From 21a4337dc2f969dc3ec81e6ba3170119bcb67016 Mon Sep 17 00:00:00 2001
From: Mike Buland <eichlan@xagasoft.com>
Date: Tue, 22 Jul 2014 16:39:01 +0000
Subject: Deferred erase now works on cache entries.  You can erase a cache
 entry while it still has active references, and it will be safely cleaned up
 when the last reference is released.

---
 src/unstable/cachebase.h   | 76 ++++++++++++++++++++++++++++++++++++++++------
 src/unstable/cacheobject.h |  3 +-
 2 files changed, 69 insertions(+), 10 deletions(-)

(limited to 'src/unstable')

diff --git a/src/unstable/cachebase.h b/src/unstable/cachebase.h
index 1584246..b17d377 100644
--- a/src/unstable/cachebase.h
+++ b/src/unstable/cachebase.h
@@ -29,6 +29,7 @@ namespace Bu
     private:
         CacheEntry( obtype *pObject ) :
             iRefCount( 0 ),
+            bDeleted( false ),
             pObject( pObject )
         {
         }
@@ -78,10 +79,29 @@ namespace Bu
             return bRet;
         }
 
+        bool isDeleted()
+        {
+            mEntry.lock();
+            bool bRet = bDeleted;
+            mEntry.unlock();
+            return bRet;
+        }
+
+        // Indicates that the entry was both deleted
+        // and has a refcount of zero
+        bool isReadyForCleanup()
+        {
+            mEntry.lock();
+            bool bRet = bDeleted && iRefCount == 0;
+            mEntry.unlock();
+            return bRet;
+        }
+
     private:
         mutable Bu::Mutex mEntry;
         mutable Bu::Mutex mObject;
         int iRefCount;
+        bool bDeleted;
         obtype *pObject;
     };
 
@@ -104,7 +124,7 @@ namespace Bu
                 obtype * &rpData )
         {
             if( pCache == NULL )
-                throw Bu::ExceptionBase("Invalid pointer");
+                throw Bu::ExceptionBase("Invalid cache pointer");
 
             if( !rpData )
             {
@@ -241,6 +261,12 @@ namespace Bu
             return pCache->template cast<obtype, castto>( *this );
         }
         
+        template<typename castto>
+        CachePtr<keytype, castto, basetype> cast() const
+        {
+            return pCache->template cast<obtype, castto>( *this );
+        }
+        
         bool operator==( const MyType &rhs ) const
         {
             return pCache == rhs.pCache &&
@@ -410,19 +436,46 @@ namespace Bu
             else
                 return CachePtr<keytype, castto, obtype>( this, ptr.kId );
         }
+        
+        template<typename supertype, typename castto>
+        CachePtr<keytype, castto, obtype> cast( const CachePtr<keytype, supertype, obtype> &ptr )
+        {
+            if( ptr.pEnt )
+                return CachePtr<keytype, castto, obtype>( this, ptr.pEnt, ptr.kId );
+            else
+                return CachePtr<keytype, castto, obtype>( this, ptr.kId );
+        }
 
         /**
          * Removes an item from the cache.
-         * This routine calls eraseNow for now.  Later the intention is that
-         * this function will always succeed.  It will remove the object from
-         * the backing store and the active tables.  It will not be able to
-         * be requested again, and all changes will be ignored.  When the
-         * object's last references are released the memory will be freed
-         * automatically.
+         * The object in question can have references to it, and those
+         * references will still work after the erase is called.  When erase
+         * is called the object is immediately removed from the backing store
+         * as well as from the main index.  At that point existing references
+         * can be used as normal, but when the last reference is released
+         * the memory will be automatically cleaned up.
          */
         void erase( const keytype &key )
         {
-            eraseNow( key );
+            Bu::ReadWriteMutex::WriteLocker wl( mCacheEntry );
+            if( hCacheEntry.has( key ) )
+            {
+                Entry *pEnt = hCacheEntry.get( key );
+                pEnt->mEntry.lock();
+                if( pEnt->iRefCount == 0 )
+                {
+                    pEnt->mEntry.unlock();
+                    delete pEnt->pObject;
+                    delete pEnt;
+                }
+                else
+                {
+                    pEnt->bDeleted = true;
+                    pEnt->mEntry.unlock();
+                }
+                hCacheEntry.erase( key );
+            }
+            _erase( key );
         }
 
         /**
@@ -467,8 +520,13 @@ namespace Bu
             return pEnt;
         }
 
-        void releaseRef( Entry * )//pEnt )
+        void releaseRef( Entry *pEnt )
         {
+            if( pEnt->isReadyForCleanup() )
+            {
+                delete pEnt->pObject;
+                delete pEnt;
+            }
         }
 
         void objectChanged( const keytype &k )
diff --git a/src/unstable/cacheobject.h b/src/unstable/cacheobject.h
index 6eb507b..47e09de 100644
--- a/src/unstable/cacheobject.h
+++ b/src/unstable/cacheobject.h
@@ -86,7 +86,8 @@ namespace Bu
     protected:
         void changed( bool bChanged=true )
         {
-            if( this->bChanged == false && bChanged == true && pCache )
+            if( this->bChanged == false && bChanged == true && pCache &&
+                    pEntry && !pEntry->isDeleted() )
                 pCache->objectChanged( getKey() );
 
             this->bChanged = bChanged;
-- 
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