108 lines
2.4 KiB
Go
108 lines
2.4 KiB
Go
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package contenthash
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import (
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"errors"
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"os"
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"path/filepath"
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)
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var (
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errTooManyLinks = errors.New("too many links")
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)
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type onSymlinkFunc func(string, string) error
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// rootPath joins a path with a root, evaluating and bounding any
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// symlink to the root directory.
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// This is containerd/continuity/fs RootPath implementation with a callback on
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// resolving the symlink.
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func rootPath(root, path string, cb onSymlinkFunc) (string, error) {
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if path == "" {
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return root, nil
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}
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var linksWalked int // to protect against cycles
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for {
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i := linksWalked
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newpath, err := walkLinks(root, path, &linksWalked, cb)
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if err != nil {
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return "", err
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}
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path = newpath
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if i == linksWalked {
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newpath = filepath.Join("/", newpath)
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if path == newpath {
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return filepath.Join(root, newpath), nil
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}
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path = newpath
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}
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}
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}
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func walkLink(root, path string, linksWalked *int, cb onSymlinkFunc) (newpath string, islink bool, err error) {
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if *linksWalked > 255 {
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return "", false, errTooManyLinks
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}
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path = filepath.Join("/", path)
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if path == "/" {
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return path, false, nil
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}
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realPath := filepath.Join(root, path)
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fi, err := os.Lstat(realPath)
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if err != nil {
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// If path does not yet exist, treat as non-symlink
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if os.IsNotExist(err) {
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return path, false, nil
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}
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return "", false, err
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}
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if fi.Mode()&os.ModeSymlink == 0 {
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return path, false, nil
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}
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newpath, err = os.Readlink(realPath)
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if err != nil {
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return "", false, err
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}
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if cb != nil {
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if err := cb(path, newpath); err != nil {
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return "", false, err
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}
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}
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*linksWalked++
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return newpath, true, nil
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}
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func walkLinks(root, path string, linksWalked *int, cb onSymlinkFunc) (string, error) {
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switch dir, file := filepath.Split(path); {
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case dir == "":
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newpath, _, err := walkLink(root, file, linksWalked, cb)
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return newpath, err
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case file == "":
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if os.IsPathSeparator(dir[len(dir)-1]) {
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if dir == "/" {
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return dir, nil
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}
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return walkLinks(root, dir[:len(dir)-1], linksWalked, cb)
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}
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newpath, _, err := walkLink(root, dir, linksWalked, cb)
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return newpath, err
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default:
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newdir, err := walkLinks(root, dir, linksWalked, cb)
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if err != nil {
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return "", err
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}
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newpath, islink, err := walkLink(root, filepath.Join(newdir, file), linksWalked, cb)
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if err != nil {
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return "", err
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}
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if !islink {
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return newpath, nil
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}
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if filepath.IsAbs(newpath) {
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return newpath, nil
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}
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return filepath.Join(newdir, newpath), nil
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}
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}
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