diff --git a/vendor/google.golang.org/protobuf/internal/impl/encode.go b/vendor/google.golang.org/protobuf/internal/impl/encode.go
new file mode 100644
index 0000000..845c67d
--- /dev/null
+++ b/vendor/google.golang.org/protobuf/internal/impl/encode.go
@@ -0,0 +1,201 @@
+// 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 (
+	"math"
+	"sort"
+	"sync/atomic"
+
+	"google.golang.org/protobuf/internal/flags"
+	proto "google.golang.org/protobuf/proto"
+	piface "google.golang.org/protobuf/runtime/protoiface"
+)
+
+type marshalOptions struct {
+	flags piface.MarshalInputFlags
+}
+
+func (o marshalOptions) Options() proto.MarshalOptions {
+	return proto.MarshalOptions{
+		AllowPartial:  true,
+		Deterministic: o.Deterministic(),
+		UseCachedSize: o.UseCachedSize(),
+	}
+}
+
+func (o marshalOptions) Deterministic() bool { return o.flags&piface.MarshalDeterministic != 0 }
+func (o marshalOptions) UseCachedSize() bool { return o.flags&piface.MarshalUseCachedSize != 0 }
+
+// size is protoreflect.Methods.Size.
+func (mi *MessageInfo) size(in piface.SizeInput) piface.SizeOutput {
+	var p pointer
+	if ms, ok := in.Message.(*messageState); ok {
+		p = ms.pointer()
+	} else {
+		p = in.Message.(*messageReflectWrapper).pointer()
+	}
+	size := mi.sizePointer(p, marshalOptions{
+		flags: in.Flags,
+	})
+	return piface.SizeOutput{Size: size}
+}
+
+func (mi *MessageInfo) sizePointer(p pointer, opts marshalOptions) (size int) {
+	mi.init()
+	if p.IsNil() {
+		return 0
+	}
+	if opts.UseCachedSize() && mi.sizecacheOffset.IsValid() {
+		if size := atomic.LoadInt32(p.Apply(mi.sizecacheOffset).Int32()); size >= 0 {
+			return int(size)
+		}
+	}
+	return mi.sizePointerSlow(p, opts)
+}
+
+func (mi *MessageInfo) sizePointerSlow(p pointer, opts marshalOptions) (size int) {
+	if flags.ProtoLegacy && mi.isMessageSet {
+		size = sizeMessageSet(mi, p, opts)
+		if mi.sizecacheOffset.IsValid() {
+			atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), int32(size))
+		}
+		return size
+	}
+	if mi.extensionOffset.IsValid() {
+		e := p.Apply(mi.extensionOffset).Extensions()
+		size += mi.sizeExtensions(e, opts)
+	}
+	for _, f := range mi.orderedCoderFields {
+		if f.funcs.size == nil {
+			continue
+		}
+		fptr := p.Apply(f.offset)
+		if f.isPointer && fptr.Elem().IsNil() {
+			continue
+		}
+		size += f.funcs.size(fptr, f, opts)
+	}
+	if mi.unknownOffset.IsValid() {
+		if u := mi.getUnknownBytes(p); u != nil {
+			size += len(*u)
+		}
+	}
+	if mi.sizecacheOffset.IsValid() {
+		if size > math.MaxInt32 {
+			// The size is too large for the int32 sizecache field.
+			// We will need to recompute the size when encoding;
+			// unfortunately expensive, but better than invalid output.
+			atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), -1)
+		} else {
+			atomic.StoreInt32(p.Apply(mi.sizecacheOffset).Int32(), int32(size))
+		}
+	}
+	return size
+}
+
+// marshal is protoreflect.Methods.Marshal.
+func (mi *MessageInfo) marshal(in piface.MarshalInput) (out piface.MarshalOutput, err error) {
+	var p pointer
+	if ms, ok := in.Message.(*messageState); ok {
+		p = ms.pointer()
+	} else {
+		p = in.Message.(*messageReflectWrapper).pointer()
+	}
+	b, err := mi.marshalAppendPointer(in.Buf, p, marshalOptions{
+		flags: in.Flags,
+	})
+	return piface.MarshalOutput{Buf: b}, err
+}
+
+func (mi *MessageInfo) marshalAppendPointer(b []byte, p pointer, opts marshalOptions) ([]byte, error) {
+	mi.init()
+	if p.IsNil() {
+		return b, nil
+	}
+	if flags.ProtoLegacy && mi.isMessageSet {
+		return marshalMessageSet(mi, b, p, opts)
+	}
+	var err error
+	// The old marshaler encodes extensions at beginning.
+	if mi.extensionOffset.IsValid() {
+		e := p.Apply(mi.extensionOffset).Extensions()
+		// TODO: Special handling for MessageSet?
+		b, err = mi.appendExtensions(b, e, opts)
+		if err != nil {
+			return b, err
+		}
+	}
+	for _, f := range mi.orderedCoderFields {
+		if f.funcs.marshal == nil {
+			continue
+		}
+		fptr := p.Apply(f.offset)
+		if f.isPointer && fptr.Elem().IsNil() {
+			continue
+		}
+		b, err = f.funcs.marshal(b, fptr, f, opts)
+		if err != nil {
+			return b, err
+		}
+	}
+	if mi.unknownOffset.IsValid() && !mi.isMessageSet {
+		if u := mi.getUnknownBytes(p); u != nil {
+			b = append(b, (*u)...)
+		}
+	}
+	return b, nil
+}
+
+func (mi *MessageInfo) sizeExtensions(ext *map[int32]ExtensionField, opts marshalOptions) (n int) {
+	if ext == nil {
+		return 0
+	}
+	for _, x := range *ext {
+		xi := getExtensionFieldInfo(x.Type())
+		if xi.funcs.size == nil {
+			continue
+		}
+		n += xi.funcs.size(x.Value(), xi.tagsize, opts)
+	}
+	return n
+}
+
+func (mi *MessageInfo) appendExtensions(b []byte, ext *map[int32]ExtensionField, opts marshalOptions) ([]byte, error) {
+	if ext == nil {
+		return b, nil
+	}
+
+	switch len(*ext) {
+	case 0:
+		return b, nil
+	case 1:
+		// Fast-path for one extension: Don't bother sorting the keys.
+		var err error
+		for _, x := range *ext {
+			xi := getExtensionFieldInfo(x.Type())
+			b, err = xi.funcs.marshal(b, x.Value(), xi.wiretag, opts)
+		}
+		return b, err
+	default:
+		// Sort the keys to provide a deterministic encoding.
+		// Not sure this is required, but the old code does it.
+		keys := make([]int, 0, len(*ext))
+		for k := range *ext {
+			keys = append(keys, int(k))
+		}
+		sort.Ints(keys)
+		var err error
+		for _, k := range keys {
+			x := (*ext)[int32(k)]
+			xi := getExtensionFieldInfo(x.Type())
+			b, err = xi.funcs.marshal(b, x.Value(), xi.wiretag, opts)
+			if err != nil {
+				return b, err
+			}
+		}
+		return b, nil
+	}
+}