1 <?xml version="1.0" encoding="utf-8"?>

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     7     Nokia Corporation - initial contribution.

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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-2EE70A59-7EF0-5A1B-986B-00ED5ACD8BD4" xml:lang="en"><title>Patchable

    13 Constants: KListImplBufferSize</title><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <codeblock id="GUID-A819292B-1CC3-5378-82E8-01ECBCA1EF1C" xml:space="preserve"># define ECOM_PATCHDATA_KLISTIMPLBUFFERSIZE 2048</codeblock>

    15 <table id="GUID-5C9F05F1-89BD-5AE1-9C12-217EE4AE91A6">

    16 <tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/>

    17 <tbody>

    18 <row>

    19 <entry><p>Exported from: </p> </entry>

    20 <entry><p> <filepath>ECOMPATCHDATA.DLL</filepath>  </p> </entry>

    21 </row>

    22 <row>

    23 <entry><p>Defined in: </p> </entry>

    24 <entry><p> <filepath>                 .../os/ossrv/lowlevellibsandfws/pluginfw/framework/frame/ecompatchdataconstant.cpp</filepath> </p> </entry>

    25 </row>

    26 <row>

    27 <entry><p>Purpose: </p> </entry>

    28 <entry><p>This constant is used to define the size of the buffer that is pre-allocated

    29 on the ECOM client side to hold the list of Implementation Information records.

    30 The records are copied from the server as a result of a call to one of the <xref href="GUID-1344F049-81C4-3D17-AF46-8B5584680ADB.dita#GUID-1344F049-81C4-3D17-AF46-8B5584680ADB/GUID-AE9D4F24-8554-3151-AAF3-D63F400821C4"><apiname>REComSession::ListImplementationsL()</apiname></xref> functions. </p> <p>If the result of a call to <codeph>ListImplementationsL()</codeph> does

    31 not fit into the initial buffer, the server stores the result and tells the

    32 client the required size. <codeph>ListImplementationsL()</codeph> then reallocates

    33 the buffer and makes a second call to the server to retrieve the results. </p> <p>This

    34 value can be adjusted during ROM build time to suit a particular device. In

    35 general, a smaller value results in more client-server requests, while a larger

    36 value results in fewer client-server requests. Care must be taken when choosing

    37 the value. A large value, increases the temporary heap consumption by ECOM

    38 client processes, but results in faster completion of the call to <codeph>ListImplementationsL()</codeph> because

    39 of fewer client-server calls. System start-up can benefit from fine-tuning

    40 this value. </p> <p>The default size is 2048 bytes. This value optimises performance

    41 on the Symbian test UI platform. Larger values do not result in any significant

    42 gain in performance; smaller values reduce performance. </p> <p>To work out

    43 the optimum value for this constant, you need to discover the typical size

    44 of the buffer required for each call to <codeph>ListImplementationsL()</codeph>.

    45 To get such values, you need to enable the <codeph>ECOM_TRACE</codeph> macro

    46 and rebuild <codeph>ECOM</codeph>. After booting up the device, you will see

    47 output in the following format from the serial port: </p> <codeblock id="GUID-13659F9E-02AC-5752-BE1B-DC08E351A8BC" xml:space="preserve">ECOM ListImplementations request buffer size required=88</codeblock> <codeblock id="GUID-28532E84-E2BA-59F8-9E9A-7B144FD2BF90" xml:space="preserve">ECOM ListImplementations request buffer size required=1562</codeblock> <p> </p> <p>You

    48 can use this information to calculate mean and median values, which will help

    49 you to choose the optimum value for your platform. </p> </entry>

    50 </row>

    51 </tbody>

    52 </tgroup>

    53 </table>

    54 <p>ECom uses a customized scheme to handle patchable constants. Device creators

    55 should follow the scheme described below to set patch values: </p>

    56 <ul>

    57 <li id="GUID-E3EFD7AA-7B91-5CF9-8E9E-F027C35C167D"><p>Each patchable constant

    58 is represented by a macro listed in <filepath>\epoc32\rom\include\ecompatchconstants.hby</filepath>.

    59 The macros in the HBY file are all commented out. </p> </li>

    60 <li id="GUID-51E1005E-60FF-55CF-8D51-BEAE67E38D7A"><p>To activate a patch

    61 macro, uncomment the line and change the example value in the line to your

    62 custom value. </p> </li>

    63 </ul>

    64 </conbody></concept>