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- // Copyright (c) 2012 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.
- #ifndef MEDIA_BASE_RANGES_H_
- #define MEDIA_BASE_RANGES_H_
- #include <stddef.h>
- #include <stdint.h>
- #include <algorithm>
- #include <ostream>
- #include <vector>
- #include "base/check_op.h"
- #include "base/time/time.h"
- #include "media/base/media_export.h"
- namespace media {
- // Ranges allows holding an ordered list of ranges of [start,end) intervals.
- // The canonical example use-case is holding the list of ranges of buffered
- // bytes or times in a <video> tag.
- template <class T> // Endpoint type; typically a base::TimeDelta or an int64_t.
- class Ranges {
- public:
- // Allow copy & assign.
- // Add (start,end) to this object, coallescing overlaps as appropriate.
- // Returns the number of stored ranges, post coallescing.
- size_t Add(T start, T end);
- // Return the number of disjoint ranges.
- size_t size() const;
- // Return the "i"'th range's start & end (0-based).
- T start(size_t i) const;
- T end(size_t i) const;
- // Clear all ranges.
- void clear();
- // Computes the intersection between this range and |other|.
- Ranges<T> IntersectionWith(const Ranges<T>& other) const;
- private:
- // Wrapper around DCHECK_LT allowing comparisons of operator<<'able T's.
- void DCheckLT(const T& lhs, const T& rhs) const;
- // Disjoint, in increasing order of start.
- std::vector<std::pair<T, T> > ranges_;
- };
- //////////////////////////////////////////////////////////////////////
- // EVERYTHING BELOW HERE IS IMPLEMENTATION DETAIL!!
- //////////////////////////////////////////////////////////////////////
- template<class T>
- size_t Ranges<T>::Add(T start, T end) {
- if (start == end) // Nothing to be done with empty ranges.
- return ranges_.size();
- DCheckLT(start, end);
- size_t i;
- // Walk along the array of ranges until |start| is no longer larger than the
- // current interval's end.
- for (i = 0; i < ranges_.size() && ranges_[i].second < start; ++i) {
- // Empty body
- }
- // Now we know |start| belongs in the i'th slot.
- // If i is the end of the range, append new range and done.
- if (i == ranges_.size()) {
- ranges_.push_back(std::make_pair(start, end));
- return ranges_.size();
- }
- // If |end| is less than i->first, then [start,end) is a new (non-overlapping)
- // i'th entry pushing everyone else back, and done.
- if (end < ranges_[i].first) {
- ranges_.insert(ranges_.begin() + i, std::make_pair(start, end));
- return ranges_.size();
- }
- // Easy cases done. Getting here means there is overlap between [start,end)
- // and the existing ranges.
- // Now: start <= i->second && i->first <= end
- if (start < ranges_[i].first)
- ranges_[i].first = start;
- if (ranges_[i].second < end)
- ranges_[i].second = end;
- // Now: [start,end) is contained in the i'th range, and we'd be done, except
- // for the fact that the newly-extended i'th range might now overlap
- // subsequent ranges. Merge until discontinuities appear. Note that there's
- // no need to test/merge previous ranges, since needing that would mean the
- // original loop went too far.
- while ((i + 1) < ranges_.size() &&
- ranges_[i + 1].first <= ranges_[i].second) {
- ranges_[i].second = std::max(ranges_[i].second, ranges_[i + 1].second);
- ranges_.erase(ranges_.begin() + i + 1);
- }
- return ranges_.size();
- }
- template<>
- MEDIA_EXPORT void
- Ranges<base::TimeDelta>::DCheckLT(const base::TimeDelta& lhs,
- const base::TimeDelta& rhs) const;
- template<class T>
- void Ranges<T>::DCheckLT(const T& lhs, const T& rhs) const {
- DCHECK_LT(lhs, rhs);
- }
- template<class T>
- size_t Ranges<T>::size() const {
- return ranges_.size();
- }
- template<class T>
- T Ranges<T>::start(size_t i) const {
- return ranges_[i].first;
- }
- template<class T>
- T Ranges<T>::end(size_t i) const {
- return ranges_[i].second;
- }
- template<class T>
- void Ranges<T>::clear() {
- ranges_.clear();
- }
- template<class T>
- Ranges<T> Ranges<T>::IntersectionWith(const Ranges<T>& other) const {
- Ranges<T> result;
- size_t i = 0;
- size_t j = 0;
- while (i < size() && j < other.size()) {
- T max_start = std::max(start(i), other.start(j));
- T min_end = std::min(end(i), other.end(j));
- // Add an intersection range to the result if the ranges overlap.
- if (max_start < min_end)
- result.Add(max_start, min_end);
- if (end(i) < other.end(j))
- ++i;
- else
- ++j;
- }
- return result;
- }
- } // namespace media
- #endif // MEDIA_BASE_RANGES_H_
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