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main.go
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main.go
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package jsondz
import (
"bytes"
"encoding/json"
"errors"
"reflect"
"strconv"
"strings"
)
// Unmarshal ...
func Unmarshal(b []byte, intoOneOff ...interface{}) (interface{}, error) {
res, err := UnmarshalUsingFields(b, intoOneOff...)
if err != nil {
res, err = UnmarshalUsingNew(b, intoOneOff...)
}
return res, err
}
// UnmarshalUsingNew ...
func UnmarshalUsingNew(b []byte, intoOneOff ...interface{}) (interface{}, error) {
d := json.NewDecoder(bytes.NewReader(b))
d.UseNumber()
var temp interface{}
err := d.Decode(&temp)
if err != nil {
return nil, err
}
m := temp.(map[string]interface{})
var methodToCall reflect.Value
var in reflect.Type
for _, l := range intoOneOff {
// Check for proper New* functions
i, met, ok := checkForSingleValueNewFunction(l)
if !ok {
continue
}
// Check that we can call the new with given json
match := traverse(reflect.ValueOf(m), i)
if match {
if methodToCall.IsValid() {
return nil, errors.New("Duplicate match found!")
}
in = i
methodToCall = met
}
}
if !methodToCall.IsValid() {
return nil, errors.New("No match found!")
}
ins := reflect.New(in).Interface()
err = json.Unmarshal(b, &ins)
if err != nil {
// Should never happen!
panic("This should never happen, but somehow this occured: " + err.Error())
}
inArray := []reflect.Value{reflect.ValueOf(ins).Elem()}
res := methodToCall.Call(inArray)
return res[0].Interface(), nil
}
// UnmarshalUsingFields ...
func UnmarshalUsingFields(b []byte, intoOneOff ...interface{}) (interface{}, error) {
d := json.NewDecoder(bytes.NewReader(b))
d.UseNumber()
var temp interface{}
err := d.Decode(&temp)
if err != nil {
return nil, err
}
m := temp.(map[string]interface{})
var found interface{}
for _, l := range intoOneOff {
match := traverse(reflect.ValueOf(m), reflect.TypeOf(l))
if match {
if found != nil {
return nil, errors.New("Duplicate match found!")
}
found = l
}
}
if found == nil {
return nil, errors.New("No match found!")
}
ins := reflect.New(reflect.TypeOf(found)).Interface()
err = json.Unmarshal(b, &ins)
if err != nil {
// Should never happen!
panic("This should never happen, but somehow this occured: " + err.Error())
}
return ins, nil
}
func traverse(v reflect.Value, t reflect.Type) (match bool) {
switch v.Kind() {
case reflect.Map:
// TODO: Logic here bit messy, needs cleaning
// Idea: fieldNames are must, omitEmpty means that JSON can't have zero val-
// ues in golang sense for such fields because fields with omit and empty
// values will not be present in resulting json
fieldNames, omitEmpty := getJSONFieldNames(t)
if len(fieldNames) != len(v.MapKeys()) {
return false
}
for _, key := range v.MapKeys() {
must := fieldNames[key.String()]
omit := omitEmpty[key.String()]
value := v.MapIndex(key).Interface()
if must == "" && omit == "" {
return false
}
if omit != "" {
if value == nil || isZero(reflect.ValueOf(value)) {
return false
}
must = omit
}
f, _ := t.FieldByName(must)
ok := traverse(reflect.ValueOf(value), f.Type)
if !ok {
return false
}
}
case reflect.Slice:
if t.Kind() != reflect.Slice {
return false
}
trueType := t.Elem()
for i := 0; i < v.Len(); i++ {
ok := traverse(reflect.ValueOf(v.Index(i).Interface()), trueType)
if !ok {
return false
}
}
case reflect.Bool:
return t.Kind() == reflect.Bool
case reflect.String:
// If number
var number json.Number
if v.Type() == reflect.TypeOf(number) {
switch t.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
_, err := strconv.ParseInt(v.String(), 10, t.Bits())
return err == nil
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
_, err := strconv.ParseUint(v.String(), 10, t.Bits())
return err == nil
case reflect.Float32, reflect.Float64:
_, err := strconv.ParseFloat(v.String(), t.Bits())
return err == nil
default:
return false
}
}
return t.Kind() == reflect.String
}
return true
}
func isZero(v reflect.Value) bool {
switch v.Kind() {
case reflect.Func, reflect.Map, reflect.Slice:
return v.IsNil()
case reflect.Array:
z := true
for i := 0; i < v.Len(); i++ {
z = z && isZero(v.Index(i))
}
return z
case reflect.Struct:
z := true
for i := 0; i < v.NumField(); i++ {
z = z && isZero(v.Field(i))
}
return z
}
// Compare other types directly:
z := reflect.Zero(v.Type())
return v.Interface() == z.Interface()
}
func getJSONFieldNames(t reflect.Type) (
fields map[string]string,
omitEmpty map[string]string) {
fields = make(map[string]string)
omitEmpty = make(map[string]string)
for i := 0; i < t.NumField(); i++ {
field := t.Field(i)
if !field.Anonymous {
tag := field.Tag.Get("json")
omit := strings.Contains(tag, ",omitempty")
tag = strings.Replace(tag, ",omitempty", "", 1)
if tag == "-" {
continue
}
key := field.Name
if tag != "" {
key = tag
}
if omit {
omitEmpty[key] = field.Name
} else {
fields[key] = field.Name
}
} else {
// Embedded field
rFields, rOmitEmpty := getJSONFieldNames(field.Type)
for k, v := range rFields {
fields[k] = v
}
for k, v := range rOmitEmpty {
omitEmpty[k] = v
}
}
}
return
}
func checkForSingleValueNewFunction(s interface{}) (in reflect.Type, callMethod reflect.Value, ok bool) {
// Check that s is indeed a struct
sv := reflect.ValueOf(s)
if sv.Kind() != reflect.Struct {
ok = false
return
}
callMethod = sv.MethodByName("New")
if !callMethod.IsValid() {
callMethod = sv.MethodByName("New" + strings.Title(sv.Type().Name()))
if !callMethod.IsValid() {
ok = false
return
}
}
if callMethod.Type().NumIn() != 1 {
ok = false
return
}
if callMethod.Type().NumOut() != 1 {
ok = false
return
}
in = callMethod.Type().In(0)
switch in.Kind() {
// No support for types below (see http://blog.golang.org/json-and-go)
case reflect.Func, reflect.Ptr, reflect.Chan, reflect.Complex128, reflect.Complex64:
ok = false
return
}
out := callMethod.Type().Out(0)
if out.Kind() != reflect.Ptr {
ok = false
return
}
if out.Elem() != sv.Type() {
ok = false
return
}
return in, callMethod, true
}