src/pkg/json/encode.go - go - Git at Google

 // Copyright 2010 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package json

 import (
 	"os"
 	"bytes"
 	"reflect"
 	"runtime"
 	"sort"
 	"strconv"
 )

 // Marshal returns the JSON encoding of v.
 //
 // Marshal traverses the value v recursively.
 // If an encountered value implements the Marshaler interface,
 // Marshal calls its MarshalJSON method to produce JSON.
 //
 // Otherwise, Marshal uses the following type-dependent default encodings:
 //
 // Boolean values encode as JSON booleans.
 //
 // Floating point and integer values encode as JSON numbers.
 //
 // String values encode as JSON strings, with each invalid UTF-8 sequence
 // replaced by the encoding of the Unicode replacement character U+FFFD.
 //
 // Array and slice values encode as JSON arrays.
 //
 // Struct values encode as JSON objects.  Each struct field becomes
 // a member of the object.  By default the object's key name is the
 // struct field name converted to lower case.  If the struct field
 // has a tag, that tag will be used as the name instead.
 //
 // Map values encode as JSON objects.
 // The map's key type must be string; the object keys are used directly
 // as map keys.
 //
 // Pointer values encode as the value pointed to.
 // A nil pointer encodes as the null JSON object.
 //
 // Interface values encode as the value contained in the interface.
 // A nil interface value encodes as the null JSON object.
 //
 // Channel, complex, and function values cannot be encoded in JSON.
 // Attempting to encode such a value causes Marshal to return
 // an InvalidTypeError.
 //
 // JSON cannot represent cyclic data structures and Marshal does not
 // handle them.  Passing cyclic structures to Marshal will result in
 // an infinite recursion.
 //
 func Marshal(v interface{}) ([]byte, os.Error) {
 	e := &encodeState{}
 	err := e.marshal(v)
 	if err != nil {
 		return nil, err
 	}
 	return e.Bytes(), nil
 }

 // MarshalIndent is like Marshal but applies Indent to format the output.
 func MarshalIndent(v interface{}, prefix, indent string) ([]byte, os.Error) {
 	b, err := Marshal(v)
 	if err != nil {
 		return nil, err
 	}
 	var buf bytes.Buffer
 	err = Indent(&buf, b, prefix, indent)
 	if err != nil {
 		return nil, err
 	}
 	return buf.Bytes(), nil
 }

 // MarshalForHTML is like Marshal but applies HTMLEscape to the output.
 func MarshalForHTML(v interface{}) ([]byte, os.Error) {
 	b, err := Marshal(v)
 	if err != nil {
 		return nil, err
 	}
 	var buf bytes.Buffer
 	HTMLEscape(&buf, b)
 	return buf.Bytes(), nil
 }

 // HTMLEscape appends to dst the JSON-encoded src with <, >, and &
 // characters inside string literals changed to \u003c, \u003e, \u0026
 // so that the JSON will be safe to embed inside HTML <script> tags.
 // For historical reasons, web browsers don't honor standard HTML
 // escaping within <script> tags, so an alternative JSON encoding must
 // be used.
 func HTMLEscape(dst *bytes.Buffer, src []byte) {
 	// < > & can only appear in string literals,
 	// so just scan the string one byte at a time.
 	start := 0
 	for i, c := range src {
 		if c == '<' || c == '>' || c == '&' {
 			if start < i {
 				dst.Write(src[start:i])
 			}
 			dst.WriteString(`\u00`)
 			dst.WriteByte(hex[c>>4])
 			dst.WriteByte(hex[c&0xF])
 			start = i + 1
 		}
 	}
 	if start < len(src) {
 		dst.Write(src[start:])
 	}
 }

 // Marshaler is the interface implemented by objects that
 // can marshal themselves into valid JSON.
 type Marshaler interface {
 	MarshalJSON() ([]byte, os.Error)
 }

 type UnsupportedTypeError struct {
 	Type reflect.Type
 }

 func (e *UnsupportedTypeError) String() string {
 	return "json: unsupported type: " + e.Type.String()
 }

 type MarshalerError struct {
 	Type  reflect.Type
 	Error os.Error
 }

 func (e *MarshalerError) String() string {
 	return "json: error calling MarshalJSON for type " + e.Type.String() + ": " + e.Error.String()
 }

 type interfaceOrPtrValue interface {
 	IsNil() bool
 	Elem() reflect.Value
 }

 var hex = "0123456789abcdef"

 // An encodeState encodes JSON into a bytes.Buffer.
 type encodeState struct {
 	bytes.Buffer // accumulated output
 }

 func (e *encodeState) marshal(v interface{}) (err os.Error) {
 	defer func() {
 		if r := recover(); r != nil {
 			if _, ok := r.(runtime.Error); ok {
 				panic(r)
 			}
 			err = r.(os.Error)
 		}
 	}()
 	e.reflectValue(reflect.NewValue(v))
 	return nil
 }

 func (e *encodeState) error(err os.Error) {
 	panic(err)
 }

 func (e *encodeState) reflectValue(v reflect.Value) {
 	if v == nil {
 		e.WriteString("null")
 		return
 	}

 	if j, ok := v.Interface().(Marshaler); ok {
 		b, err := j.MarshalJSON()
 		if err == nil {
 			// copy JSON into buffer, checking validity.
 			err = Compact(&e.Buffer, b)
 		}
 		if err != nil {
 			e.error(&MarshalerError{v.Type(), err})
 		}
 		return
 	}

 	switch v := v.(type) {
 	case *reflect.BoolValue:
 		x := v.Get()
 		if x {
 			e.WriteString("true")
 		} else {
 			e.WriteString("false")
 		}

 	case *reflect.IntValue:
 		e.WriteString(strconv.Itoa64(v.Get()))

 	case *reflect.UintValue:
 		e.WriteString(strconv.Uitoa64(v.Get()))

 	case *reflect.FloatValue:
 		e.WriteString(strconv.FtoaN(v.Get(), 'g', -1, v.Type().Bits()))

 	case *reflect.StringValue:
 		e.string(v.Get())

 	case *reflect.StructValue:
 		e.WriteByte('{')
 		t := v.Type().(*reflect.StructType)
 		n := v.NumField()
 		for i := 0; i < n; i++ {
 			if i > 0 {
 				e.WriteByte(',')
 			}
 			f := t.Field(i)
 			if f.Tag != "" {
 				e.string(f.Tag)
 			} else {
 				e.string(f.Name)
 			}
 			e.WriteByte(':')
 			e.reflectValue(v.Field(i))
 		}
 		e.WriteByte('}')

 	case *reflect.MapValue:
 		if _, ok := v.Type().(*reflect.MapType).Key().(*reflect.StringType); !ok {
 			e.error(&UnsupportedTypeError{v.Type()})
 		}
 		if v.IsNil() {
 			e.WriteString("null")
 			break
 		}
 		e.WriteByte('{')
 		var sv stringValues = v.Keys()
 		sort.Sort(sv)
 		for i, k := range sv {
 			if i > 0 {
 				e.WriteByte(',')
 			}
 			e.string(k.(*reflect.StringValue).Get())
 			e.WriteByte(':')
 			e.reflectValue(v.Elem(k))
 		}
 		e.WriteByte('}')

 	case reflect.ArrayOrSliceValue:
 		e.WriteByte('[')
 		n := v.Len()
 		for i := 0; i < n; i++ {
 			if i > 0 {
 				e.WriteByte(',')
 			}
 			e.reflectValue(v.Elem(i))
 		}
 		e.WriteByte(']')

 	case interfaceOrPtrValue:
 		if v.IsNil() {
 			e.WriteString("null")
 			return
 		}
 		e.reflectValue(v.Elem())

 	default:
 		e.error(&UnsupportedTypeError{v.Type()})
 	}
 	return
 }

 // stringValues is a slice of reflect.Value holding *reflect.StringValue.
 // It implements the methods to sort by string.
 type stringValues []reflect.Value

 func (sv stringValues) Len() int           { return len(sv) }
 func (sv stringValues) Swap(i, j int)      { sv[i], sv[j] = sv[j], sv[i] }
 func (sv stringValues) Less(i, j int) bool { return sv.get(i) < sv.get(j) }
 func (sv stringValues) get(i int) string   { return sv[i].(*reflect.StringValue).Get() }

 func (e *encodeState) string(s string) {
 	e.WriteByte('"')
 	for _, c := range s {
 		switch {
 		case c < 0x20:
 			e.WriteString(`\u00`)
 			e.WriteByte(hex[c>>4])
 			e.WriteByte(hex[c&0xF])
 		case c == '\\' || c == '"':
 			e.WriteByte('\\')
 			fallthrough
 		default:
 			e.WriteRune(c)
 		}
 	}
 	e.WriteByte('"')
 }
	// Copyright 2010 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package json

	import (
	"os"
	"bytes"
	"reflect"
	"runtime"
	"sort"
	"strconv"
	)

	// Marshal returns the JSON encoding of v.
	//
	// Marshal traverses the value v recursively.
	// If an encountered value implements the Marshaler interface,
	// Marshal calls its MarshalJSON method to produce JSON.
	//
	// Otherwise, Marshal uses the following type-dependent default encodings:
	//
	// Boolean values encode as JSON booleans.
	//
	// Floating point and integer values encode as JSON numbers.
	//
	// String values encode as JSON strings, with each invalid UTF-8 sequence
	// replaced by the encoding of the Unicode replacement character U+FFFD.
	//
	// Array and slice values encode as JSON arrays.
	//
	// Struct values encode as JSON objects. Each struct field becomes
	// a member of the object. By default the object's key name is the
	// struct field name converted to lower case. If the struct field
	// has a tag, that tag will be used as the name instead.
	//
	// Map values encode as JSON objects.
	// The map's key type must be string; the object keys are used directly
	// as map keys.
	//
	// Pointer values encode as the value pointed to.
	// A nil pointer encodes as the null JSON object.
	//
	// Interface values encode as the value contained in the interface.
	// A nil interface value encodes as the null JSON object.
	//
	// Channel, complex, and function values cannot be encoded in JSON.
	// Attempting to encode such a value causes Marshal to return
	// an InvalidTypeError.
	//
	// JSON cannot represent cyclic data structures and Marshal does not
	// handle them. Passing cyclic structures to Marshal will result in
	// an infinite recursion.
	//
	func Marshal(v interface{}) ([]byte, os.Error) {
	e := &encodeState{}
	err := e.marshal(v)
	if err != nil {
	return nil, err
	}
	return e.Bytes(), nil
	}

	// MarshalIndent is like Marshal but applies Indent to format the output.
	func MarshalIndent(v interface{}, prefix, indent string) ([]byte, os.Error) {
	b, err := Marshal(v)
	if err != nil {
	return nil, err
	}
	var buf bytes.Buffer
	err = Indent(&buf, b, prefix, indent)
	if err != nil {
	return nil, err
	}
	return buf.Bytes(), nil
	}

	// MarshalForHTML is like Marshal but applies HTMLEscape to the output.
	func MarshalForHTML(v interface{}) ([]byte, os.Error) {
	b, err := Marshal(v)
	if err != nil {
	return nil, err
	}
	var buf bytes.Buffer
	HTMLEscape(&buf, b)
	return buf.Bytes(), nil
	}

	// HTMLEscape appends to dst the JSON-encoded src with <, >, and &
	// characters inside string literals changed to \u003c, \u003e, \u0026
	// so that the JSON will be safe to embed inside HTML <script> tags.
	// For historical reasons, web browsers don't honor standard HTML
	// escaping within <script> tags, so an alternative JSON encoding must
	// be used.
	func HTMLEscape(dst *bytes.Buffer, src []byte) {
	// < > & can only appear in string literals,
	// so just scan the string one byte at a time.
	start := 0
	for i, c := range src {
	if c == '<' \|\| c == '>' \|\| c == '&' {
	if start < i {
	dst.Write(src[start:i])
	}
	dst.WriteString(`\u00`)
	dst.WriteByte(hex[c>>4])
	dst.WriteByte(hex[c&0xF])
	start = i + 1
	}
	}
	if start < len(src) {
	dst.Write(src[start:])
	}
	}

	// Marshaler is the interface implemented by objects that
	// can marshal themselves into valid JSON.
	type Marshaler interface {
	MarshalJSON() ([]byte, os.Error)
	}

	type UnsupportedTypeError struct {
	Type reflect.Type
	}

	func (e *UnsupportedTypeError) String() string {
	return "json: unsupported type: " + e.Type.String()
	}

	type MarshalerError struct {
	Type reflect.Type
	Error os.Error
	}

	func (e *MarshalerError) String() string {
	return "json: error calling MarshalJSON for type " + e.Type.String() + ": " + e.Error.String()
	}

	type interfaceOrPtrValue interface {
	IsNil() bool
	Elem() reflect.Value
	}

	var hex = "0123456789abcdef"

	// An encodeState encodes JSON into a bytes.Buffer.
	type encodeState struct {
	bytes.Buffer // accumulated output
	}

	func (e *encodeState) marshal(v interface{}) (err os.Error) {
	defer func() {
	if r := recover(); r != nil {
	if _, ok := r.(runtime.Error); ok {
	panic(r)
	}
	err = r.(os.Error)
	}
	}()
	e.reflectValue(reflect.NewValue(v))
	return nil
	}

	func (e *encodeState) error(err os.Error) {
	panic(err)
	}

	func (e *encodeState) reflectValue(v reflect.Value) {
	if v == nil {
	e.WriteString("null")
	return
	}

	if j, ok := v.Interface().(Marshaler); ok {
	b, err := j.MarshalJSON()
	if err == nil {
	// copy JSON into buffer, checking validity.
	err = Compact(&e.Buffer, b)
	}
	if err != nil {
	e.error(&MarshalerError{v.Type(), err})
	}
	return
	}

	switch v := v.(type) {
	case *reflect.BoolValue:
	x := v.Get()
	if x {
	e.WriteString("true")
	} else {
	e.WriteString("false")
	}

	case *reflect.IntValue:
	e.WriteString(strconv.Itoa64(v.Get()))

	case *reflect.UintValue:
	e.WriteString(strconv.Uitoa64(v.Get()))

	case *reflect.FloatValue:
	e.WriteString(strconv.FtoaN(v.Get(), 'g', -1, v.Type().Bits()))

	case *reflect.StringValue:
	e.string(v.Get())

	case *reflect.StructValue:
	e.WriteByte('{')
	t := v.Type().(*reflect.StructType)
	n := v.NumField()
	for i := 0; i < n; i++ {
	if i > 0 {
	e.WriteByte(',')
	}
	f := t.Field(i)
	if f.Tag != "" {
	e.string(f.Tag)
	} else {
	e.string(f.Name)
	}
	e.WriteByte(':')
	e.reflectValue(v.Field(i))
	}
	e.WriteByte('}')

	case *reflect.MapValue:
	if _, ok := v.Type().(reflect.MapType).Key().(reflect.StringType); !ok {
	e.error(&UnsupportedTypeError{v.Type()})
	}
	if v.IsNil() {
	e.WriteString("null")
	break
	}
	e.WriteByte('{')
	var sv stringValues = v.Keys()
	sort.Sort(sv)
	for i, k := range sv {
	if i > 0 {
	e.WriteByte(',')
	}
	e.string(k.(*reflect.StringValue).Get())
	e.WriteByte(':')
	e.reflectValue(v.Elem(k))
	}
	e.WriteByte('}')

	case reflect.ArrayOrSliceValue:
	e.WriteByte('[')
	n := v.Len()
	for i := 0; i < n; i++ {
	if i > 0 {
	e.WriteByte(',')
	}
	e.reflectValue(v.Elem(i))
	}
	e.WriteByte(']')

	case interfaceOrPtrValue:
	if v.IsNil() {
	e.WriteString("null")
	return
	}
	e.reflectValue(v.Elem())

	default:
	e.error(&UnsupportedTypeError{v.Type()})
	}
	return
	}

	// stringValues is a slice of reflect.Value holding *reflect.StringValue.
	// It implements the methods to sort by string.
	type stringValues []reflect.Value

	func (sv stringValues) Len() int { return len(sv) }
	func (sv stringValues) Swap(i, j int) { sv[i], sv[j] = sv[j], sv[i] }
	func (sv stringValues) Less(i, j int) bool { return sv.get(i) < sv.get(j) }
	func (sv stringValues) get(i int) string { return sv[i].(*reflect.StringValue).Get() }

	func (e *encodeState) string(s string) {
	e.WriteByte('"')
	for _, c := range s {
	switch {
	case c < 0x20:
	e.WriteString(`\u00`)
	e.WriteByte(hex[c>>4])
	e.WriteByte(hex[c&0xF])
	case c == '\\' \|\| c == '"':
	e.WriteByte('\\')
	fallthrough
	default:
	e.WriteRune(c)
	}
	}
	e.WriteByte('"')
	}