117 lines
2.3 KiB
Go
117 lines
2.3 KiB
Go
// This software is distributed under the MIT License.
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//
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// You should have received a copy of the MIT License along with this program.
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// If not, see <https://opensource.org/licenses/MIT>
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package realpath
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import (
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"bytes"
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"os"
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"path/filepath"
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)
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// Realpath returns the real path of a given file in the os
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func Realpath(fpath string) (string, error) {
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if len(fpath) == 0 {
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return "", os.ErrInvalid
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}
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if !filepath.IsAbs(fpath) {
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pwd, err := os.Getwd()
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if err != nil {
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return "", err
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}
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fpath = filepath.Join(pwd, fpath)
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}
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path := []byte(fpath)
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nlinks := 0
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start := 1
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prev := 1
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for start < len(path) {
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c := nextComponent(path, start)
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cur := c[start:]
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switch {
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case len(cur) == 0:
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copy(path[start:], path[start+1:])
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path = path[0 : len(path)-1]
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case len(cur) == 1 && cur[0] == '.':
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if start+2 < len(path) {
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copy(path[start:], path[start+2:])
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}
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path = path[0 : len(path)-2]
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case len(cur) == 2 && cur[0] == '.' && cur[1] == '.':
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copy(path[prev:], path[start+2:])
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path = path[0 : len(path)+prev-(start+2)]
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prev = 1
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start = 1
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default:
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fi, err := os.Lstat(string(c))
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if err != nil {
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return "", err
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}
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if isSymlink(fi) {
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nlinks++
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if nlinks > 16 {
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return "", os.ErrInvalid
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}
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var link string
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link, err = os.Readlink(string(c))
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after := string(path[len(c):])
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// switch symlink component with its real path
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path = switchSymlinkCom(path, start, link, after)
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prev = 1
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start = 1
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} else {
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// Directories
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prev = start
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start = len(c) + 1
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}
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}
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}
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for len(path) > 1 && path[len(path)-1] == os.PathSeparator {
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path = path[0 : len(path)-1]
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}
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return string(path), nil
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}
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// test if a link is symbolic link
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func isSymlink(fi os.FileInfo) bool {
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return fi.Mode()&os.ModeSymlink == os.ModeSymlink
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}
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// switch a symbolic link component to its real path
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func switchSymlinkCom(path []byte, start int, link, after string) []byte {
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if link[0] == os.PathSeparator {
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// Absolute links
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return []byte(filepath.Join(link, after))
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}
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// Relative links
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return []byte(filepath.Join(string(path[0:start]), link, after))
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}
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// get the next component
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func nextComponent(path []byte, start int) []byte {
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v := bytes.IndexByte(path[start:], os.PathSeparator)
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if v < 0 {
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return path
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}
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return path[0 : start+v]
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}
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