blob: f42b34a737399c54c723d8048efbf7ac0bd19378 [file] [log] [blame]
// 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 <algorithm>
#include <ostream>
#include <vector>
#include "base/basictypes.h"
#include "base/logging.h"
#include "base/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.
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(int i) const;
T end(int 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<>
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(int i) const {
return ranges_[i].first;
}
template<class T>
T Ranges<T>::end(int 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_