1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef BASE_I18N_BREAK_ITERATOR_H_ 6 #define BASE_I18N_BREAK_ITERATOR_H_ 7 #pragma once 8 9 #include "base/basictypes.h" 10 #include "base/string16.h" 11 12 // The BreakIterator class iterates through the words, word breaks, and 13 // line breaks in a UTF-16 string. 14 // 15 // It provides several modes, BREAK_WORD, BREAK_LINE, and BREAK_NEWLINE, 16 // which modify how characters are aggregated into the returned string. 17 // 18 // Under BREAK_WORD mode, once a word is encountered any non-word 19 // characters are not included in the returned string (e.g. in the 20 // UTF-16 equivalent of the string " foo bar! ", the word breaks are at 21 // the periods in ". .foo. .bar.!. ."). 22 // Note that Chinese/Japanese/Thai do not use spaces between words so that 23 // boundaries can fall in the middle of a continuous run of non-space / 24 // non-punctuation characters. 25 // 26 // Under BREAK_LINE mode, once a line breaking opportunity is encountered, 27 // any non-word characters are included in the returned string, breaking 28 // only when a space-equivalent character or a line breaking opportunity 29 // is encountered (e.g. in the UTF16-equivalent of the string " foo bar! ", 30 // the breaks are at the periods in ". .foo .bar! ."). 31 // 32 // Note that lines can be broken at any character/syllable/grapheme cluster 33 // boundary in Chinese/Japanese/Korean and at word boundaries in Thai 34 // (Thai does not use spaces between words). Therefore, this is NOT the same 35 // as breaking only at space-equivalent characters where its former 36 // name (BREAK_SPACE) implied. 37 // 38 // Under BREAK_NEWLINE mode, all characters are included in the returned 39 // string, breking only when a newline-equivalent character is encountered 40 // (eg. in the UTF-16 equivalent of the string "foo\nbar!\n\n", the line 41 // breaks are at the periods in ".foo\n.bar\n.\n."). 42 // 43 // To extract the words from a string, move a BREAK_WORD BreakIterator 44 // through the string and test whether IsWord() is true. E.g., 45 // BreakIterator iter(&str, BreakIterator::BREAK_WORD); 46 // if (!iter.Init()) return false; 47 // while (iter.Advance()) { 48 // if (iter.IsWord()) { 49 // // region [iter.prev(),iter.pos()) contains a word. 50 // VLOG(1) << "word: " << iter.GetString(); 51 // } 52 // } 53 54 namespace base { 55 56 class BreakIterator { 57 public: 58 enum BreakType { 59 BREAK_WORD, 60 BREAK_LINE, 61 // TODO(jshin): Remove this after reviewing call sites. 62 // If call sites really need break only on space-like characters 63 // implement it separately. 64 BREAK_SPACE = BREAK_LINE, 65 BREAK_NEWLINE, 66 }; 67 68 // Requires |str| to live as long as the BreakIterator does. 69 BreakIterator(const string16* str, BreakType break_type); 70 ~BreakIterator(); 71 72 // Init() must be called before any of the iterators are valid. 73 // Returns false if ICU failed to initialize. 74 bool Init(); 75 76 // Return the current break position within the string, 77 // or BreakIterator::npos when done. 78 size_t pos() const { return pos_; } 79 80 // Return the value of pos() returned before Advance() was last called. 81 size_t prev() const { return prev_; } 82 83 // Advance to the next break. Returns false if we've run past the end of 84 // the string. (Note that the very last "break" is after the final 85 // character in the string, and when we advance to that position it's the 86 // last time Advance() returns true.) 87 bool Advance(); 88 89 // Under BREAK_WORD mode, returns true if the break we just hit is the 90 // end of a word. (Otherwise, the break iterator just skipped over e.g. 91 // whitespace or punctuation.) Under BREAK_LINE and BREAK_NEWLINE modes, 92 // this distinction doesn't apply and it always retuns false. 93 bool IsWord() const; 94 95 // Return the string between prev() and pos(). 96 // Advance() must have been called successfully at least once 97 // for pos() to have advanced to somewhere useful. 98 string16 GetString() const; 99 100 private: 101 // ICU iterator, avoiding ICU ubrk.h dependence. 102 // This is actually an ICU UBreakiterator* type, which turns out to be 103 // a typedef for a void* in the ICU headers. Using void* directly prevents 104 // callers from needing access to the ICU public headers directory. 105 void* iter_; 106 107 // The string we're iterating over. 108 const string16* string_; 109 110 // The breaking style (word/space/newline). 111 BreakType break_type_; 112 113 // Previous and current iterator positions. 114 size_t prev_, pos_; 115 116 DISALLOW_COPY_AND_ASSIGN(BreakIterator); 117 }; 118 119 } // namespace base 120 121 #endif // BASE_I18N_BREAK_ITERATOR_H__ 122
