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    10 <!DOCTYPE concept

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

    12 <concept id="GUID-3DE276E8-D2C7-5297-AF3B-40B0B8733572" xml:lang="en"><title>Inter-thread

    13 Data Transfer</title><shortdesc>The mechanism for copying data between threads is called inter-thread

    14 data transfer and is handled by the four functions provided by the <codeph>RThread</codeph> handle.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    15 <p>Data can be passed between threads. The threads can be in the same process

    16 or in different processes. The functions provides by the <xref href="GUID-B0E661BC-4058-3256-B9C3-5A4FD52F6DE5.dita"><apiname>RThread</apiname></xref> class

    17 are:</p>

    18 <ul>

    19 <li id="GUID-416730EC-5719-5633-A51A-50B0E3AAD8F4"><p><codeph>ReadL()</codeph> </p> </li>

    20 <li id="GUID-B4EF1893-D469-541A-898E-AEC8DBF1BD3A"><p><codeph>WriteL()</codeph> </p> </li>

    21 <li id="GUID-7550CBE4-FEBF-51E5-AB0D-80729D7CAC95"><p><codeph>GetDesLength()</codeph> </p> </li>

    22 <li id="GUID-0B8127FB-9FE1-5EAA-9B8B-3F0BC9F4AAF5"><p><codeph>GetDesMaxLength()</codeph> </p> </li>

    23 </ul>

    24 <p>The functions are used in the implementation of the <codeph>RMessage</codeph> class

    25 which, in turn, is used for passing information between clients and servers.</p>

    26 <p>The <codeph>ReadL()</codeph> and <codeph>WriteL()</codeph> functions, which

    27 transfer data, assume that both source and target data are descriptors.</p>

    28 <p>Typically, code executing in the current thread will have a handle to another

    29 thread. The code in the <i>current</i> thread copies data <i>from</i> the <i>other</i> thread,

    30 represented by an <codeph>RThread</codeph> handle, by calling its <codeph>ReadL()</codeph> function.

    31 Copying data <i>to</i> the <i>other</i> thread is similar, but is done using

    32 the <codeph>WriteL()</codeph> function. The following diagram illustrates

    33 this:</p>

    34 <fig id="GUID-7A4E3725-E6DA-566D-86E0-2941A8D96ACE">

    35 <image href="GUID-40C995CA-9906-59D8-A5E7-08F592031AEE_d0e251682_href.png" placement="inline"/>

    36 </fig>

    37 <p>The source or target location in the <i>other</i> thread is identified

    38 by pointer. The pointer only has meaning within the context of that thread;

    39 attempting to reference the pointer directly from within the <i>current</i> thread

    40 is meaningless and may cause an exception.</p>

    41 </conbody></concept>