empty_sequence.h
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00001 /*
00002  * Copyright 2006-2008 The FLWOR Foundation.
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  * 
00008  * http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 #ifndef ZORBA_EMPTY_SEQUENCE_API_H
00017 #define ZORBA_EMPTY_SEQUENCE_API_H
00018 
00019 #include <zorba/config.h>
00020 #include <zorba/item_sequence.h>
00021 #include <zorba/item.h>
00022 #include <zorba/iterator.h>
00023 
00024 namespace zorba { 
00025 
00026   /** \brief This class is an implementation of the ItemSequence.
00027    *         Objects of this class return, on the first next call,
00028    *         an empty sequence.
00029    *
00030    * See ItemSequence
00031    */
00032   class ZORBA_DLL_PUBLIC EmptySequence : public ItemSequence
00033   {
00034     class InternalIterator : public Iterator
00035     {
00036     private:
00037       ItemSequence    *theItemSequence;
00038       bool is_open;
00039     public:
00040       InternalIterator(ItemSequence *item_sequence);
00041 
00042       /** \brief Start iterating.
00043        *
00044        * This function needs to be called before calling next().
00045        *
00046        */
00047       virtual void open();
00048       /** \brief Get the next Item of the sequence.
00049        *
00050        * This function returns false with no item.
00051        * @param aItem not used
00052        * @return false always
00053        * @throw ZorbaException if iterator is not open.
00054        *
00055        */
00056       virtual bool next(Item& aItem);
00057       /** \brief Stop iterating.
00058        *
00059        *  Not mandatory.
00060        */
00061       virtual void close();
00062       /**
00063        * brief Check whether the iterator is open or not
00064        */
00065       virtual bool isOpen() const;
00066     };
00067     public:
00068       /** \brief Constructor
00069        */
00070       EmptySequence() { }
00071 
00072       /** \brief Destructor
00073        */
00074       virtual ~EmptySequence() { }
00075 
00076       /** \brief get the void Iterator
00077        * @return a void iterator
00078       */
00079       virtual Iterator_t  getIterator();
00080 
00081   }; /* class EmptySequence */
00082 
00083 } // namespace zorba
00084 
00085 #endif /* ZORBA_EMPTY_SEQUENCE_API_H */
00086 /* vim:set et sw=2 ts=2: */
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