Because GlobalRealloc always copies data from the source to the destination, increasing a stream object from 20 MB to 25 MB, for example, requires large amounts of time. If creating a stream object that is larger than the heap in your computer's memory and you are using an HGLOBAL handle to a global memory object, the stream object calls the GlobalRealloc method internally whe it requires more memory.
ISTREAM NO SOURCES CODE
In either case, the same IStream implementation code is used. These functions retrieve an IStorage pointer, with which you can then call CreateStream or OpenStream for an IStream pointer. To get an IStream pointer within a compound file object, call either StgCreateDocfile or StgOpenStorage. To create a simple stream based on global memory, get an IStream pointer by calling the API function CreateStreamOnHGlobal. The COM implementation also does not support stream transactioning or region locking. However, the COM implementation only supports streams up to 2³² bytes in length (4 GB) and read and write operations are always limited to 2³² bytes at a time. For example, the IStream interface defines streams up to 2⁶⁴ bytes in length requiring a 64-bit seek pointer. The specification of IStream defines more functionality than the COM implementation supports.
Simple data can be written directly to a stream, but more frequently, streams are elements nested within a storage object. In a structured storage object, stream objects contain the data and storages provide the structure. The IStream interface supports reading and writing data to stream objects.
0 kommentar(er)
