Geogarbage

utils.go

// WGS84 EPSG identifier
const WGS84 = 4326

const DEG_TO_RAD = math.Pi / 180.0
const RAD_TO_DEG = 180.0 / math.Pi

// DecodeUTF16 converts a UTF-16 string to a UTF-8 string.
func DecodeUTF16(b []byte) (string, error) {
	if len(b)%2 != 0 {
		return "", errors.New("must have even length byte slice")
	}

	u16s := make([]uint16, 1)
	ret := &bytes.Buffer{}
	b8buf := make([]byte, 4)

	lb := len(b)
	for i := 0; i < lb; i+=2 {
		u16s[0] = uint16(b[i]) + (uint16(b[i+1]) << 8)
		r := utf16.Decode(u16s)
		n := utf8.EncodeRune(b8buf, r[0])
		ret.Write(b8buf[:n])
	}

	return ret.String(), nil
}

// DmToSd converts degrees/minutes formatted WGS84 coordinate to it's
// actual value in degrees.
func DmToSd(coord string) (float64, error) {
	if coord == "0" {
		return 0, nil
	}
	rg, err := regexp.Compile(`^(\d+)(\d\d\.\d+)$`)
	if err != nil {
		return 0, err
	}
	matches := rg.FindStringSubmatch(coord)
	d, err := strconv.ParseFloat(matches[1], 64)
	if err != nil {
		return 0, err
	}
	m, err := strconv.ParseFloat(matches[2], 64)
	return d + m/60, err
}

// Near checks a and b difference against required precision.
func Near(a, b, precision float64) bool {
	return math.Abs(a-b) <= precision
}

func IpToInt(ip net.IP) uint32 {
	if len(ip) == 16 {
		return binary.BigEndian.Uint32(ip[12:16])
	}
	return binary.BigEndian.Uint32(ip)
}

func IntToIp(nn uint32) net.IP {
	ip := make(net.IP, 4)
	binary.BigEndian.PutUint32(ip, nn)
	return ip
}

// IsLocal checks if addr is a local address on any of network interfaces
// available in system. If any error occurs, assumes that the address is
// local (returns true, err).
func IsLocal(addr net.Addr) (bool, error) {
	var ifaces []net.Interface
	var addrs []net.Addr
	ifaces, err := net.Interfaces()
	if err != nil {
		return true, err
	}
	for _, iface := range ifaces {
		addrs, err = iface.Addrs()
		if err != nil {
			return true, err
		}
		var isLocal bool
		for _, lAddr := range addrs {
			if lAddr == addr {
				isLocal = true
				break
			}
		}
		if isLocal {
			return true, nil
		}
	}
	return false, nil
}

// pure magic
func randFileName(prefix string) string {
	return prefix + strconv.Itoa(int(1e9 + (uint32(time.Now().UnixNano() + int64(os.Getpid())) * 1664525 + 1013904223) % 1e9))[1:]
}