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- // Copyright 2014 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.
- // This module computes snippets of queries based on hits in the documents
- // for display in history search results.
- #ifndef COMPONENTS_QUERY_PARSER_SNIPPET_H__
- #define COMPONENTS_QUERY_PARSER_SNIPPET_H__
- #include <stddef.h>
- #include <string>
- #include <vector>
- namespace query_parser {
- class Snippet {
- public:
- // Each MatchPosition is the [begin, end) positions of a match within a
- // string.
- typedef std::pair<size_t, size_t> MatchPosition;
- typedef std::vector<MatchPosition> 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 UTF-16, 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 UTF-16 2-byte code unit.
- static void ConvertMatchPositionsToWide(
- const std::string& utf8_string,
- Snippet::MatchPositions* match_positions);
- Snippet();
- Snippet(const Snippet& other);
- Snippet(Snippet&& other) noexcept;
- ~Snippet();
- Snippet& operator=(const Snippet&);
- // 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::u16string& text() const { return text_; }
- const MatchPositions& matches() const { return matches_; }
- // Efficiently swaps the contents of this snippet with the other.
- void Swap(Snippet* other);
- private:
- // The text of the snippet.
- std::u16string text_;
- // The matches within text_.
- MatchPositions matches_;
- };
- } // namespace query_parser
- #endif // COMPONENTS_QUERY_PARSER_SNIPPET_H__
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