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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 proto
import (
"fmt"
"google.golang.org/protobuf/reflect/protoreflect"
"google.golang.org/protobuf/runtime/protoiface"
)
// Merge merges src into dst, which must be a message with the same descriptor.
//
// Populated scalar fields in src are copied to dst, while populated
// singular messages in src are merged into dst by recursively calling Merge.
// The elements of every list field in src is appended to the corresponded
// list fields in dst. The entries of every map field in src is copied into
// the corresponding map field in dst, possibly replacing existing entries.
// The unknown fields of src are appended to the unknown fields of dst.
//
// It is semantically equivalent to unmarshaling the encoded form of src
// into dst with the [UnmarshalOptions.Merge] option specified.
func Merge(dst, src Message) {
// TODO: Should nil src be treated as semantically equivalent to a
// untyped, read-only, empty message? What about a nil dst?
dstMsg, srcMsg := dst.ProtoReflect(), src.ProtoReflect()
if dstMsg.Descriptor() != srcMsg.Descriptor() {
if got, want := dstMsg.Descriptor().FullName(), srcMsg.Descriptor().FullName(); got != want {
panic(fmt.Sprintf("descriptor mismatch: %v != %v", got, want))
}
panic("descriptor mismatch")
}
mergeOptions{}.mergeMessage(dstMsg, srcMsg)
}
// Clone returns a deep copy of m.
// If the top-level message is invalid, it returns an invalid message as well.
func Clone(m Message) Message {
// NOTE: Most usages of Clone assume the following properties:
// t := reflect.TypeOf(m)
// t == reflect.TypeOf(m.ProtoReflect().New().Interface())
// t == reflect.TypeOf(m.ProtoReflect().Type().Zero().Interface())
//
// Embedding protobuf messages breaks this since the parent type will have
// a forwarded ProtoReflect method, but the Interface method will return
// the underlying embedded message type.
if m == nil {
return nil
}
src := m.ProtoReflect()
if !src.IsValid() {
return src.Type().Zero().Interface()
}
dst := src.New()
mergeOptions{}.mergeMessage(dst, src)
return dst.Interface()
}
// mergeOptions provides a namespace for merge functions, and can be
// exported in the future if we add user-visible merge options.
type mergeOptions struct{}
func (o mergeOptions) mergeMessage(dst, src protoreflect.Message) {
methods := protoMethods(dst)
if methods != nil && methods.Merge != nil {
in := protoiface.MergeInput{
Destination: dst,
Source: src,
}
out := methods.Merge(in)
if out.Flags&protoiface.MergeComplete != 0 {
return
}
}
if !dst.IsValid() {
panic(fmt.Sprintf("cannot merge into invalid %v message", dst.Descriptor().FullName()))
}
src.Range(func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
switch {
case fd.IsList():
o.mergeList(dst.Mutable(fd).List(), v.List(), fd)
case fd.IsMap():
o.mergeMap(dst.Mutable(fd).Map(), v.Map(), fd.MapValue())
case fd.Message() != nil:
o.mergeMessage(dst.Mutable(fd).Message(), v.Message())
case fd.Kind() == protoreflect.BytesKind:
dst.Set(fd, o.cloneBytes(v))
default:
dst.Set(fd, v)
}
return true
})
if len(src.GetUnknown()) > 0 {
dst.SetUnknown(append(dst.GetUnknown(), src.GetUnknown()...))
}
}
func (o mergeOptions) mergeList(dst, src protoreflect.List, fd protoreflect.FieldDescriptor) {
// Merge semantics appends to the end of the existing list.
for i, n := 0, src.Len(); i < n; i++ {
switch v := src.Get(i); {
case fd.Message() != nil:
dstv := dst.NewElement()
o.mergeMessage(dstv.Message(), v.Message())
dst.Append(dstv)
case fd.Kind() == protoreflect.BytesKind:
dst.Append(o.cloneBytes(v))
default:
dst.Append(v)
}
}
}
func (o mergeOptions) mergeMap(dst, src protoreflect.Map, fd protoreflect.FieldDescriptor) {
// Merge semantics replaces, rather than merges into existing entries.
src.Range(func(k protoreflect.MapKey, v protoreflect.Value) bool {
switch {
case fd.Message() != nil:
dstv := dst.NewValue()
o.mergeMessage(dstv.Message(), v.Message())
dst.Set(k, dstv)
case fd.Kind() == protoreflect.BytesKind:
dst.Set(k, o.cloneBytes(v))
default:
dst.Set(k, v)
}
return true
})
}
func (o mergeOptions) cloneBytes(v protoreflect.Value) protoreflect.Value {
return protoreflect.ValueOfBytes(append([]byte{}, v.Bytes()...))
}
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