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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.
#include <stddef.h>
#include <vector>
#include "base/strings/string16.h"
namespace query_parser {
class Snippet {
// 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(const Snippet& other);
Snippet(Snippet&& other) noexcept;
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 base::string16& text() const { return text_; }
const MatchPositions& matches() const { return matches_; }
// Efficiently swaps the contents of this snippet with the other.
void Swap(Snippet* other);
// The text of the snippet.
base::string16 text_;
// The matches within text_.
MatchPositions matches_;
} // namespace query_parser