delphi将MemoryStream复制到动态数组

Question

Hello please i've this packed record :

type
 TMyRecord = packed record
    BufSize: Word;
    TargetUser:array[0..80] of char;
    StreamHolder: Byte;
  end;
  PMyRecord = ^TMyRecord;

// i would like to save the MemoryStream into the StreamHolder please see my below procedure:

Procedure AddToRec(ATargetUser:String);
var
MyRecord: PMyRecord;
Strm:TMemoryStream;
Size: Integer;
begin
Strm:=TMemoryStream.Create;
try
Strm.LoadFromFile('myFile.dat');
Strm.position:=0;
Size:=Strm.size;
GetMem(MyRecord,Size);
ZeroMemory(MyRecord,Size);
MyRecord.BufSize := Size;
StrCopy(MyRecord.TargetUser,PChar(ATargetUser));

// here how could i copy the Strm into the StreamHolder ?

//SendMyBuffer(MyRecord,Size);

finally
Strm.free;
end;
end;

So please how could i copy the Strm to the StreamHolder ?

many thanks

Answer 1

You appear to want to copy the entire stream onto @MyRecord.StreamHolder . Do that like this:

Strm.ReadBuffer(MyRecord.StreamHolder, Size);

You'll also need to change your GetMem to allocate enough memory.

GetMem(MyRecord, Size + SizeOf(MyRecord^) - SizeOf(MyRecord.StreamHolder));

Or perhaps more elegantly:

GetMem(MyRecord, Size + Integer(@PMyRecord(nil)^.StreamHolder));

As it stands your code does not take account of that part of the record which appears before StreamHolder .

Answer 2

Why not holding

StreamHolder: Byte;

as

StreamHolder: tMemoryStream;

and change the procedure to

 var
   MyRecord: PMyRecord;
 begin
   GetMem(MyRecord,SizeOf(pMyRecord));
   myRecord.StreamHolder := TMemoryStream.Create;
   try
    myRecord.StreamHolder.LoadFromFile('myFile.dat');
    //Strm.position:=0;
    //Size:=Strm.size;
    //ZeroMemory(MyRecord,Size);
    //MyRecord.BufSize := Size;
    StrCopy(MyRecord.TargetUser,PChar(ATargetUser));
   finally 
     // no free in here... free the streamholder whenever you get rid of MyRecord...
   end ;