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1 // Copyright (c) 2007-2009 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 the License "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 // |
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15 |
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16 /** |
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17 @file |
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18 @internalComponent |
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19 */ |
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20 |
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21 #ifndef MREFCNTOBJ_H |
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22 #define MREFCNTOBJ_H |
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23 |
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24 #include <klib.h> |
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25 |
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26 /** |
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27 Base class for creating reference counted objects. |
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28 |
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29 This provide basic reference counting and asynchronous cleanup |
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30 for derived classes. An object whose reference count reaches zero |
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31 will be destroyed. |
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32 */ |
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33 class DReferenceCountedObject : public DBase |
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34 { |
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35 public: |
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36 /** |
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37 Constructs this object with an initial reference count of one. |
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38 */ |
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39 DReferenceCountedObject(); |
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40 |
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41 /** |
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42 Atomically increment this object's reference count. |
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43 A fault is raised if the count was initially <= 0. |
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44 |
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45 @pre Calling thread must be in a critical section |
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46 @pre #iReferenceCount>0 |
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47 */ |
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48 void Open(); |
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49 |
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50 /** |
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51 Atomically increment this object's reference count if it |
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52 was initially > 0. |
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53 |
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54 This is for use in situations where a reference counted object |
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55 is found by looking in a list, and the list may contain |
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56 objects which have had their reference counts decremented |
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57 to zero and are in the process of being cleaned up. A failure |
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58 to open a reference on these objects should be taken as an |
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59 indication that the object should be ignored, and treated as |
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60 though it were never found. |
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61 |
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62 @return True if the count was incremented. |
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63 False if it wasn't: because it was initially <= 0. |
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64 |
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65 @pre Calling thread must be in a critical section |
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66 */ |
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67 TBool TryOpen(); |
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68 |
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69 /** |
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70 Decrement this object's reference count and if it reaches zero, |
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71 delete this object. |
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72 |
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73 @pre Calling thread must be in a critical section. |
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74 @pre No fast mutex can be held. |
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75 @pre No mutexes with order greater less than KMutexOrdKernelHeap can be held. |
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76 */ |
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77 void Close(); |
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78 |
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79 /** |
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80 Decrement this object's reference count and if this reaches zero, |
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81 queue this object for asynchronous deletion. |
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82 |
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83 @pre Calling thread must be in a critical section. |
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84 @pre No fast mutex can be held. |
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85 */ |
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86 void AsyncClose(); |
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87 |
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88 protected: |
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89 /** |
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90 Destructor which asserts in debug builds that the object's reference count is zero. |
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91 */ |
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92 virtual ~DReferenceCountedObject(); |
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93 |
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94 /** |
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95 Return true if the preconditions for #Close are met. |
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96 This is for use by derived classes which overload the #Close method. |
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97 */ |
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98 TBool CheckCloseIsSafe(); |
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99 |
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100 /** |
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101 Return true if the preconditions for #AsyncClose are met. |
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102 This is for use by derived classes which overload the #AsyncClose method. |
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103 */ |
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104 TBool CheckAsyncCloseIsSafe(); |
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105 |
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106 protected: |
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107 |
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108 /** |
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109 This object's reference count. Must always be >= 0. |
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110 */ |
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111 TInt iReferenceCount; |
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112 }; |
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113 |
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114 |
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115 FORCE_INLINE DReferenceCountedObject::DReferenceCountedObject() |
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116 : iReferenceCount(1) |
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117 { |
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118 } |
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119 |
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120 #endif |