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IPortableDeviceResources::GetStream

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IPortableDeviceResources::GetStream

The GetStream method gets an IStream interface with which to read or write the content data in an object on a device. The retrieved interface enables you to read from or write to the object data.

Syntax

  HRESULT GetStream(
  LPCWSTR  pszObjectID,
  REFPROPERTYKEY  Key,
  const DWORD  dwMode,
  DWORD*  pdwOptimalBufferSize,
  IStream**  ppStream
);

Parameters

pszObjectID

[in]  Pointer to a null-terminated string that contains the object ID of the object.

Key

[in]  A REFPROPERTYKEY that specifies which resource to read. You can retrieve the keys of all the object's resources by calling GetSupportedResources.

dwMode

[in]  One of the following access modes:

  • STGM_READ  (Read-only access.)
  • STGM_WRITE  (Write-only access.)
  • STGM_READWRITE  (Read/write access.)

pdwOptimalBufferSize

[in, out]  An optional pointer to a DWORD that specifies an estimate of the best buffer size to use when reading or writing data by using ppStream. A driver is required to support this value.

ppStream

[out]  Pointer to an IStream interface pointer. This interface is used to read and write data to the object. The caller must release this interface when it is done with it.

Return Values

The method returns an HRESULT. Possible values include, but are not limited to, those in the following table.

Return code Description
S_OK The method succeeded.
E_POINTER At least one of the required pointer arguments was NULL.

Remarks

The retrieved stream cannot read the contents of a folder recursively. To copy all the resources in an object, specify WPD_RESOURCE_DEFAULT for Key.

If the object does not support resources, this method will return an error, and ppStream will be NULL.

Applications should use the buffer size returned by pdwOptimalBufferSize when allocating the buffer for read or write operations.

Requirements

Header: Defined in PortableDeviceApi.h

Library: PortableDeviceGUIDs.lib

See Also

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