descriptors.go

/*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package main

import (
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"strings"

	"github.com/golang/protobuf/proto"
	"github.com/golang/protobuf/protoc-gen-go/descriptor"
)

type descriptorSet struct {
	merged      descriptor.FileDescriptorSet
	seen        map[string]struct{}
	ignoreFiles map[string]struct{}
	descProto   string
	includeDir  string
}

func newDescriptorSet(ignoreFiles []string, d string, i string) *descriptorSet {
	ifm := make(map[string]struct{}, len(ignoreFiles))
	for _, ignore := range ignoreFiles {
		ifm[ignore] = struct{}{}
	}
	return &descriptorSet{
		seen:        make(map[string]struct{}),
		ignoreFiles: ifm,
		descProto:   d,
		includeDir:  i,
	}
}

func (d *descriptorSet) add(descs ...*descriptor.FileDescriptorProto) {
	for _, file := range descs {
		name := file.GetName()
		if _, ok := d.seen[name]; ok {
			continue
		}

		if _, ok := d.ignoreFiles[name]; ok {
			continue
		}

		// TODO(stevvooe): If we want to filter certain fields in the descriptor,
		// this is the place to do it. May be necessary if certain fields are
		// noisy, such as option fields.
		d.merged.File = append(d.merged.File, file)
		d.seen[name] = struct{}{}
	}
}

// stabilize outputs the merged protobuf descriptor set into the provided writer.
//
// This is equivalent to the following command:
//
// cat merged.pb | protoc -I /path/to --decode google.protobuf.FileDescriptorSet /path/to/google/protobuf/descriptor.proto
func (d *descriptorSet) marshalTo(w io.Writer) error {
	p, err := proto.Marshal(&d.merged)
	if err != nil {
		return err
	}

	args := []string{
		"protoc",
		"-I",
		d.includeDir,
		"--decode",
		"google.protobuf.FileDescriptorSet",
		d.descProto,
	}

	cmd := exec.Command(args[0], args[1:]...)
	cmd.Stdin = bytes.NewReader(p)
	cmd.Stdout = w
	cmd.Stderr = os.Stderr

	if !quiet {
		fmt.Println(strings.Join(args, " "))
	}
	return cmd.Run()
}

func readDesc(path string) (*descriptor.FileDescriptorSet, error) {
	var desc descriptor.FileDescriptorSet

	p, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, err
	}

	if err := proto.Unmarshal(p, &desc); err != nil {
		log.Fatalln(err)
	}

	return &desc, nil
}