goyaml.go - third_party/go-yaml/yaml - Git at Google

 //
 // goyaml - YAML support for the Go language
 //
 //   https://wiki.ubuntu.com/goyaml
 //
 // Copyright (c) 2011 Canonical Ltd.
 //
 // Written by Gustavo Niemeyer <gustavo.niemeyer@canonical.com>
 //
 package goyaml

 import (
 	"reflect"
 	"runtime"
 	"strings"
 	"sync"
 	"os"
 )

 func handleErr(err *os.Error) {
 	if r := recover(); r != nil {
 		if _, ok := r.(runtime.Error); ok {
 			panic(r)
 		} else if _, ok := r.(*reflect.ValueError); ok {
 			panic(r)
 		} else if s, ok := r.(string); ok {
 			*err = os.ErrorString("YAML error: " + s)
 		} else if e, ok := r.(os.Error); ok {
 			*err = e
 		} else {
 			panic(r)
 		}
 	}
 }

 // Objects implementing the goyaml.Setter interface will receive the YAML
 // tag and value via the SetYAML method during unmarshaling, rather than
 // being implicitly assigned by the goyaml machinery.  If setting the value
 // works, the method should return true.  If it returns false, the given
 // value will be omitted from maps and slices.
 type Setter interface {
 	SetYAML(tag string, value interface{}) bool
 }

 // Objects implementing the goyaml.Getter interface will get the GetYAML()
 // method called when goyaml is requested to marshal the given value, and
 // the result of this method will be marshaled in place of the actual object.
 type Getter interface {
 	GetYAML() (tag string, value interface{})
 }

 // Unmarshal decodes the first document found within the in byte slice
 // and assigns decoded values into the object pointed by out.
 //
 // Maps, pointers to structs and ints, etc, may all be used as out values.
 // If an internal pointer within a struct is not initialized, goyaml
 // will initialize it if necessary for unmarshalling the provided data,
 // but the struct provided as out must not be a nil pointer.
 //
 // The type of the decoded values and the type of out will be considered,
 // and Unmarshal() will do the best possible job to unmarshal values
 // appropriately.  It is NOT considered an error, though, to skip values
 // because they are not available in the decoded YAML, or if they are not
 // compatible with the out value. To ensure something was properly
 // unmarshaled use a map or compare against the previous value for the
 // field (usually the zero value).
 //
 // Struct fields are only unmarshalled if they are exported (have an
 // upper case first letter), and will be unmarshalled using the field
 // name lowercased by default. When custom field names are desired, the
 // tag value may be used to tweak the name. Everything before the last
 // slash in the field tag will be used as the name. The value following
 // the slash is used to tweak the marshalling process (see Marshal).
 //
 // For example:
 //
 //     type T struct {
 //         F int "a/c"
 //         B int
 //     }
 //     var T t
 //     goyaml.Unmarshal([]byte("a: 1\nb: 2"), &t)
 //
 func Unmarshal(in []byte, out interface{}) (err os.Error) {
 	defer handleErr(&err)
 	d := newDecoder()
 	p := newParser(in)
 	defer p.destroy()
 	node := p.parse()
 	if node != nil {
 		d.unmarshal(node, reflect.ValueOf(out))
 	}
 	return nil
 }

 // Marshal writes the object provided into a YAML document. The structure
 // of the generated document will reflect the structure of the value itself.
 // Maps, pointers to structs and ints, etc, may all be used as the in value.
 //
 // Struct fields are only marshalled if they are exported (have an
 // upper case first letter), and will be marshalled using the field
 // name lowercased by default. When custom field names are desired, the
 // tag value may be used to tweak the name. Everything before the last
 // slash in the field tag will be used as the name. The characters
 // following the slash are used as flags for the marshalling process,
 // with 'c' meaning conditional (only marshal if non-zero), and 'f'
 // meaning use flow style (useful for structs, sequences and maps).
 //
 // For example:
 //
 //     type T struct {
 //         F int "a/c"
 //         B int
 //     }
 //     goyaml.Marshal(&T{B: 2}) // Returns "b: 2\n"
 //     goyaml.Marshal(&T{F: 1}} // Returns "a: 1\nb: 0\n"
 //
 func Marshal(in interface{}) (out []byte, err os.Error) {
 	defer handleErr(&err)
 	e := newEncoder()
 	defer e.destroy()
 	e.marshal("", reflect.ValueOf(in))
 	e.finish()
 	out = e.out
 	return
 }


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

 // The code in this section was copied from gobson.

 type structFields struct {
 	Map  map[string]fieldInfo
 	List []fieldInfo
 }

 type fieldInfo struct {
 	Key         string
 	Num         int
 	Conditional bool
 	Flow        bool
 }

 var fieldMap = make(map[string]*structFields)
 var fieldMapMutex sync.RWMutex

 func getStructFields(st reflect.Type) (*structFields, os.Error) {
 	path := st.PkgPath()
 	name := st.Name()

 	fullName := path + "." + name
 	fieldMapMutex.RLock()
 	fields, found := fieldMap[fullName]
 	fieldMapMutex.RUnlock()
 	if found {
 		return fields, nil
 	}

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

 		info := fieldInfo{Num: i}

 		if s := strings.LastIndex(field.Tag, "/"); s != -1 {
 			for _, c := range field.Tag[s+1:] {
 				switch c {
 				case int('c'):
 					info.Conditional = true
 				case int('f'):
 					info.Flow = true
 				default:
 					panic("Unsupported field flag: " + string([]int{c}))
 				}
 			}
 			field.Tag = field.Tag[:s]
 		}

 		if field.Tag != "" {
 			info.Key = field.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, os.NewError(msg)
 		}

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

 	fields = &structFields{fieldsMap, fieldsList[:len(fieldsMap)]}

 	if fullName != "." {
 		fieldMapMutex.Lock()
 		fieldMap[fullName] = fields
 		fieldMapMutex.Unlock()
 	}

 	return fields, nil
 }

 func isZero(v reflect.Value) bool {
 	switch v.Kind() {
 	case reflect.String:
 		return len(v.String()) == 0
 	case reflect.Interface:
 		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.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
 		return v.Uint() == 0
 	case reflect.Bool:
 		return !v.Bool()
 	}
 	return false
 }
	//
	// goyaml - YAML support for the Go language
	//
	// https://wiki.ubuntu.com/goyaml
	//
	// Copyright (c) 2011 Canonical Ltd.
	//
	// Written by Gustavo Niemeyer <gustavo.niemeyer@canonical.com>
	//
	package goyaml

	import (
	"reflect"
	"runtime"
	"strings"
	"sync"
	"os"
	)

	func handleErr(err *os.Error) {
	if r := recover(); r != nil {
	if _, ok := r.(runtime.Error); ok {
	panic(r)
	} else if _, ok := r.(*reflect.ValueError); ok {
	panic(r)
	} else if s, ok := r.(string); ok {
	*err = os.ErrorString("YAML error: " + s)
	} else if e, ok := r.(os.Error); ok {
	*err = e
	} else {
	panic(r)
	}
	}
	}

	// Objects implementing the goyaml.Setter interface will receive the YAML
	// tag and value via the SetYAML method during unmarshaling, rather than
	// being implicitly assigned by the goyaml machinery. If setting the value
	// works, the method should return true. If it returns false, the given
	// value will be omitted from maps and slices.
	type Setter interface {
	SetYAML(tag string, value interface{}) bool
	}

	// Objects implementing the goyaml.Getter interface will get the GetYAML()
	// method called when goyaml is requested to marshal the given value, and
	// the result of this method will be marshaled in place of the actual object.
	type Getter interface {
	GetYAML() (tag string, value interface{})
	}

	// Unmarshal decodes the first document found within the in byte slice
	// and assigns decoded values into the object pointed by out.
	//
	// Maps, pointers to structs and ints, etc, may all be used as out values.
	// If an internal pointer within a struct is not initialized, goyaml
	// will initialize it if necessary for unmarshalling the provided data,
	// but the struct provided as out must not be a nil pointer.
	//
	// The type of the decoded values and the type of out will be considered,
	// and Unmarshal() will do the best possible job to unmarshal values
	// appropriately. It is NOT considered an error, though, to skip values
	// because they are not available in the decoded YAML, or if they are not
	// compatible with the out value. To ensure something was properly
	// unmarshaled use a map or compare against the previous value for the
	// field (usually the zero value).
	//
	// Struct fields are only unmarshalled if they are exported (have an
	// upper case first letter), and will be unmarshalled using the field
	// name lowercased by default. When custom field names are desired, the
	// tag value may be used to tweak the name. Everything before the last
	// slash in the field tag will be used as the name. The value following
	// the slash is used to tweak the marshalling process (see Marshal).
	//
	// For example:
	//
	// type T struct {
	// F int "a/c"
	// B int
	// }
	// var T t
	// goyaml.Unmarshal([]byte("a: 1\nb: 2"), &t)
	//
	func Unmarshal(in []byte, out interface{}) (err os.Error) {
	defer handleErr(&err)
	d := newDecoder()
	p := newParser(in)
	defer p.destroy()
	node := p.parse()
	if node != nil {
	d.unmarshal(node, reflect.ValueOf(out))
	}
	return nil
	}

	// Marshal writes the object provided into a YAML document. The structure
	// of the generated document will reflect the structure of the value itself.
	// Maps, pointers to structs and ints, etc, may all be used as the in value.
	//
	// Struct fields are only marshalled if they are exported (have an
	// upper case first letter), and will be marshalled using the field
	// name lowercased by default. When custom field names are desired, the
	// tag value may be used to tweak the name. Everything before the last
	// slash in the field tag will be used as the name. The characters
	// following the slash are used as flags for the marshalling process,
	// with 'c' meaning conditional (only marshal if non-zero), and 'f'
	// meaning use flow style (useful for structs, sequences and maps).
	//
	// For example:
	//
	// type T struct {
	// F int "a/c"
	// B int
	// }
	// goyaml.Marshal(&T{B: 2}) // Returns "b: 2\n"
	// goyaml.Marshal(&T{F: 1}} // Returns "a: 1\nb: 0\n"
	//
	func Marshal(in interface{}) (out []byte, err os.Error) {
	defer handleErr(&err)
	e := newEncoder()
	defer e.destroy()
	e.marshal("", reflect.ValueOf(in))
	e.finish()
	out = e.out
	return
	}


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

	// The code in this section was copied from gobson.

	type structFields struct {
	Map map[string]fieldInfo
	List []fieldInfo
	}

	type fieldInfo struct {
	Key string
	Num int
	Conditional bool
	Flow bool
	}

	var fieldMap = make(map[string]*structFields)
	var fieldMapMutex sync.RWMutex

	func getStructFields(st reflect.Type) (*structFields, os.Error) {
	path := st.PkgPath()
	name := st.Name()

	fullName := path + "." + name
	fieldMapMutex.RLock()
	fields, found := fieldMap[fullName]
	fieldMapMutex.RUnlock()
	if found {
	return fields, nil
	}

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

	info := fieldInfo{Num: i}

	if s := strings.LastIndex(field.Tag, "/"); s != -1 {
	for _, c := range field.Tag[s+1:] {
	switch c {
	case int('c'):
	info.Conditional = true
	case int('f'):
	info.Flow = true
	default:
	panic("Unsupported field flag: " + string([]int{c}))
	}
	}
	field.Tag = field.Tag[:s]
	}

	if field.Tag != "" {
	info.Key = field.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, os.NewError(msg)
	}

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

	fields = &structFields{fieldsMap, fieldsList[:len(fieldsMap)]}

	if fullName != "." {
	fieldMapMutex.Lock()
	fieldMap[fullName] = fields
	fieldMapMutex.Unlock()
	}

	return fields, nil
	}

	func isZero(v reflect.Value) bool {
	switch v.Kind() {
	case reflect.String:
	return len(v.String()) == 0
	case reflect.Interface:
	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.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
	return v.Uint() == 0
	case reflect.Bool:
	return !v.Bool()
	}
	return false
	}