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The Revert method discards all changes that have been made to a transacted stream since the last IStream::Commit call. The LockRegion method restricts access to a specified range of bytes in the stream. The Commit method ensures that any changes made to a stream object open in transacted mode are reflected in the parent storage.Ĭopies a specified number of bytes from the current seek pointer in the stream to the current seek pointer in another stream.

The Clone method creates a new stream object with its own seek pointer that references the same bytes as the original stream. IStream also has these types of members: Methods The IStream interface inherits from the ISequentialStream interface. Managing Memory Allocation for details on COM's rules for managing memory. There will be a subsequent call to IBindStatusCallback::OnDataAvailable with the grfBSC flag set to BSCF_LASTDATANOTIFICATION.įor general information on this topic, seeĭata-Pull-Model versus Data Push-Model for more specific information. Read is called to read all the available data and the bind operation is over (end of file) Returns E_PENDING if the bind operation has not completed, and IBindStatusCallback::OnDataAvailable will be called again when more data is available. Read is called to read all the available data Even if the client returns from IBindStatusCallback::OnDataAvailable at this point the bind operation continues and IBindStatusCallback::OnDataAvailable will be called again repeatedly until the binding finishes. (that is, read until S_FALSE or E_PENDING is returned) The client must continue to read all available data before returning from IBindStatusCallback::OnDataAvailable or else the bind operation is blocked. Read is called to read partial data (that is, not all the available data)

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IStream::Seek calls returned in IBindStatusCallback::OnDataAvailable in these two download models: IStream method call The following table compares the behavior of asynchronous IMoniker::BindToStorage operation and for receiving asynchronous notifications. Once released, the stream object is no longer valid and cannot be used.Ĭlients of asynchronous monikers can choose between a data-pull or data-push model for driving an asynchronous The IUnknown::Release method is similar to a close function on a file. Streams can remain open for long periods of time without consuming file-system resources. There are also methods for committing and reverting changes on streams that are open in transacted mode and methods for restricting access to a range of bytes in the stream. The methods in this interface present your object's data as a contiguous sequence of bytes that you can read or write.

IStream interface pointer rather than a file handle. The main difference between a DOS file and a stream object is that in the latter case, streams are opened using an For example, each stream object has its own access rights and a seek pointer. IStream interface defines methods similar to the MS-DOS FAT file functions.

Simple data can be written directly to a stream but, most frequently, streams are elements nested within a storage object. Stream objects contain the data in a structured storage object, where storages provide the structure. You can do a search on the Net.IStream interface lets you read and write data to stream objects. Stream := TMyStream.Create(TFileRec(F).Handle) Īlternatively, someone created a niffty Delphi TMappedFileStream VCL object that is freely available.

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I've derived many custom TStream objects from Delphi's THandleStream that will include its own variable to hold a Delphi untyped 'File' variable that empowers my custom THandleStream to include Delphi's file functions(ie: F.Truncate) as well as Windows API. THandleStream provides access to the file handle variable that Windows API require for many core file read/write API calls.

Istream addon code#

The IStream Object will publish these methods correctly for external COM objects expecting an IStream interface.Īlong with the previous reply, you could use most any TStream derived object within your own code implementation, including THandleStream. until these methods are defined in your code. For clarity, the IStream object defined in the Delphi Visual Component Library (VCL) is a dynamic object that doesn't have any methods, procedures, functions, etc.