58 lines
1.6 KiB
Go
58 lines
1.6 KiB
Go
// Copyright 2016 The Netstack Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package seqnum defines the types and methods for TCP sequence numbers such
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// that they fit in 32-bit words and work properly when overflows occur.
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package seqnum
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// Value represents the value of a sequence number.
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type Value uint32
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// Size represents the size (length) of a sequence number window.
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type Size uint32
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// LessThan checks if v is before w, i.e., v < w.
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func (v Value) LessThan(w Value) bool {
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return int32(v-w) < 0
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}
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// LessThanEq returns true if v==w or v is before i.e., v < w.
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func (v Value) LessThanEq(w Value) bool {
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if v == w {
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return true
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}
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return v.LessThan(w)
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}
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// InRange checks if v is in the range [a,b), i.e., a <= v < b.
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func (v Value) InRange(a, b Value) bool {
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return v-a < b-a
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}
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// InWindow checks if v is in the window that starts at 'first' and spans 'size'
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// sequence numbers.
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func (v Value) InWindow(first Value, size Size) bool {
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return v.InRange(first, first.Add(size))
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}
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// Overlap checks if the window [a,a+b) overlaps with the window [x, x+y).
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func Overlap(a Value, b Size, x Value, y Size) bool {
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return a.LessThan(x.Add(y)) && x.LessThan(a.Add(b))
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}
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// Add calculates the sequence number following the [v, v+s) window.
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func (v Value) Add(s Size) Value {
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return v + Value(s)
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}
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// Size calculates the size of the window defined by [v, w).
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func (v Value) Size(w Value) Size {
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return Size(w - v)
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}
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// UpdateForward updates v such that it becomes v + s.
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func (v *Value) UpdateForward(s Size) {
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*v += Value(s)
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}
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