json: Marshal, Unmarshal using new scanner

R=r
CC=golang-dev
http://codereview.appspot.com/953041

1 files changed, 282 insertions, 0 deletions

diff --git a/src/pkg/json/encode.go b/src/pkg/json/encode.go
new file mode 100644
index 000000000..1de22086d
--- /dev/null
+++ b/src/pkg/json/encode.go
@@ -0,0 +1,282 @@
+// 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"
+	"strings"
+)
+
+// 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 at.
+// 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
+}
+
+// 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.Itoa(v.Get()))
+	case *reflect.Int8Value:
+		e.WriteString(strconv.Itoa(int(v.Get())))
+	case *reflect.Int16Value:
+		e.WriteString(strconv.Itoa(int(v.Get())))
+	case *reflect.Int32Value:
+		e.WriteString(strconv.Itoa(int(v.Get())))
+	case *reflect.Int64Value:
+		e.WriteString(strconv.Itoa64(v.Get()))
+
+	case *reflect.UintValue:
+		e.WriteString(strconv.Uitoa(v.Get()))
+	case *reflect.Uint8Value:
+		e.WriteString(strconv.Uitoa(uint(v.Get())))
+	case *reflect.Uint16Value:
+		e.WriteString(strconv.Uitoa(uint(v.Get())))
+	case *reflect.Uint32Value:
+		e.WriteString(strconv.Uitoa(uint(v.Get())))
+	case *reflect.Uint64Value:
+		e.WriteString(strconv.Uitoa64(v.Get()))
+	case *reflect.UintptrValue:
+		e.WriteString(strconv.Uitoa64(uint64(v.Get())))
+
+	case *reflect.FloatValue:
+		e.WriteString(strconv.Ftoa(v.Get(), 'g', -1))
+	case *reflect.Float32Value:
+		e.WriteString(strconv.Ftoa32(v.Get(), 'g', -1))
+	case *reflect.Float64Value:
+		e.WriteString(strconv.Ftoa64(v.Get(), 'g', -1))
+
+	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(strings.ToLower(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('"')
+}