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structfields.go
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structfields.go
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// Copyright (c) Faye Amacker. All rights reserved.
// Licensed under the MIT License. See LICENSE in the project root for license information.
package cbor
import (
"reflect"
"sort"
"strings"
)
type field struct {
name string
cborName []byte
idx []int
typ reflect.Type
ef encodeFunc
isUnmarshaler bool
tagged bool // used to choose dominant field (at the same level tagged fields dominate untagged fields)
omitEmpty bool // used to skip empty field
keyAsInt bool // used to encode/decode field name as int
}
type fields []field
// indexFieldSorter sorts fields by field idx at each level, breaking ties with idx depth.
type indexFieldSorter struct {
fields fields
}
func (x *indexFieldSorter) Len() int {
return len(x.fields)
}
func (x *indexFieldSorter) Swap(i, j int) {
x.fields[i], x.fields[j] = x.fields[j], x.fields[i]
}
func (x *indexFieldSorter) Less(i, j int) bool {
iIdx := x.fields[i].idx
jIdx := x.fields[j].idx
for k, d := range iIdx {
if k >= len(jIdx) {
// fields[j].idx is a subset of fields[i].idx.
return false
}
if d != jIdx[k] {
// fields[i].idx and fields[j].idx are different.
return d < jIdx[k]
}
}
// fields[i].idx is either the same as, or a subset of fields[j].idx.
return true
}
// nameLevelAndTagFieldSorter sorts fields by field name, idx depth, and presence of tag.
type nameLevelAndTagFieldSorter struct {
fields fields
}
func (x *nameLevelAndTagFieldSorter) Len() int {
return len(x.fields)
}
func (x *nameLevelAndTagFieldSorter) Swap(i, j int) {
x.fields[i], x.fields[j] = x.fields[j], x.fields[i]
}
func (x *nameLevelAndTagFieldSorter) Less(i, j int) bool {
if x.fields[i].name != x.fields[j].name {
return x.fields[i].name < x.fields[j].name
}
if len(x.fields[i].idx) != len(x.fields[j].idx) {
return len(x.fields[i].idx) < len(x.fields[j].idx)
}
if x.fields[i].tagged != x.fields[j].tagged {
return x.fields[i].tagged
}
return i < j // Field i and j have the same name, depth, and tagged status. Nothing else matters.
}
// getFields returns a list of visible fields of struct type typ following Go
// visibility rules for struct fields.
func getFields(typ reflect.Type) (flds fields, structOptions string) {
// Inspired by typeFields() in stdlib's encoding/json/encode.go.
var current map[reflect.Type][][]int // key: struct type, value: field index of this struct type at the same level
next := map[reflect.Type][][]int{typ: nil}
visited := map[reflect.Type]bool{} // Inspected struct type at less nested levels.
for len(next) > 0 {
current, next = next, map[reflect.Type][][]int{}
for structType, structIdx := range current {
if len(structIdx) > 1 {
continue // Fields of the same embedded struct type at the same level are ignored.
}
if visited[structType] {
continue
}
visited[structType] = true
var fieldIdx []int
if len(structIdx) > 0 {
fieldIdx = structIdx[0]
}
for i := 0; i < structType.NumField(); i++ {
f := structType.Field(i)
ft := f.Type
if ft.Kind() == reflect.Ptr {
ft = ft.Elem()
}
exportable := f.PkgPath == ""
if f.Anonymous {
if !exportable && ft.Kind() != reflect.Struct {
// Nonexportable anonymous fields of non-struct type are ignored.
continue
}
// Nonexportable anonymous field of struct type can contain exportable fields for serialization.
} else if !exportable {
// Get special field "_" struct options
if f.Name == "_" {
tag := f.Tag.Get("cbor")
if tag != "-" {
structOptions = tag
}
}
// Nonexportable fields are ignored.
continue
}
tag := f.Tag.Get("cbor")
if tag == "" {
tag = f.Tag.Get("json")
}
if tag == "-" {
continue
}
idx := make([]int, len(fieldIdx)+1)
copy(idx, fieldIdx)
idx[len(fieldIdx)] = i
tagged := len(tag) > 0
tagFieldName, omitempty, keyasint := getFieldNameAndOptionsFromTag(tag)
fieldName := tagFieldName
if tagFieldName == "" {
fieldName = f.Name
}
if !f.Anonymous || ft.Kind() != reflect.Struct || len(tagFieldName) > 0 {
flds = append(flds, field{name: fieldName, idx: idx, typ: f.Type, tagged: tagged, omitEmpty: omitempty, keyAsInt: keyasint})
continue
}
// f is anonymous struct of type ft.
next[ft] = append(next[ft], idx)
}
}
}
sort.Sort(&nameLevelAndTagFieldSorter{flds})
// Keep visible fields.
visibleFields := flds[:0]
for i, j := 0, 0; i < len(flds); i = j {
name := flds[i].name
for j = i + 1; j < len(flds) && flds[j].name == name; j++ {
}
if j-i == 1 || len(flds[i].idx) < len(flds[i+1].idx) || (flds[i].tagged && !flds[i+1].tagged) {
// Keep the field if the field name is unique, or if the first field
// is at a less nested level, or if the first field is tagged and
// the second field is not.
visibleFields = append(visibleFields, flds[i])
}
}
sort.Sort(&indexFieldSorter{visibleFields})
return visibleFields, structOptions
}
func getFieldNameAndOptionsFromTag(tag string) (name string, omitEmpty bool, keyAsInt bool) {
if tag == "" {
return
}
idx := strings.Index(tag, ",")
if idx == -1 {
return tag, false, false
}
if idx > 0 {
name = tag[:idx]
tag = tag[idx:]
}
s := ",omitempty"
if idx = strings.Index(tag, s); idx >= 0 && (len(tag) == idx+len(s) || tag[idx+len(s)] == ',') {
omitEmpty = true
}
s = ",keyasint"
if idx = strings.Index(tag, s); idx >= 0 && (len(tag) == idx+len(s) || tag[idx+len(s)] == ',') {
keyAsInt = true
}
return
}