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    10 <!DOCTYPE concept

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

    12 <concept id="GUID-D69DD425-5F93-4238-A7E9-915F24A9C9CA" xml:lang="en"><title>Open

    13 C MessageQueue Library Example</title><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <p>The Message Queue Library example demonstrates how to use Open C APIs for

    15 developing applications that use Open C standard libraries on Symbian platform.

    16 This example uses the APIs of the message queue library to create/close message

    17 queues and send/receive messages and also get information on created message

    18 queues. </p>

    19 <section id="GUID-026FD8D6-6C4A-5958-B289-775D4AE1E756-GENID-1-10-1-12-1-1-5-1-3-1-11-1-13-1-2-2"><title>Download</title> <p>Click

    20 on the following link to download the example: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/zips/guid-9db026cc-ac23-4593-8bbc-4b251c085d4f.zip" scope="external"> opencmessagequeuelibraryex.zip</xref></p><p>Click: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/guid-9db026cc-ac23-4593-8bbc-4b251c085d4f.html" scope="peer">browse</xref> to view the example code. </p> </section>

    21 <section id="GUID-7E7C4564-B10E-41F9-8A9D-D8A6C5E9C51C-GENID-1-10-1-12-1-1-5-1-3-1-11-1-13-1-2-3"><title>Design and

    22 Implementation</title> <p>The following sections provide information about

    23 the implementation of the example. </p><p><b>Description</b></p><p>OpenCMessageQueueClientEx

    24 is a C Application that uses the  Message Queue library. This application

    25 uses main() as the entry point for the application. This is a simple console

    26 based application. The application uses Message Queue library (OpenCMessageQueueLibrary.dll)

    27 APIs.  The Main thread of the application creates two message queues, and

    28 two threads. Thread one will send message to message queue 1 and waits for

    29 messages from message queue 2. Then thread one will send message to message

    30 queue 2 and waits for messages from message queue 1. If a user tries to create

    31 a message queue using OpenCMessageQueueLibrary.dll with the already

    32 existing name, it will just return the existing message queue Id. The application

    33 has its own icon and can be launched from the UI both in the emulator  and

    34 in the device. </p><p><b>Capabilities</b> </p> The program capabilities are

    35 defined in:  <filepath>MessageQueueLibrary.mmp</filepath> (DLL - library):<codeph> CAPABILITY

    36 ALL -TCB</codeph> <filepath>MessageQueueClient.mmp</filepath>(EXE - application): <codeph>CAPABILITY

    37 NONE</codeph>. <p><b>Module hierarchy</b> </p>This application has 2 modules

    38 as below:  <p>Message Queue Library (DLL) that exports set of apis for the

    39 user.</p><p>OpenCMessageQueueLibraryEx\engine : The application (EXE) that

    40 demonstrates the usage of Open C APIs and also those APIs exported by Message

    41 Queue Library.</p><p> (OpenCMessageQueueLibraryEx\exe) : This example will

    42 create a DLL which exports set of generic APIs with which the user can do

    43 message queue related operations.   To give a rough idea on how to use these

    44 apis, an EXE is provided that creates threads and does send/receive on message

    45 queues using those exported apis.</p><p><b>APIs used</b></p><p>msgget </p><p> msgctl

    46  </p><p>msgrcv  </p><p>msgsnd  </p><p>semget  </p><p>semctl </p><p> semop </p> </section>

    47 <section id="GUID-67A72761-1D92-46D1-B1C9-7455978BDE4E-GENID-1-10-1-12-1-1-5-1-3-1-11-1-13-1-2-4"><title>Building and

    48 Using</title> To build the Message Queue Library example application, go to

    49 the <filepath>OpenCMessageQueueLibraryEx\group</filepath> directory and build

    50 the application.  The Message Queue Library application consists of two modules,

    51 which should be built in the following order:   engine - which builds the

    52 generic message queue library  exe - which builds an EXE that demonstrates

    53 the usage of this library  The definition for the whole application can be

    54 found in the<filepath>bld.inf</filepath>in the group subdirectory of the applications

    55 main directory. </section>

    56 </conbody></concept>