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<concept xml:lang="en" id="GUID-1F68D172-1090-5930-BD7B-AE7276667104"><title>How to create streams</title><prolog><metadata><keywords/></metadata></prolog><conbody><section><title>Write streams</title> <p>The following code fragment shows how a write stream is created. A write stream is represented by an instance of the <codeph>RStoreWriteStream</codeph> class and an object of this type can be created on the program stack.</p> <p>Use the <codeph>CreateL()</codeph> or <codeph>CreateLC()</codeph> member function of <codeph>RStoreWriteStream</codeph> to create a new stream in a store and return its stream ID.</p> <codeblock id="GUID-959ABC13-9EFE-5CD5-834E-DE744E1D506B" xml:space="preserve">...

RStoreWriteStream outstream;

TStreamId id = outstream.CreateLC(*store);

...

CleanupStack::PopAndDestroy();

...</codeblock> <p><codeph>store</codeph> is a pointer to an already opened stream store.</p> <p>Some stores allow their existing streams to be modified, for example, by overwriting or appending. To open an existing stream for overwriting, use <codeph>OpenL()</codeph> or <codeph>OpenLC()</codeph> and identify both the store and the stream:</p> <codeblock id="GUID-3815630B-ADCE-5251-8283-CF4488C9E2BF" xml:space="preserve">...

RStoreWriteStream outstream;

TStreamId id;

...

outstream.CreateLC(*store,id);

...

CleanupStack::PopAndDestroy();

...</codeblock> <p>In this code fragment, the id of the stream must be known before calling <codeph>CreateLC()</codeph>.</p> <p>Note that not all store types support the modification of existing streams. An attempt to open an existing stream for modification for these store types will <i>fail</i>. A direct file store is an example of a store which does <i>not</i> support the modification of existing streams. </p> </section> <section><title>Read streams</title> <p>The following code fragment shows how a read stream is created. A read stream is represented by an instance of the <codeph>RStoreReadStream</codeph> class and an object of this type can be created on the program stack.</p> <p>Use the <codeph>OpenL()</codeph> or <codeph>OpenLC()</codeph> member function of <codeph>RStoreReadStream</codeph> to open a stream for reading.</p> <codeblock id="GUID-DD8E19E5-0478-53D1-B370-9DA0E838B84F" xml:space="preserve">RStoreReadStream instream;

TStream id;

...

instream.OpenLC(*store,id);