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// Copyright 2019 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 (
"sync"
"sync/atomic"
"google.golang.org/protobuf/encoding/protowire"
"google.golang.org/protobuf/internal/errors"
"google.golang.org/protobuf/reflect/protoreflect"
)
type extensionFieldInfo struct {
wiretag uint64
tagsize int
unmarshalNeedsValue bool
funcs valueCoderFuncs
validation validationInfo
}
func getExtensionFieldInfo(xt protoreflect.ExtensionType) *extensionFieldInfo {
if xi, ok := xt.(*ExtensionInfo); ok {
xi.lazyInit()
return xi.info
}
// Ideally we'd cache the resulting *extensionFieldInfo so we don't have to
// recompute this metadata repeatedly. But without support for something like
// weak references, such a cache would pin temporary values (like dynamic
// extension types, constructed for the duration of a user request) to the
// heap forever, causing memory usage of the cache to grow unbounded.
// See discussion in https://github.com/golang/protobuf/issues/1521.
return makeExtensionFieldInfo(xt.TypeDescriptor())
}
func makeExtensionFieldInfo(xd protoreflect.ExtensionDescriptor) *extensionFieldInfo {
var wiretag uint64
if !xd.IsPacked() {
wiretag = protowire.EncodeTag(xd.Number(), wireTypes[xd.Kind()])
} else {
wiretag = protowire.EncodeTag(xd.Number(), protowire.BytesType)
}
e := &extensionFieldInfo{
wiretag: wiretag,
tagsize: protowire.SizeVarint(wiretag),
funcs: encoderFuncsForValue(xd),
}
// Does the unmarshal function need a value passed to it?
// This is true for composite types, where we pass in a message, list, or map to fill in,
// and for enums, where we pass in a prototype value to specify the concrete enum type.
switch xd.Kind() {
case protoreflect.MessageKind, protoreflect.GroupKind, protoreflect.EnumKind:
e.unmarshalNeedsValue = true
default:
if xd.Cardinality() == protoreflect.Repeated {
e.unmarshalNeedsValue = true
}
}
return e
}
type lazyExtensionValue struct {
atomicOnce uint32 // atomically set if value is valid
mu sync.Mutex
xi *extensionFieldInfo
value protoreflect.Value
b []byte
fn func() protoreflect.Value
}
type ExtensionField struct {
typ protoreflect.ExtensionType
// value is either the value of GetValue,
// or a *lazyExtensionValue that then returns the value of GetValue.
value protoreflect.Value
lazy *lazyExtensionValue
}
func (f *ExtensionField) appendLazyBytes(xt protoreflect.ExtensionType, xi *extensionFieldInfo, num protowire.Number, wtyp protowire.Type, b []byte) {
if f.lazy == nil {
f.lazy = &lazyExtensionValue{xi: xi}
}
f.typ = xt
f.lazy.xi = xi
f.lazy.b = protowire.AppendTag(f.lazy.b, num, wtyp)
f.lazy.b = append(f.lazy.b, b...)
}
func (f *ExtensionField) canLazy(xt protoreflect.ExtensionType) bool {
if f.typ == nil {
return true
}
if f.typ == xt && f.lazy != nil && atomic.LoadUint32(&f.lazy.atomicOnce) == 0 {
return true
}
return false
}
func (f *ExtensionField) lazyInit() {
f.lazy.mu.Lock()
defer f.lazy.mu.Unlock()
if atomic.LoadUint32(&f.lazy.atomicOnce) == 1 {
return
}
if f.lazy.xi != nil {
b := f.lazy.b
val := f.typ.New()
for len(b) > 0 {
var tag uint64
if b[0] < 0x80 {
tag = uint64(b[0])
b = b[1:]
} else if len(b) >= 2 && b[1] < 128 {
tag = uint64(b[0]&0x7f) + uint64(b[1])<<7
b = b[2:]
} else {
var n int
tag, n = protowire.ConsumeVarint(b)
if n < 0 {
panic(errors.New("bad tag in lazy extension decoding"))
}
b = b[n:]
}
num := protowire.Number(tag >> 3)
wtyp := protowire.Type(tag & 7)
var out unmarshalOutput
var err error
val, out, err = f.lazy.xi.funcs.unmarshal(b, val, num, wtyp, lazyUnmarshalOptions)
if err != nil {
panic(errors.New("decode failure in lazy extension decoding: %v", err))
}
b = b[out.n:]
}
f.lazy.value = val
} else {
f.lazy.value = f.lazy.fn()
}
f.lazy.xi = nil
f.lazy.fn = nil
f.lazy.b = nil
atomic.StoreUint32(&f.lazy.atomicOnce, 1)
}
// Set sets the type and value of the extension field.
// This must not be called concurrently.
func (f *ExtensionField) Set(t protoreflect.ExtensionType, v protoreflect.Value) {
f.typ = t
f.value = v
f.lazy = nil
}
// SetLazy sets the type and a value that is to be lazily evaluated upon first use.
// This must not be called concurrently.
func (f *ExtensionField) SetLazy(t protoreflect.ExtensionType, fn func() protoreflect.Value) {
f.typ = t
f.lazy = &lazyExtensionValue{fn: fn}
}
// Value returns the value of the extension field.
// This may be called concurrently.
func (f *ExtensionField) Value() protoreflect.Value {
if f.lazy != nil {
if atomic.LoadUint32(&f.lazy.atomicOnce) == 0 {
f.lazyInit()
}
return f.lazy.value
}
return f.value
}
// Type returns the type of the extension field.
// This may be called concurrently.
func (f ExtensionField) Type() protoreflect.ExtensionType {
return f.typ
}
// IsSet returns whether the extension field is set.
// This may be called concurrently.
func (f ExtensionField) IsSet() bool {
return f.typ != nil
}
// IsLazy reports whether a field is lazily encoded.
// It is exported for testing.
func IsLazy(m protoreflect.Message, fd protoreflect.FieldDescriptor) bool {
var mi *MessageInfo
var p pointer
switch m := m.(type) {
case *messageState:
mi = m.messageInfo()
p = m.pointer()
case *messageReflectWrapper:
mi = m.messageInfo()
p = m.pointer()
default:
return false
}
xd, ok := fd.(protoreflect.ExtensionTypeDescriptor)
if !ok {
return false
}
xt := xd.Type()
ext := mi.extensionMap(p)
if ext == nil {
return false
}
f, ok := (*ext)[int32(fd.Number())]
if !ok {
return false
}
return f.typ == xt && f.lazy != nil && atomic.LoadUint32(&f.lazy.atomicOnce) == 0
}
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