ipconv.go

// Copyright 2020 Kiyon Lin All rights reserved.
//
// 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 ipconv is a library providing utility functions to convert
// ip.
package ipconv

import (
	"fmt"
	"strconv"
	"unsafe"
)

// Version of current package
const Version = "0.1.1"

type ipv4Error struct {
	ip string
}

func (e ipv4Error) Error() string {
	return fmt.Sprintf("ipconv: invalid ipv4 %s", e.ip)
}

// V42Long converts an ipv4 string to an uint32 integer.
// Panic if format of ip is not ipv4
func V42Long(ip string) uint32 {
	if long, err := SafeV42Long(ip); err != nil {
		panic(err)
	} else {
		return long
	}
}

// SafeV42Long converts an ipv4 string to an uint32 integer.
// An error returns if format of ip is not ipv4
func SafeV42Long(ip string) (long uint32, err error) {
	l := len(ip)
	if l < 7 || l > 15 {
		return 0, ipv4Error{ip}
	}
	var (
		n uint32
		b = 24
	)
	for i := 0; i < l; i++ {
		c := ip[i]
		switch {
		case c == '.':
			if b <= 0 {
				return 0, ipv4Error{ip}
			}
			long |= n << b
			n, b = 0, b-8
		case c >= '0' && c <= '9':
			n = n*10 + uint32(c-'0')
			if n > 255 {
				return 0, ipv4Error{ip}
			}
		default:
			return 0, ipv4Error{ip}
		}
	}

	return long | n, nil
}

var n2s [256]string

func init() {
	for i := 0; i < 256; i++ {
		n2s[i] = strconv.Itoa(i)
	}
}

// Long2V4 convert an uint32 integer to ipv4 string
func Long2V4(ip uint32) string {
	b := make([]byte, 0, 15)

	b = append(b, n2s[byte(ip>>24)]...)
	b = append(b, '.')
	b = append(b, n2s[byte(ip>>16)]...)
	b = append(b, '.')
	b = append(b, n2s[byte(ip>>8)]...)
	b = append(b, '.')
	b = append(b, n2s[byte(ip)]...)

	/* #nosec G103 */
	return *(*string)(unsafe.Pointer(&b))
}