first version

internal/docker/docker.go

@@ -0,0 +1,73 @@
+package docker
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/client"
+)
+
+func SaveImageTar(ctx context.Context, image, path, name string) error {
+
+	cli, err := client.NewClientWithOpts(client.FromEnv, client.WithAPIVersionNegotiation())
+	if err != nil {
+		return fmt.Errorf("docker client error: %v", err)
+	}
+	defer cli.Close()
+
+	if err := pullImage(ctx, cli, image); err != nil {
+		return fmt.Errorf("pull image %s failed: %v", image, err)
+	}
+
+	if err := saveToTar(ctx, cli, image, path, name); err != nil {
+		return fmt.Errorf("save image %s failed: %v", image, err)
+	}
+
+	return nil
+}
+
+func pullImage(ctx context.Context, cli *client.Client, image string) error {
+	// try pull image
+	r, err := cli.ImagePull(ctx, image, types.ImagePullOptions{})
+	if err != nil {
+		return fmt.Errorf("pull image %s failed: %v", image, err)
+	}
+	defer r.Close()
+
+	io.Copy(os.Stdout, r)
+
+	return nil
+}
+
+func saveToTar(ctx context.Context, cli *client.Client, image, path, name string) error {
+	out, err := cli.ImageSave(ctx, []string{image})
+	if err != nil {
+		return fmt.Errorf("save image %s failed: %v", image, err)
+	}
+	defer out.Close()
+
+	filename := name
+	if filename == "" {
+		strs := strings.Split(image, "/")
+		filename = fmt.Sprintf("%s.tar", strings.ReplaceAll(strs[len(strs)-1], ":", "_"))
+	}
+
+	filep := filepath.Join(path, filename)
+
+	target, err := os.Create(filep)
+	if err != nil {
+		return fmt.Errorf("create file %s failed: %v", filep, err)
+	}
+	defer target.Close()
+
+	if _, err := io.Copy(target, out); err != nil {
+		return fmt.Errorf("copy file %s failed: %v", filep, err)
+	}
+
+	return nil
+}