Function getStructCodecLocked

datastore/prop.go:176–289

getStructCodecLocked implements getStructCodec. The structCodecsMutex must be held when calling this function.

(t reflect.Type)

// getStructCodecLocked implements getStructCodec. The structCodecsMutex must
// be held when calling this function.
func getStructCodecLocked(t reflect.Type) (ret *structCodec, retErr error) {
	c, ok := structCodecs[t]
	if ok {
		return c, nil
	}
	c = &structCodec{
		fields: make(map[string]fieldCodec),
		// We initialize keyField to -1 so that the zero-value is not
		// misinterpreted as index 0.
		keyField: -1,
	}

	// Add c to the structCodecs map before we are sure it is good. If t is
	// a recursive type, it needs to find the incomplete entry for itself in
	// the map.
	structCodecs[t] = c
	defer func() {
		if retErr != nil {
			delete(structCodecs, t)
		}
	}()

	for i := 0; i < t.NumField(); i++ {
		f := t.Field(i)
		// Skip unexported fields.
		// Note that if f is an anonymous, unexported struct field,
		// we will promote its fields.
		if f.PkgPath != "" && !f.Anonymous {
			continue
		}

		tags := strings.Split(f.Tag.Get("datastore"), ",")
		name := tags[0]
		opts := make(map[string]bool)
		for _, t := range tags[1:] {
			opts[t] = true
		}
		switch {
		case name == "":
			if !f.Anonymous {
				name = f.Name
			}
		case name == "-":
			continue
		case name == "__key__":
			if f.Type != typeOfKeyPtr {
				return nil, fmt.Errorf("datastore: __key__ field on struct %v is not a *datastore.Key", t)
			}
			c.keyField = i
		case !validPropertyName(name):
			return nil, fmt.Errorf("datastore: struct tag has invalid property name: %q", name)
		}

		substructType, fIsSlice := reflect.Type(nil), false
		switch f.Type.Kind() {
		case reflect.Struct:
			substructType = f.Type
		case reflect.Slice: