new command: crane size

Signed-off-by: Jason Hall <jason@chainguard.dev>

cmd/crane/cmd/root.go

@@ -131,6 +131,7 @@ func New(use, short string, options []crane.Option) *cobra.Command {
 		NewCmdVersion(),
 		NewCmdRegistry(),
 		NewCmdLayout(),
+		NewCmdSize(),
 	)
 
 	root.PersistentFlags().BoolVarP(&verbose, "verbose", "v", false, "Enable debug logs")

cmd/crane/cmd/size.go

@@ -0,0 +1,145 @@
+// Copyright 2024 Google LLC All Rights Reserved.
+//
+// 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 cmd
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/google/go-containerregistry/pkg/authn"
+	"github.com/google/go-containerregistry/pkg/name"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/spf13/cobra"
+)
+
+// NewCmdSize creates a new cobra.Command for the size subcommand.
+func NewCmdSize() *cobra.Command {
+	var platform string
+	var human bool
+	sizeCmd := &cobra.Command{
+		Use:   "size",
+		Short: "Return the size of an image",
+		Args:  cobra.ExactArgs(1),
+		RunE: func(_ *cobra.Command, args []string) error {
+			ref, err := name.ParseReference(args[0])
+			if err != nil {
+				return err
+			}
+
+			opts := []remote.Option{remote.WithAuthFromKeychain(authn.DefaultKeychain)}
+			if platform != "" {
+				p, err := v1.ParsePlatform(platform)
+				if err != nil {
+					return err
+				}
+				opts = append(opts, remote.WithPlatform(*p))
+			}
+
+			desc, err := remote.Get(ref, opts...)
+			if err != nil {
+				return err
+			}
+			var sz int64
+			if platform != "" {
+				isz, err := imageSize(desc.Image())
+				if err != nil {
+					return err
+				}
+				sz = isz
+			} else {
+				idx, err := desc.ImageIndex()
+				if err != nil {
+					return err
+				}
+
+				mf, err := idx.IndexManifest()
+				if err != nil {
+					return err
+				}
+				for _, m := range mf.Manifests {
+					isz, err := imageSize(remote.Image(ref.Context().Digest(m.Digest.String()), remote.WithAuthFromKeychain(authn.DefaultKeychain)))
+					if err != nil {
+						return err
+					}
+					sz += isz
+				}
+			}
+
+			if human {
+				fmt.Printf("%s\n", ibytes(uint64(sz)))
+			} else {
+				fmt.Printf("%d\n", sz)
+			}
+			return nil
+		},
+	}
+	sizeCmd.Flags().StringVar(&platform, "platform", "", "The platform to use when pulling the image. If empty, size of all platforms' blobs.")
+	sizeCmd.Flags().BoolVar(&human, "human", false, "If true, print human-readable sizes.")
+	return sizeCmd
+}
+
+func imageSize(img v1.Image, err error) (int64, error) {
+	if err != nil {
+		return 0, err
+	}
+	ls, err := img.Layers()
+	if err != nil {
+		return 0, err
+	}
+	var sz int64
+	for i, l := range ls {
+		lsz, err := l.Size()
+		if err != nil {
+			return 0, fmt.Errorf("getting layer %d size: %w", i, err)
+		}
+		sz += lsz
+	}
+	mf, err := img.Manifest()
+	if err != nil {
+		return 0, fmt.Errorf("getting manifest: %w", err)
+	}
+	sz += mf.Config.Size
+	return sz, nil
+}
+
+// Copied from https://github.com/dustin/go-humanize/blob/961771c7ab9992c55cd100b0562246e970925856/bytes.go
+
+func logn(n, b float64) float64 {
+	return math.Log(n) / math.Log(b)
+}
+
+func humanateBytes(s uint64, base float64, sizes []string) string {
+	if s < 10 {
+		return fmt.Sprintf("%d B", s)
+	}
+	e := math.Floor(logn(float64(s), base))
+	suffix := sizes[int(e)]
+	val := math.Floor(float64(s)/math.Pow(base, e)*10+0.5) / 10
+	f := "%.0f %s"
+	if val < 10 {
+		f = "%.1f %s"
+	}
+
+	return fmt.Sprintf(f, val, suffix)
+}
+
+// ibytes produces a human readable representation of an IEC size.
+//
+// ibytes(82854982) -> 79 MiB
+func ibytes(s uint64) string {
+	sizes := []string{"B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB"}
+	return humanateBytes(s, 1024, sizes)
+}