Work with BLOB field (VB, C++)

Sub sample4()
 Dim cn As New ADODB.Connection
 cn.Open "file name=d:\database\employee.ibp"

 Dim cmd As New ADODB.Command
 Dim rs As ADODB.Recordset

 cmd.ActiveConnection = cn

 cmd.CommandText = "select proj_name,proj_desc from project"
 Set rs = cmd.Execute

 While Not rs.EOF
  Debug.Print rs("proj_name")
  Debug.Print "BLOB size=" & CStr(rs("proj_desc").ActualSize)
  Debug.Print rs("proj_desc") 'BLOB

  rs.MoveNext
 Wend
 rs.Close

 ' use Field.GetChunk method for work with very large BLOB-field

 Debug.Print "Use Field.GetChink method"
 Set rs = cmd.Execute

 Dim chink As Variant
 Dim str As String

 While Not rs.EOF
  Debug.Print rs("proj_name")

  str = ""
  chink = ""

  Do
   str = str & chink
   chink = rs("proj_desc").GetChunk(16)
  Loop While VarType(chink) <> vbNull

  Debug.Print str

  rs.MoveNext
 Wend

 cn.BeginTrans

 Dim ins_cmd As New ADODB.Command
 ins_cmd.ActiveConnection = cn

 ins_cmd.CommandText = "insert into project" & Chr(13) & _
                       "(proj_id,proj_name,proj_desc,team_leader,product)" & Chr(13) & _
                       "values(?,?,?,?,?)"

 If (False) Then ' directly installation of the descriptions of parameters
  ins_cmd.Parameters.Append ins_cmd.CreateParameter("proj_id", adBSTR, , , "AAA")
  ins_cmd.Parameters.Append ins_cmd.CreateParameter("proj_name", adBSTR, , , "Test project 1")
  ins_cmd.Parameters.Append ins_cmd.CreateParameter("proj_desc", adLongVarChar, , -1, "This is test project 1")
  ins_cmd.Parameters.Append ins_cmd.CreateParameter("team_leader", adBSTR, , , Null)
  ins_cmd.Parameters.Append ins_cmd.CreateParameter("product", adBSTR, , , "software")
 Else ' Get the description of parameters
  ins_cmd.Parameters.Refresh
  ins_cmd(0) = "AAA"
  ins_cmd(1) = "Test project"
  ins_cmd(2) = "This is empty project." 'BLOB iiea
  ins_cmd(3) = Null 'no leader
  ins_cmd(4) = "software"
 End If

 ins_cmd.Execute

 'cn.CommitTrans 'no commit insert operation
End Sub

void TSampleCode4::execute()
{
 cout<<"Sample #4"<<endl;

 try
 {
  t_db_data_source source;
  t_db_session     session;

  //attach data source (auto commit mode)
  _THROW_OLEDB_FAILED(source,attach("file name=employee.ibp"))

  _THROW_OLEDB_FAILED(session,create(source))

  t_db_command cmd;
  t_db_row     row;

  _THROW_OLEDB_FAILED(cmd,create(session))

  _THROW_OLEDB_FAILED(cmd,prepare("select proj_name,proj_desc from project",&row))
  _THROW_OLEDB_FAILED(cmd,execute(NULL))

  cout<<"direct reading of BLOB..."<<endl;

  while(cmd.fetch(row)==S_OK)
  {
   cout<<"---------------"<<endl;
   cout<<row["proj_name"].as_string<<endl;
   cout<<row["proj_desc"].as_string<<endl;
  }//while

  _THROW_OLEDB_FAILED(cmd,m_last_result);

  //delete TEST records ------------------------------------------
  t_db_command del_cmd;

  _THROW_OLEDB_FAILED(del_cmd,create(session))

  _THROW_OLEDB_FAILED(del_cmd,prepare("delete from project where proj_id in (\'AAA\',\'BBB\')",NULL))

  _THROW_OLEDB_FAILED(del_cmd,execute(NULL))

  //--------------------------------------------------------------
  t_db_command ins_cmd;
  t_db_row     param;

  _THROW_OLEDB_FAILED(ins_cmd,create(session))

  //unnamed parameters ------------------------------------
  _THROW_OLEDB_FAILED(ins_cmd,
      prepare("insert into project\n"
              "(proj_id,proj_name,proj_desc,team_leader,product)\n"
              "values(?,?,?,?,?)",NULL))

  param[0]="AAA";
  param[1]="Test project";

  set_param(param,2,adLongVarChar,"This is test project");
  set_param(param,3L).null=true;
  param[4]="software";
  param.set_count(5);

  _THROW_OLEDB_FAILED(session,start_transaction())

  _THROW_OLEDB_FAILED(ins_cmd,execute(&param,false))

  //named parameters --------------------------------------
  _THROW_OLEDB_FAILED(ins_cmd,
      prepare("insert into project\n"
              "(proj_id,proj_name,proj_desc,team_leader,product)\n"
              "values(:id,:name,:desc,:leader,:prod)",NULL))

  _THROW_OLEDB_FAILED(ins_cmd,describe_params(param))

  param["id"]  ="BBB";
  param["name"]="Test Project 2";
  param["desc"]="This is desc of Test Project 2";
  param["leader"].null=true;
  param["prod"]="software";

  _THROW_OLEDB_FAILED(ins_cmd,execute(&param,false))

  _THROW_OLEDB_FAILED(session,commit())
 }
 catch(exception& exc)
 {
  cout<<"error: "<<exc.what()<<endl;
 }
}//execute