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// Copyright 2021 The Go 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 reflect
// VisibleFields returns all the visible fields in t, which must be a
// struct type. A field is defined as visible if it's accessible
// directly with a FieldByName call. The returned fields include fields
// inside anonymous struct members and unexported fields. They follow
// the same order found in the struct, with anonymous fields followed
// immediately by their promoted fields.
//
// For each element e of the returned slice, the corresponding field
// can be retrieved from a value v of type t by calling v.FieldByIndex(e.Index).
func VisibleFields(t Type) []StructField {
if t == nil {
panic("reflect: VisibleFields(nil)")
}
if t.Kind() != Struct {
panic("reflect.VisibleFields of non-struct type")
}
w := &visibleFieldsWalker{
byName: make(map[string]int),
visiting: make(map[Type]bool),
fields: make([]StructField, 0, t.NumField()),
index: make([]int, 0, 2),
}
w.walk(t)
// Remove all the fields that have been hidden.
// Use an in-place removal that avoids copying in
// the common case that there are no hidden fields.
j := 0
for i := range w.fields {
f := &w.fields[i]
if f.Name == "" {
continue
}
if i != j {
// A field has been removed. We need to shuffle
// all the subsequent elements up.
w.fields[j] = *f
}
j++
}
return w.fields[:j]
}
type visibleFieldsWalker struct {
byName map[string]int
visiting map[Type]bool
fields []StructField
index []int
}
// walk walks all the fields in the struct type t, visiting
// fields in index preorder and appending them to w.fields
// (this maintains the required ordering).
// Fields that have been overridden have their
// Name field cleared.
func (w *visibleFieldsWalker) walk(t Type) {
if w.visiting[t] {
return
}
w.visiting[t] = true
for i := 0; i < t.NumField(); i++ {
f := t.Field(i)
w.index = append(w.index, i)
add := true
if oldIndex, ok := w.byName[f.Name]; ok {
old := &w.fields[oldIndex]
if len(w.index) == len(old.Index) {
// Fields with the same name at the same depth
// cancel one another out. Set the field name
// to empty to signify that has happened, and
// there's no need to add this field.
old.Name = ""
add = false
} else if len(w.index) < len(old.Index) {
// The old field loses because it's deeper than the new one.
old.Name = ""
} else {
// The old field wins because it's shallower than the new one.
add = false
}
}
if add {
// Copy the index so that it's not overwritten
// by the other appends.
f.Index = append([]int(nil), w.index...)
w.byName[f.Name] = len(w.fields)
w.fields = append(w.fields, f)
}
if f.Anonymous {
if f.Type.Kind() == Ptr {
f.Type = f.Type.Elem()
}
if f.Type.Kind() == Struct {
w.walk(f.Type)
}
}
w.index = w.index[:len(w.index)-1]
}
delete(w.visiting, t)
}
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