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// Copyright 2011 Google Inc. All rights reserved.
// Use of this source code is governed by the Apache 2.0
// license that can be found in the LICENSE file.
package datastore
import (
"fmt"
"reflect"
"strings"
"time"
"github.com/golang/protobuf/proto"
"google.golang.org/appengine"
pb "google.golang.org/appengine/internal/datastore"
)
var (
typeOfBlobKey = reflect.TypeOf(appengine.BlobKey(""))
typeOfByteSlice = reflect.TypeOf([]byte(nil))
typeOfByteString = reflect.TypeOf(ByteString(nil))
typeOfGeoPoint = reflect.TypeOf(appengine.GeoPoint{})
typeOfTime = reflect.TypeOf(time.Time{})
typeOfKeyPtr = reflect.TypeOf(&Key{})
typeOfEntityPtr = reflect.TypeOf(&Entity{})
)
// typeMismatchReason returns a string explaining why the property p could not
// be stored in an entity field of type v.Type().
func typeMismatchReason(pValue interface{}, v reflect.Value) string {
entityType := "empty"
switch pValue.(type) {
case int64:
entityType = "int"
case bool:
entityType = "bool"
case string:
entityType = "string"
case float64:
entityType = "float"
case *Key:
entityType = "*datastore.Key"
case time.Time:
entityType = "time.Time"
case appengine.BlobKey:
entityType = "appengine.BlobKey"
case appengine.GeoPoint:
entityType = "appengine.GeoPoint"
case ByteString:
entityType = "datastore.ByteString"
case []byte:
entityType = "[]byte"
}
return fmt.Sprintf("type mismatch: %s versus %v", entityType, v.Type())
}
type propertyLoader struct {
// m holds the number of times a substruct field like "Foo.Bar.Baz" has
// been seen so far. The map is constructed lazily.
m map[string]int
}
func (l *propertyLoader) load(codec *structCodec, structValue reflect.Value, p Property, requireSlice bool) string {
var v reflect.Value
var sliceIndex int
name := p.Name
// If name ends with a '.', the last field is anonymous.
// In this case, strings.Split will give us "" as the
// last element of our fields slice, which will match the ""
// field name in the substruct codec.
fields := strings.Split(name, ".")
for len(fields) > 0 {
var decoder fieldCodec
var ok bool
// Cut off the last field (delimited by ".") and find its parent
// in the codec.
// eg. for name "A.B.C.D", split off "A.B.C" and try to
// find a field in the codec with this name.
// Loop again with "A.B", etc.
for i := len(fields); i > 0; i-- {
parent := strings.Join(fields[:i], ".")
decoder, ok = codec.fields[parent]
if ok {
fields = fields[i:]
break
}
}
// If we never found a matching field in the codec, return
// error message.
if !ok {
return "no such struct field"
}
v = initField(structValue, decoder.path)
if !v.IsValid() {
return "no such struct field"
}
if !v.CanSet() {
return "cannot set struct field"
}
if decoder.structCodec != nil {
codec = decoder.structCodec
structValue = v
}
if v.Kind() == reflect.Slice && v.Type() != typeOfByteSlice {
if l.m == nil {
l.m = make(map[string]int)
}
sliceIndex = l.m[p.Name]
l.m[p.Name] = sliceIndex + 1
for v.Len() <= sliceIndex {
v.Set(reflect.Append(v, reflect.New(v.Type().Elem()).Elem()))
}
structValue = v.Index(sliceIndex)
requireSlice = false
}
}
var slice reflect.Value
if v.Kind() == reflect.Slice && v.Type().Elem().Kind() != reflect.Uint8 {
slice = v
v = reflect.New(v.Type().Elem()).Elem()
} else if requireSlice {
return "multiple-valued property requires a slice field type"
}
// Convert indexValues to a Go value with a meaning derived from the
// destination type.
pValue := p.Value
if iv, ok := pValue.(indexValue); ok {
meaning := pb.Property_NO_MEANING
switch v.Type() {
case typeOfBlobKey:
meaning = pb.Property_BLOBKEY
case typeOfByteSlice:
meaning = pb.Property_BLOB
case typeOfByteString:
meaning = pb.Property_BYTESTRING
case typeOfGeoPoint:
meaning = pb.Property_GEORSS_POINT
case typeOfTime:
meaning = pb.Property_GD_WHEN
case typeOfEntityPtr:
meaning = pb.Property_ENTITY_PROTO
}
var err error
pValue, err = propValue(iv.value, meaning)
if err != nil {
return err.Error()
}
}
if errReason := setVal(v, pValue); errReason != "" {
// Set the slice back to its zero value.
if slice.IsValid() {
slice.Set(reflect.Zero(slice.Type()))
}
return errReason
}
if slice.IsValid() {
slice.Index(sliceIndex).Set(v)
}
return ""
}
// setVal sets v to the value pValue.
func setVal(v reflect.Value, pValue interface{}) string {
switch v.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
x, ok := pValue.(int64)
if !ok && pValue != nil {
return typeMismatchReason(pValue, v)
}
if v.OverflowInt(x) {
return fmt.Sprintf("value %v overflows struct field of type %v", x, v.Type())
}
v.SetInt(x)
case reflect.Bool:
x, ok := pValue.(bool)
if !ok && pValue != nil {
return typeMismatchReason(pValue, v)
}
v.SetBool(x)
case reflect.String:
switch x := pValue.(type) {
case appengine.BlobKey:
v.SetString(string(x))
case ByteString:
v.SetString(string(x))
case string:
v.SetString(x)
default:
if pValue != nil {
return typeMismatchReason(pValue, v)
}
}
case reflect.Float32, reflect.Float64:
x, ok := pValue.(float64)
if !ok && pValue != nil {
return typeMismatchReason(pValue, v)
}
if v.OverflowFloat(x) {
return fmt.Sprintf("value %v overflows struct field of type %v", x, v.Type())
}
v.SetFloat(x)
case reflect.Ptr:
x, ok := pValue.(*Key)
if !ok && pValue != nil {
return typeMismatchReason(pValue, v)
}
if _, ok := v.Interface().(*Key); !ok {
return typeMismatchReason(pValue, v)
}
v.Set(reflect.ValueOf(x))
case reflect.Struct:
switch v.Type() {
case typeOfTime:
x, ok := pValue.(time.Time)
if !ok && pValue != nil {
return typeMismatchReason(pValue, v)
}
v.Set(reflect.ValueOf(x))
case typeOfGeoPoint:
x, ok := pValue.(appengine.GeoPoint)
if !ok && pValue != nil {
return typeMismatchReason(pValue, v)
}
v.Set(reflect.ValueOf(x))
default:
ent, ok := pValue.(*Entity)
if !ok {
return typeMismatchReason(pValue, v)
}
// Recursively load nested struct
pls, err := newStructPLS(v.Addr().Interface())
if err != nil {
return err.Error()
}
// if ent has a Key value and our struct has a Key field,
// load the Entity's Key value into the Key field on the struct.
if ent.Key != nil && pls.codec.keyField != -1 {
pls.v.Field(pls.codec.keyField).Set(reflect.ValueOf(ent.Key))
}
err = pls.Load(ent.Properties)
if err != nil {
return err.Error()
}
}
case reflect.Slice:
x, ok := pValue.([]byte)
if !ok {
if y, yok := pValue.(ByteString); yok {
x, ok = []byte(y), true
}
}
if !ok && pValue != nil {
return typeMismatchReason(pValue, v)
}
if v.Type().Elem().Kind() != reflect.Uint8 {
return typeMismatchReason(pValue, v)
}
v.SetBytes(x)
default:
return typeMismatchReason(pValue, v)
}
return ""
}
// initField is similar to reflect's Value.FieldByIndex, in that it
// returns the nested struct field corresponding to index, but it
// initialises any nil pointers encountered when traversing the structure.
func initField(val reflect.Value, index []int) reflect.Value {
for _, i := range index[:len(index)-1] {
val = val.Field(i)
if val.Kind() == reflect.Ptr {
if val.IsNil() {
val.Set(reflect.New(val.Type().Elem()))
}
val = val.Elem()
}
}
return val.Field(index[len(index)-1])
}
// loadEntity loads an EntityProto into PropertyLoadSaver or struct pointer.
func loadEntity(dst interface{}, src *pb.EntityProto) (err error) {
ent, err := protoToEntity(src)
if err != nil {
return err
}
if e, ok := dst.(PropertyLoadSaver); ok {
return e.Load(ent.Properties)
}
return LoadStruct(dst, ent.Properties)
}
func (s structPLS) Load(props []Property) error {
var fieldName, reason string
var l propertyLoader
for _, p := range props {
if errStr := l.load(s.codec, s.v, p, p.Multiple); errStr != "" {
// We don't return early, as we try to load as many properties as possible.
// It is valid to load an entity into a struct that cannot fully represent it.
// That case returns an error, but the caller is free to ignore it.
fieldName, reason = p.Name, errStr
}
}
if reason != "" {
return &ErrFieldMismatch{
StructType: s.v.Type(),
FieldName: fieldName,
Reason: reason,
}
}
return nil
}
func protoToEntity(src *pb.EntityProto) (*Entity, error) {
props, rawProps := src.Property, src.RawProperty
outProps := make([]Property, 0, len(props)+len(rawProps))
for {
var (
x *pb.Property
noIndex bool
)
if len(props) > 0 {
x, props = props[0], props[1:]
} else if len(rawProps) > 0 {
x, rawProps = rawProps[0], rawProps[1:]
noIndex = true
} else {
break
}
var value interface{}
if x.Meaning != nil && *x.Meaning == pb.Property_INDEX_VALUE {
value = indexValue{x.Value}
} else {
var err error
value, err = propValue(x.Value, x.GetMeaning())
if err != nil {
return nil, err
}
}
outProps = append(outProps, Property{
Name: x.GetName(),
Value: value,
NoIndex: noIndex,
Multiple: x.GetMultiple(),
})
}
var key *Key
if src.Key != nil {
// Ignore any error, since nested entity values
// are allowed to have an invalid key.
key, _ = protoToKey(src.Key)
}
return &Entity{key, outProps}, nil
}
// propValue returns a Go value that combines the raw PropertyValue with a
// meaning. For example, an Int64Value with GD_WHEN becomes a time.Time.
func propValue(v *pb.PropertyValue, m pb.Property_Meaning) (interface{}, error) {
switch {
case v.Int64Value != nil:
if m == pb.Property_GD_WHEN {
return fromUnixMicro(*v.Int64Value), nil
} else {
return *v.Int64Value, nil
}
case v.BooleanValue != nil:
return *v.BooleanValue, nil
case v.StringValue != nil:
if m == pb.Property_BLOB {
return []byte(*v.StringValue), nil
} else if m == pb.Property_BLOBKEY {
return appengine.BlobKey(*v.StringValue), nil
} else if m == pb.Property_BYTESTRING {
return ByteString(*v.StringValue), nil
} else if m == pb.Property_ENTITY_PROTO {
var ent pb.EntityProto
err := proto.Unmarshal([]byte(*v.StringValue), &ent)
if err != nil {
return nil, err
}
return protoToEntity(&ent)
} else {
return *v.StringValue, nil
}
case v.DoubleValue != nil:
return *v.DoubleValue, nil
case v.Referencevalue != nil:
key, err := referenceValueToKey(v.Referencevalue)
if err != nil {
return nil, err
}
return key, nil
case v.Pointvalue != nil:
// NOTE: Strangely, latitude maps to X, longitude to Y.
return appengine.GeoPoint{Lat: v.Pointvalue.GetX(), Lng: v.Pointvalue.GetY()}, nil
}
return nil, nil
}
// indexValue is a Property value that is created when entities are loaded from
// an index, such as from a projection query.
//
// Such Property values do not contain all of the metadata required to be
// faithfully represented as a Go value, and are instead represented as an
// opaque indexValue. Load the properties into a concrete struct type (e.g. by
// passing a struct pointer to Iterator.Next) to reconstruct actual Go values
// of type int, string, time.Time, etc.
type indexValue struct {
value *pb.PropertyValue
}