1 // Copyright 2014 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 // This module computes snippets of queries based on hits in the documents 6 // for display in history search results. 7 8 #ifndef COMPONENTS_QUERY_PARSER_SNIPPET_H__ 9 #define COMPONENTS_QUERY_PARSER_SNIPPET_H__ 10 11 #include <vector> 12 13 #include "base/strings/string16.h" 14 15 namespace query_parser { 16 17 class Snippet { 18 public: 19 // Each MatchPosition is the [begin, end) positions of a match within a 20 // string. 21 typedef std::pair<size_t, size_t> MatchPosition; 22 typedef std::vector<MatchPosition> MatchPositions; 23 24 // Parses an offsets string as returned from a sqlite full text index. An 25 // offsets string encodes information about why a row matched a text query. 26 // The information is encoded in the string as a set of matches, where each 27 // match consists of the column, term-number, location, and length of the 28 // match. Each element of the match is separated by a space, as is each match 29 // from other matches. 30 // 31 // This method adds the start and end of each match whose column is 32 // column_num to match_positions. The pairs are ordered based on first, 33 // with no overlapping elements. 34 // 35 // NOTE: the positions returned are in terms of UTF8 encoding. To convert the 36 // offsets to wide, use ConvertMatchPositionsToWide. 37 static void ExtractMatchPositions(const std::string& offsets_str, 38 const std::string& column_num, 39 MatchPositions* match_positions); 40 41 // Converts match positions as returned from ExtractMatchPositions to be in 42 // terms of a wide string. 43 static void ConvertMatchPositionsToWide( 44 const std::string& utf8_string, 45 Snippet::MatchPositions* match_positions); 46 47 Snippet(); 48 ~Snippet(); 49 50 // Given |matches|, the match positions within |document|, compute the snippet 51 // for the document. 52 // Note that |document| is UTF-8 and the offsets in |matches| are byte 53 // offsets. 54 void ComputeSnippet(const MatchPositions& matches, 55 const std::string& document); 56 57 const base::string16& text() const { return text_; } 58 const MatchPositions& matches() const { return matches_; } 59 60 // Efficiently swaps the contents of this snippet with the other. 61 void Swap(Snippet* other); 62 63 private: 64 // The text of the snippet. 65 base::string16 text_; 66 67 // The matches within text_. 68 MatchPositions matches_; 69 }; 70 71 } // namespace query_parser 72 73 #endif // COMPONENTS_QUERY_PARSER_SNIPPET_H__ 74
