UCharacterIterator


1   /*
2    *******************************************************************************
3    * Copyright (C) 1996-2004, International Business Machines Corporation and    *
4    * others. All Rights Reserved.                                                *
5    *******************************************************************************
6    */
7   package com.ibm.icu.text;
8   
9   
10  import java.text.CharacterIterator  ;
11  
12  import com.ibm.icu.impl.CharacterIteratorWrapper;
13  import com.ibm.icu.impl.ReplaceableUCharacterIterator;
14  import com.ibm.icu.impl.UCharArrayIterator;
15  import com.ibm.icu.impl.UCharacterIteratorWrapper;
16  import com.ibm.icu.impl.UCharacterProperty;
17  
18  
19  /**
20   * Abstract class that defines an API for iteration on text objects.This is an 
21   * interface for forward and backward iteration and random access into a text 
22   * object. Forward iteration is done with post-increment and backward iteration 
23   * is done with pre-decrement semantics, while the 
24   * <code>java.text.CharacterIterator</code> interface methods provided forward 
25   * iteration with "pre-increment" and backward iteration with pre-decrement 
26   * semantics. This API is more efficient for forward iteration over code points.
27   * The other major difference is that this API can do both code unit and code point 
28   * iteration, <code>java.text.CharacterIterator</code> can only iterate over 
29   * code units and is limited to BMP (0 - 0xFFFF)
30   * @author Ram
31   * @stable ICU 2.4
32   */
33  public abstract class UCharacterIterator 
34                        implements Cloneable  ,UForwardCharacterIterator {
35  
36      /**
37       * Protected default constructor for the subclasses
38       * @stable ICU 2.4
39       */
40      protected UCharacterIterator(){
41      }
42      
43      // static final methods ----------------------------------------------------
44      
45      /**
46       * Returns a <code>UCharacterIterator</code> object given a 
47       * <code>Replaceable</code> object.
48       * @param source a valid source as a <code>Replaceable</code> object
49       * @return UCharacterIterator object
50       * @exception IllegalArgumentException if the argument is null
51       * @stable ICU 2.4
52       */
53      public static final UCharacterIterator getInstance(Replaceable source){
54          return new ReplaceableUCharacterIterator(source);
55      }
56      
57      /**
58       * Returns a <code>UCharacterIterator</code> object given a 
59       * source string.
60       * @param source a string
61       * @return UCharacterIterator object
62       * @exception IllegalArgumentException if the argument is null
63       * @stable ICU 2.4
64       */
65      public static final UCharacterIterator getInstance(String   source){
66          return new ReplaceableUCharacterIterator(source);
67      }
68      
69      /**
70       * Returns a <code>UCharacterIterator</code> object given a 
71       * source character array.
72       * @param source an array of UTF-16 code units
73       * @return UCharacterIterator object
74       * @exception IllegalArgumentException if the argument is null
75       * @stable ICU 2.4
76       */
77      public static final UCharacterIterator getInstance(char[] source){
78          return getInstance(source,0,source.length);
79      }
80      
81      /**
82       * Returns a <code>UCharacterIterator</code> object given a 
83       * source character array.
84       * @param source an array of UTF-16 code units
85       * @return UCharacterIterator object
86       * @exception IllegalArgumentException if the argument is null
87       * @stable ICU 2.4
88       */
89      public static final UCharacterIterator getInstance(char[] source, int start, int limit){
90          return new UCharArrayIterator(source,start,limit);
91      }
92      /**
93       * Returns a <code>UCharacterIterator</code> object given a 
94       * source StringBuffer.
95       * @param source an string buffer of UTF-16 code units
96       * @return UCharacterIterator object
97       * @exception IllegalArgumentException if the argument is null
98       * @stable ICU 2.4
99       */
100     public static final UCharacterIterator getInstance(StringBuffer   source){
101         return new ReplaceableUCharacterIterator(source);
102     }
103 
104     /**
105      * Returns a <code>UCharacterIterator</code> object given a 
106      * CharacterIterator.
107      * @param source a valid CharacterIterator object.
108      * @return UCharacterIterator object
109      * @exception IllegalArgumentException if the argument is null
110      * @stable ICU 2.4
111      */    
112     public static final UCharacterIterator getInstance(CharacterIterator   source){
113         return new CharacterIteratorWrapper(source);
114     }
115        
116     // public methods ----------------------------------------------------------
117     /**
118      * Returns a <code>java.text.CharacterIterator</code> object for
119      * the underlying text of this iterator.  The returned iterator is
120      * independent of this iterator.
121      * @return java.text.CharacterIterator object
122      * @stable ICU 2.4 
123      */
124     public CharacterIterator   getCharacterIterator(){
125         return new UCharacterIteratorWrapper(this);
126     }    
127    
128     /**
129      * Returns the code unit at the current index.  If index is out
130      * of range, returns DONE.  Index is not changed.
131      * @return current code unit
132      * @stable ICU 2.4
133      */
134     public abstract int current();
135     
136     /**
137      * Returns the codepoint at the current index.
138      * If the current index is invalid, DONE is returned.
139      * If the current index points to a lead surrogate, and there is a following
140      * trail surrogate, then the code point is returned.  Otherwise, the code
141      * unit at index is returned.  Index is not changed. 
142      * @return current codepoint
143      * @stable ICU 2.4
144      */
145     public int currentCodePoint(){
146         int ch = current();
147         if(UTF16.isLeadSurrogate((char)ch)){
148             // advance the index to get the
149             // next code point
150             next();
151             // due to post increment semantics
152             // current() after next() actually
153             // returns the char we want
154             int ch2 = current();
155             // current should never change
156             // the current index so back off
157             previous();
158             
159             if(UTF16.isTrailSurrogate((char)ch2)){
160                 // we found a surrogate pair 
161                 // return the codepoint
162                 return UCharacterProperty.getRawSupplementary(
163                                                           (char)ch,(char)ch2
164                                                              );
165             }
166         }
167         return ch;
168     }
169     
170     /**
171      * Returns the length of the text
172      * @return length of the text
173      * @stable ICU 2.4
174      */
175     public abstract int getLength();
176 
177     
178     /**
179      * Gets the current index in text.
180      * @return current index in text.
181      * @stable ICU 2.4
182      */
183     public abstract int getIndex();
184 
185 
186     /**
187      * Returns the UTF16 code unit at index, and increments to the next
188      * code unit (post-increment semantics).  If index is out of
189      * range, DONE is returned, and the iterator is reset to the limit
190      * of the text.
191      * @return the next UTF16 code unit, or DONE if the index is at the limit
192      *         of the text.
193      * @stable ICU 2.4  
194      */
195     public abstract int next();
196 
197     /**
198      * Returns the code point at index, and increments to the next code
199      * point (post-increment semantics).  If index does not point to a
200      * valid surrogate pair, the behavior is the same as
201      * <code>next()<code>.  Otherwise the iterator is incremented past
202      * the surrogate pair, and the code point represented by the pair
203      * is returned.
204      * @return the next codepoint in text, or DONE if the index is at
205      *         the limit of the text.
206      * @stable ICU 2.4  
207      */
208     public int nextCodePoint(){
209         int ch1 = next();
210         if(UTF16.isLeadSurrogate((char)ch1)){
211             int ch2 = next();
212             if(UTF16.isTrailSurrogate((char)ch2)){
213                 return UCharacterProperty.getRawSupplementary((char)ch1,
214                                                               (char)ch2);
215             }else if (ch2 != DONE) {
216                 // unmatched surrogate so back out
217                 previous();
218             }
219         }
220         return ch1;
221     }
222 
223     /**
224      * Decrement to the position of the previous code unit in the
225      * text, and return it (pre-decrement semantics).  If the
226      * resulting index is less than 0, the index is reset to 0 and
227      * DONE is returned.
228      * @return the previous code unit in the text, or DONE if the new
229      *         index is before the start of the text.
230      * @stable ICU 2.4  
231      */
232     public abstract int previous();
233 
234     
235     /**
236      * Retreat to the start of the previous code point in the text,
237      * and return it (pre-decrement semantics).  If the index is not
238      * preceeded by a valid surrogate pair, the behavior is the same
239      * as <code>previous()</code>.  Otherwise the iterator is
240      * decremented to the start of the surrogate pair, and the code
241      * point represented by the pair is returned.
242      * @return the previous code point in the text, or DONE if the new
243      *         index is before the start of the text.
244      * @stable ICU 2.4  
245      */
246     public int previousCodePoint(){
247         int ch1 = previous();
248         if(UTF16.isTrailSurrogate((char)ch1)){
249             int ch2 = previous();
250             if(UTF16.isLeadSurrogate((char)ch2)){
251                 return UCharacterProperty.getRawSupplementary((char)ch2,
252                                                               (char)ch1);
253             }else if (ch2 != DONE) {
254                 //unmatched trail surrogate so back out
255                 next();
256             }   
257         }
258         return ch1;
259     }
260 
261     /**
262      * Sets the index to the specified index in the text.
263      * @param index the index within the text. 
264      * @exception IndexOutOfBoundsException is thrown if an invalid index is 
265      *            supplied
266      * @stable ICU 2.4
267      */
268     public abstract void setIndex(int index);
269 
270     /**
271      * Sets the current index to the limit.
272      * @stable ICU 2.4
273      */
274     public void setToLimit() {
275         setIndex(getLength());
276     }
277     
278     /**
279      * Sets the current index to the start.
280      * @stable ICU 2.4
281      */
282     public void setToStart() {
283         setIndex(0);
284     }
285 
286     /**
287      * Fills the buffer with the underlying text storage of the iterator
288      * If the buffer capacity is not enough a exception is thrown. The capacity
289      * of the fill in buffer should at least be equal to length of text in the 
290      * iterator obtained by calling <code>getLength()</code).
291      * <b>Usage:</b>
292      * 
293      * <code>
294      * <pre>
295      *         UChacterIterator iter = new UCharacterIterator.getInstance(text);
296      *         char[] buf = new char[iter.getLength()];
297      *         iter.getText(buf);
298      *         
299      *         OR
300      *         char[] buf= new char[1];
301      *         int len = 0;
302      *         for(;;){
303      *             try{
304      *                 len = iter.getText(buf);
305      *                 break;
306      *             }catch(IndexOutOfBoundsException e){
307      *                 buf = new char[iter.getLength()];
308      *             }
309      *         }
310      * </pre>
311      * </code>
312      *             
313      * @param fillIn an array of chars to fill with the underlying UTF-16 code 
314      *         units.
315      * @param offset the position within the array to start putting the data.
316      * @return the number of code units added to fillIn, as a convenience
317      * @exception IndexOutOfBounds exception if there is not enough
318      *            room after offset in the array, or if offset < 0.
319      * @stable ICU 2.4  
320      */
321     public abstract int getText(char[] fillIn, int offset); 
322 
323     /**
324      * Convenience override for <code>getText(char[], int)>/code> that provides
325      * an offset of 0.
326      * @param fillIn an array of chars to fill with the underlying UTF-16 code 
327      *         units.
328      * @return the number of code units added to fillIn, as a convenience
329      * @exception IndexOutOfBounds exception if there is not enough
330      *            room in the array.
331      * @stable ICU 2.4  
332      */
333     public final int getText(char[] fillIn) {
334         return getText(fillIn, 0);
335     }
336          
337     /**
338      * Convenience method for returning the underlying text storage as as string
339      * @return the underlying text storage in the iterator as a string
340      * @stable ICU 2.4
341      */
342     public String   getText() {
343         char[] text = new char[getLength()];
344         getText(text);
345         return new String  (text);
346     }
347        
348     /**
349      * Moves the current position by the number of code units
350      * specified, either forward or backward depending on the sign
351      * of delta (positive or negative respectively).  If the resulting
352      * index would be less than zero, the index is set to zero, and if
353      * the resulting index would be greater than limit, the index is
354      * set to limit.
355      *
356      * @param delta the number of code units to move the current
357      *              index.
358      * @return the new index.
359      * @exception IndexOutOfBoundsException is thrown if an invalid index is 
360      *            supplied 
361      * @stable ICU 2.4 
362      * 
363      */
364     public int moveIndex(int delta) {
365         int x = Math.max(0, Math.min(getIndex() + delta, getLength()));
366         setIndex(x);
367         return x;
368     }
369 
370     /**
371      * Moves the current position by the number of code points
372      * specified, either forward or backward depending on the sign of
373      * delta (positive or negative respectively). If the current index
374      * is at a trail surrogate then the first adjustment is by code
375      * unit, and the remaining adjustments are by code points.  If the
376      * resulting index would be less than zero, the index is set to
377      * zero, and if the resulting index would be greater than limit,
378      * the index is set to limit.
379      * @param delta the number of code units to move the current index.
380      * @return the new index  
381      * @exception IndexOutOfBoundsException is thrown if an invalid delta is 
382      *            supplied
383      * @stable ICU 2.4
384      */
385     public int moveCodePointIndex(int delta){
386         if(delta>0){
387             while(delta>0 && nextCodePoint() != DONE){delta--;}
388         }else{
389             while(delta<0 && previousCodePoint() != DONE){delta++;}
390         }
391         if(delta!=0){
392             throw new IndexOutOfBoundsException  ();
393         }
394           
395         return getIndex();
396     }
397 
398     /**
399      * Creates a copy of this iterator, independent from other iterators.
400      * If it is not possible to clone the iterator, returns null.
401      * @return copy of this iterator
402      * @stable ICU 2.4
403      */
404     public Object   clone() throws CloneNotSupportedException  {
405         return super.clone();
406     }   
407     
408 }
409 
410
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