peridot/vendor/github.com/aws/aws-sdk-go/service/dynamodb/dynamodbattribute/field.go

291 lines
7.5 KiB
Go
Raw Normal View History

2022-07-07 20:11:50 +00:00
package dynamodbattribute
import (
"reflect"
"sort"
"strings"
)
type field struct {
tag
Name string
NameFromTag bool
Index []int
Type reflect.Type
}
type cachedFields struct {
fields []field
fieldsByName map[string]int
}
func (f *cachedFields) All() []field {
return f.fields
}
func (f *cachedFields) FieldByName(name string) (field, bool) {
if i, ok := f.fieldsByName[name]; ok {
return f.fields[i], ok
}
for _, f := range f.fields {
if strings.EqualFold(f.Name, name) {
return f, true
}
}
return field{}, false
}
func buildField(pIdx []int, i int, sf reflect.StructField, fieldTag tag) field {
f := field{
Name: sf.Name,
Type: sf.Type,
tag: fieldTag,
}
if len(fieldTag.Name) != 0 {
f.NameFromTag = true
f.Name = fieldTag.Name
}
f.Index = make([]int, len(pIdx)+1)
copy(f.Index, pIdx)
f.Index[len(pIdx)] = i
return f
}
// unionStructFields returns a list of fields for the given type. Type info is cached
// to avoid repeated calls into the reflect package
func unionStructFields(t reflect.Type, opts MarshalOptions) *cachedFields {
if cached, ok := fieldCache.Load(t); ok {
return cached
}
f := enumFields(t, opts)
sort.Sort(fieldsByName(f))
f = visibleFields(f)
fs := &cachedFields{
fields: f,
fieldsByName: make(map[string]int, len(f)),
}
for i, f := range fs.fields {
fs.fieldsByName[f.Name] = i
}
cached, _ := fieldCache.LoadOrStore(t, fs)
return cached
}
// enumFields will recursively iterate through a structure and its nested
// anonymous fields.
//
// Based on the enoding/json struct field enumeration of the Go Stdlib
// https://golang.org/src/encoding/json/encode.go typeField func.
func enumFields(t reflect.Type, opts MarshalOptions) []field {
// Fields to explore
current := []field{}
next := []field{{Type: t}}
// count of queued names
count := map[reflect.Type]int{}
nextCount := map[reflect.Type]int{}
visited := map[reflect.Type]struct{}{}
fields := []field{}
for len(next) > 0 {
current, next = next, current[:0]
count, nextCount = nextCount, map[reflect.Type]int{}
for _, f := range current {
if _, ok := visited[f.Type]; ok {
continue
}
visited[f.Type] = struct{}{}
for i := 0; i < f.Type.NumField(); i++ {
sf := f.Type.Field(i)
if sf.PkgPath != "" && !sf.Anonymous {
// Ignore unexported and non-anonymous fields
// unexported but anonymous field may still be used if
// the type has exported nested fields
continue
}
fieldTag := tag{}
fieldTag.parseAVTag(sf.Tag)
// Because MarshalOptions.TagKey must be explicitly set, use it
// over JSON, which is enabled by default.
if opts.TagKey != "" && fieldTag == (tag{}) {
fieldTag.parseStructTag(opts.TagKey, sf.Tag)
} else if opts.SupportJSONTags && fieldTag == (tag{}) {
fieldTag.parseStructTag("json", sf.Tag)
}
if fieldTag.Ignore {
continue
}
ft := sf.Type
if ft.Name() == "" && ft.Kind() == reflect.Ptr {
ft = ft.Elem()
}
structField := buildField(f.Index, i, sf, fieldTag)
structField.Type = ft
if !sf.Anonymous || ft.Kind() != reflect.Struct {
fields = append(fields, structField)
if count[f.Type] > 1 {
// If there were multiple instances, add a second,
// so that the annihilation code will see a duplicate.
// It only cares about the distinction between 1 or 2,
// so don't bother generating any more copies.
fields = append(fields, structField)
}
continue
}
// Record new anon struct to explore next round
nextCount[ft]++
if nextCount[ft] == 1 {
next = append(next, structField)
}
}
}
}
return fields
}
// visibleFields will return a slice of fields which are visible based on
// Go's standard visiblity rules with the exception of ties being broken
// by depth and struct tag naming.
//
// Based on the enoding/json field filtering of the Go Stdlib
// https://golang.org/src/encoding/json/encode.go typeField func.
func visibleFields(fields []field) []field {
// Delete all fields that are hidden by the Go rules for embedded fields,
// except that fields with JSON tags are promoted.
// The fields are sorted in primary order of name, secondary order
// of field index length. Loop over names; for each name, delete
// hidden fields by choosing the one dominant field that survives.
out := fields[:0]
for advance, i := 0, 0; i < len(fields); i += advance {
// One iteration per name.
// Find the sequence of fields with the name of this first field.
fi := fields[i]
name := fi.Name
for advance = 1; i+advance < len(fields); advance++ {
fj := fields[i+advance]
if fj.Name != name {
break
}
}
if advance == 1 { // Only one field with this name
out = append(out, fi)
continue
}
dominant, ok := dominantField(fields[i : i+advance])
if ok {
out = append(out, dominant)
}
}
fields = out
sort.Sort(fieldsByIndex(fields))
return fields
}
// dominantField looks through the fields, all of which are known to
// have the same name, to find the single field that dominates the
// others using Go's embedding rules, modified by the presence of
// JSON tags. If there are multiple top-level fields, the boolean
// will be false: This condition is an error in Go and we skip all
// the fields.
//
// Based on the enoding/json field filtering of the Go Stdlib
// https://golang.org/src/encoding/json/encode.go dominantField func.
func dominantField(fields []field) (field, bool) {
// The fields are sorted in increasing index-length order. The winner
// must therefore be one with the shortest index length. Drop all
// longer entries, which is easy: just truncate the slice.
length := len(fields[0].Index)
tagged := -1 // Index of first tagged field.
for i, f := range fields {
if len(f.Index) > length {
fields = fields[:i]
break
}
if f.NameFromTag {
if tagged >= 0 {
// Multiple tagged fields at the same level: conflict.
// Return no field.
return field{}, false
}
tagged = i
}
}
if tagged >= 0 {
return fields[tagged], true
}
// All remaining fields have the same length. If there's more than one,
// we have a conflict (two fields named "X" at the same level) and we
// return no field.
if len(fields) > 1 {
return field{}, false
}
return fields[0], true
}
// fieldsByName sorts field by name, breaking ties with depth,
// then breaking ties with "name came from json tag", then
// breaking ties with index sequence.
//
// Based on the enoding/json field filtering of the Go Stdlib
// https://golang.org/src/encoding/json/encode.go fieldsByName type.
type fieldsByName []field
func (x fieldsByName) Len() int { return len(x) }
func (x fieldsByName) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
func (x fieldsByName) Less(i, j int) bool {
if x[i].Name != x[j].Name {
return x[i].Name < x[j].Name
}
if len(x[i].Index) != len(x[j].Index) {
return len(x[i].Index) < len(x[j].Index)
}
if x[i].NameFromTag != x[j].NameFromTag {
return x[i].NameFromTag
}
return fieldsByIndex(x).Less(i, j)
}
// fieldsByIndex sorts field by index sequence.
//
// Based on the enoding/json field filtering of the Go Stdlib
// https://golang.org/src/encoding/json/encode.go fieldsByIndex type.
type fieldsByIndex []field
func (x fieldsByIndex) Len() int { return len(x) }
func (x fieldsByIndex) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
func (x fieldsByIndex) Less(i, j int) bool {
for k, xik := range x[i].Index {
if k >= len(x[j].Index) {
return false
}
if xik != x[j].Index[k] {
return xik < x[j].Index[k]
}
}
return len(x[i].Index) < len(x[j].Index)
}