text: // Copyright 2018 The gVisor Authors.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //     http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  package tcp
  
  import "container/heap"
  
  type segmentHeap []*segment
  
  var _ heap.Interface = (*segmentHeap)(nil)
  
  // Len returns the length of h.
  func (h *segmentHeap) Len() int {
  	return len(*h)
  }
  
  // Less determines whether the i-th element of h is less than the j-th element.
  func (h *segmentHeap) Less(i, j int) bool {
  	return (*h)[i].sequenceNumber.LessThan((*h)[j].sequenceNumber)
  }
  
  // Swap swaps the i-th and j-th elements of h.
  func (h *segmentHeap) Swap(i, j int) {
  	(*h)[i], (*h)[j] = (*h)[j], (*h)[i]
  }
  
  // Push adds x as the last element of h.
  func (h *segmentHeap) Push(x interface{}) {
  	*h = append(*h, x.(*segment))
  }
  
  // Pop removes the last element of h and returns it.
  func (h *segmentHeap) Pop() interface{} {
  	old := *h
  	n := len(old)
  	x := old[n-1]
  	old[n-1] = nil
  	*h = old[:n-1]
  	return x
  }
  