Go 实现 IP 地址与十进制互转：IPv4/IPv6 位运算与 net 包两种方案详解

package main

import (
    "fmt"
    "math/big"
    "net"
)

// IPv4ToDecimal 将 IPv4 地址字符串转换为十进制字符串
func IPv4ToDecimal(ipStr string) (string, error) {
    ip := net.ParseIP(ipStr)
    if ip == nil {
        return "", fmt.Errorf("无效的 IP 地址: %s", ipStr)
    }
    ip4 := ip.To4()
    if ip4 == nil {
        return "", fmt.Errorf("不是 IPv4 地址: %s", ipStr)
    }
    decimal := big.NewInt(0)
    for _, b := range ip4 {
        decimal.Lsh(decimal, 8).Add(decimal, big.NewInt(int64(b)))
    }
    return decimal.String(), nil
}

// DecimalToIPv4 将十进制字符串转换为 IPv4 地址
func DecimalToIPv4(decimalStr string) (string, error) {
    decimal := new(big.Int)
    _, ok := decimal.SetString(decimalStr, 10)
    if !ok {
        return "", fmt.Errorf("无效的十进制数字: %s", decimalStr)
    }
    maxIPv4 := new(big.Int).Sub(
        new(big.Int).Lsh(big.NewInt(1), 32),
        big.NewInt(1),
    )
    if decimal.Sign() < 0 || decimal.Cmp(maxIPv4) > 0 {
        return "", fmt.Errorf("数值超出 IPv4 范围 (0 ~ 4294967295): %s", decimalStr)
    }
    ip4Bytes := make([]byte, 4)
    for i := 3; i >= 0; i-- {
        ip4Bytes[i] = byte(decimal.Uint64() & 0xFF)
        decimal.Rsh(decimal, 8)
    }
    return net.IPv4(ip4Bytes[0], ip4Bytes[1], ip4Bytes[2], ip4Bytes[3]).String(), nil
}

func main() {
    ipStr := "192.168.1.1"
    dec, _ := IPv4ToDecimal(ipStr)
    fmt.Printf("%s -> %s\n", ipStr, dec) // 192.168.1.1 -> 3232235777

    restored, _ := DecimalToIPv4(dec)
    fmt.Printf("%s -> %s\n", dec, restored) // 3232235777 -> 192.168.1.1
}

package main

import (
    "fmt"
    "strconv"
    "strings"
)

// CustomIPv4ToDecimal 用位运算将 IPv4 字符串转为十进制
func CustomIPv4ToDecimal(ipStr string) (uint32, error) {
    segments := strings.Split(ipStr, ".")
    if len(segments) != 4 {
        return 0, fmt.Errorf("IPv4 格式错误，需要 4 段: %s", ipStr)
    }
    var result uint32
    for i, seg := range segments {
        val, err := strconv.Atoi(seg)
        if err != nil || val < 0 || val > 255 {
            return 0, fmt.Errorf("第 %d 段数值无效 (应为 0-255): %s", i+1, seg)
        }
        // 第 1 段左移 24 位，第 2 段左移 16 位，第 3 段左移 8 位，第 4 段不移
        result += uint32(val) << ((3 - i) * 8)
    }
    return result, nil
}

// CustomDecimalToIPv4 用位运算将十进制转为 IPv4 字符串
func CustomDecimalToIPv4(decimal uint32) string {
    return fmt.Sprintf("%d.%d.%d.%d",
        (decimal>>24)&0xFF,
        (decimal>>16)&0xFF,
        (decimal>>8)&0xFF,
        decimal&0xFF,
    )
}

func main() {
    ipStr := "192.168.1.1"
    dec, _ := CustomIPv4ToDecimal(ipStr)
    fmt.Printf("%s -> %d\n", ipStr, dec) // 192.168.1.1 -> 3232235777

    restored := CustomDecimalToIPv4(dec)
    fmt.Printf("%d -> %s\n", dec, restored) // 3232235777 -> 192.168.1.1
}

package main

import (
    "fmt"
    "math/big"
    "net"
)

// IPv6ToDecimal 将 IPv6 地址转换为十进制字符串
func IPv6ToDecimal(ipStr string) (string, error) {
    ip := net.ParseIP(ipStr)
    if ip == nil {
        return "", fmt.Errorf("无效的 IPv6 地址: %s", ipStr)
    }
    ip6 := ip.To16()
    if ip6 == nil {
        return "", fmt.Errorf("无法转换为 IPv6: %s", ipStr)
    }
    decimal := big.NewInt(0)
    for _, b := range ip6 {
        decimal.Lsh(decimal, 8).Add(decimal, big.NewInt(int64(b)))
    }
    return decimal.String(), nil
}

// DecimalToIPv6 将十进制字符串转换为 IPv6 地址
func DecimalToIPv6(decimalStr string) (string, error) {
    decimal := new(big.Int)
    _, ok := decimal.SetString(decimalStr, 10)
    if !ok {
        return "", fmt.Errorf("无效的十进制数字: %s", decimalStr)
    }
    maxIPv6 := new(big.Int).Sub(
        new(big.Int).Lsh(big.NewInt(1), 128),
        big.NewInt(1),
    )
    if decimal.Sign() < 0 || decimal.Cmp(maxIPv6) > 0 {
        return "", fmt.Errorf("数值超出 IPv6 范围: %s", decimalStr)
    }
    ip6Bytes := make([]byte, 16)
    for i := 15; i >= 0; i-- {
        ip6Bytes[i] = byte(decimal.Uint64() & 0xFF)
        decimal.Rsh(decimal, 8)
    }
    return net.IP(ip6Bytes).String(), nil
}

func main() {
    ipv6Str := "2001:0db8:85a3:0000:0000:8a2e:0370:7334"
    dec, _ := IPv6ToDecimal(ipv6Str)
    fmt.Printf("%s -> %s\n", ipv6Str, dec)

    restored, _ := DecimalToIPv6(dec)
    fmt.Printf("%s -> %s\n", dec, restored)
    // 输出: 2001:db8:85a3::8a2e:370:7334（Go 会自动压缩连续零段为 ::）
}