Imported Upstream version 60upstream/60

1 files changed, 428 insertions, 0 deletions

diff --git a/src/pkg/json/encode.go b/src/pkg/json/encode.go
new file mode 100644
index 000000000..3e593fec1
--- /dev/null
+++ b/src/pkg/json/encode.go
@@ -0,0 +1,428 @@
+// 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 implements encoding and decoding of JSON objects as defined in
+// RFC 4627.
+package json
+
+import (
+	"bytes"
+	"encoding/base64"
+	"os"
+	"reflect"
+	"runtime"
+	"sort"
+	"strconv"
+	"strings"
+	"unicode"
+	"utf8"
+)
+
+// 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, except that
+// []byte encodes as a base64-encoded string.
+//
+// Struct values encode as JSON objects. Each exported struct field
+// becomes a member of the object unless the field is empty and its tag
+// specifies the "omitempty" option. The empty values are false, 0, any
+// nil pointer or interface value, and any array, slice, map, or string of
+// length zero. The object's default key string is the struct field name
+// but can be specified in the struct field's tag value. The "json" key in
+// struct field's tag value is the key name, followed by an optional comma
+// and options. Examples:
+//
+//   // Specifies that Field appears in JSON as key "myName"
+//   Field int `json:"myName"`
+//
+//   // Specifies that Field appears in JSON as key "myName" and
+//   // the field is omitted from the object if its value is empty,
+//   // as defined above.
+//   Field int `json:"myName,omitempty"`
+//
+//   // Field appears in JSON as key "Field" (the default), but
+//   // the field is skipped if empty.
+//   // Note the leading comma.
+//   Field int `json:",omitempty"`
+//
+// The key name will be used if it's a non-empty string consisting of
+// only Unicode letters, digits, dollar signs, hyphens, and underscores.
+//
+// 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 InvalidUTF8Error struct {
+	S string
+}
+
+func (e *InvalidUTF8Error) String() string {
+	return "json: invalid UTF-8 in string: " + strconv.Quote(e.S)
+}
+
+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.ValueOf(v))
+	return nil
+}
+
+func (e *encodeState) error(err os.Error) {
+	panic(err)
+}
+
+var byteSliceType = reflect.TypeOf([]byte(nil))
+
+func isEmptyValue(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len() == 0
+	case reflect.Bool:
+		return !v.Bool()
+	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.Float32, reflect.Float64:
+		return v.Float() == 0
+	case reflect.Interface, reflect.Ptr:
+		return v.IsNil()
+	}
+	return false
+}
+
+func (e *encodeState) reflectValue(v reflect.Value) {
+	if !v.IsValid() {
+		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.Kind() {
+	case reflect.Bool:
+		x := v.Bool()
+		if x {
+			e.WriteString("true")
+		} else {
+			e.WriteString("false")
+		}
+
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		e.WriteString(strconv.Itoa64(v.Int()))
+
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		e.WriteString(strconv.Uitoa64(v.Uint()))
+
+	case reflect.Float32, reflect.Float64:
+		e.WriteString(strconv.FtoaN(v.Float(), 'g', -1, v.Type().Bits()))
+
+	case reflect.String:
+		e.string(v.String())
+
+	case reflect.Struct:
+		e.WriteByte('{')
+		t := v.Type()
+		n := v.NumField()
+		first := true
+		for i := 0; i < n; i++ {
+			f := t.Field(i)
+			if f.PkgPath != "" {
+				continue
+			}
+			tag, omitEmpty := f.Name, false
+			if tv := f.Tag.Get("json"); tv != "" {
+				ss := strings.SplitN(tv, ",", 2)
+				if isValidTag(ss[0]) {
+					tag = ss[0]
+				}
+				if len(ss) > 1 {
+					// Currently the only option is omitempty,
+					// so parsing is trivial.
+					omitEmpty = ss[1] == "omitempty"
+				}
+			}
+			fieldValue := v.Field(i)
+			if omitEmpty && isEmptyValue(fieldValue) {
+				continue
+			}
+			if first {
+				first = false
+			} else {
+				e.WriteByte(',')
+			}
+			e.string(tag)
+			e.WriteByte(':')
+			e.reflectValue(fieldValue)
+		}
+		e.WriteByte('}')
+
+	case reflect.Map:
+		if v.Type().Key().Kind() != reflect.String {
+			e.error(&UnsupportedTypeError{v.Type()})
+		}
+		if v.IsNil() {
+			e.WriteString("null")
+			break
+		}
+		e.WriteByte('{')
+		var sv stringValues = v.MapKeys()
+		sort.Sort(sv)
+		for i, k := range sv {
+			if i > 0 {
+				e.WriteByte(',')
+			}
+			e.string(k.String())
+			e.WriteByte(':')
+			e.reflectValue(v.MapIndex(k))
+		}
+		e.WriteByte('}')
+
+	case reflect.Array, reflect.Slice:
+		if v.Type() == byteSliceType {
+			e.WriteByte('"')
+			s := v.Interface().([]byte)
+			if len(s) < 1024 {
+				// for small buffers, using Encode directly is much faster.
+				dst := make([]byte, base64.StdEncoding.EncodedLen(len(s)))
+				base64.StdEncoding.Encode(dst, s)
+				e.Write(dst)
+			} else {
+				// for large buffers, avoid unnecessary extra temporary
+				// buffer space.
+				enc := base64.NewEncoder(base64.StdEncoding, e)
+				enc.Write(s)
+				enc.Close()
+			}
+			e.WriteByte('"')
+			break
+		}
+		e.WriteByte('[')
+		n := v.Len()
+		for i := 0; i < n; i++ {
+			if i > 0 {
+				e.WriteByte(',')
+			}
+			e.reflectValue(v.Index(i))
+		}
+		e.WriteByte(']')
+
+	case reflect.Interface, reflect.Ptr:
+		if v.IsNil() {
+			e.WriteString("null")
+			return
+		}
+		e.reflectValue(v.Elem())
+
+	default:
+		e.error(&UnsupportedTypeError{v.Type()})
+	}
+	return
+}
+
+func isValidTag(s string) bool {
+	if s == "" {
+		return false
+	}
+	for _, c := range s {
+		if c != '$' && c != '-' && c != '_' && !unicode.IsLetter(c) && !unicode.IsDigit(c) {
+			return false
+		}
+	}
+	return true
+}
+
+// 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].String() }
+
+func (e *encodeState) string(s string) {
+	e.WriteByte('"')
+	start := 0
+	for i := 0; i < len(s); {
+		if b := s[i]; b < utf8.RuneSelf {
+			if 0x20 <= b && b != '\\' && b != '"' && b != '<' && b != '>' {
+				i++
+				continue
+			}
+			if start < i {
+				e.WriteString(s[start:i])
+			}
+			switch b {
+			case '\\', '"':
+				e.WriteByte('\\')
+				e.WriteByte(b)
+			case '\n':
+				e.WriteByte('\\')
+				e.WriteByte('n')
+			case '\r':
+				e.WriteByte('\\')
+				e.WriteByte('r')
+			default:
+				// This encodes bytes < 0x20 except for \n and \r,
+				// as well as < and >. The latter are escaped because they
+				// can lead to security holes when user-controlled strings
+				// are rendered into JSON and served to some browsers.
+				e.WriteString(`\u00`)
+				e.WriteByte(hex[b>>4])
+				e.WriteByte(hex[b&0xF])
+			}
+			i++
+			start = i
+			continue
+		}
+		c, size := utf8.DecodeRuneInString(s[i:])
+		if c == utf8.RuneError && size == 1 {
+			e.error(&InvalidUTF8Error{s})
+		}
+		i += size
+	}
+	if start < len(s) {
+		e.WriteString(s[start:])
+	}
+	e.WriteByte('"')
+}