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// Copyright 2018 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 impl
import (
"fmt"
"reflect"
"strconv"
"strings"
"sync"
"sync/atomic"
"google.golang.org/protobuf/internal/genname"
"google.golang.org/protobuf/reflect/protoreflect"
pref "google.golang.org/protobuf/reflect/protoreflect"
)
// MessageInfo provides protobuf related functionality for a given Go type
// that represents a message. A given instance of MessageInfo is tied to
// exactly one Go type, which must be a pointer to a struct type.
//
// The exported fields must be populated before any methods are called
// and cannot be mutated after set.
type MessageInfo struct {
// GoReflectType is the underlying message Go type and must be populated.
GoReflectType reflect.Type // pointer to struct
// Desc is the underlying message descriptor type and must be populated.
Desc pref.MessageDescriptor
// Exporter must be provided in a purego environment in order to provide
// access to unexported fields.
Exporter exporter
// OneofWrappers is list of pointers to oneof wrapper struct types.
OneofWrappers []interface{}
initMu sync.Mutex // protects all unexported fields
initDone uint32
reflectMessageInfo // for reflection implementation
coderMessageInfo // for fast-path method implementations
}
// exporter is a function that returns a reference to the ith field of v,
// where v is a pointer to a struct. It returns nil if it does not support
// exporting the requested field (e.g., already exported).
type exporter func(v interface{}, i int) interface{}
// getMessageInfo returns the MessageInfo for any message type that
// is generated by our implementation of protoc-gen-go (for v2 and on).
// If it is unable to obtain a MessageInfo, it returns nil.
func getMessageInfo(mt reflect.Type) *MessageInfo {
m, ok := reflect.Zero(mt).Interface().(pref.ProtoMessage)
if !ok {
return nil
}
mr, ok := m.ProtoReflect().(interface{ ProtoMessageInfo() *MessageInfo })
if !ok {
return nil
}
return mr.ProtoMessageInfo()
}
func (mi *MessageInfo) init() {
// This function is called in the hot path. Inline the sync.Once logic,
// since allocating a closure for Once.Do is expensive.
// Keep init small to ensure that it can be inlined.
if atomic.LoadUint32(&mi.initDone) == 0 {
mi.initOnce()
}
}
func (mi *MessageInfo) initOnce() {
mi.initMu.Lock()
defer mi.initMu.Unlock()
if mi.initDone == 1 {
return
}
t := mi.GoReflectType
if t.Kind() != reflect.Ptr && t.Elem().Kind() != reflect.Struct {
panic(fmt.Sprintf("got %v, want *struct kind", t))
}
t = t.Elem()
si := mi.makeStructInfo(t)
mi.makeReflectFuncs(t, si)
mi.makeCoderMethods(t, si)
atomic.StoreUint32(&mi.initDone, 1)
}
// getPointer returns the pointer for a message, which should be of
// the type of the MessageInfo. If the message is of a different type,
// it returns ok==false.
func (mi *MessageInfo) getPointer(m pref.Message) (p pointer, ok bool) {
switch m := m.(type) {
case *messageState:
return m.pointer(), m.messageInfo() == mi
case *messageReflectWrapper:
return m.pointer(), m.messageInfo() == mi
}
return pointer{}, false
}
type (
SizeCache = int32
WeakFields = map[int32]protoreflect.ProtoMessage
UnknownFields = []byte
ExtensionFields = map[int32]ExtensionField
)
var (
sizecacheType = reflect.TypeOf(SizeCache(0))
weakFieldsType = reflect.TypeOf(WeakFields(nil))
unknownFieldsType = reflect.TypeOf(UnknownFields(nil))
extensionFieldsType = reflect.TypeOf(ExtensionFields(nil))
)
type structInfo struct {
sizecacheOffset offset
weakOffset offset
unknownOffset offset
extensionOffset offset
fieldsByNumber map[pref.FieldNumber]reflect.StructField
oneofsByName map[pref.Name]reflect.StructField
oneofWrappersByType map[reflect.Type]pref.FieldNumber
oneofWrappersByNumber map[pref.FieldNumber]reflect.Type
}
func (mi *MessageInfo) makeStructInfo(t reflect.Type) structInfo {
si := structInfo{
sizecacheOffset: invalidOffset,
weakOffset: invalidOffset,
unknownOffset: invalidOffset,
extensionOffset: invalidOffset,
fieldsByNumber: map[pref.FieldNumber]reflect.StructField{},
oneofsByName: map[pref.Name]reflect.StructField{},
oneofWrappersByType: map[reflect.Type]pref.FieldNumber{},
oneofWrappersByNumber: map[pref.FieldNumber]reflect.Type{},
}
fieldLoop:
for i := 0; i < t.NumField(); i++ {
switch f := t.Field(i); f.Name {
case genname.SizeCache, genname.SizeCacheA:
if f.Type == sizecacheType {
si.sizecacheOffset = offsetOf(f, mi.Exporter)
}
case genname.WeakFields, genname.WeakFieldsA:
if f.Type == weakFieldsType {
si.weakOffset = offsetOf(f, mi.Exporter)
}
case genname.UnknownFields, genname.UnknownFieldsA:
if f.Type == unknownFieldsType {
si.unknownOffset = offsetOf(f, mi.Exporter)
}
case genname.ExtensionFields, genname.ExtensionFieldsA, genname.ExtensionFieldsB:
if f.Type == extensionFieldsType {
si.extensionOffset = offsetOf(f, mi.Exporter)
}
default:
for _, s := range strings.Split(f.Tag.Get("protobuf"), ",") {
if len(s) > 0 && strings.Trim(s, "0123456789") == "" {
n, _ := strconv.ParseUint(s, 10, 64)
si.fieldsByNumber[pref.FieldNumber(n)] = f
continue fieldLoop
}
}
if s := f.Tag.Get("protobuf_oneof"); len(s) > 0 {
si.oneofsByName[pref.Name(s)] = f
continue fieldLoop
}
}
}
// Derive a mapping of oneof wrappers to fields.
oneofWrappers := mi.OneofWrappers
for _, method := range []string{"XXX_OneofFuncs", "XXX_OneofWrappers"} {
if fn, ok := reflect.PtrTo(t).MethodByName(method); ok {
for _, v := range fn.Func.Call([]reflect.Value{reflect.Zero(fn.Type.In(0))}) {
if vs, ok := v.Interface().([]interface{}); ok {
oneofWrappers = vs
}
}
}
}
for _, v := range oneofWrappers {
tf := reflect.TypeOf(v).Elem()
f := tf.Field(0)
for _, s := range strings.Split(f.Tag.Get("protobuf"), ",") {
if len(s) > 0 && strings.Trim(s, "0123456789") == "" {
n, _ := strconv.ParseUint(s, 10, 64)
si.oneofWrappersByType[tf] = pref.FieldNumber(n)
si.oneofWrappersByNumber[pref.FieldNumber(n)] = tf
break
}
}
}
return si
}
func (mi *MessageInfo) New() protoreflect.Message {
return mi.MessageOf(reflect.New(mi.GoReflectType.Elem()).Interface())
}
func (mi *MessageInfo) Zero() protoreflect.Message {
return mi.MessageOf(reflect.Zero(mi.GoReflectType).Interface())
}
func (mi *MessageInfo) Descriptor() protoreflect.MessageDescriptor { return mi.Desc }
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