mirror of
https://github.com/autc04/Retro68.git
synced 2024-09-08 20:55:01 +00:00
894 lines
26 KiB
Go
894 lines
26 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package gob
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import (
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"encoding"
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"errors"
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"fmt"
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"os"
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"reflect"
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"sync"
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"unicode"
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"unicode/utf8"
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)
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// userTypeInfo stores the information associated with a type the user has handed
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// to the package. It's computed once and stored in a map keyed by reflection
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// type.
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type userTypeInfo struct {
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user reflect.Type // the type the user handed us
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base reflect.Type // the base type after all indirections
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indir int // number of indirections to reach the base type
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externalEnc int // xGob, xBinary, or xText
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externalDec int // xGob, xBinary or xText
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encIndir int8 // number of indirections to reach the receiver type; may be negative
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decIndir int8 // number of indirections to reach the receiver type; may be negative
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}
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// externalEncoding bits
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const (
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xGob = 1 + iota // GobEncoder or GobDecoder
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xBinary // encoding.BinaryMarshaler or encoding.BinaryUnmarshaler
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xText // encoding.TextMarshaler or encoding.TextUnmarshaler
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)
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var (
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// Protected by an RWMutex because we read it a lot and write
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// it only when we see a new type, typically when compiling.
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userTypeLock sync.RWMutex
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userTypeCache = make(map[reflect.Type]*userTypeInfo)
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)
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// validType returns, and saves, the information associated with user-provided type rt.
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// If the user type is not valid, err will be non-nil. To be used when the error handler
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// is not set up.
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func validUserType(rt reflect.Type) (ut *userTypeInfo, err error) {
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userTypeLock.RLock()
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ut = userTypeCache[rt]
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userTypeLock.RUnlock()
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if ut != nil {
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return
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}
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// Now set the value under the write lock.
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userTypeLock.Lock()
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defer userTypeLock.Unlock()
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if ut = userTypeCache[rt]; ut != nil {
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// Lost the race; not a problem.
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return
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}
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ut = new(userTypeInfo)
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ut.base = rt
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ut.user = rt
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// A type that is just a cycle of pointers (such as type T *T) cannot
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// be represented in gobs, which need some concrete data. We use a
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// cycle detection algorithm from Knuth, Vol 2, Section 3.1, Ex 6,
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// pp 539-540. As we step through indirections, run another type at
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// half speed. If they meet up, there's a cycle.
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slowpoke := ut.base // walks half as fast as ut.base
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for {
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pt := ut.base
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if pt.Kind() != reflect.Ptr {
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break
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}
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ut.base = pt.Elem()
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if ut.base == slowpoke { // ut.base lapped slowpoke
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// recursive pointer type.
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return nil, errors.New("can't represent recursive pointer type " + ut.base.String())
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}
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if ut.indir%2 == 0 {
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slowpoke = slowpoke.Elem()
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}
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ut.indir++
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}
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if ok, indir := implementsInterface(ut.user, gobEncoderInterfaceType); ok {
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ut.externalEnc, ut.encIndir = xGob, indir
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} else if ok, indir := implementsInterface(ut.user, binaryMarshalerInterfaceType); ok {
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ut.externalEnc, ut.encIndir = xBinary, indir
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}
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// NOTE(rsc): Would like to allow MarshalText here, but results in incompatibility
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// with older encodings for net.IP. See golang.org/issue/6760.
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// } else if ok, indir := implementsInterface(ut.user, textMarshalerInterfaceType); ok {
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// ut.externalEnc, ut.encIndir = xText, indir
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// }
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if ok, indir := implementsInterface(ut.user, gobDecoderInterfaceType); ok {
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ut.externalDec, ut.decIndir = xGob, indir
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} else if ok, indir := implementsInterface(ut.user, binaryUnmarshalerInterfaceType); ok {
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ut.externalDec, ut.decIndir = xBinary, indir
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}
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// See note above.
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// } else if ok, indir := implementsInterface(ut.user, textUnmarshalerInterfaceType); ok {
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// ut.externalDec, ut.decIndir = xText, indir
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// }
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userTypeCache[rt] = ut
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return
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}
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var (
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gobEncoderInterfaceType = reflect.TypeOf((*GobEncoder)(nil)).Elem()
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gobDecoderInterfaceType = reflect.TypeOf((*GobDecoder)(nil)).Elem()
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binaryMarshalerInterfaceType = reflect.TypeOf((*encoding.BinaryMarshaler)(nil)).Elem()
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binaryUnmarshalerInterfaceType = reflect.TypeOf((*encoding.BinaryUnmarshaler)(nil)).Elem()
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textMarshalerInterfaceType = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
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textUnmarshalerInterfaceType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
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)
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// implementsInterface reports whether the type implements the
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// gobEncoder/gobDecoder interface.
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// It also returns the number of indirections required to get to the
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// implementation.
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func implementsInterface(typ, gobEncDecType reflect.Type) (success bool, indir int8) {
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if typ == nil {
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return
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}
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rt := typ
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// The type might be a pointer and we need to keep
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// dereferencing to the base type until we find an implementation.
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for {
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if rt.Implements(gobEncDecType) {
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return true, indir
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}
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if p := rt; p.Kind() == reflect.Ptr {
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indir++
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if indir > 100 { // insane number of indirections
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return false, 0
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}
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rt = p.Elem()
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continue
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}
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break
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}
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// No luck yet, but if this is a base type (non-pointer), the pointer might satisfy.
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if typ.Kind() != reflect.Ptr {
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// Not a pointer, but does the pointer work?
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if reflect.PtrTo(typ).Implements(gobEncDecType) {
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return true, -1
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}
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}
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return false, 0
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}
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// userType returns, and saves, the information associated with user-provided type rt.
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// If the user type is not valid, it calls error.
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func userType(rt reflect.Type) *userTypeInfo {
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ut, err := validUserType(rt)
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if err != nil {
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error_(err)
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}
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return ut
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}
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// A typeId represents a gob Type as an integer that can be passed on the wire.
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// Internally, typeIds are used as keys to a map to recover the underlying type info.
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type typeId int32
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var nextId typeId // incremented for each new type we build
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var typeLock sync.Mutex // set while building a type
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const firstUserId = 64 // lowest id number granted to user
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type gobType interface {
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id() typeId
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setId(id typeId)
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name() string
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string() string // not public; only for debugging
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safeString(seen map[typeId]bool) string
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}
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var types = make(map[reflect.Type]gobType)
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var idToType = make(map[typeId]gobType)
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var builtinIdToType map[typeId]gobType // set in init() after builtins are established
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func setTypeId(typ gobType) {
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// When building recursive types, someone may get there before us.
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if typ.id() != 0 {
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return
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}
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nextId++
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typ.setId(nextId)
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idToType[nextId] = typ
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}
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func (t typeId) gobType() gobType {
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if t == 0 {
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return nil
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}
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return idToType[t]
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}
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// string returns the string representation of the type associated with the typeId.
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func (t typeId) string() string {
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if t.gobType() == nil {
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return "<nil>"
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}
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return t.gobType().string()
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}
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// Name returns the name of the type associated with the typeId.
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func (t typeId) name() string {
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if t.gobType() == nil {
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return "<nil>"
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}
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return t.gobType().name()
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}
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// CommonType holds elements of all types.
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// It is a historical artifact, kept for binary compatibility and exported
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// only for the benefit of the package's encoding of type descriptors. It is
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// not intended for direct use by clients.
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type CommonType struct {
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Name string
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Id typeId
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}
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func (t *CommonType) id() typeId { return t.Id }
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func (t *CommonType) setId(id typeId) { t.Id = id }
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func (t *CommonType) string() string { return t.Name }
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func (t *CommonType) safeString(seen map[typeId]bool) string {
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return t.Name
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}
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func (t *CommonType) name() string { return t.Name }
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// Create and check predefined types
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// The string for tBytes is "bytes" not "[]byte" to signify its specialness.
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var (
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// Primordial types, needed during initialization.
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// Always passed as pointers so the interface{} type
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// goes through without losing its interfaceness.
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tBool = bootstrapType("bool", (*bool)(nil), 1)
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tInt = bootstrapType("int", (*int)(nil), 2)
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tUint = bootstrapType("uint", (*uint)(nil), 3)
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tFloat = bootstrapType("float", (*float64)(nil), 4)
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tBytes = bootstrapType("bytes", (*[]byte)(nil), 5)
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tString = bootstrapType("string", (*string)(nil), 6)
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tComplex = bootstrapType("complex", (*complex128)(nil), 7)
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tInterface = bootstrapType("interface", (*interface{})(nil), 8)
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// Reserve some Ids for compatible expansion
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tReserved7 = bootstrapType("_reserved1", (*struct{ r7 int })(nil), 9)
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tReserved6 = bootstrapType("_reserved1", (*struct{ r6 int })(nil), 10)
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tReserved5 = bootstrapType("_reserved1", (*struct{ r5 int })(nil), 11)
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tReserved4 = bootstrapType("_reserved1", (*struct{ r4 int })(nil), 12)
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tReserved3 = bootstrapType("_reserved1", (*struct{ r3 int })(nil), 13)
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tReserved2 = bootstrapType("_reserved1", (*struct{ r2 int })(nil), 14)
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tReserved1 = bootstrapType("_reserved1", (*struct{ r1 int })(nil), 15)
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)
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// Predefined because it's needed by the Decoder
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var tWireType = mustGetTypeInfo(reflect.TypeOf(wireType{})).id
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var wireTypeUserInfo *userTypeInfo // userTypeInfo of (*wireType)
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func init() {
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// Some magic numbers to make sure there are no surprises.
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checkId(16, tWireType)
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checkId(17, mustGetTypeInfo(reflect.TypeOf(arrayType{})).id)
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checkId(18, mustGetTypeInfo(reflect.TypeOf(CommonType{})).id)
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checkId(19, mustGetTypeInfo(reflect.TypeOf(sliceType{})).id)
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checkId(20, mustGetTypeInfo(reflect.TypeOf(structType{})).id)
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checkId(21, mustGetTypeInfo(reflect.TypeOf(fieldType{})).id)
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checkId(23, mustGetTypeInfo(reflect.TypeOf(mapType{})).id)
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builtinIdToType = make(map[typeId]gobType)
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for k, v := range idToType {
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builtinIdToType[k] = v
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}
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// Move the id space upwards to allow for growth in the predefined world
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// without breaking existing files.
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if nextId > firstUserId {
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panic(fmt.Sprintln("nextId too large:", nextId))
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}
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nextId = firstUserId
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registerBasics()
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wireTypeUserInfo = userType(reflect.TypeOf((*wireType)(nil)))
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}
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// Array type
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type arrayType struct {
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CommonType
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Elem typeId
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Len int
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}
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func newArrayType(name string) *arrayType {
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a := &arrayType{CommonType{Name: name}, 0, 0}
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return a
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}
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func (a *arrayType) init(elem gobType, len int) {
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// Set our type id before evaluating the element's, in case it's our own.
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setTypeId(a)
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a.Elem = elem.id()
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a.Len = len
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}
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func (a *arrayType) safeString(seen map[typeId]bool) string {
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if seen[a.Id] {
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return a.Name
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}
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seen[a.Id] = true
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return fmt.Sprintf("[%d]%s", a.Len, a.Elem.gobType().safeString(seen))
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}
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func (a *arrayType) string() string { return a.safeString(make(map[typeId]bool)) }
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// GobEncoder type (something that implements the GobEncoder interface)
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type gobEncoderType struct {
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CommonType
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}
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func newGobEncoderType(name string) *gobEncoderType {
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g := &gobEncoderType{CommonType{Name: name}}
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setTypeId(g)
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return g
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}
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func (g *gobEncoderType) safeString(seen map[typeId]bool) string {
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return g.Name
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}
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func (g *gobEncoderType) string() string { return g.Name }
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// Map type
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type mapType struct {
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CommonType
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Key typeId
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Elem typeId
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}
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func newMapType(name string) *mapType {
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m := &mapType{CommonType{Name: name}, 0, 0}
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return m
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}
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func (m *mapType) init(key, elem gobType) {
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// Set our type id before evaluating the element's, in case it's our own.
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setTypeId(m)
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m.Key = key.id()
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m.Elem = elem.id()
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}
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func (m *mapType) safeString(seen map[typeId]bool) string {
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if seen[m.Id] {
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return m.Name
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}
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seen[m.Id] = true
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key := m.Key.gobType().safeString(seen)
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elem := m.Elem.gobType().safeString(seen)
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return fmt.Sprintf("map[%s]%s", key, elem)
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}
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func (m *mapType) string() string { return m.safeString(make(map[typeId]bool)) }
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// Slice type
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type sliceType struct {
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CommonType
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Elem typeId
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}
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func newSliceType(name string) *sliceType {
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s := &sliceType{CommonType{Name: name}, 0}
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return s
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}
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func (s *sliceType) init(elem gobType) {
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// Set our type id before evaluating the element's, in case it's our own.
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setTypeId(s)
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// See the comments about ids in newTypeObject. Only slices and
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// structs have mutual recursion.
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if elem.id() == 0 {
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setTypeId(elem)
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}
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s.Elem = elem.id()
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}
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func (s *sliceType) safeString(seen map[typeId]bool) string {
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if seen[s.Id] {
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return s.Name
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}
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seen[s.Id] = true
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return fmt.Sprintf("[]%s", s.Elem.gobType().safeString(seen))
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}
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func (s *sliceType) string() string { return s.safeString(make(map[typeId]bool)) }
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// Struct type
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type fieldType struct {
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Name string
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Id typeId
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}
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type structType struct {
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CommonType
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Field []*fieldType
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}
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func (s *structType) safeString(seen map[typeId]bool) string {
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if s == nil {
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return "<nil>"
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}
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if _, ok := seen[s.Id]; ok {
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return s.Name
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}
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seen[s.Id] = true
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str := s.Name + " = struct { "
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for _, f := range s.Field {
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str += fmt.Sprintf("%s %s; ", f.Name, f.Id.gobType().safeString(seen))
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}
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str += "}"
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return str
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}
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func (s *structType) string() string { return s.safeString(make(map[typeId]bool)) }
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func newStructType(name string) *structType {
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s := &structType{CommonType{Name: name}, nil}
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// For historical reasons we set the id here rather than init.
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// See the comment in newTypeObject for details.
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setTypeId(s)
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return s
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}
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// newTypeObject allocates a gobType for the reflection type rt.
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// Unless ut represents a GobEncoder, rt should be the base type
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// of ut.
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// This is only called from the encoding side. The decoding side
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// works through typeIds and userTypeInfos alone.
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func newTypeObject(name string, ut *userTypeInfo, rt reflect.Type) (gobType, error) {
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// Does this type implement GobEncoder?
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if ut.externalEnc != 0 {
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return newGobEncoderType(name), nil
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}
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var err error
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var type0, type1 gobType
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defer func() {
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if err != nil {
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delete(types, rt)
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}
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}()
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// Install the top-level type before the subtypes (e.g. struct before
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// fields) so recursive types can be constructed safely.
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switch t := rt; t.Kind() {
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// All basic types are easy: they are predefined.
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case reflect.Bool:
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return tBool.gobType(), nil
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return tInt.gobType(), nil
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return tUint.gobType(), nil
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case reflect.Float32, reflect.Float64:
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return tFloat.gobType(), nil
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case reflect.Complex64, reflect.Complex128:
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return tComplex.gobType(), nil
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case reflect.String:
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return tString.gobType(), nil
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case reflect.Interface:
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return tInterface.gobType(), nil
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case reflect.Array:
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at := newArrayType(name)
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types[rt] = at
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type0, err = getBaseType("", t.Elem())
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if err != nil {
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return nil, err
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}
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// Historical aside:
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// For arrays, maps, and slices, we set the type id after the elements
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// are constructed. This is to retain the order of type id allocation after
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// a fix made to handle recursive types, which changed the order in
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// which types are built. Delaying the setting in this way preserves
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// type ids while allowing recursive types to be described. Structs,
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// done below, were already handling recursion correctly so they
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// assign the top-level id before those of the field.
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at.init(type0, t.Len())
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return at, nil
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case reflect.Map:
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mt := newMapType(name)
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types[rt] = mt
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type0, err = getBaseType("", t.Key())
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if err != nil {
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return nil, err
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}
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type1, err = getBaseType("", t.Elem())
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if err != nil {
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return nil, err
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}
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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.Ptr {
|
|
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 interface{}, 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
|
|
encoder *encEngine
|
|
wire *wireType
|
|
}
|
|
|
|
var typeInfoMap = make(map[reflect.Type]*typeInfo) // protected by typeLock
|
|
|
|
// typeLock must be held.
|
|
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
|
|
}
|
|
info, ok := typeInfoMap[rt]
|
|
if ok {
|
|
return info, nil
|
|
}
|
|
info = new(typeInfo)
|
|
gt, err := getBaseType(rt.Name(), rt)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
info.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}
|
|
}
|
|
typeInfoMap[ut.user] = info
|
|
return info, nil
|
|
}
|
|
|
|
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)}
|
|
}
|
|
typeInfoMap[rt] = info
|
|
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 (
|
|
registerLock sync.RWMutex
|
|
nameToConcreteType = make(map[string]reflect.Type)
|
|
concreteTypeToName = make(map[reflect.Type]string)
|
|
)
|
|
|
|
// RegisterName is like Register but uses the provided name rather than the
|
|
// type's default.
|
|
func RegisterName(name string, value interface{}) {
|
|
if name == "" {
|
|
// reserved for nil
|
|
panic("attempt to register empty name")
|
|
}
|
|
registerLock.Lock()
|
|
defer registerLock.Unlock()
|
|
ut := userType(reflect.TypeOf(value))
|
|
// Check for incompatible duplicates. The name must refer to the
|
|
// same user type, and vice versa.
|
|
if t, ok := nameToConcreteType[name]; ok && t != ut.user {
|
|
panic(fmt.Sprintf("gob: registering duplicate types for %q: %s != %s", name, t, ut.user))
|
|
}
|
|
if n, ok := concreteTypeToName[ut.base]; ok && n != name {
|
|
panic(fmt.Sprintf("gob: registering duplicate names for %s: %q != %q", ut.user, n, name))
|
|
}
|
|
// Store the name and type provided by the user....
|
|
nameToConcreteType[name] = reflect.TypeOf(value)
|
|
// but the flattened type in the type table, since that's what decode needs.
|
|
concreteTypeToName[ut.base] = 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 interface{}) {
|
|
// 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.Ptr {
|
|
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))
|
|
}
|