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package toml
import "strings"
// MetaData allows access to meta information about TOML data that may not
// be inferrable via reflection. In particular, whether a key has been defined
// and the TOML type of a key.
type MetaData struct {
mapping map[string]interface{}
types map[string]tomlType
keys []Key
decoded map[string]bool
context Key // Used only during decoding.
// IsDefined returns true if the key given exists in the TOML data. The key
// should be specified hierarchially. e.g.,
// // access the TOML key 'a.b.c'
// IsDefined("a", "b", "c")
// IsDefined will return false if an empty key given. Keys are case sensitive.
func (md *MetaData) IsDefined(key ...string) bool {
if len(key) == 0 {
return false
var hash map[string]interface{}
var ok bool
var hashOrVal interface{} = md.mapping
for _, k := range key {
if hash, ok = hashOrVal.(map[string]interface{}); !ok {
return false
if hashOrVal, ok = hash[k]; !ok {
return false
return true
// Type returns a string representation of the type of the key specified.
// Type will return the empty string if given an empty key or a key that
// does not exist. Keys are case sensitive.
func (md *MetaData) Type(key ...string) string {
fullkey := strings.Join(key, ".")
if typ, ok := md.types[fullkey]; ok {
return typ.typeString()
return ""
// Key is the type of any TOML key, including key groups. Use (MetaData).Keys
// to get values of this type.
type Key []string
func (k Key) String() string {
return strings.Join(k, ".")
func (k Key) maybeQuotedAll() string {
var ss []string
for i := range k {
ss = append(ss, k.maybeQuoted(i))
return strings.Join(ss, ".")
func (k Key) maybeQuoted(i int) string {
quote := false
for _, c := range k[i] {
if !isBareKeyChar(c) {
quote = true
if quote {
return "\"" + strings.Replace(k[i], "\"", "\\\"", -1) + "\""
return k[i]
func (k Key) add(piece string) Key {
newKey := make(Key, len(k)+1)
copy(newKey, k)
newKey[len(k)] = piece
return newKey
// Keys returns a slice of every key in the TOML data, including key groups.
// Each key is itself a slice, where the first element is the top of the
// hierarchy and the last is the most specific.
// The list will have the same order as the keys appeared in the TOML data.
// All keys returned are non-empty.
func (md *MetaData) Keys() []Key {
return md.keys
// Undecoded returns all keys that have not been decoded in the order in which
// they appear in the original TOML document.
// This includes keys that haven't been decoded because of a Primitive value.
// Once the Primitive value is decoded, the keys will be considered decoded.
// Also note that decoding into an empty interface will result in no decoding,
// and so no keys will be considered decoded.
// In this sense, the Undecoded keys correspond to keys in the TOML document
// that do not have a concrete type in your representation.
func (md *MetaData) Undecoded() []Key {
undecoded := make([]Key, 0, len(md.keys))
for _, key := range md.keys {
if !md.decoded[key.String()] {
undecoded = append(undecoded, key)
return undecoded
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