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@@ -0,0 +1,195 @@
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+package schema
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+
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+import (
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+ "errors"
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+ "fmt"
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+ "reflect"
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+ "strconv"
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+)
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+
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+type encoderFunc func(reflect.Value) string
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+
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+// Encoder encodes values from a struct into url.Values.
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+type Encoder struct {
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+ cache *cache
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+ regenc map[reflect.Type]encoderFunc
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+}
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+
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+// NewEncoder returns a new Encoder with defaults.
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+func NewEncoder() *Encoder {
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+ return &Encoder{cache: newCache(), regenc: make(map[reflect.Type]encoderFunc)}
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+}
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+
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+// Encode encodes a struct into map[string][]string.
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+//
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+// Intended for use with url.Values.
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+func (e *Encoder) Encode(src interface{}, dst map[string][]string) error {
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+ v := reflect.ValueOf(src)
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+
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+ return e.encode(v, dst)
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+}
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+
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+// RegisterEncoder registers a converter for encoding a custom type.
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+func (e *Encoder) RegisterEncoder(value interface{}, encoder func(reflect.Value) string) {
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+ e.regenc[reflect.TypeOf(value)] = encoder
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+}
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+
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+// SetAliasTag changes the tag used to locate custom field aliases.
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+// The default tag is "schema".
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+func (e *Encoder) SetAliasTag(tag string) {
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+ e.cache.tag = tag
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+}
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+
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+// isValidStructPointer test if input value is a valid struct pointer.
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+func isValidStructPointer(v reflect.Value) bool {
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+ return v.Type().Kind() == reflect.Ptr && v.Elem().IsValid() && v.Elem().Type().Kind() == reflect.Struct
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+}
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+
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+func isZero(v reflect.Value) bool {
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+ switch v.Kind() {
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+ case reflect.Func:
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+ case reflect.Map, reflect.Slice:
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+ return v.IsNil() || v.Len() == 0
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+ case reflect.Array:
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+ z := true
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+ for i := 0; i < v.Len(); i++ {
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+ z = z && isZero(v.Index(i))
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+ }
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+ return z
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+ case reflect.Struct:
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+ z := true
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+ for i := 0; i < v.NumField(); i++ {
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+ z = z && isZero(v.Field(i))
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+ }
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+ return z
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+ }
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+ // Compare other types directly:
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+ z := reflect.Zero(v.Type())
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+ return v.Interface() == z.Interface()
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+}
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+
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+func (e *Encoder) encode(v reflect.Value, dst map[string][]string) error {
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+ if v.Kind() == reflect.Ptr {
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+ v = v.Elem()
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+ }
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+ if v.Kind() != reflect.Struct {
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+ return errors.New("schema: interface must be a struct")
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+ }
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+ t := v.Type()
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+
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+ errors := MultiError{}
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+
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+ for i := 0; i < v.NumField(); i++ {
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+ name, opts := fieldAlias(t.Field(i), e.cache.tag)
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+ if name == "-" {
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+ continue
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+ }
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+
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+ // Encode struct pointer types if the field is a valid pointer and a struct.
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+ if isValidStructPointer(v.Field(i)) {
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+ e.encode(v.Field(i).Elem(), dst)
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+ continue
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+ }
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+
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+ encFunc := typeEncoder(v.Field(i).Type(), e.regenc)
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+
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+ // Encode non-slice types and custom implementations immediately.
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+ if encFunc != nil {
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+ value := encFunc(v.Field(i))
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+ if opts.Contains("omitempty") && isZero(v.Field(i)) {
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+ continue
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+ }
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+
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+ dst[name] = append(dst[name], value)
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+ continue
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+ }
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+
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+ if v.Field(i).Type().Kind() == reflect.Struct {
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+ e.encode(v.Field(i), dst)
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+ continue
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+ }
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+
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+ if v.Field(i).Type().Kind() == reflect.Slice {
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+ encFunc = typeEncoder(v.Field(i).Type().Elem(), e.regenc)
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+ }
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+
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+ if encFunc == nil {
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+ errors[v.Field(i).Type().String()] = fmt.Errorf("schema: encoder not found for %v", v.Field(i))
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+ continue
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+ }
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+
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+ // Encode a slice.
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+ if v.Field(i).Len() == 0 && opts.Contains("omitempty") {
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+ continue
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+ }
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+
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+ dst[name] = []string{}
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+ for j := 0; j < v.Field(i).Len(); j++ {
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+ dst[name] = append(dst[name], encFunc(v.Field(i).Index(j)))
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+ }
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+ }
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+
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+ if len(errors) > 0 {
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+ return errors
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+ }
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+ return nil
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+}
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+
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+func typeEncoder(t reflect.Type, reg map[reflect.Type]encoderFunc) encoderFunc {
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+ if f, ok := reg[t]; ok {
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+ return f
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+ }
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+
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+ switch t.Kind() {
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+ case reflect.Bool:
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+ return encodeBool
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+ case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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+ return encodeInt
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+ case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
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+ return encodeUint
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+ case reflect.Float32:
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+ return encodeFloat32
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+ case reflect.Float64:
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+ return encodeFloat64
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+ case reflect.Ptr:
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+ f := typeEncoder(t.Elem(), reg)
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+ return func(v reflect.Value) string {
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+ if v.IsNil() {
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+ return "null"
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+ }
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+ return f(v.Elem())
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+ }
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+ case reflect.String:
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+ return encodeString
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+ default:
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+ return nil
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+ }
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+}
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+
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+func encodeBool(v reflect.Value) string {
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+ return strconv.FormatBool(v.Bool())
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+}
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+
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+func encodeInt(v reflect.Value) string {
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+ return strconv.FormatInt(int64(v.Int()), 10)
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+}
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+
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+func encodeUint(v reflect.Value) string {
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+ return strconv.FormatUint(uint64(v.Uint()), 10)
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+}
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+
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+func encodeFloat(v reflect.Value, bits int) string {
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+ return strconv.FormatFloat(v.Float(), 'f', 6, bits)
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+}
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+
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+func encodeFloat32(v reflect.Value) string {
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+ return encodeFloat(v, 32)
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+}
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+
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+func encodeFloat64(v reflect.Value) string {
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+ return encodeFloat(v, 64)
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+}
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+
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+func encodeString(v reflect.Value) string {
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+ return v.String()
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+}
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