Simple SteamID conversion

steamid.go

/**
 * See https://developer.valvesoftware.com/wiki/SteamID for details.
 */
package steamid

import "strconv"

const (
	ACCOUNT_ID_BITS       = 32
	ACCOUNT_TYPE_BITS     = 4
	ACCOUNT_INSTANCE_BITS = 20
	ACCOUNT_UNIVERSE_BITS = 8

	DEFAULT_ACCOUNT_TYPE     int64 = 1
	DEFAULT_ACCOUNT_UNIVERSE int64 = 1
	DEFAULT_ACCOUNT_INSTANCE int64 = 1
)

func pad(binStr string, toLength int) string {
	delta := toLength - len(binStr)
	for i := 0; i < delta; i++ {
		binStr = "0" + binStr
	}
	return binStr
}

func ToAccountID(steamID int64) (int64, error) {
	padding, err := FromAccountID(0)
	if err != nil {
		return 0, err
	}
	return (steamID - padding), nil
}

func FromAccountID(accountID int64) (int64, error) {
	var (
		idBin       = pad(strconv.FormatInt(accountID,                2), ACCOUNT_ID_BITS)
		typeBin     = pad(strconv.FormatInt(DEFAULT_ACCOUNT_TYPE,     2), ACCOUNT_TYPE_BITS)
		instanceBin = pad(strconv.FormatInt(DEFAULT_ACCOUNT_INSTANCE, 2), ACCOUNT_INSTANCE_BITS)
		universeBin = pad(strconv.FormatInt(DEFAULT_ACCOUNT_UNIVERSE, 2), ACCOUNT_UNIVERSE_BITS)
	)
	return strconv.ParseInt(universeBin + typeBin + instanceBin + idBin, 2, 64)
}