ISequentialStream::Write method

The Write method writes a specified number of bytes into the stream object starting at the current seek pointer.


  const void *pv,
  ULONG      cb,
  ULONG      *pcbWritten



A pointer to the buffer that contains the data that is to be written to the stream. A valid pointer must be provided for this parameter even when cb is zero.


The number of bytes of data to attempt to write into the stream. This value can be zero.


A pointer to a ULONG variable where this method writes the actual number of bytes written to the stream object. The caller can set this pointer to NULL, in which case this method does not provide the actual number of bytes written.

Return value

This method can return one of these values.


ISequentialStream::Write writes the specified data to a stream object. The seek pointer is adjusted for the number of bytes actually written. The number of bytes actually written is returned in the pcbWritten parameter. If the byte count is zero bytes, the write operation has no effect.

If the seek pointer is currently past the end of the stream and the byte count is nonzero, this method increases the size of the stream to the seek pointer and writes the specified bytes starting at the seek pointer. The fill bytes written to the stream are not initialized to any particular value. This is the same as the end-of-file behavior in the MS-DOS FAT file system.

With a zero byte count and a seek pointer past the end of the stream, this method does not create the fill bytes to increase the stream to the seek pointer. In this case, you must call the IStream::SetSize method to increase the size of the stream and write the fill bytes.

The pcbWritten parameter can have a value even if an error occurs.

In the COM-provided implementation, stream objects are not sparse. Any fill bytes are eventually allocated on the disk and assigned to the stream.


Minimum supported client Windows 2000 Professional [desktop apps | UWP apps]
Minimum supported server Windows 2000 Server [desktop apps | UWP apps]
Target Platform Windows
Header objidl.h
Library Uuid.lib
DLL Ole32.dll

See also




IStream - Compound File Implementation