golang type 代码
文件路径：/src/encoding/gob/type.go
/ Copyright 2009 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 gob
import (
"encoding"
"errors"
"fmt"
"os"
"reflect"
"sync"
"sync/atomic"
"unicode"
"unicode/utf8"
)
/ userTypeInfo stores the information associated with a type the user has handed
/ to the package. It's computed once and stored in a map keyed by reflection
/ type.
type userTypeInfo struct {
user reflect.Type / the type the user handed us
base reflect.Type / the base type after all indirections
indir int / number of indirections to reach the base type
externalEnc int / xGob, xBinary, or xText
externalDec int / xGob, xBinary or xText
encIndir int8 / number of indirections to reach the receiver type; may be negative
decIndir int8 / number of indirections to reach the receiver type; may be negative
}
/ externalEncoding bits
const (
xGob = 1 + iota / GobEncoder or GobDecoder
xBinary / encoding.BinaryMarshaler or encoding.BinaryUnmarshaler
xText / encoding.TextMarshaler or encoding.TextUnmarshaler
)
var userTypeCache sync.Map / map[reflect.Type]*userTypeInfo
/ validType returns, and saves, the information associated with user-provided type rt.
/ If the user type is not valid, err will be non-nil. To be used when the error handler
/ is not set up.
func validUserType(rt reflect.Type) (*userTypeInfo, error) {
if ui, ok := userTypeCache.Load(rt); ok {
return ui.(*userTypeInfo), nil
}
/ Construct a new userTypeInfo and atomically add it to the userTypeCache.
/ If we lose the race, we'll waste a little CPU and create a little garbage
/ but return the existing value anyway.
ut := new(userTypeInfo)
ut.base = rt
ut.user = rt
/ A type that is just a cycle of pointers (such as type T *T) cannot
/ be represented in gobs, which need some concrete data. We use a
/ cycle detection algorithm from Knuth, Vol 2, Section 3.1, Ex 6,
/ pp 539-540. As we step through indirections, run another type at
/ half speed. If they meet up, there's a cycle.
slowpoke := ut.base / walks half as fast as ut.base
for {
pt := ut.base
if pt.Kind() != reflect.Pointer {
break
}
ut.base = pt.Elem()
if ut.base == slowpoke { / ut.base lapped slowpoke
/ recursive pointer type.
return nil, errors.New("can't represent recursive pointer type " + ut.base.String())
}
if ut.indir%2 == 0 {
slowpoke = slowpoke.Elem()
}
ut.indir++
}
if ok, indir := implementsInterface(ut.user, gobEncoderInterfaceType); ok {
ut.externalEnc, ut.encIndir = xGob, indir
} else if ok, indir := implementsInterface(ut.user, binaryMarshalerInterfaceType); ok {
ut.externalEnc, ut.encIndir = xBinary, indir
}
/ NOTE(rsc): Would like to allow MarshalText here, but results in incompatibility
/ with older encodings for net.IP. See golang.org/issue/6760.
/ } else if ok, indir := implementsInterface(ut.user, textMarshalerInterfaceType); ok {
/ ut.externalEnc, ut.encIndir = xText, indir
/ }
if ok, indir := implementsInterface(ut.user, gobDecoderInterfaceType); ok {
ut.externalDec, ut.decIndir = xGob, indir
} else if ok, indir := implementsInterface(ut.user, binaryUnmarshalerInterfaceType); ok {
ut.externalDec, ut.decIndir = xBinary, indir
}
/ See note above.
/ } else if ok, indir := implementsInterface(ut.user, textUnmarshalerInterfaceType); ok {
/ ut.externalDec, ut.decIndir = xText, indir
/ }
ui, _ := userTypeCache.LoadOrStore(rt, ut)
return ui.(*userTypeInfo), nil
}
var (
gobEncoderInterfaceType = reflect.TypeOf((*GobEncoder)(nil)).Elem()
gobDecoderInterfaceType = reflect.TypeOf((*GobDecoder)(nil)).Elem()
binaryMarshalerInterfaceType = reflect.TypeOf((*encoding.BinaryMarshaler)(nil)).Elem()
binaryUnmarshalerInterfaceType = reflect.TypeOf((*encoding.BinaryUnmarshaler)(nil)).Elem()
textMarshalerInterfaceType = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
textUnmarshalerInterfaceType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
)
/ implementsInterface reports whether the type implements the
/ gobEncoder/gobDecoder interface.
/ It also returns the number of indirections required to get to the
/ implementation.
func implementsInterface(typ, gobEncDecType reflect.Type) (success bool, indir int8) {
if typ == nil {
return
}
rt := typ
/ The type might be a pointer and we need to keep
/ dereferencing to the base type until we find an implementation.
for {
if rt.Implements(gobEncDecType) {
return true, indir
}
if p := rt; p.Kind() == reflect.Pointer {
indir++
if indir > 100 { / insane number of indirections
return false, 0
}
rt = p.Elem()
continue
}
break
}
/ No luck yet, but if this is a base type (non-pointer), the pointer might satisfy.
if typ.Kind() != reflect.Pointer {
/ Not a pointer, but does the pointer work?
if reflect.PointerTo(typ).Implements(gobEncDecType) {
return true, -1
}
}
return false, 0
}
/ userType returns, and saves, the information associated with user-provided type rt.
/ If the user type is not valid, it calls error.
func userType(rt reflect.Type) *userTypeInfo {
ut, err := validUserType(rt)
if err != nil {
error_(err)
}
return ut
}
/ A typeId represents a gob Type as an integer that can be passed on the wire.
/ Internally, typeIds are used as keys to a map to recover the underlying type info.
type typeId int32
var nextId typeId / incremented for each new type we build
var typeLock sync.Mutex / set while building a type
const firstUserId = 64 / lowest id number granted to user
type gobType interface {
id() typeId
setId(id typeId)
name() string
string() string / not public; only for debugging
safeString(seen map[typeId]bool) string
}
var types = make(map[reflect.Type]gobType)
var idToType = make(map[typeId]gobType)
var builtinIdToType map[typeId]gobType / set in init() after builtins are established
func setTypeId(typ gobType) {
/ When building recursive types, someone may get there before us.
if typ.id() != 0 {
return
}
nextId++
typ.setId(nextId)
idToType[nextId] = typ
}
func (t typeId) gobType() gobType {
if t == 0 {
return nil
}
return idToType[t]
}
/ string returns the string representation of the type associated with the typeId.
func (t typeId) string() string {
if t.gobType() == nil {
return "<nil>"
}
return t.gobType().string()
}
/ Name returns the name of the type associated with the typeId.
func (t typeId) name() string {
if t.gobType() == nil {
return "<nil>"
}
return t.gobType().name()
}
/ CommonType holds elements of all types.
/ It is a historical artifact, kept for binary compatibility and exported
/ only for the benefit of the package's encoding of type descriptors. It is
/ not intended for direct use by clients.
type CommonType struct {
Name string
Id typeId
}
func (t *CommonType) id() typeId { return t.Id }
func (t *CommonType) setId(id typeId) { t.Id = id }
func (t *CommonType) string() string { return t.Name }
func (t *CommonType) safeString(seen map[typeId]bool) string {
return t.Name
}
func (t *CommonType) name() string { return t.Name }
/ Create and check predefined types
/ The string for tBytes is "bytes" not "[]byte" to signify its specialness.
var (
/ Primordial types, needed during initialization.
/ Always passed as pointers so the interface{} type
/ goes through without losing its interfaceness.
tBool = bootstrapType("bool", (*bool)(nil), 1)
tInt = bootstrapType("int", (*int)(nil), 2)
tUint = bootstrapType("uint", (*uint)(nil), 3)
tFloat = bootstrapType("float", (*float64)(nil), 4)
tBytes = bootstrapType("bytes", (*[]byte)(nil), 5)
tString = bootstrapType("string", (*string)(nil), 6)
tComplex = bootstrapType("complex", (*complex128)(nil), 7)
tInterface = bootstrapType("interface", (*any)(nil), 8)
/ Reserve some Ids for compatible expansion
tReserved7 = bootstrapType("_reserved1", (*struct{ r7 int })(nil), 9)
tReserved6 = bootstrapType("_reserved1", (*struct{ r6 int })(nil), 10)
tReserved5 = bootstrapType("_reserved1", (*struct{ r5 int })(nil), 11)
tReserved4 = bootstrapType("_reserved1", (*struct{ r4 int })(nil), 12)
tReserved3 = bootstrapType("_reserved1", (*struct{ r3 int })(nil), 13)
tReserved2 = bootstrapType("_reserved1", (*struct{ r2 int })(nil), 14)
tReserved1 = bootstrapType("_reserved1", (*struct{ r1 int })(nil), 15)
)
/ Predefined because it's needed by the Decoder
var tWireType = mustGetTypeInfo(reflect.TypeOf(wireType{})).id
var wireTypeUserInfo *userTypeInfo / userTypeInfo of (*wireType)
func init() {
/ Some magic numbers to make sure there are no surprises.
checkId(16, tWireType)
checkId(17, mustGetTypeInfo(reflect.TypeOf(arrayType{})).id)
checkId(18, mustGetTypeInfo(reflect.TypeOf(CommonType{})).id)
checkId(19, mustGetTypeInfo(reflect.TypeOf(sliceType{})).id)
checkId(20, mustGetTypeInfo(reflect.TypeOf(structType{})).id)
checkId(21, mustGetTypeInfo(reflect.TypeOf(fieldType{})).id)
checkId(23, mustGetTypeInfo(reflect.TypeOf(mapType{})).id)
builtinIdToType = make(map[typeId]gobType)
for k, v := range idToType {
builtinIdToType[k] = v
}
/ Move the id space upwards to allow for growth in the predefined world
/ without breaking existing files.
if nextId > firstUserId {
panic(fmt.Sprintln("nextId too large:", nextId))
}
nextId = firstUserId
registerBasics()
wireTypeUserInfo = userType(reflect.TypeOf((*wireType)(nil)))
}
/ Array type
type arrayType struct {
CommonType
Elem typeId
Len int
}
func newArrayType(name string) *arrayType {
a := &arrayType{CommonType{Name: name}, 0, 0}
return a
}
func (a *arrayType) init(elem gobType, len int) {
/ Set our type id before evaluating the element's, in case it's our own.
setTypeId(a)
a.Elem = elem.id()
a.Len = len
}
func (a *arrayType) safeString(seen map[typeId]bool) string {
if seen[a.Id] {
return a.Name
}
seen[a.Id] = true
return fmt.Sprintf("[%d]%s", a.Len, a.Elem.gobType().safeString(seen))
}
func (a *arrayType) string() string { return a.safeString(make(map[typeId]bool)) }
/ GobEncoder type (something that implements the GobEncoder interface)
type gobEncoderType struct {
CommonType
}
func newGobEncoderType(name string) *gobEncoderType {
g := &gobEncoderType{CommonType{Name: name}}
setTypeId(g)
return g
}
func (g *gobEncoderType) safeString(seen map[typeId]bool) string {
return g.Name
}
func (g *gobEncoderType) string() string { return g.Name }
/ Map type
type mapType struct {
CommonType
Key typeId
Elem typeId
}
func newMapType(name string) *mapType {
m := &mapType{CommonType{Name: name}, 0, 0}
return m
}
func (m *mapType) init(key, elem gobType) {
/ Set our type id before evaluating the element's, in case it's our own.
setTypeId(m)
m.Key = key.id()
m.Elem = elem.id()
}
func (m *mapType) safeString(seen map[typeId]bool) string {
if seen[m.Id] {
return m.Name
}
seen[m.Id] = true
key := m.Key.gobType().safeString(seen)
elem := m.Elem.gobType().safeString(seen)
return fmt.Sprintf("map[%s]%s", key, elem)
}
func (m *mapType) string() string { return m.safeString(make(map[typeId]bool)) }
/ Slice type
type sliceType struct {
CommonType
Elem typeId
}
func newSliceType(name string) *sliceType {
s := &sliceType{CommonType{Name: name}, 0}
return s
}
func (s *sliceType) init(elem gobType) {
/ Set our type id before evaluating the element's, in case it's our own.
setTypeId(s)
/ See the comments about ids in newTypeObject. Only slices and
/ structs have mutual recursion.
if elem.id() == 0 {
setTypeId(elem)
}
s.Elem = elem.id()
}
func (s *sliceType) safeString(seen map[typeId]bool) string {
if seen[s.Id] {
return s.Name
}
seen[s.Id] = true
return fmt.Sprintf("[]%s", s.Elem.gobType().safeString(seen))
}
func (s *sliceType) string() string { return s.safeString(make(map[typeId]bool)) }
/ Struct type
type fieldType struct {
Name string
Id typeId
}
type structType struct {
CommonType
Field []*fieldType
}
func (s *structType) safeString(seen map[typeId]bool) string {
if s == nil {
return "<nil>"
}
if _, ok := seen[s.Id]; ok {
return s.Name
}
seen[s.Id] = true
str := s.Name + " = struct { "
for _, f := range s.Field {
str += fmt.Sprintf("%s %s; ", f.Name, f.Id.gobType().safeString(seen))
}
str += "}"
return str
}
func (s *structType) string() string { return s.safeString(make(map[typeId]bool)) }
func newStructType(name string) *structType {
s := &structType{CommonType{Name: name}, nil}
/ For historical reasons we set the id here rather than init.
/ See the comment in newTypeObject for details.
setTypeId(s)
return s
}
/ newTypeObject allocates a gobType for the reflection type rt.
/ Unless ut represents a GobEncoder, rt should be the base type
/ of ut.
/ This is only called from the encoding side. The decoding side
/ works through typeIds and userTypeInfos alone.
func newTypeObject(name string, ut *userTypeInfo, rt reflect.Type) (gobType, error) {
/ Does this type implement GobEncoder?
if ut.externalEnc != 0 {
return newGobEncoderType(name), nil
}
var err error
var type0, type1 gobType
defer func() {
if err != nil {
delete(types, rt)
}
}()
/ Install the top-level type before the subtypes (e.g. struct before
/ fields) so recursive types can be constructed safely.
switch t := rt; t.Kind() {
/ All basic types are easy: they are predefined.
case reflect.Bool:
return tBool.gobType(), nil
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return tInt.gobType(), nil
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return tUint.gobType(), nil
case reflect.Float32, reflect.Float64:
return tFloat.gobType(), nil
case reflect.Complex64, reflect.Complex128:
return tComplex.gobType(), nil
case reflect.String:
return tString.gobType(), nil
case reflect.Interface:
return tInterface.gobType(), nil
case reflect.Array:
at := newArrayType(name)
types[rt] = at
type0, err = getBaseType("", t.Elem())
if err != nil {
return nil, err
}
/ Historical aside:
/ For arrays, maps, and slices, we set the type id after the elements
/ are constructed. This is to retain the order of type id allocation after
/ a fix made to handle recursive types, which changed the order in
/ which types are built. Delaying the setting in this way preserves
/ type ids while allowing recursive types to be described. Structs,
/ done below, were already handling recursion correctly so they
/ assign the top-level id before those of the field.
at.init(type0, t.Len())
return at, nil
case reflect.Map:
mt := newMapType(name)
types[rt] = mt
type0, err = getBaseType("", t.Key())
if err != nil {
return nil, err
}
type1, err = getBaseType("", t.Elem())
if err != nil {
return nil, err
}
mt.init(type0, type1)
return mt, nil
case reflect.Slice:
/ []byte == []uint8 is a special case
if t.Elem().Kind() == reflect.Uint8 {
return tBytes.gobType(), nil
}
st := newSliceType(name)
types[rt] = st
type0, err = getBaseType(t.Elem().Name(), t.Elem())
if err != nil {
return nil, err
}
st.init(type0)
return st, nil
case reflect.Struct:
st := newStructType(name)
types[rt] = st
idToType[st.id()] = st
for i := 0; i < t.NumField(); i++ {
f := t.Field(i)
if !isSent(&f) {
continue
}
typ := userType(f.Type).base
tname := typ.Name()
if tname == "" {
t := userType(f.Type).base
tname = t.String()
}
gt, err := getBaseType(tname, f.Type)
if err != nil {
return nil, err
}
/ Some mutually recursive types can cause us to be here while
/ still defining the element. Fix the element type id here.
/ We could do this more neatly by setting the id at the start of
/ building every type, but that would break binary compatibility.
if gt.id() == 0 {
setTypeId(gt)
}
st.Field = append(st.Field, &fieldType{f.Name, gt.id()})
}
return st, nil
default:
return nil, errors.New("gob NewTypeObject can't handle type: " + rt.String())
}
}
/ isExported reports whether this is an exported - upper case - name.
func isExported(name string) bool {
rune, _ := utf8.DecodeRuneInString(name)
return unicode.IsUpper(rune)
}
/ isSent reports whether this struct field is to be transmitted.
/ It will be transmitted only if it is exported and not a chan or func field
/ or pointer to chan or func.
func isSent(field *reflect.StructField) bool {
if !isExported(field.Name) {
return false
}
/ If the field is a chan or func or pointer thereto, don't send it.
/ That is, treat it like an unexported field.
typ := field.Type
for typ.Kind() == reflect.Pointer {
typ = typ.Elem()
}
if typ.Kind() == reflect.Chan || typ.Kind() == reflect.Func {
return false
}
return true
}
/ getBaseType returns the Gob type describing the given reflect.Type's base type.
/ typeLock must be held.
func getBaseType(name string, rt reflect.Type) (gobType, error) {
ut := userType(rt)
return getType(name, ut, ut.base)
}
/ getType returns the Gob type describing the given reflect.Type.
/ Should be called only when handling GobEncoders/Decoders,
/ which may be pointers. All other types are handled through the
/ base type, never a pointer.
/ typeLock must be held.
func getType(name string, ut *userTypeInfo, rt reflect.Type) (gobType, error) {
typ, present := types[rt]
if present {
return typ, nil
}
typ, err := newTypeObject(name, ut, rt)
if err == nil {
types[rt] = typ
}
return typ, err
}
func checkId(want, got typeId) {
if want != got {
fmt.Fprintf(os.Stderr, "checkId: %d should be %d\n", int(got), int(want))
panic("bootstrap type wrong id: " + got.name() + " " + got.string() + " not " + want.string())
}
}
/ used for building the basic types; called only from init(). the incoming
/ interface always refers to a pointer.
func bootstrapType(name string, e any, expect typeId) typeId {
rt := reflect.TypeOf(e).Elem()
_, present := types[rt]
if present {
panic("bootstrap type already present: " + name + ", " + rt.String())
}
typ := &CommonType{Name: name}
types[rt] = typ
setTypeId(typ)
checkId(expect, nextId)
userType(rt) / might as well cache it now
return nextId
}
/ Representation of the information we send and receive about this type.
/ Each value we send is preceded by its type definition: an encoded int.
/ However, the very first time we send the value, we first send the pair
/ (-id, wireType).
/ For bootstrapping purposes, we assume that the recipient knows how
/ to decode a wireType; it is exactly the wireType struct here, interpreted
/ using the gob rules for sending a structure, except that we assume the
/ ids for wireType and structType etc. are known. The relevant pieces
/ are built in encode.go's init() function.
/ To maintain binary compatibility, if you extend this type, always put
/ the new fields last.
type wireType struct {
ArrayT *arrayType
SliceT *sliceType
StructT *structType
MapT *mapType
GobEncoderT *gobEncoderType
BinaryMarshalerT *gobEncoderType
TextMarshalerT *gobEncoderType
}
func (w *wireType) string() string {
const unknown = "unknown type"
if w == nil {
return unknown
}
switch {
case w.ArrayT != nil:
return w.ArrayT.Name
case w.SliceT != nil:
return w.SliceT.Name
case w.StructT != nil:
return w.StructT.Name
case w.MapT != nil:
return w.MapT.Name
case w.GobEncoderT != nil:
return w.GobEncoderT.Name
case w.BinaryMarshalerT != nil:
return w.BinaryMarshalerT.Name
case w.TextMarshalerT != nil:
return w.TextMarshalerT.Name
}
return unknown
}
type typeInfo struct {
id typeId
encInit sync.Mutex / protects creation of encoder
encoder atomic.Value / *encEngine
wire *wireType
}
/ typeInfoMap is an atomic pointer to map[reflect.Type]*typeInfo.
/ It's updated copy-on-write. Readers just do an atomic load
/ to get the current version of the map. Writers make a full copy of
/ the map and atomically update the pointer to point to the new map.
/ Under heavy read contention, this is significantly faster than a map
/ protected by a mutex.
var typeInfoMap atomic.Value
func lookupTypeInfo(rt reflect.Type) *typeInfo {
m, _ := typeInfoMap.Load().(map[reflect.Type]*typeInfo)
return m[rt]
}
func getTypeInfo(ut *userTypeInfo) (*typeInfo, error) {
rt := ut.base
if ut.externalEnc != 0 {
/ We want the user type, not the base type.
rt = ut.user
}
if info := lookupTypeInfo(rt); info != nil {
return info, nil
}
return buildTypeInfo(ut, rt)
}
/ buildTypeInfo constructs the type information for the type
/ and stores it in the type info map.
func buildTypeInfo(ut *userTypeInfo, rt reflect.Type) (*typeInfo, error) {
typeLock.Lock()
defer typeLock.Unlock()
if info := lookupTypeInfo(rt); info != nil {
return info, nil
}
gt, err := getBaseType(rt.Name(), rt)
if err != nil {
return nil, err
}
info := &typeInfo{id: gt.id()}
if ut.externalEnc != 0 {
userType, err := getType(rt.Name(), ut, rt)
if err != nil {
return nil, err
}
gt := userType.id().gobType().(*gobEncoderType)
switch ut.externalEnc {
case xGob:
info.wire = &wireType{GobEncoderT: gt}
case xBinary:
info.wire = &wireType{BinaryMarshalerT: gt}
case xText:
info.wire = &wireType{TextMarshalerT: gt}
}
rt = ut.user
} else {
t := info.id.gobType()
switch typ := rt; typ.Kind() {
case reflect.Array:
info.wire = &wireType{ArrayT: t.(*arrayType)}
case reflect.Map:
info.wire = &wireType{MapT: t.(*mapType)}
case reflect.Slice:
/ []byte == []uint8 is a special case handled separately
if typ.Elem().Kind() != reflect.Uint8 {
info.wire = &wireType{SliceT: t.(*sliceType)}
}
case reflect.Struct:
info.wire = &wireType{StructT: t.(*structType)}
}
}
/ Create new map with old contents plus new entry.
newm := make(map[reflect.Type]*typeInfo)
m, _ := typeInfoMap.Load().(map[reflect.Type]*typeInfo)
for k, v := range m {
newm[k] = v
}
newm[rt] = info
typeInfoMap.Store(newm)
return info, nil
}
/ Called only when a panic is acceptable and unexpected.
func mustGetTypeInfo(rt reflect.Type) *typeInfo {
t, err := getTypeInfo(userType(rt))
if err != nil {
panic("getTypeInfo: " + err.Error())
}
return t
}
/ GobEncoder is the interface describing data that provides its own
/ representation for encoding values for transmission to a GobDecoder.
/ A type that implements GobEncoder and GobDecoder has complete
/ control over the representation of its data and may therefore
/ contain things such as private fields, channels, and functions,
/ which are not usually transmissible in gob streams.
/
/ Note: Since gobs can be stored permanently, it is good design
/ to guarantee the encoding used by a GobEncoder is stable as the
/ software evolves. For instance, it might make sense for GobEncode
/ to include a version number in the encoding.
type GobEncoder interface {
/ GobEncode returns a byte slice representing the encoding of the
/ receiver for transmission to a GobDecoder, usually of the same
/ concrete type.
GobEncode() ([]byte, error)
}
/ GobDecoder is the interface describing data that provides its own
/ routine for decoding transmitted values sent by a GobEncoder.
type GobDecoder interface {
/ GobDecode overwrites the receiver, which must be a pointer,
/ with the value represented by the byte slice, which was written
/ by GobEncode, usually for the same concrete type.
GobDecode([]byte) error
}
var (
nameToConcreteType sync.Map / map[string]reflect.Type
concreteTypeToName sync.Map / map[reflect.Type]string
)
/ RegisterName is like Register but uses the provided name rather than the
/ type's default.
func RegisterName(name string, value any) {
if name == "" {
/ reserved for nil
panic("attempt to register empty name")
}
ut := userType(reflect.TypeOf(value))
/ Check for incompatible duplicates. The name must refer to the
/ same user type, and vice versa.
/ Store the name and type provided by the user....
if t, dup := nameToConcreteType.LoadOrStore(name, reflect.TypeOf(value)); dup && t != ut.user {
panic(fmt.Sprintf("gob: registering duplicate types for %q: %s != %s", name, t, ut.user))
}
/ but the flattened type in the type table, since that's what decode needs.
if n, dup := concreteTypeToName.LoadOrStore(ut.base, name); dup && n != name {
nameToConcreteType.Delete(name)
panic(fmt.Sprintf("gob: registering duplicate names for %s: %q != %q", ut.user, n, name))
}
}
/ Register records a type, identified by a value for that type, under its
/ internal type name. That name will identify the concrete type of a value
/ sent or received as an interface variable. Only types that will be
/ transferred as implementations of interface values need to be registered.
/ Expecting to be used only during initialization, it panics if the mapping
/ between types and names is not a bijection.
func Register(value any) {
/ Default to printed representation for unnamed types
rt := reflect.TypeOf(value)
name := rt.String()
/ But for named types (or pointers to them), qualify with import path (but see inner comment).
/ Dereference one pointer looking for a named type.
star := ""
if rt.Name() == "" {
if pt := rt; pt.Kind() == reflect.Pointer {
star = "*"
/ NOTE: The following line should be rt = pt.Elem() to implement
/ what the comment above claims, but fixing it would break compatibility
/ with existing gobs.
/
/ Given package p imported as "full/p" with these definitions:
/ package p
/ type T1 struct { ... }
/ this table shows the intended and actual strings used by gob to
/ name the types:
/
/ Type Correct string Actual string
/
/ T1 full/p.T1 full/p.T1
/ *T1 *full/p.T1 *p.T1
/
/ The missing full path cannot be fixed without breaking existing gob decoders.
rt = pt
}
}
if rt.Name() != "" {
if rt.PkgPath() == "" {
name = star + rt.Name()
} else {
name = star + rt.PkgPath() + "." + rt.Name()
}
}
RegisterName(name, value)
}
func registerBasics() {
Register(int(0))
Register(int8(0))
Register(int16(0))
Register(int32(0))
Register(int64(0))
Register(uint(0))
Register(uint8(0))
Register(uint16(0))
Register(uint32(0))
Register(uint64(0))
Register(float32(0))
Register(float64(0))
Register(complex64(0i))
Register(complex128(0i))
Register(uintptr(0))
Register(false)
Register("")
Register([]byte(nil))
Register([]int(nil))
Register([]int8(nil))
Register([]int16(nil))
Register([]int32(nil))
Register([]int64(nil))
Register([]uint(nil))
Register([]uint8(nil))
Register([]uint16(nil))
Register([]uint32(nil))
Register([]uint64(nil))
Register([]float32(nil))
Register([]float64(nil))
Register([]complex64(nil))
Register([]complex128(nil))
Register([]uintptr(nil))
Register([]bool(nil))
Register([]string(nil))
}