port.go

package net

import (
	"encoding/binary"
	"strconv"
)

// Port represents a network port in TCP and UDP protocol.
type Port uint16

// PortFromBytes converts a byte array to a Port, assuming bytes are in big endian order.
// @unsafe Caller must ensure that the byte array has at least 2 elements.
func PortFromBytes(port []byte) Port {
	return Port(binary.BigEndian.Uint16(port))
}

// PortFromInt converts an integer to a Port.
// @error when the integer is not positive or larger then 65535
func PortFromInt(val uint32) (Port, error) {
	if val > 65535 {
		return Port(0), newError("invalid port range: ", val)
	}
	return Port(val), nil
}

// PortFromString converts a string to a Port.
// @error when the string is not an integer or the integral value is a not a valid Port.
func PortFromString(s string) (Port, error) {
	val, err := strconv.ParseUint(s, 10, 32)
	if err != nil {
		return Port(0), newError("invalid port range: ", s)
	}
	return PortFromInt(uint32(val))
}

// Value return the correspoding uint16 value of a Port.
func (p Port) Value() uint16 {
	return uint16(p)
}

// String returns the string presentation of a Port.
func (p Port) String() string {
	return strconv.Itoa(int(p))
}

// FromPort returns the beginning port of this PortRange.
func (p PortRange) FromPort() Port {
	return Port(p.From)
}

// ToPort returns the end port of this PortRange.
func (p PortRange) ToPort() Port {
	return Port(p.To)
}

// Contains returns true if the given port is within the range of a PortRange.
func (p PortRange) Contains(port Port) bool {
	return p.FromPort() <= port && port <= p.ToPort()
}

// SinglePortRange returns a PortRange contains a single port.
func SinglePortRange(p Port) *PortRange {
	return &PortRange{
		From: uint32(p),
		To:   uint32(p),
	}
}