vendor/gopkg.in/yaml.v3/yaml.go - voltha-openonu-adapter-go - Gitiles

 //
 // Copyright (c) 2011-2019 Canonical Ltd
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 // Package yaml implements YAML support for the Go language.
 //
 // Source code and other details for the project are available at GitHub:
 //
 //   https://github.com/go-yaml/yaml
 //
 package yaml

 import (
 	"errors"
 	"fmt"
 	"io"
 	"reflect"
 	"strings"
 	"sync"
 	"unicode/utf8"
 )

 // The Unmarshaler interface may be implemented by types to customize their
 // behavior when being unmarshaled from a YAML document.
 type Unmarshaler interface {
 	UnmarshalYAML(value *Node) error
 }

 type obsoleteUnmarshaler interface {
 	UnmarshalYAML(unmarshal func(interface{}) error) error
 }

 // The Marshaler interface may be implemented by types to customize their
 // behavior when being marshaled into a YAML document. The returned value
 // is marshaled in place of the original value implementing Marshaler.
 //
 // If an error is returned by MarshalYAML, the marshaling procedure stops
 // and returns with the provided error.
 type Marshaler interface {
 	MarshalYAML() (interface{}, error)
 }

 // Unmarshal decodes the first document found within the in byte slice
 // and assigns decoded values into the out value.
 //
 // Maps and pointers (to a struct, string, int, etc) are accepted as out
 // values. If an internal pointer within a struct is not initialized,
 // the yaml package will initialize it if necessary for unmarshalling
 // the provided data. The out parameter must not be nil.
 //
 // The type of the decoded values should be compatible with the respective
 // values in out. If one or more values cannot be decoded due to a type
 // mismatches, decoding continues partially until the end of the YAML
 // content, and a *yaml.TypeError is returned with details for all
 // missed values.
 //
 // Struct fields are only unmarshalled if they are exported (have an
 // upper case first letter), and are unmarshalled using the field name
 // lowercased as the default key. Custom keys may be defined via the
 // "yaml" name in the field tag: the content preceding the first comma
 // is used as the key, and the following comma-separated options are
 // used to tweak the marshalling process (see Marshal).
 // Conflicting names result in a runtime error.
 //
 // For example:
 //
 //     type T struct {
 //         F int `yaml:"a,omitempty"`
 //         B int
 //     }
 //     var t T
 //     yaml.Unmarshal([]byte("a: 1\nb: 2"), &t)
 //
 // See the documentation of Marshal for the format of tags and a list of
 // supported tag options.
 //
 func Unmarshal(in []byte, out interface{}) (err error) {
 	return unmarshal(in, out, false)
 }

 // A Decoder reads and decodes YAML values from an input stream.
 type Decoder struct {
 	parser      *parser
 	knownFields bool
 }

 // NewDecoder returns a new decoder that reads from r.
 //
 // The decoder introduces its own buffering and may read
 // data from r beyond the YAML values requested.
 func NewDecoder(r io.Reader) *Decoder {
 	return &Decoder{
 		parser: newParserFromReader(r),
 	}
 }

 // KnownFields ensures that the keys in decoded mappings to
 // exist as fields in the struct being decoded into.
 func (dec *Decoder) KnownFields(enable bool) {
 	dec.knownFields = enable
 }

 // Decode reads the next YAML-encoded value from its input
 // and stores it in the value pointed to by v.
 //
 // See the documentation for Unmarshal for details about the
 // conversion of YAML into a Go value.
 func (dec *Decoder) Decode(v interface{}) (err error) {
 	d := newDecoder()
 	d.knownFields = dec.knownFields
 	defer handleErr(&err)
 	node := dec.parser.parse()
 	if node == nil {
 		return io.EOF
 	}
 	out := reflect.ValueOf(v)
 	if out.Kind() == reflect.Ptr && !out.IsNil() {
 		out = out.Elem()
 	}
 	d.unmarshal(node, out)
 	if len(d.terrors) > 0 {
 		return &TypeError{d.terrors}
 	}
 	return nil
 }

 // Decode decodes the node and stores its data into the value pointed to by v.
 //
 // See the documentation for Unmarshal for details about the
 // conversion of YAML into a Go value.
 func (n *Node) Decode(v interface{}) (err error) {
 	d := newDecoder()
 	defer handleErr(&err)
 	out := reflect.ValueOf(v)
 	if out.Kind() == reflect.Ptr && !out.IsNil() {
 		out = out.Elem()
 	}
 	d.unmarshal(n, out)
 	if len(d.terrors) > 0 {
 		return &TypeError{d.terrors}
 	}
 	return nil
 }

 func unmarshal(in []byte, out interface{}, strict bool) (err error) {
 	defer handleErr(&err)
 	d := newDecoder()
 	p := newParser(in)
 	defer p.destroy()
 	node := p.parse()
 	if node != nil {
 		v := reflect.ValueOf(out)
 		if v.Kind() == reflect.Ptr && !v.IsNil() {
 			v = v.Elem()
 		}
 		d.unmarshal(node, v)
 	}
 	if len(d.terrors) > 0 {
 		return &TypeError{d.terrors}
 	}
 	return nil
 }

 // Marshal serializes the value provided into a YAML document. The structure
 // of the generated document will reflect the structure of the value itself.
 // Maps and pointers (to struct, string, int, etc) are accepted as the in value.
 //
 // Struct fields are only marshalled if they are exported (have an upper case
 // first letter), and are marshalled using the field name lowercased as the
 // default key. Custom keys may be defined via the "yaml" name in the field
 // tag: the content preceding the first comma is used as the key, and the
 // following comma-separated options are used to tweak the marshalling process.
 // Conflicting names result in a runtime error.
 //
 // The field tag format accepted is:
 //
 //     `(...) yaml:"[<key>][,<flag1>[,<flag2>]]" (...)`
 //
 // The following flags are currently supported:
 //
 //     omitempty    Only include the field if it's not set to the zero
 //                  value for the type or to empty slices or maps.
 //                  Zero valued structs will be omitted if all their public
 //                  fields are zero, unless they implement an IsZero
 //                  method (see the IsZeroer interface type), in which
 //                  case the field will be excluded if IsZero returns true.
 //
 //     flow         Marshal using a flow style (useful for structs,
 //                  sequences and maps).
 //
 //     inline       Inline the field, which must be a struct or a map,
 //                  causing all of its fields or keys to be processed as if
 //                  they were part of the outer struct. For maps, keys must
 //                  not conflict with the yaml keys of other struct fields.
 //
 // In addition, if the key is "-", the field is ignored.
 //
 // For example:
 //
 //     type T struct {
 //         F int `yaml:"a,omitempty"`
 //         B int
 //     }
 //     yaml.Marshal(&T{B: 2}) // Returns "b: 2\n"
 //     yaml.Marshal(&T{F: 1}} // Returns "a: 1\nb: 0\n"
 //
 func Marshal(in interface{}) (out []byte, err error) {
 	defer handleErr(&err)
 	e := newEncoder()
 	defer e.destroy()
 	e.marshalDoc("", reflect.ValueOf(in))
 	e.finish()
 	out = e.out
 	return
 }

 // An Encoder writes YAML values to an output stream.
 type Encoder struct {
 	encoder *encoder
 }

 // NewEncoder returns a new encoder that writes to w.
 // The Encoder should be closed after use to flush all data
 // to w.
 func NewEncoder(w io.Writer) *Encoder {
 	return &Encoder{
 		encoder: newEncoderWithWriter(w),
 	}
 }

 // Encode writes the YAML encoding of v to the stream.
 // If multiple items are encoded to the stream, the
 // second and subsequent document will be preceded
 // with a "---" document separator, but the first will not.
 //
 // See the documentation for Marshal for details about the conversion of Go
 // values to YAML.
 func (e *Encoder) Encode(v interface{}) (err error) {
 	defer handleErr(&err)
 	e.encoder.marshalDoc("", reflect.ValueOf(v))
 	return nil
 }

 // Encode encodes value v and stores its representation in n.
 //
 // See the documentation for Marshal for details about the
 // conversion of Go values into YAML.
 func (n *Node) Encode(v interface{}) (err error) {
 	defer handleErr(&err)
 	e := newEncoder()
 	defer e.destroy()
 	e.marshalDoc("", reflect.ValueOf(v))
 	e.finish()
 	p := newParser(e.out)
 	p.textless = true
 	defer p.destroy()
 	doc := p.parse()
 	*n = *doc.Content[0]
 	return nil
 }

 // SetIndent changes the used indentation used when encoding.
 func (e *Encoder) SetIndent(spaces int) {
 	if spaces < 0 {
 		panic("yaml: cannot indent to a negative number of spaces")
 	}
 	e.encoder.indent = spaces
 }

 // Close closes the encoder by writing any remaining data.
 // It does not write a stream terminating string "...".
 func (e *Encoder) Close() (err error) {
 	defer handleErr(&err)
 	e.encoder.finish()
 	return nil
 }

 func handleErr(err *error) {
 	if v := recover(); v != nil {
 		if e, ok := v.(yamlError); ok {
 			*err = e.err
 		} else {
 			panic(v)
 		}
 	}
 }

 type yamlError struct {
 	err error
 }

 func fail(err error) {
 	panic(yamlError{err})
 }

 func failf(format string, args ...interface{}) {
 	panic(yamlError{fmt.Errorf("yaml: "+format, args...)})
 }

 // A TypeError is returned by Unmarshal when one or more fields in
 // the YAML document cannot be properly decoded into the requested
 // types. When this error is returned, the value is still
 // unmarshaled partially.
 type TypeError struct {
 	Errors []string
 }

 func (e *TypeError) Error() string {
 	return fmt.Sprintf("yaml: unmarshal errors:\n  %s", strings.Join(e.Errors, "\n  "))
 }

 type Kind uint32

 const (
 	DocumentNode Kind = 1 << iota
 	SequenceNode
 	MappingNode
 	ScalarNode
 	AliasNode
 )

 type Style uint32

 const (
 	TaggedStyle Style = 1 << iota
 	DoubleQuotedStyle
 	SingleQuotedStyle
 	LiteralStyle
 	FoldedStyle
 	FlowStyle
 )

 // Node represents an element in the YAML document hierarchy. While documents
 // are typically encoded and decoded into higher level types, such as structs
 // and maps, Node is an intermediate representation that allows detailed
 // control over the content being decoded or encoded.
 //
 // It's worth noting that although Node offers access into details such as
 // line numbers, colums, and comments, the content when re-encoded will not
 // have its original textual representation preserved. An effort is made to
 // render the data plesantly, and to preserve comments near the data they
 // describe, though.
 //
 // Values that make use of the Node type interact with the yaml package in the
 // same way any other type would do, by encoding and decoding yaml data
 // directly or indirectly into them.
 //
 // For example:
 //
 //     var person struct {
 //             Name    string
 //             Address yaml.Node
 //     }
 //     err := yaml.Unmarshal(data, &person)
 //
 // Or by itself:
 //
 //     var person Node
 //     err := yaml.Unmarshal(data, &person)
 //
 type Node struct {
 	// Kind defines whether the node is a document, a mapping, a sequence,
 	// a scalar value, or an alias to another node. The specific data type of
 	// scalar nodes may be obtained via the ShortTag and LongTag methods.
 	Kind  Kind

 	// Style allows customizing the apperance of the node in the tree.
 	Style Style

 	// Tag holds the YAML tag defining the data type for the value.
 	// When decoding, this field will always be set to the resolved tag,
 	// even when it wasn't explicitly provided in the YAML content.
 	// When encoding, if this field is unset the value type will be
 	// implied from the node properties, and if it is set, it will only
 	// be serialized into the representation if TaggedStyle is used or
 	// the implicit tag diverges from the provided one.
 	Tag string

 	// Value holds the unescaped and unquoted represenation of the value.
 	Value string

 	// Anchor holds the anchor name for this node, which allows aliases to point to it.
 	Anchor string

 	// Alias holds the node that this alias points to. Only valid when Kind is AliasNode.
 	Alias *Node

 	// Content holds contained nodes for documents, mappings, and sequences.
 	Content []*Node

 	// HeadComment holds any comments in the lines preceding the node and
 	// not separated by an empty line.
 	HeadComment string

 	// LineComment holds any comments at the end of the line where the node is in.
 	LineComment string

 	// FootComment holds any comments following the node and before empty lines.
 	FootComment string

 	// Line and Column hold the node position in the decoded YAML text.
 	// These fields are not respected when encoding the node.
 	Line   int
 	Column int
 }

 // IsZero returns whether the node has all of its fields unset.
 func (n *Node) IsZero() bool {
 	return n.Kind == 0 && n.Style == 0 && n.Tag == "" && n.Value == "" && n.Anchor == "" && n.Alias == nil && n.Content == nil &&
 		n.HeadComment == "" && n.LineComment == "" && n.FootComment == "" && n.Line == 0 && n.Column == 0
 }


 // LongTag returns the long form of the tag that indicates the data type for
 // the node. If the Tag field isn't explicitly defined, one will be computed
 // based on the node properties.
 func (n *Node) LongTag() string {
 	return longTag(n.ShortTag())
 }

 // ShortTag returns the short form of the YAML tag that indicates data type for
 // the node. If the Tag field isn't explicitly defined, one will be computed
 // based on the node properties.
 func (n *Node) ShortTag() string {
 	if n.indicatedString() {
 		return strTag
 	}
 	if n.Tag == "" || n.Tag == "!" {
 		switch n.Kind {
 		case MappingNode:
 			return mapTag
 		case SequenceNode:
 			return seqTag
 		case AliasNode:
 			if n.Alias != nil {
 				return n.Alias.ShortTag()
 			}
 		case ScalarNode:
 			tag, _ := resolve("", n.Value)
 			return tag
 		case 0:
 			// Special case to make the zero value convenient.
 			if n.IsZero() {
 				return nullTag
 			}
 		}
 		return ""
 	}
 	return shortTag(n.Tag)
 }

 func (n *Node) indicatedString() bool {
 	return n.Kind == ScalarNode &&
 		(shortTag(n.Tag) == strTag ||
 			(n.Tag == "" || n.Tag == "!") && n.Style&(SingleQuotedStyle|DoubleQuotedStyle|LiteralStyle|FoldedStyle) != 0)
 }

 // SetString is a convenience function that sets the node to a string value
 // and defines its style in a pleasant way depending on its content.
 func (n *Node) SetString(s string) {
 	n.Kind = ScalarNode
 	if utf8.ValidString(s) {
 		n.Value = s
 		n.Tag = strTag
 	} else {
 		n.Value = encodeBase64(s)
 		n.Tag = binaryTag
 	}
 	if strings.Contains(n.Value, "\n") {
 		n.Style = LiteralStyle
 	}
 }

 // --------------------------------------------------------------------------
 // Maintain a mapping of keys to structure field indexes

 // The code in this section was copied from mgo/bson.

 // structInfo holds details for the serialization of fields of
 // a given struct.
 type structInfo struct {
 	FieldsMap  map[string]fieldInfo
 	FieldsList []fieldInfo

 	// InlineMap is the number of the field in the struct that
 	// contains an ,inline map, or -1 if there's none.
 	InlineMap int

 	// InlineUnmarshalers holds indexes to inlined fields that
 	// contain unmarshaler values.
 	InlineUnmarshalers [][]int
 }

 type fieldInfo struct {
 	Key       string
 	Num       int
 	OmitEmpty bool
 	Flow      bool
 	// Id holds the unique field identifier, so we can cheaply
 	// check for field duplicates without maintaining an extra map.
 	Id int

 	// Inline holds the field index if the field is part of an inlined struct.
 	Inline []int
 }

 var structMap = make(map[reflect.Type]*structInfo)
 var fieldMapMutex sync.RWMutex
 var unmarshalerType reflect.Type

 func init() {
 	var v Unmarshaler
 	unmarshalerType = reflect.ValueOf(&v).Elem().Type()
 }

 func getStructInfo(st reflect.Type) (*structInfo, error) {
 	fieldMapMutex.RLock()
 	sinfo, found := structMap[st]
 	fieldMapMutex.RUnlock()
 	if found {
 		return sinfo, nil
 	}

 	n := st.NumField()
 	fieldsMap := make(map[string]fieldInfo)
 	fieldsList := make([]fieldInfo, 0, n)
 	inlineMap := -1
 	inlineUnmarshalers := [][]int(nil)
 	for i := 0; i != n; i++ {
 		field := st.Field(i)
 		if field.PkgPath != "" && !field.Anonymous {
 			continue // Private field
 		}

 		info := fieldInfo{Num: i}

 		tag := field.Tag.Get("yaml")
 		if tag == "" && strings.Index(string(field.Tag), ":") < 0 {
 			tag = string(field.Tag)
 		}
 		if tag == "-" {
 			continue
 		}

 		inline := false
 		fields := strings.Split(tag, ",")
 		if len(fields) > 1 {
 			for _, flag := range fields[1:] {
 				switch flag {
 				case "omitempty":
 					info.OmitEmpty = true
 				case "flow":
 					info.Flow = true
 				case "inline":
 					inline = true
 				default:
 					return nil, errors.New(fmt.Sprintf("unsupported flag %q in tag %q of type %s", flag, tag, st))
 				}
 			}
 			tag = fields[0]
 		}

 		if inline {
 			switch field.Type.Kind() {
 			case reflect.Map:
 				if inlineMap >= 0 {
 					return nil, errors.New("multiple ,inline maps in struct " + st.String())
 				}
 				if field.Type.Key() != reflect.TypeOf("") {
 					return nil, errors.New("option ,inline needs a map with string keys in struct " + st.String())
 				}
 				inlineMap = info.Num
 			case reflect.Struct, reflect.Ptr:
 				ftype := field.Type
 				for ftype.Kind() == reflect.Ptr {
 					ftype = ftype.Elem()
 				}
 				if ftype.Kind() != reflect.Struct {
 					return nil, errors.New("option ,inline may only be used on a struct or map field")
 				}
 				if reflect.PtrTo(ftype).Implements(unmarshalerType) {
 					inlineUnmarshalers = append(inlineUnmarshalers, []int{i})
 				} else {
 					sinfo, err := getStructInfo(ftype)
 					if err != nil {
 						return nil, err
 					}
 					for _, index := range sinfo.InlineUnmarshalers {
 						inlineUnmarshalers = append(inlineUnmarshalers, append([]int{i}, index...))
 					}
 					for _, finfo := range sinfo.FieldsList {
 						if _, found := fieldsMap[finfo.Key]; found {
 							msg := "duplicated key '" + finfo.Key + "' in struct " + st.String()
 							return nil, errors.New(msg)
 						}
 						if finfo.Inline == nil {
 							finfo.Inline = []int{i, finfo.Num}
 						} else {
 							finfo.Inline = append([]int{i}, finfo.Inline...)
 						}
 						finfo.Id = len(fieldsList)
 						fieldsMap[finfo.Key] = finfo
 						fieldsList = append(fieldsList, finfo)
 					}
 				}
 			default:
 				return nil, errors.New("option ,inline may only be used on a struct or map field")
 			}
 			continue
 		}

 		if tag != "" {
 			info.Key = tag
 		} else {
 			info.Key = strings.ToLower(field.Name)
 		}

 		if _, found = fieldsMap[info.Key]; found {
 			msg := "duplicated key '" + info.Key + "' in struct " + st.String()
 			return nil, errors.New(msg)
 		}

 		info.Id = len(fieldsList)
 		fieldsList = append(fieldsList, info)
 		fieldsMap[info.Key] = info
 	}

 	sinfo = &structInfo{
 		FieldsMap:          fieldsMap,
 		FieldsList:         fieldsList,
 		InlineMap:          inlineMap,
 		InlineUnmarshalers: inlineUnmarshalers,
 	}

 	fieldMapMutex.Lock()
 	structMap[st] = sinfo
 	fieldMapMutex.Unlock()
 	return sinfo, nil
 }

 // IsZeroer is used to check whether an object is zero to
 // determine whether it should be omitted when marshaling
 // with the omitempty flag. One notable implementation
 // is time.Time.
 type IsZeroer interface {
 	IsZero() bool
 }

 func isZero(v reflect.Value) bool {
 	kind := v.Kind()
 	if z, ok := v.Interface().(IsZeroer); ok {
 		if (kind == reflect.Ptr || kind == reflect.Interface) && v.IsNil() {
 			return true
 		}
 		return z.IsZero()
 	}
 	switch kind {
 	case reflect.String:
 		return len(v.String()) == 0
 	case reflect.Interface, reflect.Ptr:
 		return v.IsNil()
 	case reflect.Slice:
 		return v.Len() == 0
 	case reflect.Map:
 		return v.Len() == 0
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
 		return v.Int() == 0
 	case reflect.Float32, reflect.Float64:
 		return v.Float() == 0
 	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
 		return v.Uint() == 0
 	case reflect.Bool:
 		return !v.Bool()
 	case reflect.Struct:
 		vt := v.Type()
 		for i := v.NumField() - 1; i >= 0; i-- {
 			if vt.Field(i).PkgPath != "" {
 				continue // Private field
 			}
 			if !isZero(v.Field(i)) {
 				return false
 			}
 		}
 		return true
 	}
 	return false
 }
	//
	// Copyright (c) 2011-2019 Canonical Ltd
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	// Package yaml implements YAML support for the Go language.
	//
	// Source code and other details for the project are available at GitHub:
	//
	// https://github.com/go-yaml/yaml
	//
	package yaml

	import (
	"errors"
	"fmt"
	"io"
	"reflect"
	"strings"
	"sync"
	"unicode/utf8"
	)

	// The Unmarshaler interface may be implemented by types to customize their
	// behavior when being unmarshaled from a YAML document.
	type Unmarshaler interface {
	UnmarshalYAML(value *Node) error
	}

	type obsoleteUnmarshaler interface {
	UnmarshalYAML(unmarshal func(interface{}) error) error
	}

	// The Marshaler interface may be implemented by types to customize their
	// behavior when being marshaled into a YAML document. The returned value
	// is marshaled in place of the original value implementing Marshaler.
	//
	// If an error is returned by MarshalYAML, the marshaling procedure stops
	// and returns with the provided error.
	type Marshaler interface {
	MarshalYAML() (interface{}, error)
	}

	// Unmarshal decodes the first document found within the in byte slice
	// and assigns decoded values into the out value.
	//
	// Maps and pointers (to a struct, string, int, etc) are accepted as out
	// values. If an internal pointer within a struct is not initialized,
	// the yaml package will initialize it if necessary for unmarshalling
	// the provided data. The out parameter must not be nil.
	//
	// The type of the decoded values should be compatible with the respective
	// values in out. If one or more values cannot be decoded due to a type
	// mismatches, decoding continues partially until the end of the YAML
	// content, and a *yaml.TypeError is returned with details for all
	// missed values.
	//
	// Struct fields are only unmarshalled if they are exported (have an
	// upper case first letter), and are unmarshalled using the field name
	// lowercased as the default key. Custom keys may be defined via the
	// "yaml" name in the field tag: the content preceding the first comma
	// is used as the key, and the following comma-separated options are
	// used to tweak the marshalling process (see Marshal).
	// Conflicting names result in a runtime error.
	//
	// For example:
	//
	// type T struct {
	// F int `yaml:"a,omitempty"`
	// B int
	// }
	// var t T
	// yaml.Unmarshal([]byte("a: 1\nb: 2"), &t)
	//
	// See the documentation of Marshal for the format of tags and a list of
	// supported tag options.
	//
	func Unmarshal(in []byte, out interface{}) (err error) {
	return unmarshal(in, out, false)
	}

	// A Decoder reads and decodes YAML values from an input stream.
	type Decoder struct {
	parser *parser
	knownFields bool
	}

	// NewDecoder returns a new decoder that reads from r.
	//
	// The decoder introduces its own buffering and may read
	// data from r beyond the YAML values requested.
	func NewDecoder(r io.Reader) *Decoder {
	return &Decoder{
	parser: newParserFromReader(r),
	}
	}

	// KnownFields ensures that the keys in decoded mappings to
	// exist as fields in the struct being decoded into.
	func (dec *Decoder) KnownFields(enable bool) {
	dec.knownFields = enable
	}

	// Decode reads the next YAML-encoded value from its input
	// and stores it in the value pointed to by v.
	//
	// See the documentation for Unmarshal for details about the
	// conversion of YAML into a Go value.
	func (dec *Decoder) Decode(v interface{}) (err error) {
	d := newDecoder()
	d.knownFields = dec.knownFields
	defer handleErr(&err)
	node := dec.parser.parse()
	if node == nil {
	return io.EOF
	}
	out := reflect.ValueOf(v)
	if out.Kind() == reflect.Ptr && !out.IsNil() {
	out = out.Elem()
	}
	d.unmarshal(node, out)
	if len(d.terrors) > 0 {
	return &TypeError{d.terrors}
	}
	return nil
	}

	// Decode decodes the node and stores its data into the value pointed to by v.
	//
	// See the documentation for Unmarshal for details about the
	// conversion of YAML into a Go value.
	func (n *Node) Decode(v interface{}) (err error) {
	d := newDecoder()
	defer handleErr(&err)
	out := reflect.ValueOf(v)
	if out.Kind() == reflect.Ptr && !out.IsNil() {
	out = out.Elem()
	}
	d.unmarshal(n, out)
	if len(d.terrors) > 0 {
	return &TypeError{d.terrors}
	}
	return nil
	}

	func unmarshal(in []byte, out interface{}, strict bool) (err error) {
	defer handleErr(&err)
	d := newDecoder()
	p := newParser(in)
	defer p.destroy()
	node := p.parse()
	if node != nil {
	v := reflect.ValueOf(out)
	if v.Kind() == reflect.Ptr && !v.IsNil() {
	v = v.Elem()
	}
	d.unmarshal(node, v)
	}
	if len(d.terrors) > 0 {
	return &TypeError{d.terrors}
	}
	return nil
	}

	// Marshal serializes the value provided into a YAML document. The structure
	// of the generated document will reflect the structure of the value itself.
	// Maps and pointers (to struct, string, int, etc) are accepted as the in value.
	//
	// Struct fields are only marshalled if they are exported (have an upper case
	// first letter), and are marshalled using the field name lowercased as the
	// default key. Custom keys may be defined via the "yaml" name in the field
	// tag: the content preceding the first comma is used as the key, and the
	// following comma-separated options are used to tweak the marshalling process.
	// Conflicting names result in a runtime error.
	//
	// The field tag format accepted is:
	//
	// `(...) yaml:"[<key>][,<flag1>[,<flag2>]]" (...)`
	//
	// The following flags are currently supported:
	//
	// omitempty Only include the field if it's not set to the zero
	// value for the type or to empty slices or maps.
	// Zero valued structs will be omitted if all their public
	// fields are zero, unless they implement an IsZero
	// method (see the IsZeroer interface type), in which
	// case the field will be excluded if IsZero returns true.
	//
	// flow Marshal using a flow style (useful for structs,
	// sequences and maps).
	//
	// inline Inline the field, which must be a struct or a map,
	// causing all of its fields or keys to be processed as if
	// they were part of the outer struct. For maps, keys must
	// not conflict with the yaml keys of other struct fields.
	//
	// In addition, if the key is "-", the field is ignored.
	//
	// For example:
	//
	// type T struct {
	// F int `yaml:"a,omitempty"`
	// B int
	// }
	// yaml.Marshal(&T{B: 2}) // Returns "b: 2\n"
	// yaml.Marshal(&T{F: 1}} // Returns "a: 1\nb: 0\n"
	//
	func Marshal(in interface{}) (out []byte, err error) {
	defer handleErr(&err)
	e := newEncoder()
	defer e.destroy()
	e.marshalDoc("", reflect.ValueOf(in))
	e.finish()
	out = e.out
	return
	}

	// An Encoder writes YAML values to an output stream.
	type Encoder struct {
	encoder *encoder
	}

	// NewEncoder returns a new encoder that writes to w.
	// The Encoder should be closed after use to flush all data
	// to w.
	func NewEncoder(w io.Writer) *Encoder {
	return &Encoder{
	encoder: newEncoderWithWriter(w),
	}
	}

	// Encode writes the YAML encoding of v to the stream.
	// If multiple items are encoded to the stream, the
	// second and subsequent document will be preceded
	// with a "---" document separator, but the first will not.
	//
	// See the documentation for Marshal for details about the conversion of Go
	// values to YAML.
	func (e *Encoder) Encode(v interface{}) (err error) {
	defer handleErr(&err)
	e.encoder.marshalDoc("", reflect.ValueOf(v))
	return nil
	}

	// Encode encodes value v and stores its representation in n.
	//
	// See the documentation for Marshal for details about the
	// conversion of Go values into YAML.
	func (n *Node) Encode(v interface{}) (err error) {
	defer handleErr(&err)
	e := newEncoder()
	defer e.destroy()
	e.marshalDoc("", reflect.ValueOf(v))
	e.finish()
	p := newParser(e.out)
	p.textless = true
	defer p.destroy()
	doc := p.parse()
	n = doc.Content[0]
	return nil
	}

	// SetIndent changes the used indentation used when encoding.
	func (e *Encoder) SetIndent(spaces int) {
	if spaces < 0 {
	panic("yaml: cannot indent to a negative number of spaces")
	}
	e.encoder.indent = spaces
	}

	// Close closes the encoder by writing any remaining data.
	// It does not write a stream terminating string "...".
	func (e *Encoder) Close() (err error) {
	defer handleErr(&err)
	e.encoder.finish()
	return nil
	}

	func handleErr(err *error) {
	if v := recover(); v != nil {
	if e, ok := v.(yamlError); ok {
	*err = e.err
	} else {
	panic(v)
	}
	}
	}

	type yamlError struct {
	err error
	}

	func fail(err error) {
	panic(yamlError{err})
	}

	func failf(format string, args ...interface{}) {
	panic(yamlError{fmt.Errorf("yaml: "+format, args...)})
	}

	// A TypeError is returned by Unmarshal when one or more fields in
	// the YAML document cannot be properly decoded into the requested
	// types. When this error is returned, the value is still
	// unmarshaled partially.
	type TypeError struct {
	Errors []string
	}

	func (e *TypeError) Error() string {
	return fmt.Sprintf("yaml: unmarshal errors:\n %s", strings.Join(e.Errors, "\n "))
	}

	type Kind uint32

	const (
	DocumentNode Kind = 1 << iota
	SequenceNode
	MappingNode
	ScalarNode
	AliasNode
	)

	type Style uint32

	const (
	TaggedStyle Style = 1 << iota
	DoubleQuotedStyle
	SingleQuotedStyle
	LiteralStyle
	FoldedStyle
	FlowStyle
	)

	// Node represents an element in the YAML document hierarchy. While documents
	// are typically encoded and decoded into higher level types, such as structs
	// and maps, Node is an intermediate representation that allows detailed
	// control over the content being decoded or encoded.
	//
	// It's worth noting that although Node offers access into details such as
	// line numbers, colums, and comments, the content when re-encoded will not
	// have its original textual representation preserved. An effort is made to
	// render the data plesantly, and to preserve comments near the data they
	// describe, though.
	//
	// Values that make use of the Node type interact with the yaml package in the
	// same way any other type would do, by encoding and decoding yaml data
	// directly or indirectly into them.
	//
	// For example:
	//
	// var person struct {
	// Name string
	// Address yaml.Node
	// }
	// err := yaml.Unmarshal(data, &person)
	//
	// Or by itself:
	//
	// var person Node
	// err := yaml.Unmarshal(data, &person)
	//
	type Node struct {
	// Kind defines whether the node is a document, a mapping, a sequence,
	// a scalar value, or an alias to another node. The specific data type of
	// scalar nodes may be obtained via the ShortTag and LongTag methods.
	Kind Kind

	// Style allows customizing the apperance of the node in the tree.
	Style Style

	// Tag holds the YAML tag defining the data type for the value.
	// When decoding, this field will always be set to the resolved tag,
	// even when it wasn't explicitly provided in the YAML content.
	// When encoding, if this field is unset the value type will be
	// implied from the node properties, and if it is set, it will only
	// be serialized into the representation if TaggedStyle is used or
	// the implicit tag diverges from the provided one.
	Tag string

	// Value holds the unescaped and unquoted represenation of the value.
	Value string

	// Anchor holds the anchor name for this node, which allows aliases to point to it.
	Anchor string

	// Alias holds the node that this alias points to. Only valid when Kind is AliasNode.
	Alias *Node

	// Content holds contained nodes for documents, mappings, and sequences.
	Content []*Node

	// HeadComment holds any comments in the lines preceding the node and
	// not separated by an empty line.
	HeadComment string

	// LineComment holds any comments at the end of the line where the node is in.
	LineComment string

	// FootComment holds any comments following the node and before empty lines.
	FootComment string

	// Line and Column hold the node position in the decoded YAML text.
	// These fields are not respected when encoding the node.
	Line int
	Column int
	}

	// IsZero returns whether the node has all of its fields unset.
	func (n *Node) IsZero() bool {
	return n.Kind == 0 && n.Style == 0 && n.Tag == "" && n.Value == "" && n.Anchor == "" && n.Alias == nil && n.Content == nil &&
	n.HeadComment == "" && n.LineComment == "" && n.FootComment == "" && n.Line == 0 && n.Column == 0
	}


	// LongTag returns the long form of the tag that indicates the data type for
	// the node. If the Tag field isn't explicitly defined, one will be computed
	// based on the node properties.
	func (n *Node) LongTag() string {
	return longTag(n.ShortTag())
	}

	// ShortTag returns the short form of the YAML tag that indicates data type for
	// the node. If the Tag field isn't explicitly defined, one will be computed
	// based on the node properties.
	func (n *Node) ShortTag() string {
	if n.indicatedString() {
	return strTag
	}
	if n.Tag == "" \|\| n.Tag == "!" {
	switch n.Kind {
	case MappingNode:
	return mapTag
	case SequenceNode:
	return seqTag
	case AliasNode:
	if n.Alias != nil {
	return n.Alias.ShortTag()
	}
	case ScalarNode:
	tag, _ := resolve("", n.Value)
	return tag
	case 0:
	// Special case to make the zero value convenient.
	if n.IsZero() {
	return nullTag
	}
	}
	return ""
	}
	return shortTag(n.Tag)
	}

	func (n *Node) indicatedString() bool {
	return n.Kind == ScalarNode &&
	(shortTag(n.Tag) == strTag \|\|
	(n.Tag == "" \|\| n.Tag == "!") && n.Style&(SingleQuotedStyle\|DoubleQuotedStyle\|LiteralStyle\|FoldedStyle) != 0)
	}

	// SetString is a convenience function that sets the node to a string value
	// and defines its style in a pleasant way depending on its content.
	func (n *Node) SetString(s string) {
	n.Kind = ScalarNode
	if utf8.ValidString(s) {
	n.Value = s
	n.Tag = strTag
	} else {
	n.Value = encodeBase64(s)
	n.Tag = binaryTag
	}
	if strings.Contains(n.Value, "\n") {
	n.Style = LiteralStyle
	}
	}

	// --------------------------------------------------------------------------
	// Maintain a mapping of keys to structure field indexes

	// The code in this section was copied from mgo/bson.

	// structInfo holds details for the serialization of fields of
	// a given struct.
	type structInfo struct {
	FieldsMap map[string]fieldInfo
	FieldsList []fieldInfo

	// InlineMap is the number of the field in the struct that
	// contains an ,inline map, or -1 if there's none.
	InlineMap int

	// InlineUnmarshalers holds indexes to inlined fields that
	// contain unmarshaler values.
	InlineUnmarshalers [][]int
	}

	type fieldInfo struct {
	Key string
	Num int
	OmitEmpty bool
	Flow bool
	// Id holds the unique field identifier, so we can cheaply
	// check for field duplicates without maintaining an extra map.
	Id int

	// Inline holds the field index if the field is part of an inlined struct.
	Inline []int
	}

	var structMap = make(map[reflect.Type]*structInfo)
	var fieldMapMutex sync.RWMutex
	var unmarshalerType reflect.Type

	func init() {
	var v Unmarshaler
	unmarshalerType = reflect.ValueOf(&v).Elem().Type()
	}

	func getStructInfo(st reflect.Type) (*structInfo, error) {
	fieldMapMutex.RLock()
	sinfo, found := structMap[st]
	fieldMapMutex.RUnlock()
	if found {
	return sinfo, nil
	}

	n := st.NumField()
	fieldsMap := make(map[string]fieldInfo)
	fieldsList := make([]fieldInfo, 0, n)
	inlineMap := -1
	inlineUnmarshalers := [][]int(nil)
	for i := 0; i != n; i++ {
	field := st.Field(i)
	if field.PkgPath != "" && !field.Anonymous {
	continue // Private field
	}

	info := fieldInfo{Num: i}

	tag := field.Tag.Get("yaml")
	if tag == "" && strings.Index(string(field.Tag), ":") < 0 {
	tag = string(field.Tag)
	}
	if tag == "-" {
	continue
	}

	inline := false
	fields := strings.Split(tag, ",")
	if len(fields) > 1 {
	for _, flag := range fields[1:] {
	switch flag {
	case "omitempty":
	info.OmitEmpty = true
	case "flow":
	info.Flow = true
	case "inline":
	inline = true
	default:
	return nil, errors.New(fmt.Sprintf("unsupported flag %q in tag %q of type %s", flag, tag, st))
	}
	}
	tag = fields[0]
	}

	if inline {
	switch field.Type.Kind() {
	case reflect.Map:
	if inlineMap >= 0 {
	return nil, errors.New("multiple ,inline maps in struct " + st.String())
	}
	if field.Type.Key() != reflect.TypeOf("") {
	return nil, errors.New("option ,inline needs a map with string keys in struct " + st.String())
	}
	inlineMap = info.Num
	case reflect.Struct, reflect.Ptr:
	ftype := field.Type
	for ftype.Kind() == reflect.Ptr {
	ftype = ftype.Elem()
	}
	if ftype.Kind() != reflect.Struct {
	return nil, errors.New("option ,inline may only be used on a struct or map field")
	}
	if reflect.PtrTo(ftype).Implements(unmarshalerType) {
	inlineUnmarshalers = append(inlineUnmarshalers, []int{i})
	} else {
	sinfo, err := getStructInfo(ftype)
	if err != nil {
	return nil, err
	}
	for _, index := range sinfo.InlineUnmarshalers {
	inlineUnmarshalers = append(inlineUnmarshalers, append([]int{i}, index...))
	}
	for _, finfo := range sinfo.FieldsList {
	if _, found := fieldsMap[finfo.Key]; found {
	msg := "duplicated key '" + finfo.Key + "' in struct " + st.String()
	return nil, errors.New(msg)
	}
	if finfo.Inline == nil {
	finfo.Inline = []int{i, finfo.Num}
	} else {
	finfo.Inline = append([]int{i}, finfo.Inline...)
	}
	finfo.Id = len(fieldsList)
	fieldsMap[finfo.Key] = finfo
	fieldsList = append(fieldsList, finfo)
	}
	}
	default:
	return nil, errors.New("option ,inline may only be used on a struct or map field")
	}
	continue
	}

	if tag != "" {
	info.Key = tag
	} else {
	info.Key = strings.ToLower(field.Name)
	}

	if _, found = fieldsMap[info.Key]; found {
	msg := "duplicated key '" + info.Key + "' in struct " + st.String()
	return nil, errors.New(msg)
	}

	info.Id = len(fieldsList)
	fieldsList = append(fieldsList, info)
	fieldsMap[info.Key] = info
	}

	sinfo = &structInfo{
	FieldsMap: fieldsMap,
	FieldsList: fieldsList,
	InlineMap: inlineMap,
	InlineUnmarshalers: inlineUnmarshalers,
	}

	fieldMapMutex.Lock()
	structMap[st] = sinfo
	fieldMapMutex.Unlock()
	return sinfo, nil
	}

	// IsZeroer is used to check whether an object is zero to
	// determine whether it should be omitted when marshaling
	// with the omitempty flag. One notable implementation
	// is time.Time.
	type IsZeroer interface {
	IsZero() bool
	}

	func isZero(v reflect.Value) bool {
	kind := v.Kind()
	if z, ok := v.Interface().(IsZeroer); ok {
	if (kind == reflect.Ptr \|\| kind == reflect.Interface) && v.IsNil() {
	return true
	}
	return z.IsZero()
	}
	switch kind {
	case reflect.String:
	return len(v.String()) == 0
	case reflect.Interface, reflect.Ptr:
	return v.IsNil()
	case reflect.Slice:
	return v.Len() == 0
	case reflect.Map:
	return v.Len() == 0
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
	return v.Int() == 0
	case reflect.Float32, reflect.Float64:
	return v.Float() == 0
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
	return v.Uint() == 0
	case reflect.Bool:
	return !v.Bool()
	case reflect.Struct:
	vt := v.Type()
	for i := v.NumField() - 1; i >= 0; i-- {
	if vt.Field(i).PkgPath != "" {
	continue // Private field
	}
	if !isZero(v.Field(i)) {
	return false
	}
	}
	return true
	}
	return false
	}