| // 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 ( |
| "fmt" |
| "reflect" |
| |
| "google.golang.org/protobuf/internal/pragma" |
| pvalue "google.golang.org/protobuf/internal/value" |
| pref "google.golang.org/protobuf/reflect/protoreflect" |
| ) |
| |
| // MessageState is a data structure that is nested as the first field in a |
| // concrete message. It provides a way to implement the ProtoReflect method |
| // in an allocation-free way without needing to have a shadow Go type generated |
| // for every message type. This technique only works using unsafe. |
| // |
| // |
| // Example generated code: |
| // |
| // type M struct { |
| // state protoimpl.MessageState |
| // |
| // Field1 int32 |
| // Field2 string |
| // Field3 *BarMessage |
| // ... |
| // } |
| // |
| // func (m *M) ProtoReflect() protoreflect.Message { |
| // mi := &file_fizz_buzz_proto_msgInfos[5] |
| // if protoimpl.UnsafeEnabled && m != nil { |
| // ms := protoimpl.X.MessageStateOf(Pointer(m)) |
| // if ms.LoadMessageInfo() == nil { |
| // ms.StoreMessageInfo(mi) |
| // } |
| // return ms |
| // } |
| // return mi.MessageOf(m) |
| // } |
| // |
| // The MessageState type holds a *MessageInfo, which must be atomically set to |
| // the message info associated with a given message instance. |
| // By unsafely converting a *M into a *MessageState, the MessageState object |
| // has access to all the information needed to implement protobuf reflection. |
| // It has access to the message info as its first field, and a pointer to the |
| // MessageState is identical to a pointer to the concrete message value. |
| // |
| // |
| // Requirements: |
| // • The type M must implement protoreflect.ProtoMessage. |
| // • The address of m must not be nil. |
| // • The address of m and the address of m.state must be equal, |
| // even though they are different Go types. |
| type MessageState struct { |
| pragma.NoUnkeyedLiterals |
| pragma.DoNotCompare |
| pragma.DoNotCopy |
| |
| mi *MessageInfo |
| } |
| |
| type messageState MessageState |
| |
| var ( |
| _ pref.Message = (*messageState)(nil) |
| _ pvalue.Unwrapper = (*messageState)(nil) |
| ) |
| |
| // messageDataType is a tuple of a pointer to the message data and |
| // a pointer to the message type. It is a generalized way of providing a |
| // reflective view over a message instance. The disadvantage of this approach |
| // is the need to allocate this tuple of 16B. |
| type messageDataType struct { |
| p pointer |
| mi *MessageInfo |
| } |
| |
| type ( |
| messageReflectWrapper messageDataType |
| messageIfaceWrapper messageDataType |
| ) |
| |
| var ( |
| _ pref.Message = (*messageReflectWrapper)(nil) |
| _ pvalue.Unwrapper = (*messageReflectWrapper)(nil) |
| _ pref.ProtoMessage = (*messageIfaceWrapper)(nil) |
| _ pvalue.Unwrapper = (*messageIfaceWrapper)(nil) |
| ) |
| |
| // MessageOf returns a reflective view over a message. The input must be a |
| // pointer to a named Go struct. If the provided type has a ProtoReflect method, |
| // it must be implemented by calling this method. |
| func (mi *MessageInfo) MessageOf(m interface{}) pref.Message { |
| // TODO: Switch the input to be an opaque Pointer. |
| if reflect.TypeOf(m) != mi.GoType { |
| panic(fmt.Sprintf("type mismatch: got %T, want %v", m, mi.GoType)) |
| } |
| p := pointerOfIface(m) |
| if p.IsNil() { |
| return mi.nilMessage.Init(mi) |
| } |
| return &messageReflectWrapper{p, mi} |
| } |
| |
| func (m *messageReflectWrapper) pointer() pointer { return m.p } |
| |
| func (m *messageIfaceWrapper) ProtoReflect() pref.Message { |
| return (*messageReflectWrapper)(m) |
| } |
| func (m *messageIfaceWrapper) ProtoUnwrap() interface{} { |
| return m.p.AsIfaceOf(m.mi.GoType.Elem()) |
| } |
| |
| type extensionMap map[int32]ExtensionField |
| |
| func (m *extensionMap) Range(f func(pref.FieldDescriptor, pref.Value) bool) { |
| if m != nil { |
| for _, x := range *m { |
| xt := x.GetType() |
| if !f(xt, xt.ValueOf(x.GetValue())) { |
| return |
| } |
| } |
| } |
| } |
| func (m *extensionMap) Has(xt pref.ExtensionType) (ok bool) { |
| if m != nil { |
| _, ok = (*m)[int32(xt.Number())] |
| } |
| return ok |
| } |
| func (m *extensionMap) Clear(xt pref.ExtensionType) { |
| delete(*m, int32(xt.Number())) |
| } |
| func (m *extensionMap) Get(xt pref.ExtensionType) pref.Value { |
| if m != nil { |
| if x, ok := (*m)[int32(xt.Number())]; ok { |
| return xt.ValueOf(x.GetValue()) |
| } |
| } |
| if !isComposite(xt) { |
| return defaultValueOf(xt) |
| } |
| return frozenValueOf(xt.New()) |
| } |
| func (m *extensionMap) Set(xt pref.ExtensionType, v pref.Value) { |
| if *m == nil { |
| *m = make(map[int32]ExtensionField) |
| } |
| var x ExtensionField |
| x.SetType(xt) |
| x.SetEagerValue(xt.InterfaceOf(v)) |
| (*m)[int32(xt.Number())] = x |
| } |
| func (m *extensionMap) Mutable(xt pref.ExtensionType) pref.Value { |
| if !isComposite(xt) { |
| panic("invalid Mutable on field with non-composite type") |
| } |
| if x, ok := (*m)[int32(xt.Number())]; ok { |
| return xt.ValueOf(x.GetValue()) |
| } |
| v := xt.New() |
| m.Set(xt, v) |
| return v |
| } |
| |
| func isComposite(fd pref.FieldDescriptor) bool { |
| return fd.Kind() == pref.MessageKind || fd.Kind() == pref.GroupKind || fd.IsList() || fd.IsMap() |
| } |
| |
| // checkField verifies that the provided field descriptor is valid. |
| // Exactly one of the returned values is populated. |
| func (mi *MessageInfo) checkField(fd pref.FieldDescriptor) (*fieldInfo, pref.ExtensionType) { |
| if fi := mi.fields[fd.Number()]; fi != nil { |
| if fi.fieldDesc != fd { |
| panic("mismatching field descriptor") |
| } |
| return fi, nil |
| } |
| if fd.IsExtension() { |
| if fd.ContainingMessage().FullName() != mi.PBType.FullName() { |
| // TODO: Should this be exact containing message descriptor match? |
| panic("mismatching containing message") |
| } |
| if !mi.PBType.ExtensionRanges().Has(fd.Number()) { |
| panic("invalid extension field") |
| } |
| return nil, fd.(pref.ExtensionType) |
| } |
| panic("invalid field descriptor") |
| } |