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The storage class uses a view, with additional functionality to be able
to store and reload the data it contains (including nested subviews).
<P>
By default, data is loaded on demand, i.e. whenever data which has
not yet been referenced is used for the first time. Loading is limited
to the lifetime of this storage object, since the storage object carries
the file descriptor with it that is needed to access the data file.
<P>
To save changes, call the Commit member. This is the only time
that data is written to file - when using a read-only file simply avoid
calling Commit.
<P>
The LoadFromStream and SaveToStream members can be used to
serialize the contents of this storage row using only sequential I/O
(no seeking, only read or write calls).
<P>
The data storage mechanism implementation provides fail-safe operation:
if anything prevents Commit from completing its task, the last
succesfully committed version of the saved data will be recovered on
the next open. This also includes changes made to the table structure.
<P>
The following code creates a view with 1 row and stores it on file:
<P>
<PRE> <A HREF="c4_StringProp.html" >c4_StringProp</A> pName ("Name");
<A HREF="c4_IntProp.html" >c4_IntProp</A> pAge ("Age");</PRE>
<P>
<PRE> <A HREF="c4_Storage.html" >c4_Storage</A> storage ("myfile.dat", true);
<A HREF="c4_View.html" >c4_View</A> myView = storage.GetAs("Musicians[Name:S,Age:I]");</PRE>
<P>
<PRE> myView.Add(pName ["John Williams"] + pAge [43]);</PRE>
<P>
<PRE> storage.Commit();
</PRE>
<P>
<hr size=1>
<dl>
<if !private>
<a name="c4_Storage_AutoCommit___"><dt>
<nobr>
void
<b>AutoCommit</b> ();
</nobr>
<dd>
<font face=Helvetica size=-1>Set storage up to always call Commit in the destructor</font>
<p>
<if !private>
<a name="c4_Storage_Commit___"><dt>
<nobr>
bool
<b>Commit</b> ();
</nobr>
<dd>
<font face=Helvetica size=-1>Flush pending changes to file right now</font>
<p>
<if !private>
<a name="c4_Storage_Contents___const"><dt>
<nobr>
<A HREF="c4_RowRef.html" >c4_RowRef</A>
<b>Contents</b> () <i>const</i>;
</nobr>
<dd>
<font face=Helvetica size=-1>Give access to the stored data as a single row</font>
<p>
<if !private>
<a name="c4_Storage_Description_const__"><dt>
<nobr>
const char*
<b>Description</b> (const char* name_ =0);
</nobr>
<dd>
<font face=Helvetica size=-1>Return a description of the view structure (default is all)</font>
<p>
<if !private>
<a name="c4_Storage_GetAs_const__"><dt>
<nobr>
<A HREF="c4_View.html" >c4_View</A>
<b>GetAs</b> (const char* description_);
</nobr>
<dd>
<font face=Helvetica size=-1>Get a named view, redefining it to match the given structure</font>
<p>
<if !private>
<a name="c4_Storage_Initialize_constbool__"><dt>
<nobr>
void
<b>Initialize</b> (const char*, bool);
</nobr>
<dd>
<font face=Helvetica size=-1></font>
<p>
<if !private>
<a name="c4_Storage_LoadFrom_c4_Stream___"><dt>
<nobr>
void
<b>LoadFrom</b> (<A HREF="c4_Stream.html" >c4_Stream</A>& stream_);
</nobr>
<dd>
<font face=Helvetica size=-1>Load contents from the specified input stream</font>
<p>
<if !private>
<a name="c4_Storage_Rollback___"><dt>
<nobr>
bool
<b>Rollback</b> ();
</nobr>
<dd>
Calling Rollback will cancel all uncommitted changes.
<br>
<p>
<if !private>
<a name="c4_Storage_RootTable___const"><dt>
<nobr>
c4_HandlerSeq&
<b>RootTable</b> () <i>const</i>;
</nobr>
<dd>
<font face=Helvetica size=-1>Return the root table entry</font>
<p>
<if !private>
<a name="c4_Storage_SaveTo_c4_Stream___"><dt>
<nobr>
void
<b>SaveTo</b> (<A HREF="c4_Stream.html" >c4_Stream</A>& stream_);
</nobr>
<dd>
<font face=Helvetica size=-1>Save contents to the specified output stream</font>
<p>
<if !private>
<a name="c4_Storage_SetStructure_const__"><dt>
<nobr>
void
<b>SetStructure</b> (const char*);
</nobr>
<dd>
<font face=Helvetica size=-1></font>
<p>
<if !private>
<a name="c4_Storage_Store_constconst__"><dt>
<nobr>
<A HREF="c4_View.html" >c4_View</A>
<b>Store</b> (const char* name_, const <A HREF="c4_View.html" >c4_View</A>& view_);
</nobr>
<dd>
<font face=Helvetica size=-1>Attach a view using specified name in this storage object</font>
<p>
<if !private>
<a name="c4_Storage_Strategy___const"><dt>
<nobr>
<A HREF="c4_Strategy.html" >c4_Strategy</A>&
<b>Strategy</b> () <i>const</i>;
</nobr>
<dd>
<font face=Helvetica size=-1>Return the strategy object associated with this storage</font>
<p>
<if !private>
<a name="c4_Storage_View_const__"><dt>
<nobr>
<A HREF="c4_ViewRef.html" >c4_ViewRef</A>
<b>View</b> (const char* name_);
</nobr>
<dd>
<font face=Helvetica size=-1>Get or set a named view in this storage object</font>
<p>
<if !private>
<a name="c4_Storage__persist"><dt>
<nobr>
c4_Persist*
<b>_persist</b>;
</nobr>
<dd>
<font face=Helvetica size=-1></font>
<p>
<if !private>
<a name="c4_Storage_c4_Storage__"><dt>
<nobr>
<b>c4_Storage</b> ();
</nobr>
<dd>
<font face=Helvetica size=-1>Construct streaming-only storage object</font>
<p>
<if !private>
<a name="c4_Storage_c4_Storage_c4_Strategy_bool_"><dt>
<nobr>
<b>c4_Storage</b> (<A HREF="c4_Strategy.html" >c4_Strategy</A>& strategy_, bool owned_ =false);
</nobr>
<dd>
<font face=Helvetica size=-1>Construct a storage using the specified strategy handler</font>
<p>
<if !private>
<a name="c4_Storage_c4_Storage_const_"><dt>
<nobr>
<b>c4_Storage</b> (const <A HREF="c4_Storage.html" >c4_Storage</A>&);
</nobr>
<dd>
<font face=Helvetica size=-1>Copy constructor</font>
<p>
<if !private>
<a name="c4_Storage_c4_Storage_constbool_"><dt>
<nobr>
<b>c4_Storage</b> (const char* filename_, bool canModify_);
</nobr>
<dd>
<font face=Helvetica size=-1>Construct a storage object, keeping the current structure</font>
<p>
<if !private>
<a name="c4_Storage_c4_Storage_constconst_"><dt>
<nobr>
<b>c4_Storage</b> (const char* filename_, const char* description_);
</nobr>
<dd>
<font face=Helvetica size=-1>Construct a storage object for given file and format</font>
<p>
<if !private>
<a name="c4_Storage_operator___const__"><dt>
<nobr>
<A HREF="c4_Storage.html" >c4_Storage</A>&
<b>operator= </b> (const <A HREF="c4_Storage.html" >c4_Storage</A>&);
</nobr>
<dd>
<font face=Helvetica size=-1>Assignment of storage implements reference semantics</font>
<p>
<if !private>
<a name="c4_Storage__c4_Storage__"><dt>
<nobr>
<b>~c4_Storage</b> ();
</nobr>
<dd>
<font face=Helvetica size=-1>Destructor, usually closes file, but does not commit by default</font>
<p>
</dl>
<hr size=1 width=50 align=left>
class
<b>c4_Storage</b>
</font>
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