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.
+ * + *ForwardCharacterIterator provides nextPostInc() to access
+ * a code unit and advance an internal position into the text object,
+ * similar to a return text[position++].
+ * It provides next32PostInc() to access a code point and advance an internal
+ * position.
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().
+ * + *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: + *
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. + * + *
The API provides backward compatibility to the Java and older ICU + * CharacterIterator classes but extends them significantly: + *
Examples for some of the new functions:
+ * + * 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 + * + *Examples, especially for the old API:
+ * + * Function processing characters, in this example simple output + *
+ * \code
+ * void processChar( UChar c )
+ * {
+ * cout << " " << c;
+ * }
+ * \endcode
+ *
+ * Traverse the text from start to finish
+ *
+ * \code
+ * void traverseForward(CharacterIterator& iter)
+ * {
+ * for(UChar c = iter.first(); c != CharacterIterator.DONE; c = iter.next()) {
+ * processChar(c);
+ * }
+ * }
+ * \endcode
+ *
+ * Traverse the text backwards, from end to start
+ *
+ * \code
+ * void traverseBackward(CharacterIterator& iter)
+ * {
+ * for(UChar c = iter.last(); c != CharacterIterator.DONE; c = iter.previous()) {
+ * processChar(c);
+ * }
+ * }
+ * \endcode
+ *
+ * Traverse both forward and backward from a given position in the text.
+ * Calls to notBoundary() in this example represents some additional stopping criteria.
+ *
+ * \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
+ *
+ * Creating a StringCharacterIterator and calling the test functions
+ *
+ * \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
+ *
+ *
+ * @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