| // 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 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)) |
| } |
| |
| // 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) |
| } |