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CeOpenStream (EDB) (Windows Embedded CE 6.0)

  • Статья

1/6/2010

This function opens a stream object on a CEVT_STREAM typed property.

This function does not work with CEDB databases. For more information about CEDB, see CEDB Reference.

Syntax

HANDLE CeOpenStream(
    HANDLE hDatabase,
    CEPROPID propid,
    DWORD dwMode
);

Parameters

  • hDatabase
    [in] Handle to the database in which you want to open the stream object.
  • propid
    [in] Property ID of the property on which to open the stream object. This property must be a CEVT_STREAM type.

  • dwMode
    [in] Access mode. The following are possible values:

    • GENERIC_READ
      Provides read access to the stream.
    • GENERIC_WRITE
      Provides both write and read access to the stream.

Return Value

A handle to the stream object indicates success. INVALID_HANDLE_VALUE indicates failure. To get extended error information, call GetLastError. The following table shows possible values.

Return Value Description

ERROR_ACCESS_DENIED

Indicates one of the following:

  • The stream is compressed. A stream cannot be opened if it is compressed.
  • Another stream on this database handle is open. Only one stream at a time can be opened for write access on a particular database handle.
  • The property is set to NULL. The stream cannot be read. It can only be opened for write.

ERROR_INVALID_HANDLE

The hDatabase parameter is set to NULL or equal to INVALID_HANDLE_VALUE.

ERROR_INVALID_PARAMETER

Indicates one of the following:

  • The dwMode parameter is not set to GENERIC_READ or GENERIC_WRITE.
  • The propid parameter is not a CEVT_STREAM typed property.
  • The propid parameter is not a valid property in the database.

ERROR_KEY_DELETED

The parent row of the stream object has been deleted. This can happen only if the stream object was opened for read access. When a stream is opened for write access, the parent row is locked for write access.

ERROR_NO_MORE_ITEMS

The database from which the stream object was opened had its current row seek position changed. To prevent this, open a stream, perform the operations, and then close the stream object before doing anything else on the parent database.

Remarks

A stream handle enables efficient reading from and writing to the contents of a stream. A stream can be very large, such as an image or an e-mail attachment, and it is inefficient to load the entire contents of the stream into memory at once. For smaller binary properties, use the CEVT_BLOB or the CEVT_LPWSTR property types.

The database must be positioned at the desired record in which you want to open the stream.

The following stream functions can be used once a stream object is open:

Only one stream can be opened for write access at a time for a database handle. If you open a stream for write access, you must save changes by calling the CeStreamSaveChanges (EDB) function.

A stream that has been created with the flag DB_PROP_COMPRESSED set cannot be opened with a CEVT_STREAM property. Instead, you must use the CeWriteRecordProps (EDB) function.

A stream cannot be read if there is no value assigned to the property. However, the stream can be opened for writing.

If the seek position of the database is changed, the stream handle is abandoned.

The handle returned from this function must be closed with the CloseHandle function.

Requirements

Header windbase.h
Library coredll.lib
Windows Embedded CE Windows CE 5.0 and later

See Also

Reference

EDB Functions
CeStreamRead (EDB)
CeStreamWrite (EDB)
CeStreamSaveChanges (EDB)
CeStreamSetSize (EDB)
CeStreamSeek (EDB)
CeWriteRecordProps (EDB)