );
  if( !infile ){
    cerr << "File testhl7.txt could not be opened" << endl;
    exit(1);
  }
  infile.read( &c, 1 );
  while( !infile.eof()){
    hl7 += c;
    infile.read( &c, 1 );
  }    
  infile.close();

  /* load the hl7 class with data */
  cout << "Loaded hl7 record =>" << hl7.getData() << "<=" << endl;
  cout << "hl7 message length = " << hl7.len() << endl;


  /* pull the fifth field from the first PID segment, all sub fields */
  rc = hl7.getField( "PID", 0, 0, -1, ws );
  if( rc > 0 )
    cout << "PID-0 = " << ws << endl;
  else
    cout << "error " << rc << " in getField()" << endl; 

  /* pull the fifth field from the first PID segment, all sub fields */
  rc = hl7.getField( "PID", 0, 5, -1, ws );
  if( rc > 0 )
    cout << "PID-5 = " << ws << endl;
  else
    cout << "error " << rc << " in getField()" << endl; 

  /* pull the fifth field from the first PID segment, second sub fields */
  rc = hl7.getField( "PID", 0, 5, 1, ws );
  if( rc > 0 )
    cout << "PID-5-1 = " << ws << endl;
  else
    cout << "error " << rc << " in getField()" << endl; 

  rc = hl7.deleteField( "PID", 0, 5 );
  rc = hl7.insertField( "PID", 0, 5, "WONKA^WILLY^^" );

  cout << "New hl7 record =>" << hl7.getData() << "<=" << endl;
  cout << "hl7 message length = " << hl7.len() << endl;

  cout << "There are " <<  hl7.segCount( "*" ) << " total segments" << endl;
  cout << "There are " <<  hl7.segCount( "PID" ) << " PID segments" << endl;

  rc = hl7.deleteSeg( "DG1", 0 );
  cout << "hl7 transaction without DG1 segment =>" << hl7.getData() << "<=" << endl;
  cout << "hl7 message length = " << hl7.len() << endl;

  /* update PID segment to contain 50 fields */

  hl7.expandSegFieldDelimCt( "PID", 0, 40 );
  cout << "PID record with 40 fields =>" << hl7.getData() << "<=" << endl;
  cout << "hl7 message length = " << hl7.len() << endl;

  hl7.getSeg( "PID", 0, ws );
  cout << "PID segment = " << ws << endl;

  return 0;
}

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Last updated: 07/21/2003