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1 // Copyright (c) 1998-2009 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 // DBMS object cache |
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15 // |
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16 // |
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17 |
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18 #include "UD_STD.H" |
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19 #include "D32CACHE.H" |
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20 //#include <e32svr.h> |
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21 |
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22 NONSHARABLE_CLASS(RDbCache::CCache) : private CBase |
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23 { |
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24 public: |
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25 static CCache* OpenL( TInt aSize, TBool aUseTimer ); |
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26 void Close(); |
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27 // |
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28 void Flush(); |
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29 void Hold( CBase* aObject, TUint aMicroSeconds ); |
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30 void Release ( const CBase& aObject ); |
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31 private: |
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32 struct TEntry |
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33 { |
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34 TEntry* iNext; |
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35 TInt iDelta; |
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36 CBase* iObject; |
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37 }; |
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38 enum { ETimerPriority = -10 }; |
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39 enum { ETimerPeriod = 0x100000 }; // ~1.0s |
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40 private: |
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41 static inline TInt TlsHandle(); |
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42 CCache( TInt aSize ); |
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43 ~CCache(); |
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44 // |
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45 static CCache* NewL( TInt aSize, TBool aUseTimer ); |
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46 inline void Open(); |
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47 void Expire( TInt aElapsedTime ); |
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48 void Remove( TEntry*& aRef ); |
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49 void ExpireFirst(); |
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50 static void DoFlush( TAny* aPtr ); |
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51 private: |
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52 TInt iRef; |
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53 // CPeriodic* iTimer; |
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54 TTimeIntervalMicroSeconds32 iTickPeriod; |
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55 TUint iZeroTime; |
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56 TEntry* iCache; |
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57 TEntry* iFree; |
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58 TEntry iEntries[1]; // or maybe more |
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59 }; |
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60 |
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61 // Class CDbObjectCache |
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62 |
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63 //inline TInt RDbCache::CCache::TlsHandle() |
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64 //// use the address of a static function for the handle |
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65 // { return TInt( NewL ); } |
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66 |
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67 TAny* gCachePtr; |
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68 |
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69 RDbCache::CCache::CCache( TInt aSize ) |
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70 // |
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71 // Initialise the free entry list |
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72 // |
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73 { |
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74 TEntry* entry = iEntries; |
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75 while ( --aSize != 0 ) |
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76 { |
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77 entry[1].iNext = entry; |
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78 ++entry; |
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79 } |
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80 iFree = entry; |
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81 } |
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82 |
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83 RDbCache::CCache::~CCache() |
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84 { |
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85 __ASSERT( iRef < 0 ); |
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86 // empty the cache (destory the items now) |
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87 Expire( KMaxTInt ); |
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88 __ASSERT( iCache == 0 ); |
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89 // delete iTimer; |
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90 gCachePtr = NULL; |
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91 } |
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92 |
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93 const TInt KTickPeriod = 10000000; |
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94 const TTimeIntervalMicroSeconds32 gTickPeriod(KTickPeriod); |
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95 RDbCache::CCache* RDbCache::CCache::NewL( TInt aSize, TBool aUseTimer ) |
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96 // |
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97 // Construct a cache with aSize slots and one referee |
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98 // |
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99 { |
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100 //#warning !! RDbCache::CCache::NewL not implemented (uses UserHal/UserSvr) !! |
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101 CCache* cache = new( ELeave, sizeof( TEntry ) * ( aSize - 1 ) ) CCache( aSize ); // get the extra size for the cache entries, leaves on error |
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102 CleanupClosePushL( *cache ); |
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103 cache->iTickPeriod = gTickPeriod; |
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104 //User::LeaveIfError( UserHal::TickPeriod( cache->iTickPeriod ) ); |
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105 //User::LeaveIfError( UserSvr::DllSetTls( TlsHandle(), cache ) ); |
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106 gCachePtr = cache; |
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107 // if (aUseTimer) |
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108 // cache->iTimer = CPeriodic::NewL( ETimerPriority ); |
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109 CleanupStack::Pop(); |
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110 return cache; |
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111 } |
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112 |
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113 inline void RDbCache::CCache::Open() |
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114 // add a referee |
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115 { ++iRef; } |
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116 |
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117 void RDbCache::CCache::Close() |
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118 // |
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119 // remove a referee and delete as required |
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120 // |
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121 { |
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122 __ASSERT( iRef >= 0 ); |
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123 if ( --iRef < 0 ) |
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124 delete this; |
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125 } |
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126 |
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127 RDbCache::CCache* RDbCache::CCache::OpenL( TInt aSize, TBool aUseTimer ) |
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128 // |
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129 // Grab a reference to the cache, constructing it if required |
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130 // |
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131 { |
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132 // CCache* cache = ( CCache* )UserSvr::DllTls( TlsHandle() ); |
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133 CCache* cache = ( CCache* )gCachePtr; |
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134 if (!cache) |
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135 return NewL( aSize, aUseTimer ); |
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136 cache->Open(); |
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137 return cache; |
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138 } |
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139 |
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140 void RDbCache::CCache::Hold( CBase* aObject, TUint aMicroSeconds ) |
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141 // |
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142 // Hold aObject in the cache or destroy it |
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143 // |
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144 { |
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145 Flush(); // Destroy expired entries and re-assess Zero-time |
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146 TInt ticks = aMicroSeconds / TUint( iTickPeriod.Int() ); |
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147 TEntry* entry = iFree; |
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148 if ( entry == 0 ) |
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149 { // no free slots: check the first cache entry |
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150 __ASSERT( iCache ); |
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151 if ( iCache->iDelta > ticks ) |
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152 { // aObject expires first |
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153 delete aObject; |
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154 return; |
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155 } |
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156 ExpireFirst(); // remove the first entry and use it |
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157 entry = iFree; |
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158 } |
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159 iFree = entry->iNext; // move the free list pointer to the next entry |
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160 // |
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161 // find the insertion point in the cache delta-list |
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162 TEntry** pcache = &iCache; |
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163 TEntry* cache; |
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164 for ( ; ; ) |
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165 { |
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166 __ASSERT( ticks >= 0 ); |
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167 cache = *pcache; |
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168 if ( !cache ) |
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169 break; // add to end |
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170 TInt t = ticks - cache->iDelta; |
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171 if ( t < 0 ) |
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172 { // add to the list here |
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173 cache->iDelta = -t; // reduce the following delta |
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174 break; |
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175 } |
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176 ticks = t; // reduce the entry delta |
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177 pcache = &cache->iNext; |
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178 } |
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179 *pcache = entry; // set up the entry |
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180 entry->iDelta = ticks; |
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181 entry->iNext = cache; |
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182 entry->iObject = aObject; |
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183 // // kick the timer if we need to |
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184 // if ( iTimer && !iTimer->IsActive() ) |
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185 // iTimer->Start( ETimerPeriod, ETimerPeriod, TCallBack( ( TInt (*)(TAny*) )DoFlush, this ) ); |
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186 } |
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187 |
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188 void RDbCache::CCache::Remove( RDbCache::CCache::TEntry*& aRef ) |
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189 // |
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190 // Remove the entry at aRef from the cache |
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191 // |
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192 { |
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193 TEntry& entry = *aRef; |
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194 TEntry* next = entry.iNext; |
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195 entry.iNext = iFree; |
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196 iFree = &entry; |
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197 aRef = next; |
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198 if ( next ) |
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199 next->iDelta += entry.iDelta; |
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200 // else if ( iTimer ) // the cache is now empty, so stop the timer if we have one |
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201 // iTimer->Cancel(); |
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202 } |
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203 |
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204 void RDbCache::CCache::ExpireFirst() |
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205 // |
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206 // Expire the first entry in the cache |
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207 // |
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208 { |
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209 __ASSERT( iCache != 0 ); |
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210 // the ordering here is important. Removing the entry first allows the |
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211 // object d'tor to call Release() without causing re-entrancy problems. |
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212 CBase* object = iCache->iObject; |
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213 Remove( iCache ); |
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214 delete object; |
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215 } |
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216 |
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217 void RDbCache::CCache::Release( const CBase& aObject ) |
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218 // |
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219 // Remove the cache entry for aObject, if it is in the cache |
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220 // |
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221 { |
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222 TEntry** pcache = &iCache; |
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223 for ( ; ; ) |
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224 { |
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225 TEntry* entry = *pcache; |
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226 if ( !entry ) |
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227 return; |
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228 if ( entry->iObject == &aObject ) |
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229 { |
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230 Remove( *pcache ); |
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231 return; |
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232 } |
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233 pcache = &entry->iNext; |
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234 } |
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235 } |
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236 |
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237 void RDbCache::CCache::Expire( TInt aElapsedTime ) |
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238 // |
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239 // Destroy entries which expire with aElapsedTime |
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240 // |
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241 { |
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242 __ASSERT( aElapsedTime > 0 ); |
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243 if ( iCache && ( iCache->iDelta -= aElapsedTime ) < 0 ) |
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244 { |
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245 Open(); // This allows the cache to be owned by an object in the cache |
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246 do ExpireFirst(); |
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247 while ( iCache && iCache->iDelta < 0 ); |
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248 Close(); // The cache may be destroyed now |
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249 } |
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250 } |
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251 |
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252 void RDbCache::CCache::Flush() |
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253 // |
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254 // Check the execution clock and destroy any expired entries |
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255 // |
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256 // Care has to be taken to handle the 32-bit wraparound of the tick-count |
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257 // e.g. iZeroTime = 0xffffffffu, now = 0 |
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258 // |
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259 { |
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260 TUint now = User::TickCount(); |
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261 TUint elapsed = now - iZeroTime; |
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262 iZeroTime = now; |
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263 if ( elapsed ) |
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264 Expire( elapsed <= TUint( KMaxTInt ) ? elapsed : TUint( KMaxTInt ) ); |
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265 } |
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266 |
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267 void RDbCache::CCache::DoFlush( TAny* aPtr ) |
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268 // |
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269 // Callback for the timer |
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270 // |
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271 { |
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272 static_cast<CCache*>( aPtr )->Flush(); |
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273 } |
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274 |
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275 |
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276 // Class RDbCache |
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277 |
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278 TInt RDbCache::Open( TInt aSize, TBool aUseTimer ) |
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279 // |
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280 // Get a handle on the cache |
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281 // |
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282 { |
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283 __ASSERT( aSize > 0 ); |
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284 TRAPD( r, iCache = CCache::OpenL( aSize, aUseTimer ) ); |
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285 return r; |
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286 } |
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287 |
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288 void RDbCache::Close() |
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289 // |
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290 // Close this handle on the cache |
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291 // |
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292 { |
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293 CCache* cache = iCache; |
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294 if ( cache ) |
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295 { |
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296 iCache = 0; |
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297 cache->Close(); |
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298 } |
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299 } |
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300 |
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301 void RDbCache::Hold( CBase* aObject, TUint aMicroSeconds ) |
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302 // |
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303 // Hold aObject on the cache, if open |
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304 // We are now responsible for deleting the object |
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305 // |
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306 { |
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307 if ( iCache ) |
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308 iCache->Hold( aObject, aMicroSeconds ); |
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309 else |
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310 delete aObject; // no cache available |
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311 } |
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312 |
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313 void RDbCache::Release( const CBase& aObject ) const |
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314 // |
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315 // Retrieve aObject from the cache |
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316 // |
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317 { |
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318 if ( iCache ) |
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319 iCache->Release( aObject ); |
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320 } |
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321 |
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322 void RDbCache::Flush() |
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323 // |
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324 // Destroy any cached objects which have expired |
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325 // |
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326 { |
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327 if ( iCache ) |
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328 iCache->Flush(); |
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329 } |
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330 |
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331 |
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332 |