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+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// This module computes snippets of queries based on hits in the documents
+// for display in history search results.
+
+#ifndef CHROME_BROWSER_HISTORY_SNIPPET_H__
+#define CHROME_BROWSER_HISTORY_SNIPPET_H__
+
+#include <vector>
+
+class Snippet {
+ public:
+  // Each pair in MatchPositions is the [begin, end) positions of a match
+  // within a string.
+  typedef std::vector<std::pair<int, int> > MatchPositions;
+
+  // Parses an offsets string as returned from a sqlite full text index. An
+  // offsets string encodes information about why a row matched a text query.
+  // The information is encoded in the string as a set of matches, where each
+  // match consists of the column, term-number, location, and length of the
+  // match. Each element of the match is separated by a space, as is each match
+  // from other matches.
+  //
+  // This method adds the start and end of each match whose column is
+  // column_num to match_positions. The pairs are ordered based on first,
+  // with no overlapping elements.
+  //
+  // NOTE: the positions returned are in terms of UTF8 encoding. To convert the
+  // offsets to wide, use ConvertMatchPositionsToWide.
+  static void ExtractMatchPositions(const std::string& offsets_str,
+                                    const std::string& column_num,
+                                    MatchPositions* match_positions);
+
+  // Converts match positions as returned from ExtractMatchPositions to be in
+  // terms of a wide string.
+  static void ConvertMatchPositionsToWide(
+      const std::string& utf8_string,
+      Snippet::MatchPositions* match_positions);
+
+  // Given |matches|, the match positions within |document|, compute the snippet
+  // for the document.
+  // Note that |document| is UTF-8 and the offsets in |matches| are byte
+  // offsets.
+  void ComputeSnippet(const MatchPositions& matches,
+                      const std::string& document);
+
+  const std::wstring& text() const { return text_; }
+  const MatchPositions& matches() const { return matches_; }
+
+  // Efficiently swaps the contents of this snippet with the other.
+  void Swap(Snippet* other) {
+    text_.swap(other->text_);
+    matches_.swap(other->matches_);
+  }
+
+ private:
+  // The text of the snippet.
+  std::wstring text_;
+
+  // The matches within text_.
+  MatchPositions matches_;
+};
+
+#endif  // CHROME_BROWSER_HISTORY_SNIPPET_H__