/*
* 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>
using Range = std::pair<size_t, size_t>;
class RangeSet {
public:
RangeSet() : blocks_(0) {}
explicit RangeSet(std::vector<Range>&& pairs);
// Parses the given string into a RangeSet. Returns the parsed RangeSet, or an empty RangeSet on
// errors.
static RangeSet Parse(const std::string& range_text);
// Appends the given Range to the current RangeSet.
bool PushBack(Range range);
// Clears all the ranges from the RangeSet.
void Clear();
std::string ToString() const;
// Gets the block number for the i-th (starting from 0) block in the RangeSet.
size_t GetBlockNumber(size_t idx) const;
// Returns whether the current RangeSet overlaps with other. 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;
// Returns the number of Range's in this RangeSet.
size_t size() const {
return ranges_.size();
}
// Returns the total number of blocks in this RangeSet.
size_t blocks() const {
return blocks_;
}
std::vector<Range>::const_iterator cbegin() const {
return ranges_.cbegin();
}
std::vector<Range>::const_iterator cend() const {
return ranges_.cend();
}
std::vector<Range>::iterator begin() {
return ranges_.begin();
}
std::vector<Range>::iterator end() {
return ranges_.end();
}
std::vector<Range>::const_iterator begin() const {
return ranges_.begin();
}
std::vector<Range>::const_iterator end() const {
return ranges_.end();
}
// 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();
}
// Returns whether the RangeSet is valid (i.e. non-empty).
explicit operator bool() const {
return !ranges_.empty();
}
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_;
}
protected:
// Actual limit for each value and the total number are both INT_MAX.
std::vector<Range> ranges_;
size_t blocks_;
};
// The class is a sorted version of a RangeSet; and it's useful in imgdiff to split the input
// files when we're handling large zip files. Specifically, we can treat the input file as a
// continuous RangeSet (i.e. RangeSet("0-99") for a 100 blocks file); and break it down into
// several smaller chunks based on the zip entries.
// For example, [source: 0-99] can be split into
// [split_src1: 10-29]; [split_src2: 40-49, 60-69]; [split_src3: 70-89]
// Here "10-29" simply means block 10th to block 29th with respect to the original input file.
// Also, note that the split sources should be mutual exclusive, but they don't need to cover
// every block in the original source.
class SortedRangeSet : public RangeSet {
public:
// The block size when working with offset and file length.
static constexpr size_t kBlockSize = 4096;
SortedRangeSet() {}
// Ranges in the the set should be mutually exclusive; and they're sorted by the start block.
explicit SortedRangeSet(std::vector<Range>&& pairs);
void Insert(const Range& to_insert);
// Insert the input SortedRangeSet; keep the ranges sorted and merge the overlap ranges.
void Insert(const SortedRangeSet& rs);
// Compute the block range the file occupies, and insert that range.
void Insert(size_t start, size_t len);
using RangeSet::Overlaps;
bool Overlaps(size_t start, size_t len) const;
// Given an offset of the file, checks if the corresponding block (by considering the file as
// 0-based continuous block ranges) is covered by the SortedRangeSet. If so, returns the offset
// within this SortedRangeSet.
//
// For example, the 4106-th byte of a file is from block 1, assuming a block size of 4096-byte.
// The mapped offset within a SortedRangeSet("1-9 15-19") is 10.
//
// An offset of 65546 falls into the 16-th block in a file. Block 16 is contained as the 10-th
// item in SortedRangeSet("1-9 15-19"). So its data can be found at offset 40970 (i.e. 4096 * 10
// + 10) in a range represented by this SortedRangeSet.
size_t GetOffsetInRangeSet(size_t old_offset) const;
};
