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
|
// Copyright 2014 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 webdav
// The If header is covered by Section 10.4.
// http://www.webdav.org/specs/rfc4918.html#HEADER_If
import (
"strings"
)
// ifHeader is a disjunction (OR) of ifLists.
type ifHeader struct {
lists []ifList
}
// ifList is a conjunction (AND) of Conditions, and an optional resource tag.
type ifList struct {
resourceTag string
conditions []Condition
}
// parseIfHeader parses the "If: foo bar" HTTP header. The httpHeader string
// should omit the "If:" prefix and have any "\r\n"s collapsed to a " ", as is
// returned by req.Header.Get("If") for a http.Request req.
func parseIfHeader(httpHeader string) (h ifHeader, ok bool) {
s := strings.TrimSpace(httpHeader)
switch tokenType, _, _ := lex(s); tokenType {
case '(':
return parseNoTagLists(s)
case angleTokenType:
return parseTaggedLists(s)
default:
return ifHeader{}, false
}
}
func parseNoTagLists(s string) (h ifHeader, ok bool) {
for {
l, remaining, ok := parseList(s)
if !ok {
return ifHeader{}, false
}
h.lists = append(h.lists, l)
if remaining == "" {
return h, true
}
s = remaining
}
}
func parseTaggedLists(s string) (h ifHeader, ok bool) {
resourceTag, n := "", 0
for first := true; ; first = false {
tokenType, tokenStr, remaining := lex(s)
switch tokenType {
case angleTokenType:
if !first && n == 0 {
return ifHeader{}, false
}
resourceTag, n = tokenStr, 0
s = remaining
case '(':
n++
l, remaining, ok := parseList(s)
if !ok {
return ifHeader{}, false
}
l.resourceTag = resourceTag
h.lists = append(h.lists, l)
if remaining == "" {
return h, true
}
s = remaining
default:
return ifHeader{}, false
}
}
}
func parseList(s string) (l ifList, remaining string, ok bool) {
tokenType, _, s := lex(s)
if tokenType != '(' {
return ifList{}, "", false
}
for {
tokenType, _, remaining = lex(s)
if tokenType == ')' {
if len(l.conditions) == 0 {
return ifList{}, "", false
}
return l, remaining, true
}
c, remaining, ok := parseCondition(s)
if !ok {
return ifList{}, "", false
}
l.conditions = append(l.conditions, c)
s = remaining
}
}
func parseCondition(s string) (c Condition, remaining string, ok bool) {
tokenType, tokenStr, s := lex(s)
if tokenType == notTokenType {
c.Not = true
tokenType, tokenStr, s = lex(s)
}
switch tokenType {
case strTokenType, angleTokenType:
c.Token = tokenStr
case squareTokenType:
c.ETag = tokenStr
default:
return Condition{}, "", false
}
return c, s, true
}
// Single-rune tokens like '(' or ')' have a token type equal to their rune.
// All other tokens have a negative token type.
const (
errTokenType = rune(-1)
eofTokenType = rune(-2)
strTokenType = rune(-3)
notTokenType = rune(-4)
angleTokenType = rune(-5)
squareTokenType = rune(-6)
)
func lex(s string) (tokenType rune, tokenStr string, remaining string) {
// The net/textproto Reader that parses the HTTP header will collapse
// Linear White Space that spans multiple "\r\n" lines to a single " ",
// so we don't need to look for '\r' or '\n'.
for len(s) > 0 && (s[0] == '\t' || s[0] == ' ') {
s = s[1:]
}
if len(s) == 0 {
return eofTokenType, "", ""
}
i := 0
loop:
for ; i < len(s); i++ {
switch s[i] {
case '\t', ' ', '(', ')', '<', '>', '[', ']':
break loop
}
}
if i != 0 {
tokenStr, remaining = s[:i], s[i:]
if tokenStr == "Not" {
return notTokenType, "", remaining
}
return strTokenType, tokenStr, remaining
}
j := 0
switch s[0] {
case '<':
j, tokenType = strings.IndexByte(s, '>'), angleTokenType
case '[':
j, tokenType = strings.IndexByte(s, ']'), squareTokenType
default:
return rune(s[0]), "", s[1:]
}
if j < 0 {
return errTokenType, "", ""
}
return tokenType, s[1:j], s[j+1:]
}
|
