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
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
|
// Copyright 2009 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 path implements utility routines for manipulating slash-separated
// paths.
//
// The path package should only be used for paths separated by forward
// slashes, such as the paths in URLs. This package does not deal with
// Windows paths with drive letters or backslashes; to manipulate
// operating system paths, use the path/filepath package.
package path
// A lazybuf is a lazily constructed path buffer.
// It supports append, reading previously appended bytes,
// and retrieving the final string. It does not allocate a buffer
// to hold the output until that output diverges from s.
type lazybuf struct {
s string
buf []byte
w int
}
func (b *lazybuf) index(i int) byte {
if b.buf != nil {
return b.buf[i]
}
return b.s[i]
}
func (b *lazybuf) append(c byte) {
if b.buf == nil {
if b.w < len(b.s) && b.s[b.w] == c {
b.w++
return
}
b.buf = make([]byte, len(b.s))
copy(b.buf, b.s[:b.w])
}
b.buf[b.w] = c
b.w++
}
func (b *lazybuf) string() string {
if b.buf == nil {
return b.s[:b.w]
}
return string(b.buf[:b.w])
}
// Clean returns the shortest path name equivalent to path
// by purely lexical processing. It applies the following rules
// iteratively until no further processing can be done:
//
// 1. Replace multiple slashes with a single slash.
// 2. Eliminate each . path name element (the current directory).
// 3. Eliminate each inner .. path name element (the parent directory)
// along with the non-.. element that precedes it.
// 4. Eliminate .. elements that begin a rooted path:
// that is, replace "/.." by "/" at the beginning of a path.
//
// The returned path ends in a slash only if it is the root "/".
//
// If the result of this process is an empty string, Clean
// returns the string ".".
//
// See also Rob Pike, ``Lexical File Names in Plan 9 or
// Getting Dot-Dot Right,''
// https://9p.io/sys/doc/lexnames.html
func Clean(path string) string {
if path == "" {
return "."
}
rooted := path[0] == '/'
n := len(path)
// Invariants:
// reading from path; r is index of next byte to process.
// writing to buf; w is index of next byte to write.
// dotdot is index in buf where .. must stop, either because
// it is the leading slash or it is a leading ../../.. prefix.
out := lazybuf{s: path}
r, dotdot := 0, 0
if rooted {
out.append('/')
r, dotdot = 1, 1
}
for r < n {
switch {
case path[r] == '/':
// empty path element
r++
case path[r] == '.' && (r+1 == n || path[r+1] == '/'):
// . element
r++
case path[r] == '.' && path[r+1] == '.' && (r+2 == n || path[r+2] == '/'):
// .. element: remove to last /
r += 2
switch {
case out.w > dotdot:
// can backtrack
out.w--
for out.w > dotdot && out.index(out.w) != '/' {
out.w--
}
case !rooted:
// cannot backtrack, but not rooted, so append .. element.
if out.w > 0 {
out.append('/')
}
out.append('.')
out.append('.')
dotdot = out.w
}
default:
// real path element.
// add slash if needed
if rooted && out.w != 1 || !rooted && out.w != 0 {
out.append('/')
}
// copy element
for ; r < n && path[r] != '/'; r++ {
out.append(path[r])
}
}
}
// Turn empty string into "."
if out.w == 0 {
return "."
}
return out.string()
}
// lastSlash(s) is strings.LastIndex(s, "/") but we can't import strings.
func lastSlash(s string) int {
i := len(s) - 1
for i >= 0 && s[i] != '/' {
i--
}
return i
}
// Split splits path immediately following the final slash,
// separating it into a directory and file name component.
// If there is no slash in path, Split returns an empty dir and
// file set to path.
// The returned values have the property that path = dir+file.
func Split(path string) (dir, file string) {
i := lastSlash(path)
return path[:i+1], path[i+1:]
}
// Join joins any number of path elements into a single path,
// separating them with slashes. Empty elements are ignored.
// The result is Cleaned. However, if the argument list is
// empty or all its elements are empty, Join returns
// an empty string.
func Join(elem ...string) string {
size := 0
for _, e := range elem {
size += len(e)
}
if size == 0 {
return ""
}
buf := make([]byte, 0, size+len(elem)-1)
for _, e := range elem {
if len(buf) > 0 || e != "" {
if len(buf) > 0 {
buf = append(buf, '/')
}
buf = append(buf, e...)
}
}
return Clean(string(buf))
}
// Ext returns the file name extension used by path.
// The extension is the suffix beginning at the final dot
// in the final slash-separated element of path;
// it is empty if there is no dot.
func Ext(path string) string {
for i := len(path) - 1; i >= 0 && path[i] != '/'; i-- {
if path[i] == '.' {
return path[i:]
}
}
return ""
}
// Base returns the last element of path.
// Trailing slashes are removed before extracting the last element.
// If the path is empty, Base returns ".".
// If the path consists entirely of slashes, Base returns "/".
func Base(path string) string {
if path == "" {
return "."
}
// Strip trailing slashes.
for len(path) > 0 && path[len(path)-1] == '/' {
path = path[0 : len(path)-1]
}
// Find the last element
if i := lastSlash(path); i >= 0 {
path = path[i+1:]
}
// If empty now, it had only slashes.
if path == "" {
return "/"
}
return path
}
// IsAbs reports whether the path is absolute.
func IsAbs(path string) bool {
return len(path) > 0 && path[0] == '/'
}
// Dir returns all but the last element of path, typically the path's directory.
// After dropping the final element using Split, the path is Cleaned and trailing
// slashes are removed.
// If the path is empty, Dir returns ".".
// If the path consists entirely of slashes followed by non-slash bytes, Dir
// returns a single slash. In any other case, the returned path does not end in a
// slash.
func Dir(path string) string {
dir, _ := Split(path)
return Clean(dir)
}
|
