TextRenderer only pushes new cues downstream

media/base/text_ranges.cc

+// Copyright 2014 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.
+
+#include "media/base/text_ranges.h"
+
+#include "base/logging.h"
+
+namespace media {
+
+TextRanges::TextRanges() {
+  Reset();
+}
+
+TextRanges::~TextRanges() {
+}
+
+void TextRanges::Reset() {
+  curr_range_itr_ = range_map_.end();
+}
+
+bool TextRanges::AddCue(base::TimeDelta start_time) {
+  typedef RangeMap::iterator Itr;
+
+  if (curr_range_itr_ == range_map_.end()) {
+    // There is no active time range, so this is the first AddCue()
+    // attempt that follows a Reset().
+
+    if (range_map_.empty()) {
+      NewRange(start_time);
+      return true;
+    }
+
+    if (start_time < range_map_.begin()->first) {
+      NewRange(start_time);
+      return true;
+    }
+
+    const Itr itr = --Itr(range_map_.upper_bound(start_time));
+    DCHECK(start_time >= itr->first);
+
+    Range& range = itr->second;
+
+    if (start_time > range.last_time()) {
+      NewRange(start_time);
+      return true;
+    }
+
+    range.ResetCount(start_time);
+    curr_range_itr_ = itr;
+    return false;
+  }
+
+  DCHECK(start_time >= curr_range_itr_->first);
+
+  Range& curr_range = curr_range_itr_->second;
+
+  if (start_time <= curr_range.last_time())
+    return curr_range.AddCue(start_time);
+
+  const Itr next_range_itr = ++Itr(curr_range_itr_);
+
+  if (next_range_itr != range_map_.end()) {
+    DCHECK(next_range_itr->first > curr_range.last_time());
+    DCHECK(start_time <= next_range_itr->first);
+
+    if (start_time == next_range_itr->first) {
+      // We have walked off the current range, and onto the next one.
+      // There is now no ambiguity about where the current time range
+      // ends, and so we coalesce the current and next ranges.
+
+      Merge(curr_range, next_range_itr);
+      return false;
+    }
+  }
+
+  // Either |curr_range| is the last range in the map, or there is a
+  // next range beyond |curr_range|, but its start time is ahead of
+  // this cue's start time.  In either case, this cue becomes the new
+  // last_time for |curr_range|.  Eventually we will see a cue whose
+  // time matches the start time of the next range, in which case we
+  // coalesce the current and next ranges.
+
+  curr_range.SetLastTime(start_time);
+  return true;
+}
+
+size_t TextRanges::RangeCountForTesting() const {
+  return range_map_.size();
+}
+
+void TextRanges::NewRange(base::TimeDelta start_time) {
+  Range range;
+  range.SetLastTime(start_time);
+
+  std::pair<RangeMap::iterator, bool> result =
+      range_map_.insert(std::make_pair(start_time, range));
+  DCHECK(result.second);
+
+  curr_range_itr_ = result.first;
+}
+
+void TextRanges::Merge(
+    Range& curr_range,
+    const RangeMap::iterator& next_range_itr) {
+  curr_range = next_range_itr->second;
+  curr_range.ResetCount(next_range_itr->first);
+  range_map_.erase(next_range_itr);
+}
+
+void TextRanges::Range::ResetCount(base::TimeDelta start_time) {
+  count_ = (start_time < last_time_) ? 0 : 1;
+}
+
+void TextRanges::Range::SetLastTime(base::TimeDelta last_time) {
+  last_time_ = last_time;
+  count_ = 1;
+  max_count_ = 1;
+}
+
+bool TextRanges::Range::AddCue(base::TimeDelta start_time) {
+  if (start_time < last_time_) {
+    DCHECK_EQ(count_, 0);
+    return false;
+  }
+
+  DCHECK(start_time == last_time_);
+
+  ++count_;
+  if (count_ <= max_count_)
+    return false;
+
+  ++max_count_;
+  return true;
+}
+
+base::TimeDelta TextRanges::Range::last_time() const {
+  return last_time_;
+}
+
+}  // namespace media