package symlink import ( "bytes" "errors" "os" "path/filepath" "strings" "syscall" "github.com/docker/docker/pkg/longpath" ) func toShort(path string) (string, error) { p, err := syscall.UTF16FromString(path) if err != nil { return "", err } b := p // GetShortPathName says we can reuse buffer n, err := syscall.GetShortPathName(&p[0], &b[0], uint32(len(b))) if err != nil { return "", err } if n > uint32(len(b)) { b = make([]uint16, n) if _, err = syscall.GetShortPathName(&p[0], &b[0], uint32(len(b))); err != nil { return "", err } } return syscall.UTF16ToString(b), nil } func toLong(path string) (string, error) { p, err := syscall.UTF16FromString(path) if err != nil { return "", err } b := p // GetLongPathName says we can reuse buffer n, err := syscall.GetLongPathName(&p[0], &b[0], uint32(len(b))) if err != nil { return "", err } if n > uint32(len(b)) { b = make([]uint16, n) n, err = syscall.GetLongPathName(&p[0], &b[0], uint32(len(b))) if err != nil { return "", err } } b = b[:n] return syscall.UTF16ToString(b), nil } func evalSymlinks(path string) (string, error) { path, err := walkSymlinks(path) if err != nil { return "", err } p, err := toShort(path) if err != nil { return "", err } p, err = toLong(p) if err != nil { return "", err } // syscall.GetLongPathName does not change the case of the drive letter, // but the result of EvalSymlinks must be unique, so we have // EvalSymlinks(`c:\a`) == EvalSymlinks(`C:\a`). // Make drive letter upper case. if len(p) >= 2 && p[1] == ':' && 'a' <= p[0] && p[0] <= 'z' { p = string(p[0]+'A'-'a') + p[1:] } else if len(p) >= 6 && p[5] == ':' && 'a' <= p[4] && p[4] <= 'z' { p = p[:3] + string(p[4]+'A'-'a') + p[5:] } return filepath.Clean(p), nil } const utf8RuneSelf = 0x80 func walkSymlinks(path string) (string, error) { const maxIter = 255 originalPath := path // consume path by taking each frontmost path element, // expanding it if it's a symlink, and appending it to b var b bytes.Buffer for n := 0; path != ""; n++ { if n > maxIter { return "", errors.New("EvalSymlinks: too many links in " + originalPath) } // A path beginning with `\\?\` represents the root, so automatically // skip that part and begin processing the next segment. if strings.HasPrefix(path, longpath.Prefix) { b.WriteString(longpath.Prefix) path = path[4:] continue } // find next path component, p var i = -1 for j, c := range path { if c < utf8RuneSelf && os.IsPathSeparator(uint8(c)) { i = j break } } var p string if i == -1 { p, path = path, "" } else { p, path = path[:i], path[i+1:] } if p == "" { if b.Len() == 0 { // must be absolute path b.WriteRune(filepath.Separator) } continue } // If this is the first segment after the long path prefix, accept the // current segment as a volume root or UNC share and move on to the next. if b.String() == longpath.Prefix { b.WriteString(p) b.WriteRune(filepath.Separator) continue } fi, err := os.Lstat(b.String() + p) if err != nil { return "", err } if fi.Mode()&os.ModeSymlink == 0 { b.WriteString(p) if path != "" || (b.Len() == 2 && len(p) == 2 && p[1] == ':') { b.WriteRune(filepath.Separator) } continue } // it's a symlink, put it at the front of path dest, err := os.Readlink(b.String() + p) if err != nil { return "", err } if filepath.IsAbs(dest) || os.IsPathSeparator(dest[0]) { b.Reset() } path = dest + string(filepath.Separator) + path } return filepath.Clean(b.String()), nil }