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1 // Copyright (c) 2004-2009 Nokia Corporation and/or its subsidiary(-ies). |
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2 // All rights reserved. |
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3 // This component and the accompanying materials are made available |
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4 // under the terms of "Eclipse Public License v1.0" |
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5 // which accompanies this distribution, and is available |
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6 // at the URL "http://www.eclipse.org/legal/epl-v10.html". |
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7 // |
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8 // Initial Contributors: |
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9 // Nokia Corporation - initial contribution. |
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10 // |
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11 // Contributors: |
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12 // |
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13 // Description: |
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14 // cache.h - the record cache |
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15 // |
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16 |
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17 #ifndef __CACHE_H__ |
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18 #define __CACHE_H__ |
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19 /** |
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20 @file cache.h |
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21 DNS cache |
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22 @internalComponent Domain Name Resolver |
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23 */ |
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24 |
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25 #include "record.h" // ...for TDndRecordLRU (and indirectly class, type symbols and TInetAddr) |
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26 |
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27 const TInt KDndMaxRecords = 100; //< Maximum mumber of records allowed in the cache. |
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28 |
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29 class CDndNameSpace; |
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30 class CDndEngine; |
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31 |
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32 /** |
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33 // The cache maintains a collection of (question, answer) pairs. |
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34 // |
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35 // The question (= the search key for the cache) has the |
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36 // following components: |
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37 // |
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38 // @li namespace id |
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39 // @li domain-name (dotted notation) |
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40 // @li DNS query type (EDnsQType) |
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41 // @li DNS query class (EDnsQClass) |
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42 // |
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43 // The answer is contained within CDndRecord class. Among other |
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44 // things, it contains the full original reply from some DNS server |
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45 // for the question. |
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46 // |
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47 // The cache is implemented as a forest of trees, one tree |
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48 // for each name space. Each component of the domain-name |
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49 // becomes a node in the tree. A node at any non-leaf level can have |
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50 // zero or more answers attached (for. example, the domain name "nokia.fi" |
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51 // can have both "A" (address) and "NS" (name server) answers |
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52 // associated it. |
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53 // |
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54 // The leaf nodes must have at least one answer. When |
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55 // the last answer is expired or otherwise removed from a leaf node, |
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56 // the node itself is also removed. A tree containing no answers |
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57 // consists just of the root node (name space node). |
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58 // |
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59 // For example, if in the below example, the "A" answer associated with |
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60 // query (namespace=\\<global\\>, domain-name="www.nokia.com", query=A, class=IN) |
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61 // is removed, then also the nodes for "www" and "nokia" are pruned away. |
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62 @verbatim |
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63 |
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64 cache |
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65 ............. |
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66 <global> <local> |
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67 / | / \ |
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68 fi com | | |
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69 / | \ muu foo |
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70 / | \ | / \ |
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71 nokia symbian nokia ..A.A....AAAA... (lru) |
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72 / | \ | | . |
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73 ..A..NS www www www . |
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74 . | | | . |
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75 .A....A......A |
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76 @endverbatim |
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77 // The tree implementation is not directly visible outside the cache |
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78 // implementation. The CDndCache::FindL returns only a pointer to the |
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79 // answer (CDndRecord). |
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80 // |
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81 // There is a limit to the number of answers (KDndMaxRecords) that |
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82 // can be stored. If this limit is reached, the <b>least recently used</b> |
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83 // answers are deleted, if possible. An answer cannot be deleted |
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84 // is it is currently being used (locked) by some resolver. |
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85 */ |
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86 class CDndCache : public CBase |
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87 { |
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88 // See implementation for methods comments! |
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89 public: |
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90 CDndCache(); |
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91 void ConstructL(); |
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92 ~CDndCache(); |
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93 |
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94 TInt GetServerAddress(const TUint32 aNameSpace, TInetAddr &aAddr); |
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95 void SetServerAddress(const TUint32 aNameSpace, const TInetAddr &aAddr, const TInt aState); |
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96 CDndRecord *FindL(const TUint32 aNameSpace, const TDesC8 &aName, const EDnsQType aType, const EDnsQClass aClass, |
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97 const TTime &aReqTime); |
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98 void Dump(CDndEngine &aControl); |
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99 void Flush(); |
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100 private: |
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101 CDndNameSpace *GetNameSpace(const TUint32 aNameSpace); |
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102 // The roots of the name-spaces |
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103 CDndNameSpace *iRootList; |
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104 // The LRU list of cache records |
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105 TDndRecordLRU iRecordList; |
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106 }; |
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107 |
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108 #endif |