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// Copyright (c) 2006-2008 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 CHROME_BROWSER_HISTORY_SNIPPET_H__
#define CHROME_BROWSER_HISTORY_SNIPPET_H__
#include <vector>
#include "base/string16.h"
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 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 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) {
text_.swap(other->text_);
matches_.swap(other->matches_);
}
private:
// The text of the snippet.
string16 text_;
// The matches within text_.
MatchPositions matches_;
};
#endif // CHROME_BROWSER_HISTORY_SNIPPET_H__
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