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// Copyright 2009 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.
// Marshalling and unmarshalling of
// JSON data into Go structs using reflection.
package json
import (
"reflect";
"strings";
)
type structBuilder struct {
val reflect.Value;
// if map_ != nil, write val to map_[key] on each change
map_ *reflect.MapValue;
key reflect.Value;
}
var nobuilder *structBuilder
func isfloat(v reflect.Value) bool {
switch v.(type) {
case *reflect.FloatValue, *reflect.Float32Value, *reflect.Float64Value:
return true
}
return false;
}
func setfloat(v reflect.Value, f float64) {
switch v := v.(type) {
case *reflect.FloatValue:
v.Set(float(f))
case *reflect.Float32Value:
v.Set(float32(f))
case *reflect.Float64Value:
v.Set(float64(f))
}
}
func setint(v reflect.Value, i int64) {
switch v := v.(type) {
case *reflect.IntValue:
v.Set(int(i))
case *reflect.Int8Value:
v.Set(int8(i))
case *reflect.Int16Value:
v.Set(int16(i))
case *reflect.Int32Value:
v.Set(int32(i))
case *reflect.Int64Value:
v.Set(int64(i))
case *reflect.UintValue:
v.Set(uint(i))
case *reflect.Uint8Value:
v.Set(uint8(i))
case *reflect.Uint16Value:
v.Set(uint16(i))
case *reflect.Uint32Value:
v.Set(uint32(i))
case *reflect.Uint64Value:
v.Set(uint64(i))
}
}
// If updating b.val is not enough to update the original,
// copy a changed b.val out to the original.
func (b *structBuilder) Flush() {
if b == nil {
return
}
if b.map_ != nil {
b.map_.SetElem(b.key, b.val)
}
}
func (b *structBuilder) Int64(i int64) {
if b == nil {
return
}
v := b.val;
if isfloat(v) {
setfloat(v, float64(i))
} else {
setint(v, i)
}
}
func (b *structBuilder) Uint64(i uint64) {
if b == nil {
return
}
v := b.val;
if isfloat(v) {
setfloat(v, float64(i))
} else {
setint(v, int64(i))
}
}
func (b *structBuilder) Float64(f float64) {
if b == nil {
return
}
v := b.val;
if isfloat(v) {
setfloat(v, f)
} else {
setint(v, int64(f))
}
}
func (b *structBuilder) Null() {}
func (b *structBuilder) String(s string) {
if b == nil {
return
}
if v, ok := b.val.(*reflect.StringValue); ok {
v.Set(s)
}
}
func (b *structBuilder) Bool(tf bool) {
if b == nil {
return
}
if v, ok := b.val.(*reflect.BoolValue); ok {
v.Set(tf)
}
}
func (b *structBuilder) Array() {
if b == nil {
return
}
if v, ok := b.val.(*reflect.SliceValue); ok {
if v.IsNil() {
v.Set(reflect.MakeSlice(v.Type().(*reflect.SliceType), 0, 8))
}
}
}
func (b *structBuilder) Elem(i int) Builder {
if b == nil || i < 0 {
return nobuilder
}
switch v := b.val.(type) {
case *reflect.ArrayValue:
if i < v.Len() {
return &structBuilder{val: v.Elem(i)}
}
case *reflect.SliceValue:
if i > v.Cap() {
n := v.Cap();
if n < 8 {
n = 8
}
for n <= i {
n *= 2
}
nv := reflect.MakeSlice(v.Type().(*reflect.SliceType), v.Len(), n);
reflect.ArrayCopy(nv, v);
v.Set(nv);
}
if v.Len() <= i && i < v.Cap() {
v.SetLen(i + 1)
}
if i < v.Len() {
return &structBuilder{val: v.Elem(i)}
}
}
return nobuilder;
}
func (b *structBuilder) Map() {
if b == nil {
return
}
if v, ok := b.val.(*reflect.PtrValue); ok && v.IsNil() {
if v.IsNil() {
v.PointTo(reflect.MakeZero(v.Type().(*reflect.PtrType).Elem()));
b.Flush();
}
b.map_ = nil;
b.val = v.Elem();
}
if v, ok := b.val.(*reflect.MapValue); ok && v.IsNil() {
v.Set(reflect.MakeMap(v.Type().(*reflect.MapType)))
}
}
func (b *structBuilder) Key(k string) Builder {
if b == nil {
return nobuilder
}
switch v := reflect.Indirect(b.val).(type) {
case *reflect.StructValue:
t := v.Type().(*reflect.StructType);
// Case-insensitive field lookup.
k = strings.ToLower(k);
for i := 0; i < t.NumField(); i++ {
if strings.ToLower(t.Field(i).Name) == k {
return &structBuilder{val: v.Field(i)}
}
}
case *reflect.MapValue:
t := v.Type().(*reflect.MapType);
if t.Key() != reflect.Typeof(k) {
break
}
key := reflect.NewValue(k);
elem := v.Elem(key);
if elem == nil {
v.SetElem(key, reflect.MakeZero(t.Elem()));
elem = v.Elem(key);
}
return &structBuilder{val: elem, map_: v, key: key};
}
return nobuilder;
}
// Unmarshal parses the JSON syntax string s and fills in
// an arbitrary struct or array pointed at by val.
// It uses the reflect package to assign to fields
// and arrays embedded in val. Well-formed data that does not fit
// into the struct is discarded.
//
// For example, given these definitions:
//
// type Email struct {
// Where string;
// Addr string;
// }
//
// type Result struct {
// Name string;
// Phone string;
// Email []Email
// }
//
// var r = Result{ "name", "phone", nil }
//
// unmarshalling the JSON syntax string
//
// {
// "email": [
// {
// "where": "home",
// "addr": "gre@example.com"
// },
// {
// "where": "work",
// "addr": "gre@work.com"
// }
// ],
// "name": "Grace R. Emlin",
// "address": "123 Main Street"
// }
//
// via Unmarshal(s, &r) is equivalent to assigning
//
// r = Result{
// "Grace R. Emlin", // name
// "phone", // no phone given
// []Email{
// Email{ "home", "gre@example.com" },
// Email{ "work", "gre@work.com" }
// }
// }
//
// Note that the field r.Phone has not been modified and
// that the JSON field "address" was discarded.
//
// Because Unmarshal uses the reflect package, it can only
// assign to upper case fields. Unmarshal uses a case-insensitive
// comparison to match JSON field names to struct field names.
//
// On success, Unmarshal returns with ok set to true.
// On a syntax error, it returns with ok set to false and errtok
// set to the offending token.
func Unmarshal(s string, val interface{}) (ok bool, errtok string) {
b := &structBuilder{val: reflect.NewValue(val)};
ok, _, errtok = Parse(s, b);
if !ok {
return false, errtok
}
return true, "";
}