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@ken39arg @kisielk @spirozh @shkw @chrneumann @moraes @rafaeljusto @rwl @sqs @nvanbenschoten @hjr265 @kuangchanglang
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// Copyright 2012 The Gorilla Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package schema
import (
"errors"
"reflect"
"strconv"
"strings"
"sync"
)
var invalidPath = errors.New("schema: invalid path")
// newCache returns a new cache.
func newCache() *cache {
c := cache{
m: make(map[reflect.Type]*structInfo),
regconv: make(map[reflect.Type]Converter),
tag: "schema",
}
return &c
}
// cache caches meta-data about a struct.
type cache struct {
l sync.RWMutex
m map[reflect.Type]*structInfo
regconv map[reflect.Type]Converter
tag string
}
// registerConverter registers a converter function for a custom type.
func (c *cache) registerConverter(value interface{}, converterFunc Converter) {
c.regconv[reflect.TypeOf(value)] = converterFunc
}
// parsePath parses a path in dotted notation verifying that it is a valid
// path to a struct field.
//
// It returns "path parts" which contain indices to fields to be used by
// reflect.Value.FieldByString(). Multiple parts are required for slices of
// structs.
func (c *cache) parsePath(p string, t reflect.Type) ([]pathPart, error) {
var struc *structInfo
var field *fieldInfo
var index64 int64
var err error
parts := make([]pathPart, 0)
path := make([]string, 0)
keys := strings.Split(p, ".")
for i := 0; i < len(keys); i++ {
if t.Kind() != reflect.Struct {
return nil, invalidPath
}
if struc = c.get(t); struc == nil {
return nil, invalidPath
}
if field = struc.get(keys[i]); field == nil {
return nil, invalidPath
}
// Valid field. Append index.
path = append(path, field.name)
if field.isSliceOfStructs && (!field.unmarshalerInfo.IsValid || (field.unmarshalerInfo.IsValid && field.unmarshalerInfo.IsSliceElement)) {
// Parse a special case: slices of structs.
// i+1 must be the slice index.
//
// Now that struct can implements TextUnmarshaler interface,
// we don't need to force the struct's fields to appear in the path.
// So checking i+2 is not necessary anymore.
i++
if i+1 > len(keys) {
return nil, invalidPath
}
if index64, err = strconv.ParseInt(keys[i], 10, 0); err != nil {
return nil, invalidPath
}
parts = append(parts, pathPart{
path: path,
field: field,
index: int(index64),
})
path = make([]string, 0)
// Get the next struct type, dropping ptrs.
if field.typ.Kind() == reflect.Ptr {
t = field.typ.Elem()
} else {
t = field.typ
}
if t.Kind() == reflect.Slice {
t = t.Elem()
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
}
} else if field.typ.Kind() == reflect.Ptr {
t = field.typ.Elem()
} else {
t = field.typ
}
}
// Add the remaining.
parts = append(parts, pathPart{
path: path,
field: field,
index: -1,
})
return parts, nil
}
// get returns a cached structInfo, creating it if necessary.
func (c *cache) get(t reflect.Type) *structInfo {
c.l.RLock()
info := c.m[t]
c.l.RUnlock()
if info == nil {
info = c.create(t, "")
c.l.Lock()
c.m[t] = info
c.l.Unlock()
}
return info
}
// create creates a structInfo with meta-data about a struct.
func (c *cache) create(t reflect.Type, parentAlias string) *structInfo {
info := &structInfo{}
var anonymousInfos []*structInfo
for i := 0; i < t.NumField(); i++ {
if f := c.createField(t.Field(i), parentAlias); f != nil {
info.fields = append(info.fields, f)
if ft := indirectType(f.typ); ft.Kind() == reflect.Struct && f.isAnonymous {
anonymousInfos = append(anonymousInfos, c.create(ft, f.canonicalAlias))
}
}
}
for i, a := range anonymousInfos {
others := []*structInfo{info}
others = append(others, anonymousInfos[:i]...)
others = append(others, anonymousInfos[i+1:]...)
for _, f := range a.fields {
if !containsAlias(others, f.alias) {
info.fields = append(info.fields, f)
}
}
}
return info
}
// createField creates a fieldInfo for the given field.
func (c *cache) createField(field reflect.StructField, parentAlias string) *fieldInfo {
alias, options := fieldAlias(field, c.tag)
if alias == "-" {
// Ignore this field.
return nil
}
canonicalAlias := alias
if parentAlias != "" {
canonicalAlias = parentAlias + "." + alias
}
// Check if the type is supported and don't cache it if not.
// First let's get the basic type.
isSlice, isStruct := false, false
ft := field.Type
m := isTextUnmarshaler(reflect.Zero(ft))
if ft.Kind() == reflect.Ptr {
ft = ft.Elem()
}
if isSlice = ft.Kind() == reflect.Slice; isSlice {
ft = ft.Elem()
if ft.Kind() == reflect.Ptr {
ft = ft.Elem()
}
}
if ft.Kind() == reflect.Array {
ft = ft.Elem()
if ft.Kind() == reflect.Ptr {
ft = ft.Elem()
}
}
if isStruct = ft.Kind() == reflect.Struct; !isStruct {
if c.converter(ft) == nil && builtinConverters[ft.Kind()] == nil {
// Type is not supported.
return nil
}
}
return &fieldInfo{
typ: field.Type,
name: field.Name,
alias: alias,
canonicalAlias: canonicalAlias,
unmarshalerInfo: m,
isSliceOfStructs: isSlice && isStruct,
isAnonymous: field.Anonymous,
isRequired: options.Contains("required"),
}
}
// converter returns the converter for a type.
func (c *cache) converter(t reflect.Type) Converter {
return c.regconv[t]
}
// ----------------------------------------------------------------------------
type structInfo struct {
fields []*fieldInfo
}
func (i *structInfo) get(alias string) *fieldInfo {
for _, field := range i.fields {
if strings.EqualFold(field.alias, alias) {
return field
}
}
return nil
}
func containsAlias(infos []*structInfo, alias string) bool {
for _, info := range infos {
if info.get(alias) != nil {
return true
}
}
return false
}
type fieldInfo struct {
typ reflect.Type
// name is the field name in the struct.
name string
alias string
// canonicalAlias is almost the same as the alias, but is prefixed with
// an embedded struct field alias in dotted notation if this field is
// promoted from the struct.
// For instance, if the alias is "N" and this field is an embedded field
// in a struct "X", canonicalAlias will be "X.N".
canonicalAlias string
// unmarshalerInfo contains information regarding the
// encoding.TextUnmarshaler implementation of the field type.
unmarshalerInfo unmarshaler
// isSliceOfStructs indicates if the field type is a slice of structs.
isSliceOfStructs bool
// isAnonymous indicates whether the field is embedded in the struct.
isAnonymous bool
isRequired bool
}
func (f *fieldInfo) paths(prefix string) []string {
if f.alias == f.canonicalAlias {
return []string{prefix + f.alias}
}
return []string{prefix + f.alias, prefix + f.canonicalAlias}
}
type pathPart struct {
field *fieldInfo
path []string // path to the field: walks structs using field names.
index int // struct index in slices of structs.
}
// ----------------------------------------------------------------------------
func indirectType(typ reflect.Type) reflect.Type {
if typ.Kind() == reflect.Ptr {
return typ.Elem()
}
return typ
}
// fieldAlias parses a field tag to get a field alias.
func fieldAlias(field reflect.StructField, tagName string) (alias string, options tagOptions) {
if tag := field.Tag.Get(tagName); tag != "" {
alias, options = parseTag(tag)
}
if alias == "" {
alias = field.Name
}
return alias, options
}
// tagOptions is the string following a comma in a struct field's tag, or
// the empty string. It does not include the leading comma.
type tagOptions []string
// parseTag splits a struct field's url tag into its name and comma-separated
// options.
func parseTag(tag string) (string, tagOptions) {
s := strings.Split(tag, ",")
return s[0], s[1:]
}
// Contains checks whether the tagOptions contains the specified option.
func (o tagOptions) Contains(option string) bool {
for _, s := range o {
if s == option {
return true
}
}
return false
}