This repository has been archived by the owner on Aug 5, 2018. It is now read-only.
-
Notifications
You must be signed in to change notification settings - Fork 52
/
path.go
123 lines (103 loc) · 2.6 KB
/
path.go
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
// Copyright 2013 Julien Schmidt. All rights reserved.
// Based on the path package, Copyright 2009 The Go Authors.
// Use of this source code is governed by a BSD-style license that can be found
// in the LICENSE file.
package gin
// CleanPath is the URL version of path.Clean, it returns a canonical URL path
// for p, eliminating . and .. elements.
//
// The following rules are applied 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.
//
// If the result of this process is an empty string, "/" is returned
func cleanPath(p string) string {
// Turn empty string into "/"
if p == "" {
return "/"
}
n := len(p)
var buf []byte
// Invariants:
// reading from path; r is index of next byte to process.
// writing to buf; w is index of next byte to write.
// path must start with '/'
r := 1
w := 1
if p[0] != '/' {
r = 0
buf = make([]byte, n+1)
buf[0] = '/'
}
trailing := n > 2 && p[n-1] == '/'
// A bit more clunky without a 'lazybuf' like the path package, but the loop
// gets completely inlined (bufApp). So in contrast to the path package this
// loop has no expensive function calls (except 1x make)
for r < n {
switch {
case p[r] == '/':
// empty path element, trailing slash is added after the end
r++
case p[r] == '.' && r+1 == n:
trailing = true
r++
case p[r] == '.' && p[r+1] == '/':
// . element
r++
case p[r] == '.' && p[r+1] == '.' && (r+2 == n || p[r+2] == '/'):
// .. element: remove to last /
r += 2
if w > 1 {
// can backtrack
w--
if buf == nil {
for w > 1 && p[w] != '/' {
w--
}
} else {
for w > 1 && buf[w] != '/' {
w--
}
}
}
default:
// real path element.
// add slash if needed
if w > 1 {
bufApp(&buf, p, w, '/')
w++
}
// copy element
for r < n && p[r] != '/' {
bufApp(&buf, p, w, p[r])
w++
r++
}
}
}
// re-append trailing slash
if trailing && w > 1 {
bufApp(&buf, p, w, '/')
w++
}
if buf == nil {
return p[:w]
}
return string(buf[:w])
}
// internal helper to lazily create a buffer if necessary
func bufApp(buf *[]byte, s string, w int, c byte) {
if *buf == nil {
if s[w] == c {
return
}
*buf = make([]byte, len(s))
copy(*buf, s[:w])
}
(*buf)[w] = c
}