ISequentialStream::Read

Reads a specified number of bytes from the stream object into memory starting at the current seek pointer.

HRESULT Read(
  void *pv,  //Pointer to buffer into which the stream is read
  ULONG cb,  //Specifies the number of bytes to read
  ULONG *pcbRead
             //Pointer to location that contains actual
             // number of bytes read
);

Parameters

pv

[out] Pointer to the buffer into which the stream data is read. If an error occurs, this value is NULL.

cb

[in] Specifies the number of bytes of data to attempt to read from the stream object.

pcbRead

[out] Pointer to a ULONG variable that receives the actual number of bytes read from the stream object. 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.

Return Values

S_OK

Data was successfully read from the stream object.

S_FALSE

The data could not be read from the stream object.

E_PENDING

Asynchronous storage only: Part or all of the data to be read is currently unavailable. For more information see IFillLockBytes and Asynchronous Storage.

STG_E_ACCESSDENIED

The caller does not have enough permissions for reading this stream object.

STG_E_INVALIDPOINTER

One of the pointer values is not valid.

STG_E_REVERTED

The object has been invalidated by a revert operation above it in the transaction tree.

Remarks

This method reads bytes from this stream object into memory. The stream object must be opened in STGM_READ mode. This method adjusts the seek pointer by the actual number of bytes read.

The number of bytes actually read is also returned in the pcbRead parameter.

Notes to Callers

The actual number of bytes read can be less than the number of bytes requested if an error occurs or if the end of the stream is reached during the read operation.

Some implementations might return an error if the end of the stream is reached during the read operation. You must be prepared to deal with the error return or S_OK return values on end-of-stream read operations.

Requirements

  Windows NT/2000: Requires Windows NT 4.0 or later.
  Windows 95/98: Requires Windows 95 or later.
  Header: Objidl.idl.

See Also

ISequentialStream::Write, STGMOVE, IStorage::OpenStream, IStream, IStream - Compound File Implementation