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 // © 2016 and later: Unicode, Inc. and others.
 // License & terms of use: http://www.unicode.org/copyright.html
 /*
 ********************************************************************
 *
 *   Copyright (C) 1997-2011, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 *
 ********************************************************************
 */
 
 #ifndef CHARITER_H
 #define CHARITER_H
 
 #include "unicode/utypes.h"
 
 #if U_SHOW_CPLUSPLUS_API
 
 #include "unicode/uobject.h"
 #include "unicode/unistr.h"
 /**
  * \file
  * \brief C++ API: Character Iterator
  */
  
 U_NAMESPACE_BEGIN
 /**
  * Abstract class that defines an API for forward-only iteration
  * on text objects.
  * This is a minimal interface for iteration without random access
  * or backwards iteration. It is especially useful for wrapping
  * streams with converters into an object for collation or
  * normalization.
  *
  * <p>Characters can be accessed in two ways: as code units or as
  * code points.
  * Unicode code points are 21-bit integers and are the scalar values
  * of Unicode characters. ICU uses the type UChar32 for them.
  * Unicode code units are the storage units of a given
  * Unicode/UCS Transformation Format (a character encoding scheme).
  * With UTF-16, all code points can be represented with either one
  * or two code units ("surrogates").
  * String storage is typically based on code units, while properties
  * of characters are typically determined using code point values.
  * Some processes may be designed to work with sequences of code units,
  * or it may be known that all characters that are important to an
  * algorithm can be represented with single code units.
  * Other processes will need to use the code point access functions.</p>
  *
  * <p>ForwardCharacterIterator provides nextPostInc() to access
  * a code unit and advance an internal position into the text object,
  * similar to a <code>return text[position++]</code>.<br>
  * It provides next32PostInc() to access a code point and advance an internal
  * position.</p>
  *
  * <p>next32PostInc() assumes that the current position is that of
  * the beginning of a code point, i.e., of its first code unit.
  * After next32PostInc(), this will be true again.
  * In general, access to code units and code points in the same
  * iteration loop should not be mixed. In UTF-16, if the current position
  * is on a second code unit (Low Surrogate), then only that code unit
  * is returned even by next32PostInc().</p>
  *
  * <p>For iteration with either function, there are two ways to
  * check for the end of the iteration. When there are no more
  * characters in the text object:
  * <ul>
  * <li>The hasNext() function returns false.</li>
  * <li>nextPostInc() and next32PostInc() return DONE
  *     when one attempts to read beyond the end of the text object.</li>
  * </ul>
  *
  * Example:
  * \code 
  * void function1(ForwardCharacterIterator &it) {
  *     UChar32 c;
  *     while(it.hasNext()) {
  *         c=it.next32PostInc();
  *         // use c
  *     }
  * }
  *
  * void function1(ForwardCharacterIterator &it) {
  *     char16_t c;
  *     while((c=it.nextPostInc())!=ForwardCharacterIterator::DONE) {
  *         // use c
  *      }
  *  }
  * \endcode
  * </p>
  *
  * @stable ICU 2.0
  */
 class U_COMMON_API ForwardCharacterIterator : public UObject {
 public:
     /**
      * Value returned by most of ForwardCharacterIterator's functions
      * when the iterator has reached the limits of its iteration.
      * @stable ICU 2.0
      */
     enum { DONE = 0xffff };
     
     /**
      * Destructor.  
      * @stable ICU 2.0
      */
     virtual ~ForwardCharacterIterator();
     
     /**
      * Returns true when both iterators refer to the same
      * character in the same character-storage object.  
      * @param that The ForwardCharacterIterator to be compared for equality
      * @return true when both iterators refer to the same
      * character in the same character-storage object
      * @stable ICU 2.0
      */
     virtual bool operator==(const ForwardCharacterIterator& that) const = 0;
     
     /**
      * Returns true when the iterators refer to different
      * text-storage objects, or to different characters in the
      * same text-storage object.  
      * @param that The ForwardCharacterIterator to be compared for inequality
      * @return true when the iterators refer to different
      * text-storage objects, or to different characters in the
      * same text-storage object
      * @stable ICU 2.0
      */
     inline bool operator!=(const ForwardCharacterIterator& that) const;
     
     /**
      * Generates a hash code for this iterator.  
      * @return the hash code.
      * @stable ICU 2.0
      */
     virtual int32_t hashCode(void) const = 0;
     
     /**
      * Returns a UClassID for this ForwardCharacterIterator ("poor man's
      * RTTI").<P> Despite the fact that this function is public,
      * DO NOT CONSIDER IT PART OF CHARACTERITERATOR'S API! 
      * @return a UClassID for this ForwardCharacterIterator 
      * @stable ICU 2.0
      */
     virtual UClassID getDynamicClassID(void) const override = 0;
     
     /**
      * Gets the current code unit for returning and advances to the next code unit
      * in the iteration range
      * (toward endIndex()).  If there are
      * no more code units to return, returns DONE.
      * @return the current code unit.
      * @stable ICU 2.0
      */
     virtual char16_t         nextPostInc(void) = 0;
     
     /**
      * Gets the current code point for returning and advances to the next code point
      * in the iteration range
      * (toward endIndex()).  If there are
      * no more code points to return, returns DONE.
      * @return the current code point.
      * @stable ICU 2.0
      */
     virtual UChar32       next32PostInc(void) = 0;
     
     /**
      * Returns false if there are no more code units or code points
      * at or after the current position in the iteration range.
      * This is used with nextPostInc() or next32PostInc() in forward
      * iteration.
      * @returns false if there are no more code units or code points
      * at or after the current position in the iteration range.
      * @stable ICU 2.0
      */
     virtual UBool        hasNext() = 0;
     
 protected:
     /** Default constructor to be overridden in the implementing class. @stable ICU 2.0*/
     ForwardCharacterIterator();
     
     /** Copy constructor to be overridden in the implementing class. @stable ICU 2.0*/
     ForwardCharacterIterator(const ForwardCharacterIterator &other);
     
     /**
      * Assignment operator to be overridden in the implementing class.
      * @stable ICU 2.0
      */
     ForwardCharacterIterator &operator=(const ForwardCharacterIterator&) { return *this; }
 };
 
 /**
  * Abstract class that defines an API for iteration
  * on text objects.
  * This is an interface for forward and backward iteration
  * and random access into a text object.
  *
  * <p>The API provides backward compatibility to the Java and older ICU
  * CharacterIterator classes but extends them significantly:
  * <ol>
  * <li>CharacterIterator is now a subclass of ForwardCharacterIterator.</li>
  * <li>While the old API functions provided forward iteration with
  *     "pre-increment" semantics, the new one also provides functions
  *     with "post-increment" semantics. They are more efficient and should
  *     be the preferred iterator functions for new implementations.
  *     The backward iteration always had "pre-decrement" semantics, which
  *     are efficient.</li>
  * <li>Just like ForwardCharacterIterator, it provides access to
  *     both code units and code points. Code point access versions are available
  *     for the old and the new iteration semantics.</li>
  * <li>There are new functions for setting and moving the current position
  *     without returning a character, for efficiency.</li>
  * </ol>
  *
  * See ForwardCharacterIterator for examples for using the new forward iteration
  * functions. For backward iteration, there is also a hasPrevious() function
  * that can be used analogously to hasNext().
  * The old functions work as before and are shown below.</p>
  *
  * <p>Examples for some of the new functions:</p>
  *
  * Forward iteration with hasNext():
  * \code
  * void forward1(CharacterIterator &it) {
  *     UChar32 c;
  *     for(it.setToStart(); it.hasNext();) {
  *         c=it.next32PostInc();
  *         // use c
  *     }
  *  }
  * \endcode
  * Forward iteration more similar to loops with the old forward iteration,
  * showing a way to convert simple for() loops:
  * \code
  * void forward2(CharacterIterator &it) {
  *     char16_t c;
  *     for(c=it.firstPostInc(); c!=CharacterIterator::DONE; c=it.nextPostInc()) {
  *          // use c
  *      }
  * }
  * \endcode
  * Backward iteration with setToEnd() and hasPrevious():
  * \code
  *  void backward1(CharacterIterator &it) {
  *      UChar32 c;
  *      for(it.setToEnd(); it.hasPrevious();) {
  *         c=it.previous32();
  *          // use c
  *      }
  *  }
  * \endcode
  * Backward iteration with a more traditional for() loop:
  * \code
  * void backward2(CharacterIterator &it) {
  *     char16_t c;
  *     for(c=it.last(); c!=CharacterIterator::DONE; c=it.previous()) {
  *         // use c
  *      }
  *  }
  * \endcode
  *
  * Example for random access:
  * \code
  *  void random(CharacterIterator &it) {
  *      // set to the third code point from the beginning
  *      it.move32(3, CharacterIterator::kStart);
  *      // get a code point from here without moving the position
  *      UChar32 c=it.current32();
  *      // get the position
  *      int32_t pos=it.getIndex();
  *      // get the previous code unit
  *      char16_t u=it.previous();
  *      // move back one more code unit
  *      it.move(-1, CharacterIterator::kCurrent);
  *      // set the position back to where it was
  *      // and read the same code point c and move beyond it
  *      it.setIndex(pos);
  *      if(c!=it.next32PostInc()) {
  *          exit(1); // CharacterIterator inconsistent
  *      }
  *  }
  * \endcode
  *
  * <p>Examples, especially for the old API:</p>
  *
  * Function processing characters, in this example simple output
  * <pre>
  * \code
  *  void processChar( char16_t c )
  *  {
  *      cout << " " << c;
  *  }
  * \endcode
  * </pre>
  * Traverse the text from start to finish
  * <pre> 
  * \code
  *  void traverseForward(CharacterIterator& iter)
  *  {
  *      for(char16_t c = iter.first(); c != CharacterIterator::DONE; c = iter.next()) {
  *          processChar(c);
  *      }
  *  }
  * \endcode
  * </pre>
  * Traverse the text backwards, from end to start
  * <pre>
  * \code
  *  void traverseBackward(CharacterIterator& iter)
  *  {
  *      for(char16_t c = iter.last(); c != CharacterIterator::DONE; c = iter.previous()) {
  *          processChar(c);
  *      }
  *  }
  * \endcode
  * </pre>
  * Traverse both forward and backward from a given position in the text. 
  * Calls to notBoundary() in this example represents some additional stopping criteria.
  * <pre>
  * \code
  * void traverseOut(CharacterIterator& iter, int32_t pos)
  * {
  *      char16_t c;
  *      for (c = iter.setIndex(pos);
  *      c != CharacterIterator::DONE && (Unicode::isLetter(c) || Unicode::isDigit(c));
  *          c = iter.next()) {}
  *      int32_t end = iter.getIndex();
  *      for (c = iter.setIndex(pos);
  *          c != CharacterIterator::DONE && (Unicode::isLetter(c) || Unicode::isDigit(c));
  *          c = iter.previous()) {}
  *      int32_t start = iter.getIndex() + 1;
  *  
  *      cout << "start: " << start << " end: " << end << endl;
  *      for (c = iter.setIndex(start); iter.getIndex() < end; c = iter.next() ) {
  *          processChar(c);
  *     }
  *  }
  * \endcode
  * </pre>
  * Creating a StringCharacterIterator and calling the test functions
  * <pre>
  * \code
  *  void CharacterIterator_Example( void )
  *   {
  *       cout << endl << "===== CharacterIterator_Example: =====" << endl;
  *       UnicodeString text("Ein kleiner Satz.");
  *       StringCharacterIterator iterator(text);
  *       cout << "----- traverseForward: -----------" << endl;
  *       traverseForward( iterator );
  *       cout << endl << endl << "----- traverseBackward: ----------" << endl;
  *       traverseBackward( iterator );
  *       cout << endl << endl << "----- traverseOut: ---------------" << endl;
  *       traverseOut( iterator, 7 );
  *       cout << endl << endl << "-----" << endl;
  *   }
  * \endcode
  * </pre>
  *
  * @stable ICU 2.0
  */
 class U_COMMON_API CharacterIterator : public ForwardCharacterIterator {
 public:
     /**
      * Origin enumeration for the move() and move32() functions.
      * @stable ICU 2.0
      */
     enum EOrigin { kStart, kCurrent, kEnd };
 
     /**
      * Destructor.
      * @stable ICU 2.0
      */
     virtual ~CharacterIterator();
 
     /**
      * Returns a pointer to a new CharacterIterator of the same
      * concrete class as this one, and referring to the same
      * character in the same text-storage object as this one.  The
      * caller is responsible for deleting the new clone.  
      * @return a pointer to a new CharacterIterator
      * @stable ICU 2.0
      */
     virtual CharacterIterator* clone() const = 0;
 
     /**
      * Sets the iterator to refer to the first code unit in its
      * iteration range, and returns that code unit.
      * This can be used to begin an iteration with next().
      * @return the first code unit in its iteration range.
      * @stable ICU 2.0
      */
     virtual char16_t         first(void) = 0;
 
     /**
      * Sets the iterator to refer to the first code unit in its
      * iteration range, returns that code unit, and moves the position
      * to the second code unit. This is an alternative to setToStart()
      * for forward iteration with nextPostInc().
      * @return the first code unit in its iteration range.
      * @stable ICU 2.0
      */
     virtual char16_t         firstPostInc(void);
 
     /**
      * Sets the iterator to refer to the first code point in its
      * iteration range, and returns that code unit,
      * This can be used to begin an iteration with next32().
      * Note that an iteration with next32PostInc(), beginning with,
      * e.g., setToStart() or firstPostInc(), is more efficient.
      * @return the first code point in its iteration range.
      * @stable ICU 2.0
      */
     virtual UChar32       first32(void) = 0;
 
     /**
      * Sets the iterator to refer to the first code point in its
      * iteration range, returns that code point, and moves the position
      * to the second code point. This is an alternative to setToStart()
      * for forward iteration with next32PostInc().
      * @return the first code point in its iteration range.
      * @stable ICU 2.0
      */
     virtual UChar32       first32PostInc(void);
 
     /**
      * Sets the iterator to refer to the first code unit or code point in its
      * iteration range. This can be used to begin a forward
      * iteration with nextPostInc() or next32PostInc().
      * @return the start position of the iteration range
      * @stable ICU 2.0
      */
     inline int32_t    setToStart();
 
     /**
      * Sets the iterator to refer to the last code unit in its
      * iteration range, and returns that code unit.
      * This can be used to begin an iteration with previous().
      * @return the last code unit.
      * @stable ICU 2.0
      */
     virtual char16_t         last(void) = 0;
         
     /**
      * Sets the iterator to refer to the last code point in its
      * iteration range, and returns that code unit.
      * This can be used to begin an iteration with previous32().
      * @return the last code point.
      * @stable ICU 2.0
      */
     virtual UChar32       last32(void) = 0;
 
     /**
      * Sets the iterator to the end of its iteration range, just behind
      * the last code unit or code point. This can be used to begin a backward
      * iteration with previous() or previous32().
      * @return the end position of the iteration range
      * @stable ICU 2.0
      */
     inline int32_t    setToEnd();
 
     /**
      * Sets the iterator to refer to the "position"-th code unit
      * in the text-storage object the iterator refers to, and
      * returns that code unit.  
      * @param position the "position"-th code unit in the text-storage object
      * @return the "position"-th code unit.
      * @stable ICU 2.0
      */
     virtual char16_t         setIndex(int32_t position) = 0;
 
     /**
      * Sets the iterator to refer to the beginning of the code point
      * that contains the "position"-th code unit
      * in the text-storage object the iterator refers to, and
      * returns that code point.
      * The current position is adjusted to the beginning of the code point
      * (its first code unit).
      * @param position the "position"-th code unit in the text-storage object
      * @return the "position"-th code point.
      * @stable ICU 2.0
      */
     virtual UChar32       setIndex32(int32_t position) = 0;
 
     /**
      * Returns the code unit the iterator currently refers to. 
      * @return the current code unit. 
      * @stable ICU 2.0
      */
     virtual char16_t         current(void) const = 0;
         
     /**
      * Returns the code point the iterator currently refers to.  
      * @return the current code point.
      * @stable ICU 2.0
      */
     virtual UChar32       current32(void) const = 0;
         
     /**
      * Advances to the next code unit in the iteration range
      * (toward endIndex()), and returns that code unit.  If there are
      * no more code units to return, returns DONE.
      * @return the next code unit.
      * @stable ICU 2.0
      */
     virtual char16_t         next(void) = 0;
         
     /**
      * Advances to the next code point in the iteration range
      * (toward endIndex()), and returns that code point.  If there are
      * no more code points to return, returns DONE.
      * Note that iteration with "pre-increment" semantics is less
      * efficient than iteration with "post-increment" semantics
      * that is provided by next32PostInc().
      * @return the next code point.
      * @stable ICU 2.0
      */
     virtual UChar32       next32(void) = 0;
         
     /**
      * Advances to the previous code unit in the iteration range
      * (toward startIndex()), and returns that code unit.  If there are
      * no more code units to return, returns DONE.  
      * @return the previous code unit.
      * @stable ICU 2.0
      */
     virtual char16_t         previous(void) = 0;
 
     /**
      * Advances to the previous code point in the iteration range
      * (toward startIndex()), and returns that code point.  If there are
      * no more code points to return, returns DONE. 
      * @return the previous code point. 
      * @stable ICU 2.0
      */
     virtual UChar32       previous32(void) = 0;
 
     /**
      * Returns false if there are no more code units or code points
      * before the current position in the iteration range.
      * This is used with previous() or previous32() in backward
      * iteration.
      * @return false if there are no more code units or code points
      * before the current position in the iteration range, return true otherwise.
      * @stable ICU 2.0
      */
     virtual UBool        hasPrevious() = 0;
 
     /**
      * Returns the numeric index in the underlying text-storage
      * object of the character returned by first().  Since it's
      * possible to create an iterator that iterates across only
      * part of a text-storage object, this number isn't
      * necessarily 0.  
      * @returns the numeric index in the underlying text-storage
      * object of the character returned by first().
      * @stable ICU 2.0
      */
     inline int32_t       startIndex(void) const;
         
     /**
      * Returns the numeric index in the underlying text-storage
      * object of the position immediately BEYOND the character
      * returned by last().  
      * @return the numeric index in the underlying text-storage
      * object of the position immediately BEYOND the character
      * returned by last().
      * @stable ICU 2.0
      */
     inline int32_t       endIndex(void) const;
         
     /**
      * Returns the numeric index in the underlying text-storage
      * object of the character the iterator currently refers to
      * (i.e., the character returned by current()).  
      * @return the numeric index in the text-storage object of 
      * the character the iterator currently refers to
      * @stable ICU 2.0
      */
     inline int32_t       getIndex(void) const;
 
     /**
      * Returns the length of the entire text in the underlying
      * text-storage object.
      * @return the length of the entire text in the text-storage object
      * @stable ICU 2.0
      */
     inline int32_t           getLength() const;
 
     /**
      * Moves the current position relative to the start or end of the
      * iteration range, or relative to the current position itself.
      * The movement is expressed in numbers of code units forward
      * or backward by specifying a positive or negative delta.
      * @param delta the position relative to origin. A positive delta means forward;
      * a negative delta means backward.
      * @param origin Origin enumeration {kStart, kCurrent, kEnd}
      * @return the new position
      * @stable ICU 2.0
      */
     virtual int32_t      move(int32_t delta, EOrigin origin) = 0;
 
     /**
      * Moves the current position relative to the start or end of the
      * iteration range, or relative to the current position itself.
      * The movement is expressed in numbers of code points forward
      * or backward by specifying a positive or negative delta.
      * @param delta the position relative to origin. A positive delta means forward;
      * a negative delta means backward.
      * @param origin Origin enumeration {kStart, kCurrent, kEnd}
      * @return the new position
      * @stable ICU 2.0
      */
 #ifdef move32
      // One of the system headers right now is sometimes defining a conflicting macro we don't use
 #undef move32
 #endif
     virtual int32_t      move32(int32_t delta, EOrigin origin) = 0;
 
     /**
      * Copies the text under iteration into the UnicodeString
      * referred to by "result".  
      * @param result Receives a copy of the text under iteration.  
      * @stable ICU 2.0
      */
     virtual void            getText(UnicodeString&  result) = 0;
 
 protected:
     /**
      * Empty constructor.
      * @stable ICU 2.0
      */
     CharacterIterator();
 
     /**
      * Constructor, just setting the length field in this base class.
      * @stable ICU 2.0
      */
     CharacterIterator(int32_t length);
 
     /**
      * Constructor, just setting the length and position fields in this base class.
      * @stable ICU 2.0
      */
     CharacterIterator(int32_t length, int32_t position);
 
     /**
      * Constructor, just setting the length, start, end, and position fields in this base class.
      * @stable ICU 2.0
      */
     CharacterIterator(int32_t length, int32_t textBegin, int32_t textEnd, int32_t position);
   
     /**
      * Copy constructor.
      *
      * @param that The CharacterIterator to be copied
      * @stable ICU 2.0
      */
     CharacterIterator(const CharacterIterator &that);
 
     /**
      * Assignment operator.  Sets this CharacterIterator to have the same behavior,
      * as the one passed in.
      * @param that The CharacterIterator passed in.
      * @return the newly set CharacterIterator.
      * @stable ICU 2.0
      */
     CharacterIterator &operator=(const CharacterIterator &that);
 
     /**
      * Base class text length field.
      * Necessary this for correct getText() and hashCode().
      * @stable ICU 2.0
      */
     int32_t textLength;
 
     /**
      * Base class field for the current position.
      * @stable ICU 2.0
      */
     int32_t  pos;
 
     /**
      * Base class field for the start of the iteration range.
      * @stable ICU 2.0
      */
     int32_t  begin;
 
     /**
      * Base class field for the end of the iteration range.
      * @stable ICU 2.0
      */
     int32_t  end;
 };
 
 inline bool
 ForwardCharacterIterator::operator!=(const ForwardCharacterIterator& that) const {
     return !operator==(that);
 }
 
 inline int32_t
 CharacterIterator::setToStart() {
     return move(0, kStart);
 }
 
 inline int32_t
 CharacterIterator::setToEnd() {
     return move(0, kEnd);
 }
 
 inline int32_t
 CharacterIterator::startIndex(void) const {
     return begin;
 }
 
 inline int32_t
 CharacterIterator::endIndex(void) const {
     return end;
 }
 
 inline int32_t
 CharacterIterator::getIndex(void) const {
     return pos;
 }
 
 inline int32_t
 CharacterIterator::getLength(void) const {
     return textLength;
 }
 
 U_NAMESPACE_END
 
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif

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