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// Copyright 2016 The Netstack Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package fragmentation
import (
"container/heap"
"fmt"
"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
)
type fragment struct {
offset uint16
vv *buffer.VectorisedView
}
type fragHeap []fragment
func (h *fragHeap) Len() int {
return len(*h)
}
func (h *fragHeap) Less(i, j int) bool {
return (*h)[i].offset < (*h)[j].offset
}
func (h *fragHeap) Swap(i, j int) {
(*h)[i], (*h)[j] = (*h)[j], (*h)[i]
}
func (h *fragHeap) Push(x interface{}) {
*h = append(*h, x.(fragment))
}
func (h *fragHeap) Pop() interface{} {
old := *h
n := len(old)
x := old[n-1]
*h = old[:n-1]
return x
}
// reassamble empties the heap and returns a VectorisedView
// containing a reassambled version of the fragments inside the heap.
func (h *fragHeap) reassemble() (buffer.VectorisedView, error) {
curr := heap.Pop(h).(fragment)
views := curr.vv.Views()
size := curr.vv.Size()
if curr.offset != 0 {
return buffer.NewVectorisedView(0, nil), fmt.Errorf("offset of the first packet is != 0 (%d)", curr.offset)
}
for h.Len() > 0 {
curr := heap.Pop(h).(fragment)
if int(curr.offset) < size {
curr.vv.TrimFront(size - int(curr.offset))
} else if int(curr.offset) > size {
return buffer.NewVectorisedView(0, nil), fmt.Errorf("packet has a hole, expected offset %d, got %d", size, curr.offset)
}
size += curr.vv.Size()
views = append(views, curr.vv.Views()...)
}
return buffer.NewVectorisedView(size, views), nil
}
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