/*

 * Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 * 

 *      http://www.apache.org/licenses/LICENSE-2.0

 * 

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

/*

 * $Id: StringPool.hpp 568078 2007-08-21 11:43:25Z amassari $

 */

#if !defined(STRINGPOOL_HPP)

#define STRINGPOOL_HPP

#include <xercesc/util/RefHashTableOf.hpp>

#include <xercesc/internal/XSerializable.hpp>

XERCES_CPP_NAMESPACE_BEGIN

//

//  This class implements a string pool, in which strings can be added and

//  given a unique id by which they can be refered. It has to provide fast

//  access both mapping from a string to its id and mapping from an id to

//  its string. This requires that it provide two separate data structures.

//  The map one is a hash table for quick storage and look up by name. The

//  other is an array ordered by unique id which maps to the element in the

//  hash table.

//

//  This works because strings cannot be removed from the pool once added,

//  other than flushing it completely, and because ids are assigned

//  sequentially from 1.

//

class XMLUTIL_EXPORT XMLStringPool : public XSerializable, public XMemory

{

public :

    // -----------------------------------------------------------------------

    //  Constructors and Destructor

    // -----------------------------------------------------------------------

    XMLStringPool

    (

          const unsigned int   modulus = 109

        , MemoryManager* const manager = XMLPlatformUtils::fgMemoryManager

    );

    virtual ~XMLStringPool();

    // -----------------------------------------------------------------------

    //  Pool management methods

    // -----------------------------------------------------------------------

    virtual unsigned int addOrFind(const XMLCh* const newString);

    virtual bool exists(const XMLCh* const newString) const;

    virtual bool exists(const unsigned int id) const;

    virtual void flushAll();

    virtual unsigned int getId(const XMLCh* const toFind) const;

    virtual const XMLCh* getValueForId(const unsigned int id) const;

    virtual unsigned int getStringCount() const;

    /***

     * Support for Serialization/De-serialization

     ***/

    DECL_XSERIALIZABLE(XMLStringPool)

    XMLStringPool(MemoryManager* const manager);

private :

    // -----------------------------------------------------------------------

    //  Private data types

    // -----------------------------------------------------------------------

    struct PoolElem

    {

        unsigned int  fId;

        XMLCh*        fString;

    };

    // -----------------------------------------------------------------------

    //  Unimplemented constructors and operators

    // -----------------------------------------------------------------------

    XMLStringPool(const XMLStringPool&);

    XMLStringPool& operator=(const XMLStringPool&);

    // -----------------------------------------------------------------------

    //  Private helper methods

    // -----------------------------------------------------------------------

    unsigned int addNewEntry(const XMLCh* const newString);

    // -----------------------------------------------------------------------

    //  Private data members

    //

    //  fIdMap

    //      This is an array of pointers to the pool elements. It is ordered

    //      by unique id, so using an id to index it gives instant access to

    //      the string of that id. This is grown as required.

    //

    //  fHashTable

    //      This is the hash table used to store and quickly access the

    //      strings.

    //

    //  fMapCapacity

    //      The current capacity of the id map. When the current id hits this

    //      value the map must must be expanded.

    //

    // -----------------------------------------------------------------------

    MemoryManager*              fMemoryManager;

    PoolElem**                  fIdMap;

    RefHashTableOf<PoolElem>*   fHashTable;

    unsigned int                fMapCapacity;

protected:

    // protected data members

    //  fCurId

    //      This is the counter used to assign unique ids. It is just bumped

    //      up one for each new string added.

    unsigned int                fCurId;

};

// Provid inline versions of some of the simple functions to improve performance.

inline unsigned int XMLStringPool::addOrFind(const XMLCh* const newString)

{

    PoolElem* elemToFind = fHashTable->get(newString);

    if (elemToFind)

        return elemToFind->fId;

    return addNewEntry(newString);

}

inline unsigned int XMLStringPool::getId(const XMLCh* const toFind) const

{

    PoolElem* elemToFind = fHashTable->get(toFind);

    if (elemToFind)

        return elemToFind->fId;

    // Not found, so return zero, which is never a legal id

    return 0;

}

inline bool XMLStringPool::exists(const XMLCh* const newString) const

{

    return fHashTable->containsKey(newString);

}

inline bool XMLStringPool::exists(const unsigned int id) const

{

    if (!id || (id >= fCurId))

        return false;

    return true;

}

inline const XMLCh* XMLStringPool::getValueForId(const unsigned int id) const

{

    if (!id || (id >= fCurId))

        ThrowXMLwithMemMgr(IllegalArgumentException, XMLExcepts::StrPool_IllegalId, fMemoryManager);

    // Just index the id map and return that element's string

    return fIdMap[id]->fString;

}

inline unsigned int XMLStringPool::getStringCount() const

{

    return fCurId-1;

}

XERCES_CPP_NAMESPACE_END

#endif