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// 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:]
}
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