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// Copyright 2014 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package datastore
import (
"fmt"
"reflect"
"strings"
"unicode"
"cloud.google.com/go/internal/fields"
)
// Entities with more than this many indexed properties will not be saved.
const maxIndexedProperties = 20000
// Property is a name/value pair plus some metadata. A datastore entity's
// contents are loaded and saved as a sequence of Properties. Each property
// name must be unique within an entity.
type Property struct {
// Name is the property name.
Name string
// Value is the property value. The valid types are:
// - int64
// - bool
// - string
// - float64
// - *Key
// - time.Time (retrieved as local time)
// - GeoPoint
// - []byte (up to 1 megabyte in length)
// - *Entity (representing a nested struct)
// Value can also be:
// - []interface{} where each element is one of the above types
// This set is smaller than the set of valid struct field types that the
// datastore can load and save. A Value's type must be explicitly on
// the list above; it is not sufficient for the underlying type to be
// on that list. For example, a Value of "type myInt64 int64" is
// invalid. Smaller-width integers and floats are also invalid. Again,
// this is more restrictive than the set of valid struct field types.
//
// A Value will have an opaque type when loading entities from an index,
// such as via a projection query. Load entities into a struct instead
// of a PropertyLoadSaver when using a projection query.
//
// A Value may also be the nil interface value; this is equivalent to
// Python's None but not directly representable by a Go struct. Loading
// a nil-valued property into a struct will set that field to the zero
// value.
Value interface{}
// NoIndex is whether the datastore cannot index this property.
// If NoIndex is set to false, []byte and string values are limited to
// 1500 bytes.
NoIndex bool
}
// An Entity is the value type for a nested struct.
// This type is only used for a Property's Value.
type Entity struct {
Key *Key
Properties []Property
}
// PropertyLoadSaver can be converted from and to a slice of Properties.
type PropertyLoadSaver interface {
Load([]Property) error
Save() ([]Property, error)
}
// KeyLoader can store a Key.
type KeyLoader interface {
// PropertyLoadSaver is embedded because a KeyLoader
// must also always implement PropertyLoadSaver.
PropertyLoadSaver
LoadKey(k *Key) error
}
// PropertyList converts a []Property to implement PropertyLoadSaver.
type PropertyList []Property
var (
typeOfPropertyLoadSaver = reflect.TypeOf((*PropertyLoadSaver)(nil)).Elem()
typeOfPropertyList = reflect.TypeOf(PropertyList(nil))
)
// Load loads all of the provided properties into l.
// It does not first reset *l to an empty slice.
func (l *PropertyList) Load(p []Property) error {
*l = append(*l, p...)
return nil
}
// Save saves all of l's properties as a slice of Properties.
func (l *PropertyList) Save() ([]Property, error) {
return *l, nil
}
// validPropertyName returns whether name consists of one or more valid Go
// identifiers joined by ".".
func validPropertyName(name string) bool {
if name == "" {
return false
}
for _, s := range strings.Split(name, ".") {
if s == "" {
return false
}
first := true
for _, c := range s {
if first {
first = false
if c != '_' && !unicode.IsLetter(c) {
return false
}
} else {
if c != '_' && !unicode.IsLetter(c) && !unicode.IsDigit(c) {
return false
}
}
}
}
return true
}
// parseTag interprets datastore struct field tags
func parseTag(t reflect.StructTag) (name string, keep bool, other interface{}, err error) {
s := t.Get("datastore")
parts := strings.Split(s, ",")
if parts[0] == "-" && len(parts) == 1 {
return "", false, nil, nil
}
if parts[0] != "" && !validPropertyName(parts[0]) {
err = fmt.Errorf("datastore: struct tag has invalid property name: %q", parts[0])
return "", false, nil, err
}
var opts saveOpts
if len(parts) > 1 {
for _, p := range parts[1:] {
switch p {
case "flatten":
opts.flatten = true
case "omitempty":
opts.omitEmpty = true
case "noindex":
opts.noIndex = true
default:
err = fmt.Errorf("datastore: struct tag has invalid option: %q", p)
return "", false, nil, err
}
}
other = opts
}
return parts[0], true, other, nil
}
func validateType(t reflect.Type) error {
if t.Kind() != reflect.Struct {
return fmt.Errorf("datastore: validate called with non-struct type %s", t)
}
return validateChildType(t, "", false, false, map[reflect.Type]bool{})
}
// validateChildType is a recursion helper func for validateType
func validateChildType(t reflect.Type, fieldName string, flatten, prevSlice bool, prevTypes map[reflect.Type]bool) error {
if prevTypes[t] {
return nil
}
prevTypes[t] = true
switch t.Kind() {
case reflect.Slice:
if flatten && prevSlice {
return fmt.Errorf("datastore: flattening nested structs leads to a slice of slices: field %q", fieldName)
}
return validateChildType(t.Elem(), fieldName, flatten, true, prevTypes)
case reflect.Struct:
if t == typeOfTime || t == typeOfGeoPoint {
return nil
}
for i := 0; i < t.NumField(); i++ {
f := t.Field(i)
// If a named field is unexported, ignore it. An anonymous
// unexported field is processed, because it may contain
// exported fields, which are visible.
exported := (f.PkgPath == "")
if !exported && !f.Anonymous {
continue
}
_, keep, other, err := parseTag(f.Tag)
// Handle error from parseTag now instead of later (in cache.Fields call).
if err != nil {
return err
}
if !keep {
continue
}
if other != nil {
opts := other.(saveOpts)
flatten = flatten || opts.flatten
}
if err := validateChildType(f.Type, f.Name, flatten, prevSlice, prevTypes); err != nil {
return err
}
}
case reflect.Ptr:
if t == typeOfKeyPtr {
return nil
}
return validateChildType(t.Elem(), fieldName, flatten, prevSlice, prevTypes)
}
return nil
}
// isLeafType determines whether or not a type is a 'leaf type'
// and should not be recursed into, but considered one field.
func isLeafType(t reflect.Type) bool {
return t == typeOfTime || t == typeOfGeoPoint
}
// structCache collects the structs whose fields have already been calculated.
var structCache = fields.NewCache(parseTag, validateType, isLeafType)
// structPLS adapts a struct to be a PropertyLoadSaver.
type structPLS struct {
v reflect.Value
codec fields.List
}
// newStructPLS returns a structPLS, which implements the
// PropertyLoadSaver interface, for the struct pointer p.
func newStructPLS(p interface{}) (*structPLS, error) {
v := reflect.ValueOf(p)
if v.Kind() != reflect.Ptr || v.Elem().Kind() != reflect.Struct {
return nil, ErrInvalidEntityType
}
v = v.Elem()
f, err := structCache.Fields(v.Type())
if err != nil {
return nil, err
}
return &structPLS{v, f}, nil
}
// LoadStruct loads the properties from p to dst.
// dst must be a struct pointer.
//
// The values of dst's unmatched struct fields are not modified,
// and matching slice-typed fields are not reset before appending to
// them. In particular, it is recommended to pass a pointer to a zero
// valued struct on each LoadStruct call.
func LoadStruct(dst interface{}, p []Property) error {
x, err := newStructPLS(dst)
if err != nil {
return err
}
return x.Load(p)
}
// SaveStruct returns the properties from src as a slice of Properties.
// src must be a struct pointer.
func SaveStruct(src interface{}) ([]Property, error) {
x, err := newStructPLS(src)
if err != nil {
return nil, err
}
return x.Save()
}
// plsForLoad tries to convert v to a PropertyLoadSaver.
// If successful, plsForLoad returns a settable v as a PropertyLoadSaver.
//
// plsForLoad is intended to be used with nested struct fields which
// may implement PropertyLoadSaver.
//
// v must be settable.
func plsForLoad(v reflect.Value) (PropertyLoadSaver, error) {
var nilPtr bool
if v.Kind() == reflect.Ptr && v.IsNil() {
nilPtr = true
v.Set(reflect.New(v.Type().Elem()))
}
vpls, err := pls(v)
if nilPtr && (vpls == nil || err != nil) {
// unset v
v.Set(reflect.Zero(v.Type()))
}
return vpls, err
}
// plsForSave tries to convert v to a PropertyLoadSaver.
// If successful, plsForSave returns v as a PropertyLoadSaver.
//
// plsForSave is intended to be used with nested struct fields which
// may implement PropertyLoadSaver.
//
// v must be settable.
func plsForSave(v reflect.Value) (PropertyLoadSaver, error) {
switch v.Kind() {
case reflect.Ptr, reflect.Slice, reflect.Map, reflect.Interface, reflect.Chan, reflect.Func:
// If v is nil, return early. v contains no data to save.
if v.IsNil() {
return nil, nil
}
}
return pls(v)
}
func pls(v reflect.Value) (PropertyLoadSaver, error) {
if v.Kind() != reflect.Ptr {
if _, ok := v.Interface().(PropertyLoadSaver); ok {
return nil, fmt.Errorf("datastore: PropertyLoadSaver methods must be implemented on a pointer to %T", v.Interface())
}
v = v.Addr()
}
vpls, _ := v.Interface().(PropertyLoadSaver)
return vpls, nil
}
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