147 lines
3.2 KiB
Go
147 lines
3.2 KiB
Go
// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package filepath
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import (
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"errors"
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"io/fs"
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"os"
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"runtime"
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"syscall"
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)
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func walkSymlinks(path string) (string, error) {
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volLen := volumeNameLen(path)
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pathSeparator := string(os.PathSeparator)
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if volLen < len(path) && os.IsPathSeparator(path[volLen]) {
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volLen++
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}
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vol := path[:volLen]
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dest := vol
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linksWalked := 0
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for start, end := volLen, volLen; start < len(path); start = end {
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for start < len(path) && os.IsPathSeparator(path[start]) {
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start++
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}
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end = start
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for end < len(path) && !os.IsPathSeparator(path[end]) {
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end++
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}
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// On Windows, "." can be a symlink.
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// We look it up, and use the value if it is absolute.
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// If not, we just return ".".
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isWindowsDot := runtime.GOOS == "windows" && path[volumeNameLen(path):] == "."
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// The next path component is in path[start:end].
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if end == start {
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// No more path components.
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break
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} else if path[start:end] == "." && !isWindowsDot {
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// Ignore path component ".".
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continue
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} else if path[start:end] == ".." {
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// Back up to previous component if possible.
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// Note that volLen includes any leading slash.
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// Set r to the index of the last slash in dest,
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// after the volume.
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var r int
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for r = len(dest) - 1; r >= volLen; r-- {
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if os.IsPathSeparator(dest[r]) {
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break
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}
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}
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if r < volLen || dest[r+1:] == ".." {
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// Either path has no slashes
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// (it's empty or just "C:")
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// or it ends in a ".." we had to keep.
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// Either way, keep this "..".
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if len(dest) > volLen {
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dest += pathSeparator
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}
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dest += ".."
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} else {
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// Discard everything since the last slash.
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dest = dest[:r]
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}
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continue
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}
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// Ordinary path component. Add it to result.
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if len(dest) > volumeNameLen(dest) && !os.IsPathSeparator(dest[len(dest)-1]) {
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dest += pathSeparator
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}
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dest += path[start:end]
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// Resolve symlink.
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fi, err := os.Lstat(dest)
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if err != nil {
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return "", err
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}
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if fi.Mode()&fs.ModeSymlink == 0 {
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if !fi.Mode().IsDir() && end < len(path) {
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return "", syscall.ENOTDIR
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}
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continue
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}
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// Found symlink.
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linksWalked++
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if linksWalked > 255 {
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return "", errors.New("EvalSymlinks: too many links")
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}
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link, err := os.Readlink(dest)
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if err != nil {
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return "", err
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}
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if isWindowsDot && !IsAbs(link) {
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// On Windows, if "." is a relative symlink,
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// just return ".".
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break
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}
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path = link + path[end:]
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v := volumeNameLen(link)
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if v > 0 {
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// Symlink to drive name is an absolute path.
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if v < len(link) && os.IsPathSeparator(link[v]) {
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v++
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}
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vol = link[:v]
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dest = vol
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end = len(vol)
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} else if len(link) > 0 && os.IsPathSeparator(link[0]) {
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// Symlink to absolute path.
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dest = link[:1]
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end = 1
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} else {
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// Symlink to relative path; replace last
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// path component in dest.
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var r int
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for r = len(dest) - 1; r >= volLen; r-- {
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if os.IsPathSeparator(dest[r]) {
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break
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}
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}
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if r < volLen {
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dest = vol
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} else {
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dest = dest[:r]
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}
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end = 0
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}
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}
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return Clean(dest), nil
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}
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