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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 (
"google.golang.org/protobuf/encoding/protowire"
"google.golang.org/protobuf/internal/encoding/messageset"
"google.golang.org/protobuf/internal/order"
"google.golang.org/protobuf/internal/pragma"
"google.golang.org/protobuf/reflect/protoreflect"
"google.golang.org/protobuf/runtime/protoiface"
)
// MarshalOptions configures the marshaler.
//
// Example usage:
// b, err := MarshalOptions{Deterministic: true}.Marshal(m)
type MarshalOptions struct {
pragma.NoUnkeyedLiterals
// AllowPartial allows messages that have missing required fields to marshal
// without returning an error. If AllowPartial is false (the default),
// Marshal will return an error if there are any missing required fields.
AllowPartial bool
// Deterministic controls whether the same message will always be
// serialized to the same bytes within the same binary.
//
// Setting this option guarantees that repeated serialization of
// the same message will return the same bytes, and that different
// processes of the same binary (which may be executing on different
// machines) will serialize equal messages to the same bytes.
// It has no effect on the resulting size of the encoded message compared
// to a non-deterministic marshal.
//
// Note that the deterministic serialization is NOT canonical across
// languages. It is not guaranteed to remain stable over time. It is
// unstable across different builds with schema changes due to unknown
// fields. Users who need canonical serialization (e.g., persistent
// storage in a canonical form, fingerprinting, etc.) must define
// their own canonicalization specification and implement their own
// serializer rather than relying on this API.
//
// If deterministic serialization is requested, map entries will be
// sorted by keys in lexographical order. This is an implementation
// detail and subject to change.
Deterministic bool
// UseCachedSize indicates that the result of a previous Size call
// may be reused.
//
// Setting this option asserts that:
//
// 1. Size has previously been called on this message with identical
// options (except for UseCachedSize itself).
//
// 2. The message and all its submessages have not changed in any
// way since the Size call.
//
// If either of these invariants is violated,
// the results are undefined and may include panics or corrupted output.
//
// Implementations MAY take this option into account to provide
// better performance, but there is no guarantee that they will do so.
// There is absolutely no guarantee that Size followed by Marshal with
// UseCachedSize set will perform equivalently to Marshal alone.
UseCachedSize bool
}
// Marshal returns the wire-format encoding of m.
func Marshal(m Message) ([]byte, error) {
// Treat nil message interface as an empty message; nothing to output.
if m == nil {
return nil, nil
}
out, err := MarshalOptions{}.marshal(nil, m.ProtoReflect())
if len(out.Buf) == 0 && err == nil {
out.Buf = emptyBytesForMessage(m)
}
return out.Buf, err
}
// Marshal returns the wire-format encoding of m.
func (o MarshalOptions) Marshal(m Message) ([]byte, error) {
// Treat nil message interface as an empty message; nothing to output.
if m == nil {
return nil, nil
}
out, err := o.marshal(nil, m.ProtoReflect())
if len(out.Buf) == 0 && err == nil {
out.Buf = emptyBytesForMessage(m)
}
return out.Buf, err
}
// emptyBytesForMessage returns a nil buffer if and only if m is invalid,
// otherwise it returns a non-nil empty buffer.
//
// This is to assist the edge-case where user-code does the following:
// m1.OptionalBytes, _ = proto.Marshal(m2)
// where they expect the proto2 "optional_bytes" field to be populated
// if any only if m2 is a valid message.
func emptyBytesForMessage(m Message) []byte {
if m == nil || !m.ProtoReflect().IsValid() {
return nil
}
return emptyBuf[:]
}
// MarshalAppend appends the wire-format encoding of m to b,
// returning the result.
func (o MarshalOptions) MarshalAppend(b []byte, m Message) ([]byte, error) {
// Treat nil message interface as an empty message; nothing to append.
if m == nil {
return b, nil
}
out, err := o.marshal(b, m.ProtoReflect())
return out.Buf, err
}
// MarshalState returns the wire-format encoding of a message.
//
// This method permits fine-grained control over the marshaler.
// Most users should use Marshal instead.
func (o MarshalOptions) MarshalState(in protoiface.MarshalInput) (protoiface.MarshalOutput, error) {
return o.marshal(in.Buf, in.Message)
}
// marshal is a centralized function that all marshal operations go through.
// For profiling purposes, avoid changing the name of this function or
// introducing other code paths for marshal that do not go through this.
func (o MarshalOptions) marshal(b []byte, m protoreflect.Message) (out protoiface.MarshalOutput, err error) {
allowPartial := o.AllowPartial
o.AllowPartial = true
if methods := protoMethods(m); methods != nil && methods.Marshal != nil &&
!(o.Deterministic && methods.Flags&protoiface.SupportMarshalDeterministic == 0) {
in := protoiface.MarshalInput{
Message: m,
Buf: b,
}
if o.Deterministic {
in.Flags |= protoiface.MarshalDeterministic
}
if o.UseCachedSize {
in.Flags |= protoiface.MarshalUseCachedSize
}
if methods.Size != nil {
sout := methods.Size(protoiface.SizeInput{
Message: m,
Flags: in.Flags,
})
if cap(b) < len(b)+sout.Size {
in.Buf = make([]byte, len(b), growcap(cap(b), len(b)+sout.Size))
copy(in.Buf, b)
}
in.Flags |= protoiface.MarshalUseCachedSize
}
out, err = methods.Marshal(in)
} else {
out.Buf, err = o.marshalMessageSlow(b, m)
}
if err != nil {
return out, err
}
if allowPartial {
return out, nil
}
return out, checkInitialized(m)
}
func (o MarshalOptions) marshalMessage(b []byte, m protoreflect.Message) ([]byte, error) {
out, err := o.marshal(b, m)
return out.Buf, err
}
// growcap scales up the capacity of a slice.
//
// Given a slice with a current capacity of oldcap and a desired
// capacity of wantcap, growcap returns a new capacity >= wantcap.
//
// The algorithm is mostly identical to the one used by append as of Go 1.14.
func growcap(oldcap, wantcap int) (newcap int) {
if wantcap > oldcap*2 {
newcap = wantcap
} else if oldcap < 1024 {
// The Go 1.14 runtime takes this case when len(s) < 1024,
// not when cap(s) < 1024. The difference doesn't seem
// significant here.
newcap = oldcap * 2
} else {
newcap = oldcap
for 0 < newcap && newcap < wantcap {
newcap += newcap / 4
}
if newcap <= 0 {
newcap = wantcap
}
}
return newcap
}
func (o MarshalOptions) marshalMessageSlow(b []byte, m protoreflect.Message) ([]byte, error) {
if messageset.IsMessageSet(m.Descriptor()) {
return o.marshalMessageSet(b, m)
}
fieldOrder := order.AnyFieldOrder
if o.Deterministic {
// TODO: This should use a more natural ordering like NumberFieldOrder,
// but doing so breaks golden tests that make invalid assumption about
// output stability of this implementation.
fieldOrder = order.LegacyFieldOrder
}
var err error
order.RangeFields(m, fieldOrder, func(fd protoreflect.FieldDescriptor, v protoreflect.Value) bool {
b, err = o.marshalField(b, fd, v)
return err == nil
})
if err != nil {
return b, err
}
b = append(b, m.GetUnknown()...)
return b, nil
}
func (o MarshalOptions) marshalField(b []byte, fd protoreflect.FieldDescriptor, value protoreflect.Value) ([]byte, error) {
switch {
case fd.IsList():
return o.marshalList(b, fd, value.List())
case fd.IsMap():
return o.marshalMap(b, fd, value.Map())
default:
b = protowire.AppendTag(b, fd.Number(), wireTypes[fd.Kind()])
return o.marshalSingular(b, fd, value)
}
}
func (o MarshalOptions) marshalList(b []byte, fd protoreflect.FieldDescriptor, list protoreflect.List) ([]byte, error) {
if fd.IsPacked() && list.Len() > 0 {
b = protowire.AppendTag(b, fd.Number(), protowire.BytesType)
b, pos := appendSpeculativeLength(b)
for i, llen := 0, list.Len(); i < llen; i++ {
var err error
b, err = o.marshalSingular(b, fd, list.Get(i))
if err != nil {
return b, err
}
}
b = finishSpeculativeLength(b, pos)
return b, nil
}
kind := fd.Kind()
for i, llen := 0, list.Len(); i < llen; i++ {
var err error
b = protowire.AppendTag(b, fd.Number(), wireTypes[kind])
b, err = o.marshalSingular(b, fd, list.Get(i))
if err != nil {
return b, err
}
}
return b, nil
}
func (o MarshalOptions) marshalMap(b []byte, fd protoreflect.FieldDescriptor, mapv protoreflect.Map) ([]byte, error) {
keyf := fd.MapKey()
valf := fd.MapValue()
keyOrder := order.AnyKeyOrder
if o.Deterministic {
keyOrder = order.GenericKeyOrder
}
var err error
order.RangeEntries(mapv, keyOrder, func(key protoreflect.MapKey, value protoreflect.Value) bool {
b = protowire.AppendTag(b, fd.Number(), protowire.BytesType)
var pos int
b, pos = appendSpeculativeLength(b)
b, err = o.marshalField(b, keyf, key.Value())
if err != nil {
return false
}
b, err = o.marshalField(b, valf, value)
if err != nil {
return false
}
b = finishSpeculativeLength(b, pos)
return true
})
return b, err
}
// When encoding length-prefixed fields, we speculatively set aside some number of bytes
// for the length, encode the data, and then encode the length (shifting the data if necessary
// to make room).
const speculativeLength = 1
func appendSpeculativeLength(b []byte) ([]byte, int) {
pos := len(b)
b = append(b, "\x00\x00\x00\x00"[:speculativeLength]...)
return b, pos
}
func finishSpeculativeLength(b []byte, pos int) []byte {
mlen := len(b) - pos - speculativeLength
msiz := protowire.SizeVarint(uint64(mlen))
if msiz != speculativeLength {
for i := 0; i < msiz-speculativeLength; i++ {
b = append(b, 0)
}
copy(b[pos+msiz:], b[pos+speculativeLength:])
b = b[:pos+msiz+mlen]
}
protowire.AppendVarint(b[:pos], uint64(mlen))
return b
}
