chunk_range.cc revision 731df977c0511bca2206b5f333555b1205ff1f43 
1// Copyright (c) 2010 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// Implementation of ChunkRange class.
6
7#include "chrome/browser/safe_browsing/chunk_range.h"
8
9#include "base/logging.h"
10#include "base/string_number_conversions.h"
11#include "base/string_split.h"
12#include "base/string_util.h"
13
14ChunkRange::ChunkRange(int start) : start_(start), stop_(start) {
15}
16
17ChunkRange::ChunkRange(int start, int stop) : start_(start), stop_(stop) {
18}
19
20ChunkRange::ChunkRange(const ChunkRange& rhs)
21    : start_(rhs.start()), stop_(rhs.stop()) {
22}
23
24// Helper functions -----------------------------------------------------------
25
26// Traverse the chunks vector looking for contiguous integers.
27void ChunksToRanges(const std::vector<int>& chunks,
28                    std::vector<ChunkRange>* ranges) {
29  DCHECK(ranges);
30  for (size_t i = 0; i < chunks.size(); ++i) {
31    int start = static_cast<int>(i);
32    int next = start + 1;
33    while (next < static_cast<int>(chunks.size()) &&
34           (chunks[start] == chunks[next] - 1 ||
35            chunks[start] == chunks[next])) {
36      ++start;
37      ++next;
38    }
39    ranges->push_back(ChunkRange(chunks[i], chunks[start]));
40    if (next >= static_cast<int>(chunks.size()))
41      break;
42    i = start;
43  }
44}
45
46void RangesToChunks(const std::vector<ChunkRange>& ranges,
47                    std::vector<int>* chunks) {
48  DCHECK(chunks);
49  for (size_t i = 0; i < ranges.size(); ++i) {
50    const ChunkRange& range = ranges[i];
51    for (int chunk = range.start(); chunk <= range.stop(); ++chunk) {
52      chunks->push_back(chunk);
53    }
54  }
55}
56
57void RangesToString(const std::vector<ChunkRange>& ranges,
58                    std::string* result) {
59  DCHECK(result);
60  result->clear();
61  std::vector<ChunkRange>::const_iterator it = ranges.begin();
62  for (; it != ranges.end(); ++it) {
63    if (!result->empty())
64      result->append(",");
65    if (it->start() == it->stop()) {
66      std::string num_buf = base::IntToString(it->start());
67      result->append(num_buf);
68    } else {
69      result->append(StringPrintf("%d-%d", it->start(), it->stop()));
70    }
71  }
72}
73
74bool StringToRanges(const std::string& input,
75                    std::vector<ChunkRange>* ranges) {
76  DCHECK(ranges);
77
78  // Crack the string into chunk parts, then crack each part looking for a
79  // range.
80  std::vector<std::string> chunk_parts;
81  base::SplitString(input, ',', &chunk_parts);
82
83  for (size_t i = 0; i < chunk_parts.size(); ++i) {
84    std::vector<std::string> chunk_ranges;
85    base::SplitString(chunk_parts[i], '-', &chunk_ranges);
86    int start = atoi(chunk_ranges[0].c_str());
87    int stop = start;
88    if (chunk_ranges.size() == 2)
89      stop = atoi(chunk_ranges[1].c_str());
90    if (start == 0 || stop == 0) {
91      // atoi error, since chunk numbers are guaranteed to never be 0.
92      ranges->clear();
93      return false;
94    }
95    ranges->push_back(ChunkRange(start, stop));
96  }
97
98  return true;
99}
100
101// Binary search over a series of ChunkRanges.
102bool IsChunkInRange(int chunk_number, const std::vector<ChunkRange>& ranges) {
103  if (ranges.empty())
104    return false;
105
106  int low = 0;
107  int high = ranges.size() - 1;
108
109  while (low <= high) {
110    // http://googleresearch.blogspot.com/2006/06/extra-extra-read-all-about-it-nearly.html
111    int mid = ((unsigned int)low + (unsigned int)high) >> 1;
112    const ChunkRange& chunk = ranges[mid];
113    if ((chunk.stop() >= chunk_number) && (chunk.start() <= chunk_number))
114      return true;  // chunk_number is in range.
115
116    // Adjust our mid point.
117    if (chunk.stop() < chunk_number)
118      low = mid + 1;
119    else
120      high = mid - 1;
121  }
122
123  return false;
124}
125