Merge 143765 - Ensure media's buffered ranges always have a range that includes currentTime.

media/base/ranges.h

 // 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 <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);
+
  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();
 
-  DCHECK(start < end);
+  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()) {
@@ skipping 24 matching lines @@
   // 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) {
+  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_