/*

 ********************************************************************

 *

 *   Copyright (C) 1997-2005, International Business Machines

 *   Corporation and others.  All Rights Reserved.

 *

 ********************************************************************

 */

 #ifndef CHARITER_H

 #define CHARITER_H

 #include "unicode/utypes.h"

 #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) {

  *     UChar 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 UBool 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 UBool 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 = 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 UChar         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) {

  *     UChar 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) {

  *     UChar 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

  *      UChar 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( UChar c )

  *  {

  *      cout << " " << c;

  *  }

  * \endcode

  * </pre>

  * Traverse the text from start to finish

  * <pre> 

  * \code

  *  void traverseForward(CharacterIterator& iter)

  *  {

  *      for(UChar 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(UChar 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)

  * {

  *      UChar 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 };

     /**

      * 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(void) 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 UChar         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 UChar         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 UChar         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 UChar         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 UChar         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 UChar         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 UChar         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 numberic 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

      */

     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 UBool

 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