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mkctr: support writing image archives to disk #38
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,95 @@ | ||
| // Copyright (c) 2026 Tailscale Inc & AUTHORS All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
|
|
||
| package main | ||
|
|
||
| import ( | ||
| "archive/tar" | ||
| "fmt" | ||
| "io" | ||
| "io/fs" | ||
| "os" | ||
| "path/filepath" | ||
|
|
||
| v1 "github.com/google/go-containerregistry/pkg/v1" | ||
| "github.com/google/go-containerregistry/pkg/v1/empty" | ||
| "github.com/google/go-containerregistry/pkg/v1/layout" | ||
| ) | ||
|
|
||
| func writeImageArchive(path string, img v1.Image, platform v1.Platform) error { | ||
| return writeArchive(path, func(lp layout.Path) error { | ||
| return lp.AppendImage(img, layout.WithPlatform(platform)) | ||
| }) | ||
| } | ||
|
|
||
| func writeIndexArchive(path string, idx v1.ImageIndex) error { | ||
| return writeArchive(path, func(lp layout.Path) error { | ||
| return lp.AppendIndex(idx) | ||
| }) | ||
| } | ||
|
|
||
| // writeArchive writes an OCI image layout as a tar archive. The output path | ||
| // is replaced only after the archive is complete. | ||
| func writeArchive(path string, appendContent func(layout.Path) error) error { | ||
| dir, err := os.MkdirTemp("", "mkctr-output-") | ||
| if err != nil { | ||
| return err | ||
| } | ||
| defer os.RemoveAll(dir) | ||
| lp, err := layout.Write(dir, empty.Index) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| if err := appendContent(lp); err != nil { | ||
| return fmt.Errorf("writing OCI layout: %w", err) | ||
| } | ||
| out, err := os.CreateTemp(filepath.Dir(path), ".mkctr-output-*") | ||
| if err != nil { | ||
| return err | ||
| } | ||
| defer os.Remove(out.Name()) | ||
| tw := tar.NewWriter(out) | ||
| // Use fixed tar metadata for reproducible archives. AddFS would copy | ||
| // timestamps, permissions, and ownership from the host filesystem. | ||
| err = filepath.WalkDir(dir, func(path string, d fs.DirEntry, err error) error { | ||
| if err != nil { | ||
| return err | ||
| } | ||
| if d.IsDir() { | ||
| return nil | ||
| } | ||
| info, err := d.Info() | ||
| if err != nil { | ||
| return err | ||
| } | ||
| rel, err := filepath.Rel(dir, path) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| if err := tw.WriteHeader(&tar.Header{ | ||
| Name: filepath.ToSlash(rel), | ||
| Mode: 0644, | ||
| Size: info.Size(), | ||
| }); err != nil { | ||
| return err | ||
| } | ||
| in, err := os.Open(path) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| defer in.Close() | ||
| _, err = io.Copy(tw, in) | ||
| return err | ||
| }) | ||
|
tomhjp marked this conversation as resolved.
|
||
| if closeErr := tw.Close(); err == nil { | ||
| err = closeErr | ||
| } | ||
| if closeErr := out.Close(); err == nil { | ||
| err = closeErr | ||
| } | ||
| if err != nil { | ||
| return err | ||
| } | ||
| return os.Rename(out.Name(), path) | ||
| } | ||
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