big streams with DataSnap
I'm trying to transfer some big streams (~1Mb) between DataSnap server/client but to no avail. I'm trying to understand the code of Jim Tierney (http://blogs.embarcadero.com/jimtierney/2009/04/06/31461) with no luck and i can't even compile the code because of a missing library, anyway ...
The max size of a stream i`m able to receive is 64k, so any tips/ideas/code samples you can provide for a weekend programmer like me will be very开发者_运维知识库 welcomed. Thank you!
my server code:
function TsrvMethods.getStream(iCount: integer): TStream;
begin
Result := dummyStream('0123456789', iCount);
end;
function dummyStream(sCnt: string; iCount: integer): TStream;
begin
Result := TMemoryStream.Create;
while iCount > 1 do begin
Result.Write(Pointer(sCnt)^, Length(sCnt));
Dec(iCount);
end;
Result.Seek(0, TSeekOrigin.soBeginning);
end;
my client calling code:
procedure TfrmMain.butStreamClick(Sender: TObject);
var
sStr : TStream;
begin
cycleConnection; //make sure we have an active connection
with TsrvMethodsClient.Create( SQLConn.DBXConnection, False ) do begin
sStr := getStream( Integer(SpinCount.Value) );
Free;
end;
FreeAndNil(sStr);
end;
Actually, i think i`ve got it. I'm posting this as an answer maybe somebody else need this.
procedure TfrmMain.butStreamClick(Sender: TObject);
const
iBufSize = 128;
var
sStr : TStream;
sMem : TMemoryStream;
buf: PByte;
iRead: integer;
begin
cycleConnection;
with TsrvMethodsClient.Create( SQLConn.DBXConnection, False ) do begin
sStr := getStream( 500000 ); //500k stream
GetMem(buf, iBufSize);
sMem := TMemoryStream.Create;
try
repeat
iRead := sStr.Read( Pointer(buf)^, iBufSize);
if iRead > 0 then sMem.WriteBuffer( Pointer(buf)^, iRead);
if iRead < iBufSize then break;
until iRead < iBufSize;
finally
FreeMem(buf, iBufSize);
end;
Free;
end;
FreeAndNil(sStr);
FreeAndNil(sMem);
end;
P.S.
Searching through DataSnap code samples i`ve found that one (speed related) improvement would be to have iBufSize set to 61440 (or equivalent hex value $F000) which seems to be the biggest size can be received in one go. If receiving stream is bigger then reported size will be -1 and the code above is needed to read the entire stream.
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