Source: legacy_export.go in package google.golang.org/protobuf/internal/impl


package impl

import (
	"encoding/binary"
	"encoding/json"
	"hash/crc32"
	"math"
	"reflect"

	"google.golang.org/protobuf/internal/errors"
	pref "google.golang.org/protobuf/reflect/protoreflect"
	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.

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