github.com/lightlus/netstack@v1.2.0/tcpip/seqnum/seqnum.go (about)

     1  // Copyright 2018 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Package seqnum defines the types and methods for TCP sequence numbers such
    16  // that they fit in 32-bit words and work properly when overflows occur.
    17  package seqnum
    18  
    19  // Value represents the value of a sequence number.
    20  type Value uint32
    21  
    22  // Size represents the size (length) of a sequence number window.
    23  type Size uint32
    24  
    25  // LessThan checks if v is before w, i.e., v < w.
    26  func (v Value) LessThan(w Value) bool {
    27  	return int32(v-w) < 0
    28  }
    29  
    30  // LessThanEq returns true if v==w or v is before i.e., v < w.
    31  func (v Value) LessThanEq(w Value) bool {
    32  	if v == w {
    33  		return true
    34  	}
    35  	return v.LessThan(w)
    36  }
    37  
    38  // InRange checks if v is in the range [a,b), i.e., a <= v < b.
    39  func (v Value) InRange(a, b Value) bool {
    40  	return v-a < b-a
    41  }
    42  
    43  // InWindow checks if v is in the window that starts at 'first' and spans 'size'
    44  // sequence numbers.
    45  func (v Value) InWindow(first Value, size Size) bool {
    46  	return v.InRange(first, first.Add(size))
    47  }
    48  
    49  // Overlap checks if the window [a,a+b) overlaps with the window [x, x+y).
    50  func Overlap(a Value, b Size, x Value, y Size) bool {
    51  	return a.LessThan(x.Add(y)) && x.LessThan(a.Add(b))
    52  }
    53  
    54  // Add calculates the sequence number following the [v, v+s) window.
    55  func (v Value) Add(s Size) Value {
    56  	return v + Value(s)
    57  }
    58  
    59  // Size calculates the size of the window defined by [v, w).
    60  func (v Value) Size(w Value) Size {
    61  	return Size(w - v)
    62  }
    63  
    64  // UpdateForward updates v such that it becomes v + s.
    65  func (v *Value) UpdateForward(s Size) {
    66  	*v += Value(s)
    67  }