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<task id="GUID-4862EA2E-6BFE-5E11-B527-7EBA94BB0EA2" xml:lang="en"><title>OBY Tutorial </title><shortdesc>Describes the new demand paging keywords available to the
OBY. file. </shortdesc><prolog><metadata><keywords/></metadata></prolog><taskbody>
<context id="GUID-E46B9321-49E9-545D-B38B-CF2BB7AD8E19"><p><b>Introduction</b></p><p>The new keywords that are available in the OBY file are used
to specify whether an object is paged, and if so what kind of demand
paging it supports. </p><p>          With the addition of writable
data paging, the list of paging modifiers is shown below:   </p><p><b>Procedure</b></p><p>          With the addition of writable data
paging, the list of paging modifiers is shown below:   </p><table id="GUID-1DB56A5D-823B-4E26-80A3-C1362B309773">
<tgroup cols="2"><colspec colname="col1"/><colspec colname="col2"/>
<tbody>
<row>
<entry><p><b>Keyword</b></p></entry>
<entry><p><b>Behaviour on Symbian platform</b></p></entry>
</row>
<row>
<entry><p>paged</p></entry>
<entry><p> Enables code and data paging  </p></entry>
</row>
<row>
<entry><p>unpaged</p></entry>
<entry><p> Disables code and data paging</p></entry>
</row>
<row>
<entry><p>pagedcode</p></entry>
<entry><p> Enables code paging</p></entry>
</row>
<row>
<entry><p> unpagedcode</p></entry>
<entry><p>Disables code paging</p></entry>
</row>
<row>
<entry><p>pageddata</p></entry>
<entry><p>Enables data paging</p></entry>
</row>
<row>
<entry><p>unpageddata</p></entry>
<entry><p> Disables data paging</p></entry>
</row>
</tbody>
</tgroup>
</table><p> These modifiers appear in OBY files at the end of statements
relating to user-side ROM objects i.e. <codeph>'file=', 'dll=', 'data='
and 'secondary='</codeph>statements). For example:  </p><codeblock xml:space="preserve">file=ABI_DIR\DEBUG_DIR\MyLibrary.dll \sys\bin\MyLibrary.dll unpaged</codeblock><p>The data paging keywords only make sense when applied to executable
binary files.   </p><p>For an executable file, the use of one of the
above keywords in the oby file will override the paging settings in
the mmp file. However this will not be true, if the <codeph>pagingoverride</codeph>, <codeph>codepagingoverride</codeph> or <codeph>datapagingoverride</codeph> keywords are used in the MMP file, in the case of <codeph>nopaging</codeph>  or <codeph>alwayspage</codeph> .</p> </context>
<result id="GUID-EA5E0DDD-4354-5DD4-89D2-462A0B0E8A81"><p>Executing
the buildrom command builds with no errors or warnings. </p> </result>
<example id="GUID-ED6203BD-3890-5F27-8BAA-AFE3B0FAA518"><title>OBY
file example</title> <p>An example of an OBY file that uses the new
demand paging keywords is given below: </p> <codeblock id="GUID-84F82A9B-8F29-5A58-A9C3-7DEB19D5B9ED" xml:space="preserve">// 
// MyDPConfig.oby 
//
// The section below, is used to specify if XIP ROM paging is implemented.  
#if !defined PAGED_ROM 
#define PAGED_ROM 
#endif
 
// The sections below, is used to specify if code paging is implemented.
#if !defined USE_CODE_PAGING 
// Comment out the next line if code paging is wanted 
#define USE_CODE_PAGING 
#endif
 
#if !defined CODE_PAGING_FROM_ROFS 
// Comment out the next line if code paging from primary rofs is wanted 
#define CODE_PAGING_FROM_ROFS 
#endif 

// The section below, is used to configure the writable data paging and to specify what the 
// default paging behaviour is to be. 
ROM_IMAGE[0] { 
pagedrom 
compress 
//                 Min   Max   Young/Old 
//                 Live  Live  Page 
//                 Pages Pages Ratio 
demandpagingconfig 256   512   3 
pagingoverride defaultpaged

// This section specifies what the default paging behaviour is to be for code paging. 
#if defined USE_CODE_PAGING &amp;&amp; !defined USE_DATA_PAGING 
codepagingpolicy defaultpaged 
#endif 

#if defined USE_DATA_PAGING 
#if defined USE_CODE_PAGING 
codepagingpolicy defaultpaged 
#endif 

datapagingpolicy defaultpaged 
#endif 
}

#if defined CODE_PAGING_FROM_ROFS || defined USE_DATA_PAGING 
ROM_IMAGE[1] { 
pagingoverride defaultpaged 
}
#endif 

// Now specify the files to be used
file=ABI_DIR\DEBUG_DIR\MyLibrary.dll \sys\bin\MyLibrary.dll unpaged
</codeblock> </example>
<postreq id="GUID-5000ED29-DB7E-4855-965C-6B0C335A40C2"><p>The next step is to <xref href="GUID-6B9041F7-79A6-5CCA-9B4D-B8EF377FD378.dita">Build the writable
data paging ROM</xref>  </p> </postreq>
</taskbody></task>