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package dhcpv4
import (
"fmt"
"net"
)
// This option implements the subnet mask option
// https://tools.ietf.org/html/rfc2132
// OptSubnetMask represents an option encapsulating the subnet mask.
type OptSubnetMask struct {
SubnetMask net.IPMask
}
// ParseOptSubnetMask returns a new OptSubnetMask from a byte
// stream, or error if any.
func ParseOptSubnetMask(data []byte) (*OptSubnetMask, error) {
if len(data) < 2 {
return nil, ErrShortByteStream
}
code := OptionCode(data[0])
if code != OptionSubnetMask {
return nil, fmt.Errorf("expected code %v, got %v", OptionSubnetMask, code)
}
length := int(data[1])
if length != 4 {
return nil, fmt.Errorf("unexepcted length: expected 4, got %v", length)
}
if len(data) < 6 {
return nil, ErrShortByteStream
}
return &OptSubnetMask{SubnetMask: net.IPMask(data[2 : 2+length])}, nil
}
// Code returns the option code.
func (o *OptSubnetMask) Code() OptionCode {
return OptionSubnetMask
}
// ToBytes returns a serialized stream of bytes for this option.
func (o *OptSubnetMask) ToBytes() []byte {
ret := []byte{byte(o.Code()), byte(o.Length())}
return append(ret, o.SubnetMask[:4]...)
}
// String returns a human-readable string.
func (o *OptSubnetMask) String() string {
return fmt.Sprintf("Subnet Mask -> %v", o.SubnetMask.String())
}
// Length returns the length of the data portion (excluding option code an byte
// length).
func (o *OptSubnetMask) Length() int {
return 4
}
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