StorageLayout

The StorageLayout structure describes a single block of data, including its name, location, and length. To optimize a compound file, an application or layout tool passes an array of StorageLayout structures in a call to ILayoutStorage::LayoutScript.

typedef struct tagStorageLayout 
{ 
  DWORD           LayoutType;
  OLECHAR*        pwcsElementName;
  LARGE_INTEGER   cOffset;
  LARGE_INTEGER   cBytes;
} StorageLayout;

Members

LayoutType

The type of element to be written. Values are taken from the STGTY enumeration. STGTY_STREAM means read the block of data named by pwcsElementName. STGTY_STORAGE means open the storage specified in pwcsElementName. STGTY_REPEAT is used in multimedia applications to interface audio, video, text, and other elements. An opening STGTY_REPEAT value means that the elements that follow are to be repeated a specified number of times. The closing STGTY_REPEAT value marks the end of those elements that are to be repeated. Nested STGY_REPEAT value pairs are permitted.

pwcsElementName

The name of the storage or stream. If the element is a substorage or embedded object, the fully qualified storage path must be specified; for example, RootStorageName\SubStorageName\Substream.

cOffset

Where the value of the LayoutType member is STGTY_STREAM, this flag specifies the beginning offset into the steam named in the pwscElementName member.

Where LayoutType is STGTY_STORAGE, this flag should be set to zero.

Where LayoutType is STGTY_REPEAT, this flag should be set to zero.

cBytes

Length in bytes of the data block named in pwcsElementName.

Where LayoutType is STGTY_STREAM, cBytes specifies the number of bytes to read at cOffset from the stream named in pwcsElementName.

Where LayoutType is STGTY_STORAGE, this flag is ignored.

Where LayoutType is STGTY_REPEAT, a positive cBytes specifies the beginning of a repeat block. STGTY_REPEAT with zero cBytes marks the end of a repeat block.

A beginning block value of STG_TOEND specifies that elements in a following block are to be repeated after each stream has been completely read.

An array of StorageLayout structures might appear as follows:

StorageLayout arrScript[]=
    // Read first 2k of "WordDocument" stream
    {STGTY_STREAM,L"WordDocument",{0,0},{0,2048}},
 
    //Test if "ObjectPool\88112233" storage exists
    {STGTY_STORAGE,L"ObjectPool\\88112233",{0,0},{0,0}},
 
    //Read 2k at offset 1048 of "WordDocument" stream
    {STGTY_STREAM,L"WordDocument",{0,10480},{0,2048}},
 
    //Interlace "Audio", "Video", and "Caption" streams
    {STGTY_REPEAT,NULL,0,STG_TOEND},
        {STGTY_STREAM,L"Audio", {0,0},{0,2048}},    // 2k of Audio
        {STGTY_STREAM,L"Video", {0,0},{0,65536}},   // 64k of Video
        {STGTY_STREAM,L"Caption", {0,0},{0,128}},   // 128b of text
    {STGTY_REPEAT,NULL, {0,0},{0,0}}
};

Note  The parameters cOffset and cBytes are LARGE_INTEGER structures, used to represent a 64-bit signed integer value as a union of two 32-bit members. The two 32-bit members must be represented as a LARGE_INTEGER structure with DWORD LowPart AND LONG HighPart as the structure members. (LowPart specifies the low-order 32 bits and HighPart specifies the high-order 32 bits.)}. If your compiler has built-in support for 64-bit integers, use the QuadPart member of the LARGE_INTEGER structure to store the 64-bit integer.

Requirements

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

See Also

ILayoutStorage::LayoutScript