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diff --git a/base/i18n/break_iterator.h b/base/i18n/break_iterator.h
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+++ b/base/i18n/break_iterator.h
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+// Copyright (c) 2010 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_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/string16.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_SPACE, and BREAK_NEWLINE,
+// 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.!. .").
+//
+// Under BREAK_SPACE mode, once a word is encountered, any non-word
+// characters are included in the returned string, breaking only when a
+// space-equivalent character is encountered (e.g. in the
+// UTF16-equivalent of the string " foo bar! ", the word breaks are at
+//   the periods in ". .foo .bar! .").
+//
+// Under BREAK_NEWLINE mode, all characters are included in the returned
+// string, breking 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.").
+//
+// 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 {
+
+class BreakIterator {
+ public:
+  enum BreakType {
+    BREAK_WORD,
+    BREAK_SPACE,
+    BREAK_NEWLINE,
+  };
+
+  // Requires |str| to live as long as the BreakIterator does.
+  BreakIterator(const string16* str, BreakType break_type);
+  ~BreakIterator();
+
+  // Init() must be called before any of the iterators are valid.
+  // Returns false if ICU failed to initialize.
+  bool Init();
+
+  // Return the current break position within the string,
+  // or BreakIterator::npos when done.
+  size_t pos() const { return pos_; }
+
+  // Return the value of pos() returned before Advance() was last called.
+  size_t prev() const { return prev_; }
+
+  // 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();
+
+  // 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_SPACE and BREAK_NEWLINE modes,
+  // this distinction doesn't apply and it always retuns false.
+  bool IsWord() const;
+
+  // Return 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;
+
+ 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.
+  const string16* string_;
+
+  // The breaking style (word/space/newline).
+  BreakType break_type_;
+
+  // Previous and current iterator positions.
+  size_t prev_, pos_;
+
+  DISALLOW_COPY_AND_ASSIGN(BreakIterator);
+};
+
+}  // namespace base
+
+#endif  // BASE_I18N_BREAK_ITERATOR_H__