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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-D0BD34C9-7793-5FA0-8864-FD7444D62F90" xml:lang="en"><title>How to |
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13 form links</title><shortdesc>This document describes how to use links within a doubly linked |
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14 list.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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15 <p>To form a doubly linked list of <codeph>CMyClass</codeph> objects, include |
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16 the link object <codeph>TDblQueLink</codeph> as a component of <codeph>CMyClass</codeph>:</p> |
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17 <codeblock id="GUID-E595B603-FC0D-5AF3-9228-7D40C3A08271" xml:space="preserve">class CMyClass : public CBase |
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18 { |
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19 ... |
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20 TDblQueLink iDlink; |
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21 ... |
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22 };</codeblock> |
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23 <fig id="GUID-30C9DE23-1805-594C-9F7F-BD4A161DE59A"> |
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24 <image href="GUID-F342B002-0667-5D51-AE2D-3CF534D70B62_d0e188860_href.png" placement="inline"/> |
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25 </fig> |
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26 <p>Although any kind of object can be an element of a linked list, most lists |
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27 consist of elements which are all of the same type.</p> |
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28 <p>An object can participate in more than one list. For example, to allow <codeph>CMyClass</codeph> objects |
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29 to participate in two doubly linked lists, include two separate <codeph>TDblQueLink</codeph> objects |
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30 as components of <codeph>CMyClass</codeph>:</p> |
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31 <codeblock id="GUID-2027BF61-9834-5915-9911-3420CAC7061A" xml:space="preserve">class CMyClass : public CBase |
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32 { |
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33 ... |
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34 TDblQueLink iDlink1; |
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35 ... |
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36 TDblQueLink iDlink2; |
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37 };</codeblock> |
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38 <fig id="GUID-DC3DDF09-2F30-5704-ACB0-378622DDDD88"> |
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39 <image href="GUID-B131AE10-B9B1-53D2-8CAA-A9045957D6F9_d0e188883_href.png" placement="inline"/> |
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40 </fig> |
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41 <p>Elements can also be objects constructed from a variety of classes, all |
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42 ultimately derived from the same base class, where that base class includes |
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43 the link object as a component. For example, if <codeph>CBc</codeph> is a |
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44 base class for <codeph>CD1</codeph> which, in turn, is a base class for <codeph>CD2</codeph>, |
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45 then the elements of the list can consist of a mix of <codeph>CBc</codeph> or <codeph>CDc1</codeph> or <codeph>CDc2</codeph> objects.</p> |
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46 <codeblock id="GUID-C274DD90-E21A-5BAD-8094-79CE23CDA1B9" xml:space="preserve">class CBc : public CBase |
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47 { |
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48 ... |
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49 TDblQueLink iDlink; |
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50 ... |
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51 };</codeblock> |
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52 <codeblock id="GUID-6BAAB6AA-421F-51CE-8650-2FEDA3EB0A83" xml:space="preserve">class CDc1 : public CBclass |
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53 { |
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54 ... |
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55 } |
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56 </codeblock> |
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57 <codeblock id="GUID-1C1A9078-0F8A-5E24-82CF-BD0C199B4050" xml:space="preserve">class CDc2 : public CDc1 |
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58 { |
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59 ... |
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60 } |
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61 </codeblock> |
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62 <fig id="GUID-F8769477-6B6C-5531-9675-AC66FE6B6E3D"> |
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63 <image href="GUID-38FF81FD-0C23-586D-AFAE-9F0761A36BAD_d0e188918_href.png" placement="inline"/> |
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64 </fig> |
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65 <p>New link elements are inserted into an existing list using either <codeph>TDblQueLink::Enque()</codeph> or <codeph>TDblQueLink::AddBefore()</codeph> function. Note that <codeph>AddBefore()</codeph> is not available in v5. |
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66 These are prototyped as:</p> |
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67 <codeblock id="GUID-DDD3FDA3-4635-5AFE-9C17-994E5E4D1C59" xml:space="preserve">void Enque(TDblQueLinkBase* aLink); |
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68 </codeblock> |
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69 <codeblock id="GUID-F3E72D69-0180-5BAD-A2C6-E31704820AAF" xml:space="preserve">void AddBefore(TDblQueLinkBase* aLink);</codeblock> |
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70 <p>Calling <codeph>Enque()</codeph> on an element means that this element |
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71 is added to the list so that its position follows the element <i>aLink</i>, |
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72 as the following figure shows.</p> |
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73 <fig id="GUID-F46E770B-8BDC-5E61-9E28-043FDAA3B193"> |
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74 <image href="GUID-3E1199E4-4F19-58BB-B1EC-8975A04B68FF_d0e188950_href.png" placement="inline"/> |
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75 </fig> |
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76 <p>Calling <codeph>AddBefore()</codeph> on an element means that this element |
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77 is added to the list so that its position precedes the element <i>aLink</i>, |
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78 as the following figure shows.</p> |
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79 <fig id="GUID-0E6C9ADF-0182-52CC-A3D1-AE83F540E42B"> |
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80 <image href="GUID-2AB5AA00-71B2-58F4-AE17-9A38D1E5AA99_d0e188964_href.png" placement="inline"/> |
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81 </fig> |
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82 <p>Note that new elements cannot be inserted at the beginning or end of a |
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83 list using these functions. The <codeph>AddFirst()</codeph> and <codeph>AddLast()</codeph> members |
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84 of the header class <codeph>TDblQue<class T></codeph> must be used |
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85 instead.</p> |
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86 </conbody></concept> |