golang ipv4 string to uint32.

ipconv.go

package ipconv

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

func Conv(ip string) (uint32, error) {
	segs := strings.Split(ip, ".")
	if len(segs) != 4 {
		return 0, fmt.Errorf("invalid ip4 input string")
	}

	s := make([]int, 4)
	for i := 0; i < 4; i++ {
		n, err := strconv.Atoi(segs[i])
		if err != nil {
			return 0, err
		}
		if n <= 0 || n > 255 {
			return 0, fmt.Errorf("invalid ip4 input string")
		}
		s[i] = n
	}

	rv := uint32(s[0]<<24 | s[1]<<16 | s[2]<<8 | s[3])
	return rv, nil
}

ipconv_test.go

package ipconv

import (
	"testing"

	"gotest.tools/assert"
)

func Test_Conv(t *testing.T) {
	var n uint32
	var err error
	n, err = Conv("1.1.1.1")
	assert.Assert(t, err == nil)
	assert.Equal(t, n, uint32(16843009))

	n, err = Conv("192.168.1.1")
	assert.Assert(t, err == nil)
	assert.Equal(t, n, uint32(3232235777))

	n, err = Conv("223.5.5.5")
	assert.Assert(t, err == nil)
	assert.Equal(t, n, uint32(3741648133))

	n, err = Conv("172.16.254.1")
	assert.Assert(t, err == nil)
	assert.Equal(t, n, uint32(2886794753))

	/* invalid input */
	// less than 4-part
	n, err = Conv("1.1.1")
	assert.Assert(t, err != nil)
	assert.Equal(t, n, uint32(0))

	// more than 4-part
	n, err = Conv("1.1.1.1.1")
	assert.Assert(t, err != nil)
	assert.Equal(t, n, uint32(0))

	// less than 1
	n, err = Conv("0.1.1.1")
	assert.Assert(t, err != nil)
	assert.Equal(t, n, uint32(0))

	// greater than 255
	n, err = Conv("1.1.256.1")
	assert.Assert(t, err != nil)
	assert.Equal(t, n, uint32(0))

	// greater than 255
	n, err = Conv("1.1.2345.1")
	assert.Assert(t, err != nil)
	assert.Equal(t, n, uint32(0))

	// not even a number...
	n, err = Conv("1.1.a.1")
	assert.Assert(t, err != nil)
	assert.Equal(t, n, uint32(0))
}