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<concept id="GUID-95448841-5E5B-54C4-85A7-DCE6D078E036" xml:lang="en"><title>Constructing

an embedded store</title><shortdesc>Embedded stores are represented by an instance of the <codeph>CEmbeddedStore</codeph> class.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>A <codeph>CEmbeddedStore</codeph> object is constructed from a host stream. </p>

<p>When the <codeph>CEmbeddedStore</codeph> object represents a new embedded

store, it is constructed from an <codeph>RWriteStream</codeph> object; for

example, a class might include the following code fragment in one of its functions:</p>

<codeblock id="GUID-47D69E5D-909D-5EA3-96CD-3FB6ED5E77CB" xml:space="preserve">...

    // create the stream to contain the embedded store

RStoreWriteStream childStream;

                // we need to keep track of this stream id

iEmbeddedStoreId = childStream.CreateLC(iStore);

    // construct the embedded store

CPersistentStore* embeddedStore = CEmbeddedStore::NewLC(childStream);

...</codeblock>

<p>Here, the code assumes that <codeph>iStore</codeph> refers to the top level

store and <codeph>iEmbeddedStoreId</codeph> is a data member to hold the ID

of the hosting stream.</p>

<p>On successful construction, ownership of the host stream passes to the

embedded store which means that the embedded store takes on the responsibility

for closing the stream.</p>

<p>When the <codeph>CEmbeddedStore</codeph> object represents an existing

embedded store, it is constructed from an <codeph>RReadStream</codeph> object;

for example, a class might include the following code fragment in one of its

functions:</p>

<codeblock id="GUID-A796CC6C-69C9-5F22-B7A1-30815086EAA3" xml:space="preserve">...

RStoreReadStream childStream;

childStream.OpenL(iStore,iEmbeddedStoreId);

iEmbeddedStore = CEmbeddedStore::FromL(childStream);

...</codeblock>

<p>Where:</p>

<ul>

<li id="GUID-7A3338F6-252E-5D47-9D22-CDD505222958"><p><codeph>iStore</codeph> refers

to the top level store</p> </li>

<li id="GUID-162A3315-AA91-55CD-B07A-2F02EDBCC5ED"><p><codeph>iEmbeddedStoreId</codeph> is

a data member that holds the ID of the hosting stream</p> </li>

<li id="GUID-8AE6849E-0BA8-5CB4-8F3F-B33CC4FEED4E"><p><codeph>iEmbeddedStore</codeph> holds

a reference to the embedded store object.</p> </li>

</ul>

<p>When saving data, an application re-creates the embedded store by re-writing

the complete partial object network to the embedded store, replacing any existing

data.</p>