381 lines
10 KiB
C
381 lines
10 KiB
C
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///////////////////////////////////////////////////////////////////////////////
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//
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// Copyright (c) 2000, Microsoft Corp. All rights reserved.
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//
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// FILE
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//
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// iascache.h
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//
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// SYNOPSIS
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//
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// Declares the classes for creating hash tables and caches.
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//
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// MODIFICATION HISTORY
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//
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// 02/07/2000 Original version.
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//
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///////////////////////////////////////////////////////////////////////////////
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#ifndef IASCACHE_H
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#define IASCACHE_H
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#if _MSC_VER >= 1000
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#pragma once
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#endif
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#include <iasobj.h>
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#include <iaswin32.h>
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class HashTableBase;
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///////////////////////////////////////////////////////////////////////////////
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//
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// CLASS
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//
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// HashTableEntry
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//
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// DESCRIPTION
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//
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// Abstract base class for objects that will be stored in a hash table.
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//
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///////////////////////////////////////////////////////////////////////////////
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class HashTableEntry
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{
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public:
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virtual void AddRef() throw () = 0;
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virtual void Release() throw () = 0;
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virtual const void* getKey() const throw () = 0;
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virtual bool matches(const void* key) const throw () = 0;
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friend class HashTableBase;
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protected:
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HashTableEntry* next;
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virtual ~HashTableEntry() throw ();
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};
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///////////////////////////////////////////////////////////////////////////////
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//
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// CLASS
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//
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// HashTableBase
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//
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// DESCRIPTION
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//
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// Implements a simple hash table.
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//
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///////////////////////////////////////////////////////////////////////////////
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class HashTableBase
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{
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public:
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// Entry type.
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typedef HashTableEntry Entry;
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typedef ULONG (WINAPI *HashKey)(const void*) throw ();
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HashTableBase(
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HashKey hashFunction,
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ULONG initialSize
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);
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~HashTableBase() throw ();
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// Erases all entries from the table.
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void clear() throw ();
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// Removes and releases the entry matching key. Returns true if successful.
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bool erase(const void* key) throw ();
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// Returns the entry with the given key or null if no such entry exists. The
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// caller is responsible for releasing the returned entry.
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HashTableEntry* find(const void* key) throw ();
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// Insert a new entry in the cache. Returns 'true' if the entry was
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// successfully inserted. Note: this operation can only fail if
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// checkForDuplicates is true and the entry already exists.
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bool insert(
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HashTableEntry& entry,
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bool checkForDuplicates = true
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) throw ();
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// Removes and returns the entry with the given key or null if no such entry
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// exists. The caller is responsible for releasing the returned entry.
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HashTableEntry* remove(const void* key) throw ();
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// Resize the hash table to have newSize buckets. Returns true if
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// successful.
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bool resize(ULONG newSize) throw ();
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protected:
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void lock() throw ()
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{ monitor.lock(); }
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void unlock() throw ()
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{ monitor.unlock(); }
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HashTableEntry* bucketAsEntry(size_t bucket) throw ()
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{ return (HashTableEntry*)(table + bucket); }
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typedef HashTableEntry* Bucket;
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HashKey hash; // Hash function for hashing keys.
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Bucket* table; // Hash table of entries.
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ULONG buckets; // Number of buckets in the table.
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ULONG entries; // Number of entries in the table.
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CriticalSection monitor; // Synchronizes access to the table.
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// Not implemented.
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HashTableBase(const HashTableBase&) throw ();
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HashTableBase& operator=(const HashTableBase&) throw ();
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};
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///////////////////////////////////////////////////////////////////////////////
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//
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// CLASS
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//
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// HashTable<T>
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//
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// DESCRIPTION
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//
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// Provides a type safe wrapper around HashTableBase.
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//
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///////////////////////////////////////////////////////////////////////////////
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template <class K, class T>
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class HashTable : public HashTableBase
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{
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public:
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HashTable(
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HashKey hashFunction,
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ULONG initialSize
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) throw ()
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: HashTableBase(hashFunction, initialSize)
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{ }
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bool erase(const K& key) throw ()
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{ return HashTableBase::erase(&key); }
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bool erase(const T& value) throw ()
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{ return HashTableBase::erase(value.getKey()); }
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ObjectPointer<T> find(const K& key) throw ()
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{ return ObjectPointer<T>(narrow(HashTableBase::find(&key)), false); }
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bool insert(
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T& entry,
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bool checkForDuplicates = true
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) throw ()
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{ return HashTableBase::insert(entry, checkForDuplicates); }
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ObjectPointer<T> remove(const K& key) throw ()
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{ return ObjectPointer<T>(narrow(HashTableBase::remove(&key)), false); }
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protected:
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static T* narrow(HashTableBase::Entry* entry) throw ()
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{ return entry ? static_cast<T*>(entry) : NULL; }
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};
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class CacheBase;
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///////////////////////////////////////////////////////////////////////////////
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//
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// CLASS
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//
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// CacheEntry
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//
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// DESCRIPTION
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//
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// Abstract base class for objects that will be stored in a cache.
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//
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///////////////////////////////////////////////////////////////////////////////
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class CacheEntry : public HashTableEntry
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{
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public:
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// Methods for traversing the doubly-linked list.
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CacheEntry* prevInList() const throw ();
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CacheEntry* nextInList() const throw ();
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protected:
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friend class CacheBase;
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// Removes the node from the list.
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void removeFromList() throw ();
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// Methods for manipulating the expiration time.
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bool isExpired(const ULONG64& now) const throw ();
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bool isExpired() const throw ();
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void setExpiry(ULONG64 ttl) throw ();
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CacheEntry* flink; // Allows this to be an entry in a doubly-linked list.
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CacheEntry* blink;
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ULONG64 expiry; // Expiration time.
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};
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///////////////////////////////////////////////////////////////////////////////
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//
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// CLASS
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//
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// CacheBase
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//
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// DESCRIPTION
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//
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// Extends HashTableBase to add support for LRU and TTL based eviction.
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//
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///////////////////////////////////////////////////////////////////////////////
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class CacheBase : protected HashTableBase
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{
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public:
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// Entry type
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typedef CacheEntry Entry;
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CacheBase(
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HashKey hashFunction,
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ULONG initialSize,
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ULONG maxCapacity,
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ULONG timeToLive
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);
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~CacheBase() throw ();
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// Erases all entries from the cache.
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void clear() throw ();
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// Removes and releases the entry matching key. Returns true if successful.
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bool erase(const void* key) throw ();
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// Evict any eligible entries. Returns the number of entries evicted.
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ULONG evict() throw ();
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// Returns the entry with the given key or null if no such entry exists. The
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// caller is responsible for releasing the returned entry.
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CacheEntry* find(const void* key) throw ();
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// Insert a new entry in the cache. Returns 'true' if the entry was
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// successfully inserted. Note: this operation can only fail if
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// checkForDuplicates is true and the entry already exists.
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bool insert(
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CacheEntry& entry,
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bool checkForDuplicates = true
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) throw ();
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// Removes and returns the entry with the given key or null if no such entry
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// exists. The caller is responsible for releasing the returned entry.
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CacheEntry* remove(const void* key) throw ();
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//////////
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// iterator for traversing the cache entries.
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//////////
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class iterator
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{
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public:
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iterator() throw () {}
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iterator(CacheEntry* entry) throw () : p(entry) { }
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CacheEntry& operator*() const throw ()
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{ return *p; }
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CacheEntry* operator->() const throw ()
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{ return p; }
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iterator& operator++() throw ()
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{ p = p->nextInList(); return *this; }
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iterator operator++(int) throw ()
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{ iterator tmp = *this; ++*this; return tmp; }
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iterator& operator--() throw ()
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{ p = p->prevInList(); return *this; }
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iterator operator--(int) throw ()
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{ iterator tmp = *this; --*this; return tmp; }
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bool operator==(const iterator& i) const throw ()
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{ return p == i.p; }
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bool operator!=(const iterator& i) const throw ()
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{ return p != i.p; }
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protected:
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CacheEntry* p;
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};
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// Iterators for traversing the cache from most to least recently used.
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iterator begin() const throw ()
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{ return flink; }
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iterator end() const throw ()
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{ return listAsEntry(); }
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protected:
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CacheEntry* flink; // Doubly-linked list of entries.
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CacheEntry* blink;
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ULONG64 ttl; // Time-to-live of cache entries.
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ULONG maxEntries; // Max number of entries in the cache.
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// Evict an eligible entries without grabbing the lock.
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void unsafe_evict() throw ();
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// Remove an entry without grabbing the lock.
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CacheEntry* unsafe_remove(const void* key) throw ();
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// Returns the list as if it were a CacheEntry.
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CacheEntry* listAsEntry() const throw ()
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{
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return (CacheEntry*)
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((ULONG_PTR)&flink - FIELD_OFFSET(CacheEntry, flink));
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}
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// Add an entry to the front of the LRU list (i.e., it is the most recently
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// used entry.
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void push_front(CacheEntry* entry) throw ();
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};
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///////////////////////////////////////////////////////////////////////////////
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//
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// CLASS
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//
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// Cache<T>
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//
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// DESCRIPTION
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//
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// Provides a type safe wrapper around CacheBase.
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//
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///////////////////////////////////////////////////////////////////////////////
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template <class K, class T>
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class Cache : public CacheBase
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{
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public:
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Cache(
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HashKey hashFunction,
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ULONG initialSize,
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ULONG maxCapacity,
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ULONG timeToLive
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) throw ()
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: CacheBase(hashFunction, initialSize, maxCapacity, timeToLive)
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{ }
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bool erase(const K& key) throw ()
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{ return CacheBase::erase(&key); }
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bool erase(const T& value) throw ()
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{ return CacheBase::erase(value.getKey()); }
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ObjectPointer<T> find(const K& key) throw ()
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{ return ObjectPointer<T>(narrow(CacheBase::find(&key)), false); }
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bool insert(
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T& entry,
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bool checkForDuplicates = true
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) throw ()
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{ return CacheBase::insert(entry, checkForDuplicates); }
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ObjectPointer<T> remove(const K& key) throw ()
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{ return ObjectPointer<T>(narrow(CacheBase::remove(&key)), false); }
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protected:
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static T* narrow(CacheBase::Entry* entry) throw ()
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{ return entry ? static_cast<T*>(entry) : NULL; }
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};
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#endif // IASCACHE_H
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