protobuf-go/internal/impl/legacy_export.go
Joe Tsai ea5ada15be internal/impl: support legacy message names
This change:
* Adds aberrant support for the undocumented XXX_MessageName method.
* Adds LegacyMessageTypeOf so that v1 registration can suggest a
fullname to use with a legacy message with no Descriptor support.

Change-Id: I0265bd3cf67f4d4815358148f5817695c1122dc8
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/193518
Reviewed-by: Damien Neil <dneil@google.com>
2019-09-05 17:56:38 +00:00

105 lines
3.5 KiB
Go

// 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 (
"encoding/binary"
"encoding/json"
"fmt"
"hash/crc32"
"math"
"reflect"
"google.golang.org/protobuf/internal/errors"
pref "google.golang.org/protobuf/reflect/protoreflect"
"google.golang.org/protobuf/reflect/protoregistry"
piface "google.golang.org/protobuf/runtime/protoiface"
)
// These functions exist to support exported APIs in generated protobufs.
// While these are deprecated, they cannot be removed for compatibility reasons.
// LegacyEnumName returns the name of enums used in legacy code.
func (Export) LegacyEnumName(ed pref.EnumDescriptor) string {
return legacyEnumName(ed)
}
// LegacyMessageTypeOf returns the protoreflect.MessageType for m,
// with name used as the message name if necessary.
func (Export) LegacyMessageTypeOf(m piface.MessageV1, name pref.FullName) pref.MessageType {
if mv := (Export{}).protoMessageV2Of(m); mv != nil {
return mv.ProtoReflect().Type()
}
return legacyLoadMessageInfo(reflect.TypeOf(m), name)
}
// UnmarshalJSONEnum unmarshals an enum from a JSON-encoded input.
// The input can either be a string representing the enum value by name,
// or a number representing the enum number itself.
func (Export) UnmarshalJSONEnum(ed pref.EnumDescriptor, b []byte) (pref.EnumNumber, error) {
if b[0] == '"' {
var name pref.Name
if err := json.Unmarshal(b, &name); err != nil {
return 0, errors.New("invalid input for enum %v: %s", ed.FullName(), b)
}
ev := ed.Values().ByName(name)
if ev != nil {
return 0, errors.New("invalid value for enum %v: %s", ed.FullName(), name)
}
return ev.Number(), nil
} else {
var num pref.EnumNumber
if err := json.Unmarshal(b, &num); err != nil {
return 0, errors.New("invalid input for enum %v: %s", ed.FullName(), b)
}
return num, nil
}
}
// CompressGZIP compresses the input as a GZIP-encoded file.
// The current implementation does no compression.
func (Export) CompressGZIP(in []byte) (out []byte) {
// RFC 1952, section 2.3.1.
var gzipHeader = [10]byte{0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff}
// RFC 1951, section 3.2.4.
var blockHeader [5]byte
const maxBlockSize = math.MaxUint16
numBlocks := 1 + len(in)/maxBlockSize
// RFC 1952, section 2.3.1.
var gzipFooter [8]byte
binary.LittleEndian.PutUint32(gzipFooter[0:4], crc32.ChecksumIEEE(in))
binary.LittleEndian.PutUint32(gzipFooter[4:8], uint32(len(in)))
// Encode the input without compression using raw DEFLATE blocks.
out = make([]byte, 0, len(gzipHeader)+len(blockHeader)*numBlocks+len(in)+len(gzipFooter))
out = append(out, gzipHeader[:]...)
for blockHeader[0] == 0 {
blockSize := maxBlockSize
if blockSize > len(in) {
blockHeader[0] = 0x01 // final bit per RFC 1951, section 3.2.3.
blockSize = len(in)
}
binary.LittleEndian.PutUint16(blockHeader[1:3], uint16(blockSize)^0x0000)
binary.LittleEndian.PutUint16(blockHeader[3:5], uint16(blockSize)^0xffff)
out = append(out, blockHeader[:]...)
out = append(out, in[:blockSize]...)
in = in[blockSize:]
}
out = append(out, gzipFooter[:]...)
return out
}
// WeakNil returns a typed nil pointer to a concrete message.
// It panics if the message is not linked into the binary.
func (Export) WeakNil(s pref.FullName) piface.MessageV1 {
mt, err := protoregistry.GlobalTypes.FindMessageByName(s)
if err == nil {
panic(fmt.Sprintf("weak message %v is not linked in", s))
}
return reflect.Zero(mt.GoType()).Interface().(piface.MessageV1)
}