aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/go/_std_1.21/src/path/filepath/symlink.go
blob: f9435e0d5b9007c6de53967d0ea85bcc6a890d8e (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
// Copyright 2012 The Go 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 filepath

import (
	"errors"
	"io/fs"
	"os"
	"runtime"
	"syscall"
)

func walkSymlinks(path string) (string, error) {
	volLen := volumeNameLen(path)
	pathSeparator := string(os.PathSeparator)

	if volLen < len(path) && os.IsPathSeparator(path[volLen]) {
		volLen++
	}
	vol := path[:volLen]
	dest := vol
	linksWalked := 0
	for start, end := volLen, volLen; start < len(path); start = end {
		for start < len(path) && os.IsPathSeparator(path[start]) {
			start++
		}
		end = start
		for end < len(path) && !os.IsPathSeparator(path[end]) {
			end++
		}

		// On Windows, "." can be a symlink.
		// We look it up, and use the value if it is absolute.
		// If not, we just return ".".
		isWindowsDot := runtime.GOOS == "windows" && path[volumeNameLen(path):] == "."

		// The next path component is in path[start:end].
		if end == start {
			// No more path components.
			break
		} else if path[start:end] == "." && !isWindowsDot {
			// Ignore path component ".".
			continue
		} else if path[start:end] == ".." {
			// Back up to previous component if possible.
			// Note that volLen includes any leading slash.

			// Set r to the index of the last slash in dest,
			// after the volume.
			var r int
			for r = len(dest) - 1; r >= volLen; r-- {
				if os.IsPathSeparator(dest[r]) {
					break
				}
			}
			if r < volLen || dest[r+1:] == ".." {
				// Either path has no slashes
				// (it's empty or just "C:")
				// or it ends in a ".." we had to keep.
				// Either way, keep this "..".
				if len(dest) > volLen {
					dest += pathSeparator
				}
				dest += ".."
			} else {
				// Discard everything since the last slash.
				dest = dest[:r]
			}
			continue
		}

		// Ordinary path component. Add it to result.

		if len(dest) > volumeNameLen(dest) && !os.IsPathSeparator(dest[len(dest)-1]) {
			dest += pathSeparator
		}

		dest += path[start:end]

		// Resolve symlink.

		fi, err := os.Lstat(dest)
		if err != nil {
			return "", err
		}

		if fi.Mode()&fs.ModeSymlink == 0 {
			if !fi.Mode().IsDir() && end < len(path) {
				return "", syscall.ENOTDIR
			}
			continue
		}

		// Found symlink.

		linksWalked++
		if linksWalked > 255 {
			return "", errors.New("EvalSymlinks: too many links")
		}

		link, err := os.Readlink(dest)
		if err != nil {
			return "", err
		}

		if isWindowsDot && !IsAbs(link) {
			// On Windows, if "." is a relative symlink,
			// just return ".".
			break
		}

		path = link + path[end:]

		v := volumeNameLen(link)
		if v > 0 {
			// Symlink to drive name is an absolute path.
			if v < len(link) && os.IsPathSeparator(link[v]) {
				v++
			}
			vol = link[:v]
			dest = vol
			end = len(vol)
		} else if len(link) > 0 && os.IsPathSeparator(link[0]) {
			// Symlink to absolute path.
			dest = link[:1]
			end = 1
			vol = link[:1]
			volLen = 1
		} else {
			// Symlink to relative path; replace last
			// path component in dest.
			var r int
			for r = len(dest) - 1; r >= volLen; r-- {
				if os.IsPathSeparator(dest[r]) {
					break
				}
			}
			if r < volLen {
				dest = vol
			} else {
				dest = dest[:r]
			}
			end = 0
		}
	}
	return Clean(dest), nil
}