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 interlace audio, video, text, and other elements. An opening STGTY_REPEAT elements means that the elements that follow are to be repeated a specified number of times. The closing STGTY_REPEAT element marks the end of those elements that are to be repeated. Nested STGY_REPEAT 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 LayoutType is STGTY_STREAM, this flag specifies the beginning offset into the steam named in pwscElementName.

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 offset cOffset from the stream nemaed 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 cOffest and cBytes are LARGE_INTEGER structures and they must be represented as a structure with {LARGE_INTEGER} or {DWORD lowpart, LONG highpart}.

See Also

ILayoutStorage::LayoutScript