Mega Code Archive
Binary Streaming over COMDCOM
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Title: Binary Streaming over COM/DCOM
Question: How can I send a binary file through COM/DCOM?
Answer:
Two functions which can be used to stream a binary file or binary data over COM or DCOM using an OleVariant as the COM medium of binary transfers:
type
TByteArray = array of byte;
//******************************************************************//
// OleVariantToStream *
// *
// Inserts an OleVariant to a TStream (COM Compatible) *
//******************************************************************
procedure OleVariantToStream(var Input: OleVariant; Stream: TStream);
var
pBuf: Pointer;
begin
pBuf := VarArrayLock(Input);
Stream.Write(TByteArray(pBuf^), Length(TByteArray(Input)));
VarArrayUnlock(Input);
end;
//******************************************************************
// StreamToOleVariant *
// *
// Copies a TStream contents of Count bytes based on the
current Position *
// to an OleVariant (COM Compatible) *
//******************************************************************
function StreamToOleVariant(Stream: TStream; Count: Integer): OleVariant;
var
pBuf: Pointer;
begin
Result := VarArrayCreate([0, Count-1], varByte);
pBuf := VarArrayLock(Result);
Stream.Read(TByteArray(pBuf^), Length(TByteArray(Result)));
VarArrayUnlock(Result);
end;
To implement these functions, say you have a COM method to store a file:
procedure StoreFile(FileContents: OleVariant);
var
FS: TFileStream;
begin
FS := TFileStream.Create('some file name', fmCreate or fmOpenWrite or fmShareExclusive);
OleVariantToStream(FileContents, FS);
FS.Free;
end;
pretty simple, eh?...
To call StoreFile on the client side you would do something like this..
procedure SendFileToServer(FileName: string);
var
FS: TFileStream;
begin
FS := TFileStream.Create(FileName, fmOpenRead or fmShareCompatible);
MyServer.StoreFile(StreamToOleVariant(FS, FS.Size));
FS.Free;
end;
also, pretty simple..
Have fun!
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