dex/vendor/google.golang.org/appengine/search/struct.go

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2016-07-26 01:30:28 +05:30
// Copyright 2015 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 search
import (
"fmt"
"reflect"
"strings"
"sync"
)
// ErrFieldMismatch is returned when a field is to be loaded into a different
// than the one it was stored from, or when a field is missing or unexported in
// the destination struct.
type ErrFieldMismatch struct {
FieldName string
Reason string
}
func (e *ErrFieldMismatch) Error() string {
return fmt.Sprintf("search: cannot load field %q: %s", e.FieldName, e.Reason)
}
// ErrFacetMismatch is returned when a facet is to be loaded into a different
// type than the one it was stored from, or when a field is missing or
// unexported in the destination struct. StructType is the type of the struct
// pointed to by the destination argument passed to Iterator.Next.
type ErrFacetMismatch struct {
StructType reflect.Type
FacetName string
Reason string
}
func (e *ErrFacetMismatch) Error() string {
return fmt.Sprintf("search: cannot load facet %q into a %q: %s", e.FacetName, e.StructType, e.Reason)
}
// structCodec defines how to convert a given struct to/from a search document.
type structCodec struct {
// byIndex returns the struct tag for the i'th struct field.
byIndex []structTag
// fieldByName returns the index of the struct field for the given field name.
fieldByName map[string]int
// facetByName returns the index of the struct field for the given facet name,
facetByName map[string]int
}
// structTag holds a structured version of each struct field's parsed tag.
type structTag struct {
name string
facet bool
ignore bool
}
var (
codecsMu sync.RWMutex
codecs = map[reflect.Type]*structCodec{}
)
func loadCodec(t reflect.Type) (*structCodec, error) {
codecsMu.RLock()
codec, ok := codecs[t]
codecsMu.RUnlock()
if ok {
return codec, nil
}
codecsMu.Lock()
defer codecsMu.Unlock()
if codec, ok := codecs[t]; ok {
return codec, nil
}
codec = &structCodec{
fieldByName: make(map[string]int),
facetByName: make(map[string]int),
}
for i, I := 0, t.NumField(); i < I; i++ {
f := t.Field(i)
name, opts := f.Tag.Get("search"), ""
if i := strings.Index(name, ","); i != -1 {
name, opts = name[:i], name[i+1:]
}
ignore := false
if name == "-" {
ignore = true
} else if name == "" {
name = f.Name
} else if !validFieldName(name) {
return nil, fmt.Errorf("search: struct tag has invalid field name: %q", name)
}
facet := opts == "facet"
codec.byIndex = append(codec.byIndex, structTag{name: name, facet: facet, ignore: ignore})
if facet {
codec.facetByName[name] = i
} else {
codec.fieldByName[name] = i
}
}
codecs[t] = codec
return codec, nil
}
// structFLS adapts a struct to be a FieldLoadSaver.
type structFLS struct {
v reflect.Value
codec *structCodec
}
func (s structFLS) Load(fields []Field, meta *DocumentMetadata) error {
var err error
for _, field := range fields {
i, ok := s.codec.fieldByName[field.Name]
if !ok {
// Note the error, but keep going.
err = &ErrFieldMismatch{
FieldName: field.Name,
Reason: "no such struct field",
}
continue
}
f := s.v.Field(i)
if !f.CanSet() {
// Note the error, but keep going.
err = &ErrFieldMismatch{
FieldName: field.Name,
Reason: "cannot set struct field",
}
continue
}
v := reflect.ValueOf(field.Value)
if ft, vt := f.Type(), v.Type(); ft != vt {
err = &ErrFieldMismatch{
FieldName: field.Name,
Reason: fmt.Sprintf("type mismatch: %v for %v data", ft, vt),
}
continue
}
f.Set(v)
}
if meta == nil {
return err
}
for _, facet := range meta.Facets {
i, ok := s.codec.facetByName[facet.Name]
if !ok {
// Note the error, but keep going.
if err == nil {
err = &ErrFacetMismatch{
StructType: s.v.Type(),
FacetName: facet.Name,
Reason: "no matching field found",
}
}
continue
}
f := s.v.Field(i)
if !f.CanSet() {
// Note the error, but keep going.
if err == nil {
err = &ErrFacetMismatch{
StructType: s.v.Type(),
FacetName: facet.Name,
Reason: "unable to set unexported field of struct",
}
}
continue
}
v := reflect.ValueOf(facet.Value)
if ft, vt := f.Type(), v.Type(); ft != vt {
if err == nil {
err = &ErrFacetMismatch{
StructType: s.v.Type(),
FacetName: facet.Name,
Reason: fmt.Sprintf("type mismatch: %v for %d data", ft, vt),
}
continue
}
}
f.Set(v)
}
return err
}
func (s structFLS) Save() ([]Field, *DocumentMetadata, error) {
fields := make([]Field, 0, len(s.codec.fieldByName))
var facets []Facet
for i, tag := range s.codec.byIndex {
if tag.ignore {
continue
}
f := s.v.Field(i)
if !f.CanSet() {
continue
}
if tag.facet {
facets = append(facets, Facet{Name: tag.name, Value: f.Interface()})
} else {
fields = append(fields, Field{Name: tag.name, Value: f.Interface()})
}
}
return fields, &DocumentMetadata{Facets: facets}, nil
}
// newStructFLS returns a FieldLoadSaver for the struct pointer p.
func newStructFLS(p interface{}) (FieldLoadSaver, error) {
v := reflect.ValueOf(p)
if v.Kind() != reflect.Ptr || v.IsNil() || v.Elem().Kind() != reflect.Struct {
return nil, ErrInvalidDocumentType
}
codec, err := loadCodec(v.Elem().Type())
if err != nil {
return nil, err
}
return structFLS{v.Elem(), codec}, nil
}
func loadStructWithMeta(dst interface{}, f []Field, meta *DocumentMetadata) error {
x, err := newStructFLS(dst)
if err != nil {
return err
}
return x.Load(f, meta)
}
func saveStructWithMeta(src interface{}) ([]Field, *DocumentMetadata, error) {
x, err := newStructFLS(src)
if err != nil {
return nil, nil, err
}
return x.Save()
}
// LoadStruct loads the fields from f to dst. dst must be a struct pointer.
func LoadStruct(dst interface{}, f []Field) error {
return loadStructWithMeta(dst, f, nil)
}
// SaveStruct returns the fields from src as a slice of Field.
// src must be a struct pointer.
func SaveStruct(src interface{}) ([]Field, error) {
f, _, err := saveStructWithMeta(src)
return f, err
}