Index: net/quic/interval_set.h |
diff --git a/net/quic/interval_set.h b/net/quic/interval_set.h |
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-// Copyright 2015 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. |
-// |
-// IntervalSet<T> is a data structure used to represent a sorted set of |
-// non-empty, non-adjacent, and mutually disjoint intervals. Mutations to an |
-// interval set preserve these properties, altering the set as needed. For |
-// example, adding [2, 3) to a set containing only [1, 2) would result in the |
-// set containing the single interval [1, 3). |
-// |
-// Supported operations include testing whether an Interval is contained in the |
-// IntervalSet, comparing two IntervalSets, and performing IntervalSet union, |
-// intersection, and difference. |
-// |
-// IntervalSet maintains the minimum number of entries needed to represent the |
-// set of underlying intervals. When the IntervalSet is modified (e.g. due to an |
-// Add operation), other interval entries may be coalesced, removed, or |
-// otherwise modified in order to maintain this invariant. The intervals are |
-// maintained in sorted order, by ascending min() value. |
-// |
-// The reader is cautioned to beware of the terminology used here: this library |
-// uses the terms "min" and "max" rather than "begin" and "end" as is |
-// conventional for the STL. The terminology [min, max) refers to the half-open |
-// interval which (if the interval is not empty) contains min but does not |
-// contain max. An interval is considered empty if min >= max. |
-// |
-// T is required to be default- and copy-constructible, to have an assignment |
-// operator, a difference operator (operator-()), and the full complement of |
-// comparison operators (<, <=, ==, !=, >=, >). These requirements are inherited |
-// from Interval<T>. |
-// |
-// IntervalSet has constant-time move operations. |
-// |
-// This class is thread-compatible if T is thread-compatible. (See |
-// go/thread-compatible). |
-// |
-// Examples: |
-// IntervalSet<int> intervals; |
-// intervals.Add(Interval<int>(10, 20)); |
-// intervals.Add(Interval<int>(30, 40)); |
-// // intervals contains [10,20) and [30,40). |
-// intervals.Add(Interval<int>(15, 35)); |
-// // intervals has been coalesced. It now contains the single range [10,40). |
-// EXPECT_EQ(1, intervals.Size()); |
-// EXPECT_TRUE(intervals.Contains(Interval<int>(10, 40))); |
-// |
-// intervals.Difference(Interval<int>(10, 20)); |
-// // intervals should now contain the single range [20, 40). |
-// EXPECT_EQ(1, intervals.Size()); |
-// EXPECT_TRUE(intervals.Contains(Interval<int>(20, 40))); |
- |
-#ifndef NET_QUIC_INTERVAL_SET_H_ |
-#define NET_QUIC_INTERVAL_SET_H_ |
- |
-#include <stddef.h> |
- |
-#include <algorithm> |
-#include <set> |
-#include <string> |
-#include <utility> |
-#include <vector> |
- |
-#include "base/logging.h" |
-#include "net/quic/interval.h" |
- |
-namespace net { |
- |
-template <typename T> |
-class IntervalSet { |
- private: |
- struct IntervalComparator { |
- bool operator()(const Interval<T>& a, const Interval<T>& b) const; |
- }; |
- typedef std::set<Interval<T>, IntervalComparator> Set; |
- |
- public: |
- typedef typename Set::value_type value_type; |
- typedef typename Set::const_iterator const_iterator; |
- typedef typename Set::const_reverse_iterator const_reverse_iterator; |
- |
- // Instantiates an empty IntervalSet. |
- IntervalSet() {} |
- |
- // Instantiates an IntervalSet containing exactly one initial half-open |
- // interval [min, max), unless the given interval is empty, in which case the |
- // IntervalSet will be empty. |
- explicit IntervalSet(const Interval<T>& interval) { Add(interval); } |
- |
- // Instantiates an IntervalSet containing the half-open interval [min, max). |
- IntervalSet(const T& min, const T& max) { Add(min, max); } |
- |
-// TODO(rtenneti): Implement after suupport for std::initializer_list. |
-#if 0 |
- IntervalSet(std::initializer_list<value_type> il) { assign(il); } |
-#endif |
- |
- // Clears this IntervalSet. |
- void Clear() { intervals_.clear(); } |
- |
- // Returns the number of disjoint intervals contained in this IntervalSet. |
- size_t Size() const { return intervals_.size(); } |
- |
- // Returns the smallest interval that contains all intervals in this |
- // IntervalSet, or the empty interval if the set is empty. |
- Interval<T> SpanningInterval() const; |
- |
- // Adds "interval" to this IntervalSet. Adding the empty interval has no |
- // effect. |
- void Add(const Interval<T>& interval); |
- |
- // Adds the interval [min, max) to this IntervalSet. Adding the empty interval |
- // has no effect. |
- void Add(const T& min, const T& max) { Add(Interval<T>(min, max)); } |
- |
- // DEPRECATED(kosak). Use Union() instead. This method merges all of the |
- // values contained in "other" into this IntervalSet. |
- void Add(const IntervalSet& other); |
- |
- // Returns true if this IntervalSet represents exactly the same set of |
- // intervals as the ones represented by "other". |
- bool Equals(const IntervalSet& other) const; |
- |
- // Returns true if this IntervalSet is empty. |
- bool Empty() const { return intervals_.empty(); } |
- |
- // Returns true if any interval in this IntervalSet contains the indicated |
- // value. |
- bool Contains(const T& value) const; |
- |
- // Returns true if there is some interval in this IntervalSet that wholly |
- // contains the given interval. An interval O "wholly contains" a non-empty |
- // interval I if O.Contains(p) is true for every p in I. This is the same |
- // definition used by Interval<T>::Contains(). This method returns false on |
- // the empty interval, due to a (perhaps unintuitive) convention inherited |
- // from Interval<T>. |
- // Example: |
- // Assume an IntervalSet containing the entries { [10,20), [30,40) }. |
- // Contains(Interval(15, 16)) returns true, because [10,20) contains |
- // [15,16). However, Contains(Interval(15, 35)) returns false. |
- bool Contains(const Interval<T>& interval) const; |
- |
- // Returns true if for each interval in "other", there is some (possibly |
- // different) interval in this IntervalSet which wholly contains it. See |
- // Contains(const Interval<T>& interval) for the meaning of "wholly contains". |
- // Perhaps unintuitively, this method returns false if "other" is the empty |
- // set. The algorithmic complexity of this method is O(other.Size() * |
- // log(this->Size())), which is not efficient. The method could be rewritten |
- // to run in O(other.Size() + this->Size()). |
- bool Contains(const IntervalSet<T>& other) const; |
- |
- // Returns true if there is some interval in this IntervalSet that wholly |
- // contains the interval [min, max). See Contains(const Interval<T>&). |
- bool Contains(const T& min, const T& max) const { |
- return Contains(Interval<T>(min, max)); |
- } |
- |
- // Returns true if for some interval in "other", there is some interval in |
- // this IntervalSet that intersects with it. See Interval<T>::Intersects() |
- // for the definition of interval intersection. |
- bool Intersects(const IntervalSet& other) const; |
- |
- // Returns an iterator to the Interval<T> in the IntervalSet that contains the |
- // given value. In other words, returns an iterator to the unique interval |
- // [min, max) in the IntervalSet that has the property min <= value < max. If |
- // there is no such interval, this method returns end(). |
- const_iterator Find(const T& value) const; |
- |
- // Returns an iterator to the Interval<T> in the IntervalSet that wholly |
- // contains the given interval. In other words, returns an iterator to the |
- // unique interval outer in the IntervalSet that has the property that |
- // outer.Contains(interval). If there is no such interval, or if interval is |
- // empty, returns end(). |
- const_iterator Find(const Interval<T>& interval) const; |
- |
- // Returns an iterator to the Interval<T> in the IntervalSet that wholly |
- // contains [min, max). In other words, returns an iterator to the unique |
- // interval outer in the IntervalSet that has the property that |
- // outer.Contains(Interval<T>(min, max)). If there is no such interval, or if |
- // interval is empty, returns end(). |
- const_iterator Find(const T& min, const T& max) const { |
- return Find(Interval<T>(min, max)); |
- } |
- |
- // Returns true if every value within the passed interval is not Contained |
- // within the IntervalSet. |
- bool IsDisjoint(const Interval<T>& interval) const; |
- |
- // Merges all the values contained in "other" into this IntervalSet. |
- void Union(const IntervalSet& other); |
- |
- // Modifies this IntervalSet so that it contains only those values that are |
- // currently present both in *this and in the IntervalSet "other". |
- void Intersection(const IntervalSet& other); |
- |
- // Mutates this IntervalSet so that it contains only those values that are |
- // currently in *this but not in "interval". |
- void Difference(const Interval<T>& interval); |
- |
- // Mutates this IntervalSet so that it contains only those values that are |
- // currently in *this but not in the interval [min, max). |
- void Difference(const T& min, const T& max); |
- |
- // Mutates this IntervalSet so that it contains only those values that are |
- // currently in *this but not in the IntervalSet "other". |
- void Difference(const IntervalSet& other); |
- |
- // Mutates this IntervalSet so that it contains only those values that are |
- // in [min, max) but not currently in *this. |
- void Complement(const T& min, const T& max); |
- |
- // IntervalSet's begin() iterator. The invariants of IntervalSet guarantee |
- // that for each entry e in the set, e.min() < e.max() (because the entries |
- // are non-empty) and for each entry f that appears later in the set, |
- // e.max() < f.min() (because the entries are ordered, pairwise-disjoint, and |
- // non-adjacent). Modifications to this IntervalSet invalidate these |
- // iterators. |
- const_iterator begin() const { return intervals_.begin(); } |
- |
- // IntervalSet's end() iterator. |
- const_iterator end() const { return intervals_.end(); } |
- |
- // IntervalSet's rbegin() and rend() iterators. Iterator invalidation |
- // semantics are the same as those for begin() / end(). |
- const_reverse_iterator rbegin() const { return intervals_.rbegin(); } |
- |
- const_reverse_iterator rend() const { return intervals_.rend(); } |
- |
- // Appends the intervals in this IntervalSet to the end of *out. |
- void Get(std::vector<Interval<T>>* out) const { |
- out->insert(out->end(), begin(), end()); |
- } |
- |
- // Copies the intervals in this IntervalSet to the given output iterator. |
- template <typename Iter> |
- Iter Get(Iter out_iter) const { |
- return std::copy(begin(), end(), out_iter); |
- } |
- |
- template <typename Iter> |
- void assign(Iter first, Iter last) { |
- Clear(); |
- for (; first != last; ++first) |
- Add(*first); |
- } |
- |
-// TODO(rtenneti): Implement after suupport for std::initializer_list. |
-#if 0 |
- void assign(std::initializer_list<value_type> il) { |
- assign(il.begin(), il.end()); |
- } |
-#endif |
- |
- // Returns a human-readable representation of this set. This will typically be |
- // (though is not guaranteed to be) of the form |
- // "[a1, b1) [a2, b2) ... [an, bn)" |
- // where the intervals are in the same order as given by traversal from |
- // begin() to end(). This representation is intended for human consumption; |
- // computer programs should not rely on the output being in exactly this form. |
- std::string ToString() const; |
- |
- // Equality for IntervalSet<T>. Delegates to Equals(). |
- bool operator==(const IntervalSet& other) const { return Equals(other); } |
- |
- // Inequality for IntervalSet<T>. Delegates to Equals() (and returns its |
- // negation). |
- bool operator!=(const IntervalSet& other) const { return !Equals(other); } |
- |
-// TODO(rtenneti): Implement after suupport for std::initializer_list. |
-#if 0 |
- IntervalSet& operator=(std::initializer_list<value_type> il) { |
- assign(il.begin(), il.end()); |
- return *this; |
- } |
-#endif |
- |
- // Swap this IntervalSet with *other. This is a constant-time operation. |
- void Swap(IntervalSet<T>* other) { intervals_.swap(other->intervals_); } |
- |
- private: |
- // Removes overlapping ranges and coalesces adjacent intervals as needed. |
- void Compact(const typename Set::iterator& begin, |
- const typename Set::iterator& end); |
- |
- // Returns true if this set is valid (i.e. all intervals in it are non-empty, |
- // non-adjacent, and mutually disjoint). Currently this is used as an |
- // integrity check by the Intersection() and Difference() methods, but is only |
- // invoked for debug builds (via DCHECK). |
- bool Valid() const; |
- |
- // Finds the first interval that potentially intersects 'other'. |
- const_iterator FindIntersectionCandidate(const IntervalSet& other) const; |
- |
- // Finds the first interval that potentially intersects 'interval'. |
- const_iterator FindIntersectionCandidate(const Interval<T>& interval) const; |
- |
- // Helper for Intersection() and Difference(): Finds the next pair of |
- // intervals from 'x' and 'y' that intersect. 'mine' is an iterator |
- // over x->intervals_. 'theirs' is an iterator over y.intervals_. 'mine' |
- // and 'theirs' are advanced until an intersecting pair is found. |
- // Non-intersecting intervals (aka "holes") from x->intervals_ can be |
- // optionally erased by "on_hole". |
- template <typename X, typename Func> |
- static bool FindNextIntersectingPairImpl(X* x, |
- const IntervalSet& y, |
- const_iterator* mine, |
- const_iterator* theirs, |
- Func on_hole); |
- |
- // The variant of the above method that doesn't mutate this IntervalSet. |
- bool FindNextIntersectingPair(const IntervalSet& other, |
- const_iterator* mine, |
- const_iterator* theirs) const { |
- return FindNextIntersectingPairImpl( |
- this, other, mine, theirs, |
- [](const IntervalSet*, const_iterator, const_iterator) {}); |
- } |
- |
- // The variant of the above method that mutates this IntervalSet by erasing |
- // holes. |
- bool FindNextIntersectingPairAndEraseHoles(const IntervalSet& other, |
- const_iterator* mine, |
- const_iterator* theirs) { |
- return FindNextIntersectingPairImpl( |
- this, other, mine, theirs, |
- [](IntervalSet* x, const_iterator from, const_iterator to) { |
- x->intervals_.erase(from, to); |
- }); |
- } |
- |
- // The representation for the intervals. The intervals in this set are |
- // non-empty, pairwise-disjoint, non-adjacent and ordered in ascending order |
- // by min(). |
- Set intervals_; |
-}; |
- |
-template <typename T> |
-std::ostream& operator<<(std::ostream& out, const IntervalSet<T>& seq); |
- |
-template <typename T> |
-void swap(IntervalSet<T>& x, IntervalSet<T>& y); |
- |
-//============================================================================== |
-// Implementation details: Clients can stop reading here. |
- |
-template <typename T> |
-Interval<T> IntervalSet<T>::SpanningInterval() const { |
- Interval<T> result; |
- if (!intervals_.empty()) { |
- result.SetMin(intervals_.begin()->min()); |
- result.SetMax(intervals_.rbegin()->max()); |
- } |
- return result; |
-} |
- |
-template <typename T> |
-void IntervalSet<T>::Add(const Interval<T>& interval) { |
- if (interval.Empty()) |
- return; |
- std::pair<typename Set::iterator, bool> ins = intervals_.insert(interval); |
- if (!ins.second) { |
- // This interval already exists. |
- return; |
- } |
- // Determine the minimal range that will have to be compacted. We know that |
- // the IntervalSet was valid before the addition of the interval, so only |
- // need to start with the interval itself (although Compact takes an open |
- // range so begin needs to be the interval to the left). We don't know how |
- // many ranges this interval may cover, so we need to find the appropriate |
- // interval to end with on the right. |
- typename Set::iterator begin = ins.first; |
- if (begin != intervals_.begin()) |
- --begin; |
- const Interval<T> target_end(interval.max(), interval.max()); |
- const typename Set::iterator end = intervals_.upper_bound(target_end); |
- Compact(begin, end); |
-} |
- |
-template <typename T> |
-void IntervalSet<T>::Add(const IntervalSet& other) { |
- for (const_iterator it = other.begin(); it != other.end(); ++it) { |
- Add(*it); |
- } |
-} |
- |
-template <typename T> |
-bool IntervalSet<T>::Equals(const IntervalSet& other) const { |
- if (intervals_.size() != other.intervals_.size()) |
- return false; |
- for (typename Set::iterator i = intervals_.begin(), |
- j = other.intervals_.begin(); |
- i != intervals_.end(); ++i, ++j) { |
- // Simple member-wise equality, since all intervals are non-empty. |
- if (i->min() != j->min() || i->max() != j->max()) |
- return false; |
- } |
- return true; |
-} |
- |
-template <typename T> |
-bool IntervalSet<T>::Contains(const T& value) const { |
- Interval<T> tmp(value, value); |
- // Find the first interval with min() > value, then move back one step |
- const_iterator it = intervals_.upper_bound(tmp); |
- if (it == intervals_.begin()) |
- return false; |
- --it; |
- return it->Contains(value); |
-} |
- |
-template <typename T> |
-bool IntervalSet<T>::Contains(const Interval<T>& interval) const { |
- // Find the first interval with min() > value, then move back one step. |
- const_iterator it = intervals_.upper_bound(interval); |
- if (it == intervals_.begin()) |
- return false; |
- --it; |
- return it->Contains(interval); |
-} |
- |
-template <typename T> |
-bool IntervalSet<T>::Contains(const IntervalSet<T>& other) const { |
- if (!SpanningInterval().Contains(other.SpanningInterval())) { |
- return false; |
- } |
- |
- for (const_iterator i = other.begin(); i != other.end(); ++i) { |
- // If we don't contain the interval, can return false now. |
- if (!Contains(*i)) { |
- return false; |
- } |
- } |
- return true; |
-} |
- |
-// This method finds the interval that Contains() "value", if such an interval |
-// exists in the IntervalSet. The way this is done is to locate the "candidate |
-// interval", the only interval that could *possibly* contain value, and test it |
-// using Contains(). The candidate interval is the interval with the largest |
-// min() having min() <= value. |
-// |
-// Determining the candidate interval takes a couple of steps. First, since the |
-// underlying std::set stores intervals, not values, we need to create a "probe |
-// interval" suitable for use as a search key. The probe interval used is |
-// [value, value). Now we can restate the problem as finding the largest |
-// interval in the IntervalSet that is <= the probe interval. |
-// |
-// This restatement only works if the set's comparator behaves in a certain way. |
-// In particular it needs to order first by ascending min(), and then by |
-// descending max(). The comparator used by this library is defined in exactly |
-// this way. To see why descending max() is required, consider the following |
-// example. Assume an IntervalSet containing these intervals: |
-// |
-// [0, 5) [10, 20) [50, 60) |
-// |
-// Consider searching for the value 15. The probe interval [15, 15) is created, |
-// and [10, 20) is identified as the largest interval in the set <= the probe |
-// interval. This is the correct interval needed for the Contains() test, which |
-// will then return true. |
-// |
-// Now consider searching for the value 30. The probe interval [30, 30) is |
-// created, and again [10, 20] is identified as the largest interval <= the |
-// probe interval. This is again the correct interval needed for the Contains() |
-// test, which in this case returns false. |
-// |
-// Finally, consider searching for the value 10. The probe interval [10, 10) is |
-// created. Here the ordering relationship between [10, 10) and [10, 20) becomes |
-// vitally important. If [10, 10) were to come before [10, 20), then [0, 5) |
-// would be the largest interval <= the probe, leading to the wrong choice of |
-// interval for the Contains() test. Therefore [10, 10) needs to come after |
-// [10, 20). The simplest way to make this work in the general case is to order |
-// by ascending min() but descending max(). In this ordering, the empty interval |
-// is larger than any non-empty interval with the same min(). The comparator |
-// used by this library is careful to induce this ordering. |
-// |
-// Another detail involves the choice of which std::set method to use to try to |
-// find the candidate interval. The most appropriate entry point is |
-// set::upper_bound(), which finds the smallest interval which is > the probe |
-// interval. The semantics of upper_bound() are slightly different from what we |
-// want (namely, to find the largest interval which is <= the probe interval) |
-// but they are close enough; the interval found by upper_bound() will always be |
-// one step past the interval we are looking for (if it exists) or at begin() |
-// (if it does not). Getting to the proper interval is a simple matter of |
-// decrementing the iterator. |
-template <typename T> |
-typename IntervalSet<T>::const_iterator IntervalSet<T>::Find( |
- const T& value) const { |
- Interval<T> tmp(value, value); |
- const_iterator it = intervals_.upper_bound(tmp); |
- if (it == intervals_.begin()) |
- return intervals_.end(); |
- --it; |
- if (it->Contains(value)) |
- return it; |
- else |
- return intervals_.end(); |
-} |
- |
-// This method finds the interval that Contains() the interval "probe", if such |
-// an interval exists in the IntervalSet. The way this is done is to locate the |
-// "candidate interval", the only interval that could *possibly* contain |
-// "probe", and test it using Contains(). The candidate interval is the largest |
-// interval that is <= the probe interval. |
-// |
-// The search for the candidate interval only works if the comparator used |
-// behaves in a certain way. In particular it needs to order first by ascending |
-// min(), and then by descending max(). The comparator used by this library is |
-// defined in exactly this way. To see why descending max() is required, |
-// consider the following example. Assume an IntervalSet containing these |
-// intervals: |
-// |
-// [0, 5) [10, 20) [50, 60) |
-// |
-// Consider searching for the probe [15, 17). [10, 20) is the largest interval |
-// in the set which is <= the probe interval. This is the correct interval |
-// needed for the Contains() test, which will then return true, because [10, 20) |
-// contains [15, 17). |
-// |
-// Now consider searching for the probe [30, 32). Again [10, 20] is the largest |
-// interval <= the probe interval. This is again the correct interval needed for |
-// the Contains() test, which in this case returns false, because [10, 20) does |
-// not contain [30, 32). |
-// |
-// Finally, consider searching for the probe [10, 12). Here the ordering |
-// relationship between [10, 12) and [10, 20) becomes vitally important. If |
-// [10, 12) were to come before [10, 20), then [0, 5) would be the largest |
-// interval <= the probe, leading to the wrong choice of interval for the |
-// Contains() test. Therefore [10, 12) needs to come after [10, 20). The |
-// simplest way to make this work in the general case is to order by ascending |
-// min() but descending max(). In this ordering, given two intervals with the |
-// same min(), the wider one goes before the narrower one. The comparator used |
-// by this library is careful to induce this ordering. |
-// |
-// Another detail involves the choice of which std::set method to use to try to |
-// find the candidate interval. The most appropriate entry point is |
-// set::upper_bound(), which finds the smallest interval which is > the probe |
-// interval. The semantics of upper_bound() are slightly different from what we |
-// want (namely, to find the largest interval which is <= the probe interval) |
-// but they are close enough; the interval found by upper_bound() will always be |
-// one step past the interval we are looking for (if it exists) or at begin() |
-// (if it does not). Getting to the proper interval is a simple matter of |
-// decrementing the iterator. |
-template <typename T> |
-typename IntervalSet<T>::const_iterator IntervalSet<T>::Find( |
- const Interval<T>& probe) const { |
- const_iterator it = intervals_.upper_bound(probe); |
- if (it == intervals_.begin()) |
- return intervals_.end(); |
- --it; |
- if (it->Contains(probe)) |
- return it; |
- else |
- return intervals_.end(); |
-} |
- |
-template <typename T> |
-bool IntervalSet<T>::IsDisjoint(const Interval<T>& interval) const { |
- Interval<T> tmp(interval.min(), interval.min()); |
- // Find the first interval with min() > interval.min() |
- const_iterator it = intervals_.upper_bound(tmp); |
- if (it != intervals_.end() && interval.max() > it->min()) |
- return false; |
- if (it == intervals_.begin()) |
- return true; |
- --it; |
- return it->max() <= interval.min(); |
-} |
- |
-template <typename T> |
-void IntervalSet<T>::Union(const IntervalSet& other) { |
- intervals_.insert(other.begin(), other.end()); |
- Compact(intervals_.begin(), intervals_.end()); |
-} |
- |
-template <typename T> |
-typename IntervalSet<T>::const_iterator |
-IntervalSet<T>::FindIntersectionCandidate(const IntervalSet& other) const { |
- return FindIntersectionCandidate(*other.intervals_.begin()); |
-} |
- |
-template <typename T> |
-typename IntervalSet<T>::const_iterator |
-IntervalSet<T>::FindIntersectionCandidate(const Interval<T>& interval) const { |
- // Use upper_bound to efficiently find the first interval in intervals_ |
- // where min() is greater than interval.min(). If the result |
- // isn't the beginning of intervals_ then move backwards one interval since |
- // the interval before it is the first candidate where max() may be |
- // greater than interval.min(). |
- // In other words, no interval before that can possibly intersect with any |
- // of other.intervals_. |
- const_iterator mine = intervals_.upper_bound(interval); |
- if (mine != intervals_.begin()) { |
- --mine; |
- } |
- return mine; |
-} |
- |
-template <typename T> |
-template <typename X, typename Func> |
-bool IntervalSet<T>::FindNextIntersectingPairImpl(X* x, |
- const IntervalSet& y, |
- const_iterator* mine, |
- const_iterator* theirs, |
- Func on_hole) { |
- CHECK(x != nullptr); |
- if ((*mine == x->intervals_.end()) || (*theirs == y.intervals_.end())) { |
- return false; |
- } |
- while (!(**mine).Intersects(**theirs)) { |
- const_iterator erase_first = *mine; |
- // Skip over intervals in 'mine' that don't reach 'theirs'. |
- while (*mine != x->intervals_.end() && (**mine).max() <= (**theirs).min()) { |
- ++(*mine); |
- } |
- on_hole(x, erase_first, *mine); |
- // We're done if the end of intervals_ is reached. |
- if (*mine == x->intervals_.end()) { |
- return false; |
- } |
- // Skip over intervals 'theirs' that don't reach 'mine'. |
- while (*theirs != y.intervals_.end() && |
- (**theirs).max() <= (**mine).min()) { |
- ++(*theirs); |
- } |
- // If the end of other.intervals_ is reached, we're done. |
- if (*theirs == y.intervals_.end()) { |
- on_hole(x, *mine, x->intervals_.end()); |
- return false; |
- } |
- } |
- return true; |
-} |
- |
-template <typename T> |
-void IntervalSet<T>::Intersection(const IntervalSet& other) { |
- if (!SpanningInterval().Intersects(other.SpanningInterval())) { |
- intervals_.clear(); |
- return; |
- } |
- |
- const_iterator mine = FindIntersectionCandidate(other); |
- // Remove any intervals that cannot possibly intersect with other.intervals_. |
- intervals_.erase(intervals_.begin(), mine); |
- const_iterator theirs = other.FindIntersectionCandidate(*this); |
- |
- while (FindNextIntersectingPairAndEraseHoles(other, &mine, &theirs)) { |
- // OK, *mine and *theirs intersect. Now, we find the largest |
- // span of intervals in other (starting at theirs) - say [a..b] |
- // - that intersect *mine, and we replace *mine with (*mine |
- // intersect x) for all x in [a..b] Note that subsequent |
- // intervals in this can't intersect any intervals in [a..b) -- |
- // they may only intersect b or subsequent intervals in other. |
- Interval<T> i(*mine); |
- intervals_.erase(mine); |
- mine = intervals_.end(); |
- Interval<T> intersection; |
- while (theirs != other.intervals_.end() && |
- i.Intersects(*theirs, &intersection)) { |
- std::pair<typename Set::iterator, bool> ins = |
- intervals_.insert(intersection); |
- DCHECK(ins.second); |
- mine = ins.first; |
- ++theirs; |
- } |
- DCHECK(mine != intervals_.end()); |
- --theirs; |
- ++mine; |
- } |
- DCHECK(Valid()); |
-} |
- |
-template <typename T> |
-bool IntervalSet<T>::Intersects(const IntervalSet& other) const { |
- if (!SpanningInterval().Intersects(other.SpanningInterval())) { |
- return false; |
- } |
- |
- const_iterator mine = FindIntersectionCandidate(other); |
- if (mine == intervals_.end()) { |
- return false; |
- } |
- const_iterator theirs = other.FindIntersectionCandidate(*mine); |
- |
- return FindNextIntersectingPair(other, &mine, &theirs); |
-} |
- |
-template <typename T> |
-void IntervalSet<T>::Difference(const Interval<T>& interval) { |
- if (!SpanningInterval().Intersects(interval)) { |
- return; |
- } |
- Difference(IntervalSet<T>(interval)); |
-} |
- |
-template <typename T> |
-void IntervalSet<T>::Difference(const T& min, const T& max) { |
- Difference(Interval<T>(min, max)); |
-} |
- |
-template <typename T> |
-void IntervalSet<T>::Difference(const IntervalSet& other) { |
- if (!SpanningInterval().Intersects(other.SpanningInterval())) { |
- return; |
- } |
- |
- const_iterator mine = FindIntersectionCandidate(other); |
- // If no interval in mine reaches the first interval of theirs then we're |
- // done. |
- if (mine == intervals_.end()) { |
- return; |
- } |
- const_iterator theirs = other.FindIntersectionCandidate(*this); |
- |
- while (FindNextIntersectingPair(other, &mine, &theirs)) { |
- // At this point *mine and *theirs overlap. Remove mine from |
- // intervals_ and replace it with the possibly two intervals that are |
- // the difference between mine and theirs. |
- Interval<T> i(*mine); |
- intervals_.erase(mine++); |
- Interval<T> lo; |
- Interval<T> hi; |
- i.Difference(*theirs, &lo, &hi); |
- |
- if (!lo.Empty()) { |
- // We have a low end. This can't intersect anything else. |
- std::pair<typename Set::iterator, bool> ins = intervals_.insert(lo); |
- DCHECK(ins.second); |
- } |
- |
- if (!hi.Empty()) { |
- std::pair<typename Set::iterator, bool> ins = intervals_.insert(hi); |
- DCHECK(ins.second); |
- mine = ins.first; |
- } |
- } |
- DCHECK(Valid()); |
-} |
- |
-template <typename T> |
-void IntervalSet<T>::Complement(const T& min, const T& max) { |
- IntervalSet<T> span(min, max); |
- span.Difference(*this); |
- intervals_.swap(span.intervals_); |
-} |
- |
-template <typename T> |
-std::string IntervalSet<T>::ToString() const { |
- std::ostringstream os; |
- os << *this; |
- return os.str(); |
-} |
- |
-// This method compacts the IntervalSet, merging pairs of overlapping intervals |
-// into a single interval. In the steady state, the IntervalSet does not contain |
-// any such pairs. However, the way the Union() and Add() methods work is to |
-// temporarily put the IntervalSet into such a state and then to call Compact() |
-// to "fix it up" so that it is no longer in that state. |
-// |
-// Compact() needs the interval set to allow two intervals [a,b) and [a,c) |
-// (having the same min() but different max()) to briefly coexist in the set at |
-// the same time, and be adjacent to each other, so that they can be efficiently |
-// located and merged into a single interval. This state would be impossible |
-// with a comparator which only looked at min(), as such a comparator would |
-// consider such pairs equal. Fortunately, the comparator used by IntervalSet |
-// does exactly what is needed, ordering first by ascending min(), then by |
-// descending max(). |
-template <typename T> |
-void IntervalSet<T>::Compact(const typename Set::iterator& begin, |
- const typename Set::iterator& end) { |
- if (begin == end) |
- return; |
- typename Set::iterator next = begin; |
- typename Set::iterator prev = begin; |
- typename Set::iterator it = begin; |
- ++it; |
- ++next; |
- while (it != end) { |
- ++next; |
- if (prev->max() >= it->min()) { |
- // Overlapping / coalesced range; merge the two intervals. |
- T min = prev->min(); |
- T max = std::max(prev->max(), it->max()); |
- Interval<T> i(min, max); |
- intervals_.erase(prev); |
- intervals_.erase(it); |
- std::pair<typename Set::iterator, bool> ins = intervals_.insert(i); |
- DCHECK(ins.second); |
- prev = ins.first; |
- } else { |
- prev = it; |
- } |
- it = next; |
- } |
-} |
- |
-template <typename T> |
-bool IntervalSet<T>::Valid() const { |
- const_iterator prev = end(); |
- for (const_iterator it = begin(); it != end(); ++it) { |
- // invalid or empty interval. |
- if (it->min() >= it->max()) |
- return false; |
- // Not sorted, not disjoint, or adjacent. |
- if (prev != end() && prev->max() >= it->min()) |
- return false; |
- prev = it; |
- } |
- return true; |
-} |
- |
-template <typename T> |
-inline std::ostream& operator<<(std::ostream& out, const IntervalSet<T>& seq) { |
-// TODO(rtenneti): Implement << method of IntervalSet. |
-#if 0 |
- util::gtl::LogRangeToStream(out, seq.begin(), seq.end(), |
- util::gtl::LogLegacy()); |
-#endif // 0 |
- return out; |
-} |
- |
-template <typename T> |
-void swap(IntervalSet<T>& x, IntervalSet<T>& y) { |
- x.Swap(&y); |
-} |
- |
-// This comparator orders intervals first by ascending min() and then by |
-// descending max(). Readers who are satisified with that explanation can stop |
-// reading here. The remainder of this comment is for the benefit of future |
-// maintainers of this library. |
-// |
-// The reason for this ordering is that this comparator has to serve two |
-// masters. First, it has to maintain the intervals in its internal set in the |
-// order that clients expect to see them. Clients see these intervals via the |
-// iterators provided by begin()/end() or as a result of invoking Get(). For |
-// this reason, the comparator orders intervals by ascending min(). |
-// |
-// If client iteration were the only consideration, then ordering by ascending |
-// min() would be good enough. This is because the intervals in the IntervalSet |
-// are non-empty, non-adjacent, and mutually disjoint; such intervals happen to |
-// always have disjoint min() values, so such a comparator would never even have |
-// to look at max() in order to work correctly for this class. |
-// |
-// However, in addition to ordering by ascending min(), this comparator also has |
-// a second responsibility: satisfying the special needs of this library's |
-// peculiar internal implementation. These needs require the comparator to order |
-// first by ascending min() and then by descending max(). The best way to |
-// understand why this is so is to check out the comments associated with the |
-// Find() and Compact() methods. |
-template <typename T> |
-inline bool IntervalSet<T>::IntervalComparator::operator()( |
- const Interval<T>& a, |
- const Interval<T>& b) const { |
- return (a.min() < b.min() || (a.min() == b.min() && a.max() > b.max())); |
-} |
- |
-} // namespace net |
- |
-#endif // NET_QUIC_INTERVAL_SET_H_ |