podman/pkg/machine/fcos.go

package machine

import (
	"crypto/sha256"
	"io"
	"io/ioutil"
	url2 "net/url"
	"os"
	"path/filepath"
	"runtime"
	"strings"

	"github.com/containers/storage/pkg/archive"
	digest "github.com/opencontainers/go-digest"
	"github.com/sirupsen/logrus"
)

// These should eventually be moved into machine/qemu as
// they are specific to running qemu
var (
	artifact string = "qemu"
	Format   string = "qcow2.xz"
)

type FcosDownload struct {
	Download
}

func NewFcosDownloader(vmType, vmName string) (DistributionDownload, error) {
	info, err := getFCOSDownload()
	if err != nil {
		return nil, err
	}
	urlSplit := strings.Split(info.Location, "/")
	imageName := urlSplit[len(urlSplit)-1]
	url, err := url2.Parse(info.Location)
	if err != nil {
		return nil, err
	}

	dataDir, err := GetDataDir(vmType)
	if err != nil {
		return nil, err
	}

	fcd := FcosDownload{
		Download: Download{
			Arch:      getFcosArch(),
			Artifact:  artifact,
			Format:    Format,
			ImageName: imageName,
			LocalPath: filepath.Join(dataDir, imageName),
			Sha256sum: info.Sha256Sum,
			URL:       url,
			VMName:    vmName,
		},
	}
	fcd.Download.LocalUncompressedFile = fcd.getLocalUncompressedName()
	return fcd, nil
}

func (f FcosDownload) getLocalUncompressedName() string {
	uncompressedFilename := filepath.Join(filepath.Dir(f.LocalPath), f.VMName+"_"+f.ImageName)
	return strings.TrimSuffix(uncompressedFilename, ".xz")
}

func (f FcosDownload) DownloadImage() error {
	// check if the latest image is already present
	ok, err := UpdateAvailable(&f.Download)
	if err != nil {
		return err
	}
	if !ok {
		if err := DownloadVMImage(f.URL, f.LocalPath); err != nil {
			return err
		}
	}
	uncompressedFileWriter, err := os.OpenFile(f.getLocalUncompressedName(), os.O_CREATE|os.O_RDWR, 0600)
	if err != nil {
		return err
	}
	sourceFile, err := ioutil.ReadFile(f.LocalPath)
	if err != nil {
		return err
	}
	compressionType := archive.DetectCompression(sourceFile)
	f.CompressionType = compressionType.Extension()

	switch f.CompressionType {
	case "tar.xz":
		return decompressXZ(f.LocalPath, uncompressedFileWriter)
	default:
		// File seems to be uncompressed, make a copy
		if err := copyFile(f.LocalPath, uncompressedFileWriter); err != nil {
			return err
		}
	}
	return nil
}

func copyFile(src string, dest *os.File) error {
	source, err := os.Open(src)
	if err != nil {
		return err
	}
	defer func() {
		if err := source.Close(); err != nil {
			logrus.Error(err)
		}
	}()
	_, err = io.Copy(dest, source)
	return err
}

func (f FcosDownload) Get() *Download {
	return &f.Download
}

type fcosDownloadInfo struct {
	CompressionType string
	Location        string
	Release         string
	Sha256Sum       string
}

func UpdateAvailable(d *Download) (bool, error) {
	//	 check the sha of the local image if it exists
	//  get the sha of the remote image
	// == dont bother to pull
	files, err := ioutil.ReadDir(filepath.Dir(d.LocalPath))
	if err != nil {
		return false, err
	}
	for _, file := range files {
		if filepath.Base(d.LocalPath) == file.Name() {
			b, err := ioutil.ReadFile(d.LocalPath)
			if err != nil {
				return false, err
			}
			s := sha256.Sum256(b)
			sum := digest.NewDigestFromBytes(digest.SHA256, s[:])
			if sum.Encoded() == d.Sha256sum {
				return true, nil
			}
		}
	}
	return false, nil
}

func getFcosArch() string {
	var arch string
	// TODO fill in more architectures
	switch runtime.GOARCH {
	case "arm64":
		arch = "aarch64"
	default:
		arch = "x86_64"
	}
	return arch
}