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TMessagesProj/jni/voip/webrtc/base/i18n/break_iterator.h

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+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_I18N_BREAK_ITERATOR_H_
+#define BASE_I18N_BREAK_ITERATOR_H_
+
+#include <stddef.h>
+
+#include "base/i18n/base_i18n_export.h"
+#include "base/macros.h"
+#include "base/strings/string16.h"
+#include "base/strings/string_piece.h"
+
+// The BreakIterator class iterates through the words, word breaks, and
+// line breaks in a UTF-16 string.
+//
+// It provides several modes, BREAK_WORD, BREAK_LINE, BREAK_NEWLINE, and
+// BREAK_SENTENCE which modify how characters are aggregated into the returned
+// string.
+//
+// Under BREAK_WORD mode, once a word is encountered any non-word
+// characters are not included in the returned string (e.g. in the
+// UTF-16 equivalent of the string " foo bar! ", the word breaks are at
+// the periods in ". .foo. .bar.!. .").
+// Note that Chinese/Japanese/Thai do not use spaces between words so that
+// boundaries can fall in the middle of a continuous run of non-space /
+// non-punctuation characters.
+//
+// Under BREAK_LINE mode, once a line breaking opportunity is encountered,
+// any non-word  characters are included in the returned string, breaking
+// only when a space-equivalent character or a line breaking opportunity
+// is encountered (e.g. in the UTF16-equivalent of the string " foo bar! ",
+// the breaks are at the periods in ". .foo .bar! .").
+//
+// Note that lines can be broken at any character/syllable/grapheme cluster
+// boundary in Chinese/Japanese/Korean and at word boundaries in Thai
+// (Thai does not use spaces between words). Therefore, this is NOT the same
+// as breaking only at space-equivalent characters where its former
+// name (BREAK_SPACE) implied.
+//
+// Under BREAK_NEWLINE mode, all characters are included in the returned
+// string, breaking only when a newline-equivalent character is encountered
+// (eg. in the UTF-16 equivalent of the string "foo\nbar!\n\n", the line
+// breaks are at the periods in ".foo\n.bar\n.\n.").
+//
+// Under BREAK_SENTENCE mode, all characters are included in the returned
+// string, breaking only on sentence boundaries defined in "Unicode Standard
+// Annex #29: Text Segmentation." Whitespace immediately following the sentence
+// is also included. For example, in the UTF-16 equivalent of the string
+// "foo bar! baz qux?" the breaks are at the periods in ".foo bar! .baz quz?."
+//
+// To extract the words from a string, move a BREAK_WORD BreakIterator
+// through the string and test whether IsWord() is true. E.g.,
+//   BreakIterator iter(str, BreakIterator::BREAK_WORD);
+//   if (!iter.Init())
+//     return false;
+//   while (iter.Advance()) {
+//     if (iter.IsWord()) {
+//       // Region [iter.prev(), iter.pos()) contains a word.
+//       VLOG(1) << "word: " << iter.GetString();
+//     }
+//   }
+
+namespace base {
+namespace i18n {
+
+class BASE_I18N_EXPORT BreakIterator {
+ public:
+  enum BreakType {
+    BREAK_WORD,
+    BREAK_LINE,
+    // TODO(jshin): Remove this after reviewing call sites.
+    // If call sites really need break only on space-like characters
+    // implement it separately.
+    BREAK_SPACE = BREAK_LINE,
+    BREAK_NEWLINE,
+    BREAK_CHARACTER,
+    // But don't remove this one!
+    RULE_BASED,
+    BREAK_SENTENCE,
+  };
+
+  enum WordBreakStatus {
+    // The end of text that the iterator recognizes as word characters.
+    // Non-word characters are things like punctuation and spaces.
+    IS_WORD_BREAK,
+    // Characters that the iterator can skip past, such as punctuation,
+    // whitespace, and, if using RULE_BASED mode, characters from another
+    // character set.
+    IS_SKIPPABLE_WORD,
+    // Only used if not in BREAK_WORD or RULE_BASED mode. This is returned for
+    // newlines, line breaks, and character breaks.
+    IS_LINE_OR_CHAR_BREAK
+  };
+
+  // Requires |str| to live as long as the BreakIterator does.
+  BreakIterator(const StringPiece16& str, BreakType break_type);
+  // Make a rule-based iterator. BreakType == RULE_BASED is implied.
+  // TODO(andrewhayden): This signature could easily be misinterpreted as
+  // "(const string16& str, const string16& locale)". We should do something
+  // better.
+  BreakIterator(const StringPiece16& str, const string16& rules);
+  ~BreakIterator();
+
+  // Init() must be called before any of the iterators are valid.
+  // Returns false if ICU failed to initialize.
+  bool Init();
+
+  // Advance to the next break.  Returns false if we've run past the end of
+  // the string.  (Note that the very last "break" is after the final
+  // character in the string, and when we advance to that position it's the
+  // last time Advance() returns true.)
+  bool Advance();
+
+  // Updates the text used by the iterator, resetting the iterator as if
+  // if Init() had been called again. Any old state is lost. Returns true
+  // unless there is an error setting the text.
+  bool SetText(const base::char16* text, const size_t length);
+
+  // Under BREAK_WORD mode, returns true if the break we just hit is the
+  // end of a word. (Otherwise, the break iterator just skipped over e.g.
+  // whitespace or punctuation.)  Under BREAK_LINE and BREAK_NEWLINE modes,
+  // this distinction doesn't apply and it always returns false.
+  bool IsWord() const;
+
+  // Under BREAK_WORD mode:
+  //  - Returns IS_SKIPPABLE_WORD if non-word characters, such as punctuation or
+  //    spaces, are found.
+  //  - Returns IS_WORD_BREAK if the break we just hit is the end of a sequence
+  //    of word characters.
+  // Under RULE_BASED mode:
+  //  - Returns IS_SKIPPABLE_WORD if characters outside the rules' character set
+  //    or non-word characters, such as punctuation or spaces, are found.
+  //  - Returns IS_WORD_BREAK if the break we just hit is the end of a sequence
+  //    of word characters that are in the rules' character set.
+  // Not under BREAK_WORD or RULE_BASED mode:
+  //  - Returns IS_LINE_OR_CHAR_BREAK.
+  BreakIterator::WordBreakStatus GetWordBreakStatus() const;
+
+  // Under BREAK_WORD mode, returns true if |position| is at the end of word or
+  // at the start of word. It always returns false under modes that are not
+  // BREAK_WORD or RULE_BASED.
+  bool IsEndOfWord(size_t position) const;
+  bool IsStartOfWord(size_t position) const;
+
+  // Under BREAK_SENTENCE mode, returns true if |position| is at a sentence
+  // boundary. It always returns false under modes that are not BREAK_SENTENCE
+  // or RULE_BASED.
+  bool IsSentenceBoundary(size_t position) const;
+
+  // Under BREAK_CHARACTER mode, returns whether |position| is a Unicode
+  // grapheme boundary.
+  bool IsGraphemeBoundary(size_t position) const;
+
+  // Returns the string between prev() and pos().
+  // Advance() must have been called successfully at least once for pos() to
+  // have advanced to somewhere useful.
+  string16 GetString() const;
+
+  StringPiece16 GetStringPiece() const;
+
+  // Returns the value of pos() returned before Advance() was last called.
+  size_t prev() const { return prev_; }
+
+  // Returns the current break position within the string,
+  // or BreakIterator::npos when done.
+  size_t pos() const { return pos_; }
+
+ private:
+  // ICU iterator, avoiding ICU ubrk.h dependence.
+  // This is actually an ICU UBreakiterator* type, which turns out to be
+  // a typedef for a void* in the ICU headers. Using void* directly prevents
+  // callers from needing access to the ICU public headers directory.
+  void* iter_;
+
+  // The string we're iterating over. Can be changed with SetText(...)
+  StringPiece16 string_;
+
+  // Rules for our iterator. Mutually exclusive with break_type_.
+  const string16 rules_;
+
+  // The breaking style (word/space/newline). Mutually exclusive with rules_
+  BreakType break_type_;
+
+  // Previous and current iterator positions.
+  size_t prev_, pos_;
+
+  DISALLOW_COPY_AND_ASSIGN(BreakIterator);
+};
+
+}  // namespace i18n
+}  // namespace base
+
+#endif  // BASE_I18N_BREAK_ITERATOR_H_