IStream::CopyTo - OLE Programmer's Reference

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IStream::CopyTo

Copies a specified number of bytes from the current seek pointer in the stream to the current seek pointer in another stream.

HRESULT CopyTo(

IStream * pstm,	//Points to the destination stream
ULARGE_INTEGER cb,	//Specifies the number of bytes to copy
ULARGE_INTEGER * pcbRead,	//Pointer to the actual number of bytes read from the source
ULARGE_INTEGER * pcbWritten	//Pointer to the actual number of bytes written to the destination
);

Parameters
pstm

[in]Points to the destination stream. The stream pointed to by pstm can be a new stream or a clone of the source stream.

[in]Specifies the number of bytes to copy from the source stream.

pcbRead

[out]Pointer to the location where this method writes the actual number of bytes read from the source. You can set this pointer to NULL to indicate that you are not interested in this value. In this case, this method does not provide the actual number of bytes read.

pcbWritten

[out]Pointer to the location where this method writes the actual number of bytes written to the destination. You can set this pointer to NULL to indicate that you are not interested in this value. In this case, this method does not provide the actual number of bytes written.

Return Values
S_OK

The stream object was successfully copied.

STG_E_INVALIDPOINTER

The value of one of the pointer parameters is not valid.
STG_E_MEDIUMFULL

The stream is not copied because there is no space left on the storage device.

Comments
This method copies the specified bytes from one stream to another. The seek pointer in each stream instance is adjusted for the number of bytes read or written. This method is equivalent to reading cb bytes into memory using IStream::Read and then immediately writing them to the destination stream using IStream::Write, although IStream::CopyTo will be more efficient.

The destination stream can be a clone of the source stream created by calling the IStream::Clone method.

If IStream::CopyTo returns an error, you cannot assume that the seek pointers are valid for either the source or destination. Additionally, the values of pcbRead and pcbWritten are not meaningful even though they are returned.

If IStream::CopyTo returns successfully, the actual number of bytes read and written are the same.

To copy the remainder of the source from the current seek pointer, specify the maximum large integer value for the cb parameter. If the seek pointer is the beginning of the stream, this techniques copies the entire stream.

See Also
IStream::Read, IStream::Write, IStream::Clone

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