updater/include/updater/rangeset.h

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once

#include <stddef.h>

#include <string>
#include <utility>
#include <vector>

#include <android-base/logging.h>
#include <android-base/parseint.h>
#include <android-base/strings.h>

using Range = std::pair<size_t, size_t>;

class RangeSet {
 public:
  RangeSet() : blocks_(0) {}

  explicit RangeSet(std::vector<Range>&& pairs) {
    CHECK_NE(pairs.size(), static_cast<size_t>(0)) << "Invalid number of tokens";

    // Sanity check the input.
    size_t result = 0;
    for (const auto& range : pairs) {
      CHECK_LT(range.first, range.second)
          << "Empty or negative range: " << range.first << ", " << range.second;
      size_t sz = range.second - range.first;
      CHECK_LE(result, SIZE_MAX - sz) << "RangeSet size overflow";
      result += sz;
    }

    ranges_ = pairs;
    blocks_ = result;
  }

  static RangeSet Parse(const std::string& range_text) {
    std::vector<std::string> pieces = android::base::Split(range_text, ",");
    CHECK_GE(pieces.size(), static_cast<size_t>(3)) << "Invalid range text: " << range_text;

    size_t num;
    CHECK(android::base::ParseUint(pieces[0], &num, static_cast<size_t>(INT_MAX)))
        << "Failed to parse the number of tokens: " << range_text;

    CHECK_NE(num, static_cast<size_t>(0)) << "Invalid number of tokens: " << range_text;
    CHECK_EQ(num % 2, static_cast<size_t>(0)) << "Number of tokens must be even: " << range_text;
    CHECK_EQ(num, pieces.size() - 1) << "Mismatching number of tokens: " << range_text;

    std::vector<Range> pairs;
    for (size_t i = 0; i < num; i += 2) {
      size_t first;
      CHECK(android::base::ParseUint(pieces[i + 1], &first, static_cast<size_t>(INT_MAX)));
      size_t second;
      CHECK(android::base::ParseUint(pieces[i + 2], &second, static_cast<size_t>(INT_MAX)));

      pairs.emplace_back(first, second);
    }

    return RangeSet(std::move(pairs));
  }

  // Get the block number for the i-th (starting from 0) block in the RangeSet.
  size_t GetBlockNumber(size_t idx) const {
    CHECK_LT(idx, blocks_) << "Out of bound index " << idx << " (total blocks: " << blocks_ << ")";

    for (const auto& range : ranges_) {
      if (idx < range.second - range.first) {
        return range.first + idx;
      }
      idx -= (range.second - range.first);
    }

    CHECK(false) << "Failed to find block number for index " << idx;
    return 0;  // Unreachable, but to make compiler happy.
  }

  // RangeSet has half-closed half-open bounds. For example, "3,5" contains blocks 3 and 4. So "3,5"
  // and "5,7" are not overlapped.
  bool Overlaps(const RangeSet& other) const {
    for (const auto& range : ranges_) {
      size_t start = range.first;
      size_t end = range.second;
      for (const auto& other_range : other.ranges_) {
        size_t other_start = other_range.first;
        size_t other_end = other_range.second;
        // [start, end) vs [other_start, other_end)
        if (!(other_start >= end || start >= other_end)) {
          return true;
        }
      }
    }
    return false;
  }

  // size() gives the number of Range's in this RangeSet.
  size_t size() const {
    return ranges_.size();
  }

  // blocks() gives the number of all blocks in this RangeSet.
  size_t blocks() const {
    return blocks_;
  }

  // We provide const iterators only.
  std::vector<Range>::const_iterator cbegin() const {
    return ranges_.cbegin();
  }

  std::vector<Range>::const_iterator cend() const {
    return ranges_.cend();
  }

  // Need to provide begin()/end() since range-based loop expects begin()/end().
  std::vector<Range>::const_iterator begin() const {
    return ranges_.cbegin();
  }

  std::vector<Range>::const_iterator end() const {
    return ranges_.cend();
  }

  // Reverse const iterators for MoveRange().
  std::vector<Range>::const_reverse_iterator crbegin() const {
    return ranges_.crbegin();
  }

  std::vector<Range>::const_reverse_iterator crend() const {
    return ranges_.crend();
  }

  const Range& operator[](size_t i) const {
    return ranges_[i];
  }

  bool operator==(const RangeSet& other) const {
    // The orders of Range's matter. "4,1,5,8,10" != "4,8,10,1,5".
    return (ranges_ == other.ranges_);
  }

  bool operator!=(const RangeSet& other) const {
    return ranges_ != other.ranges_;
  }

 private:
  // Actual limit for each value and the total number are both INT_MAX.
  std::vector<Range> ranges_;
  size_t blocks_;
};