Streaming

1. Streaming of object data

Streaming of object data

I've been using TFileStream and TMemoryStream to read and write large quantities of record object data to and from disk. Here's an example of streaming to disk the contents of a container called DataArray that contains several thousand record objects:

  DataStream := TFileStream.Create('vccmem.dat', fmCreate);
  MakeDate := FormatDateTime('mmmm d, yyyy',date);
  DataStream.Write(MakeDate, SizeOf(MakeDate));
  RCount := DataArray.Size;
  DataStream.Write(RCount,SizeOf(RCount));

  for q := 1 to DataArray.Size do
  begin
    Application.ProcessMessages;
    ARecord := DataArray[q] as TNameRecord;
    DataStream.Write(ARecord.id, SizeOf(ARecord.id));
    DataStream.Write(ARecord.first_name, SizeOf(ARecord.first_name));
    DataStream.Write(ARecord.last_name, SizeOf(ARecord.last_name));
    DataStream.Write(ARecord.title, SizeOf(ARecord.title));
    DataStream.Write(ARecord.address, SizeOf(ARecord.address));
    DataStream.Write(ARecord.city, SizeOf(ARecord.city));
    DataStream.Write(ARecord.state, SizeOf(ARecord.state));
    DataStream.Write(ARecord.zip, SizeOf(ARecord.zip));
    DataStream.Write(ARecord.phone, SizeOf(ARecord.phone));
    DataStream.Write(ARecord.fax, SizeOf(ARecord.fax));
    DataStream.Write(ARecord.e_mail, SizeOf(ARecord.e_mail));
  end;
  DataStream.Destroy;

  DataStream := TMemoryStream.Create;
  DataStream.LoadFromFile('vccmem.dat');
  DataStream.Read(MakeDate, SizeOf(MakeDate));
  DataStream.Read(RCount, SizeOf(RCount));

  for q := 1 to RCount do
  begin
    NameRecord := TNameRecord.Create;
    DataStream.Read(NameRecord.id, SizeOf(NameRecord.id));
    DataStream.Read(NameRecord.first_name, 
      SizeOf(NameRecord.first_name));
    DataStream.Read(NameRecord.last_name, 
      SizeOf(NameRecord.last_name));
    DataStream.Read(NameRecord.title, SizeOf(NameRecord.title));
    DataStream.Read(NameRecord.address, SizeOf(NameRecord.address));
    DataStream.Read(NameRecord.city, SizeOf(NameRecord.city));
    DataStream.Read(NameRecord.state, SizeOf(NameRecord.state));
    DataStream.Read(NameRecord.zip, SizeOf(NameRecord.zip));
    DataStream.Read(NameRecord.phone, SizeOf(NameRecord.phone));
    DataStream.Read(NameRecord.fax, SizeOf(NameRecord.fax));
    DataStream.Read(NameRecord.e_mail, SizeOf(NameRecord.e_mail));
    NameArray.Insert(NameRecord);
  end;