| // 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 seqnum defines the types and methods for TCP sequence numbers such |
| // that they fit in 32-bit words and work properly when overflows occur. |
| package seqnum |
| |
| // Value represents the value of a sequence number. |
| type Value uint32 |
| |
| // Size represents the size (length) of a sequence number window. |
| type Size uint32 |
| |
| // LessThan checks if v is before w, i.e., v < w. |
| func (v Value) LessThan(w Value) bool { |
| return int32(v-w) < 0 |
| } |
| |
| // LessThanEq returns true if v==w or v is before i.e., v < w. |
| func (v Value) LessThanEq(w Value) bool { |
| if v == w { |
| return true |
| } |
| return v.LessThan(w) |
| } |
| |
| // InRange checks if v is in the range [a,b), i.e., a <= v < b. |
| func (v Value) InRange(a, b Value) bool { |
| return v-a < b-a |
| } |
| |
| // InWindow checks if v is in the window that starts at 'first' and spans 'size' |
| // sequence numbers. |
| func (v Value) InWindow(first Value, size Size) bool { |
| return v.InRange(first, first.Add(size)) |
| } |
| |
| // Overlap checks if the window [a,a+b) overlaps with the window [x, x+y). |
| func Overlap(a Value, b Size, x Value, y Size) bool { |
| return a.LessThan(x.Add(y)) && x.LessThan(a.Add(b)) |
| } |
| |
| // Add calculates the sequence number following the [v, v+s) window. |
| func (v Value) Add(s Size) Value { |
| return v + Value(s) |
| } |
| |
| // Size calculates the size of the window defined by [v, w). |
| func (v Value) Size(w Value) Size { |
| return Size(w - v) |
| } |
| |
| // UpdateForward updates v such that it becomes v + s. |
| func (v *Value) UpdateForward(s Size) { |
| *v += Value(s) |
| } |