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// Copyright 2013 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 or at
// https://developers.google.com/open-source/licenses/bsd.
// Package header provides functions for parsing HTTP headers.
package header
import (
"net/http"
"strings"
"time"
)
// Octet types from RFC 2616.
var octetTypes [256]octetType
type octetType byte
const (
isToken octetType = 1 << iota
isSpace
)
func init() {
// OCTET = <any 8-bit sequence of data>
// CHAR = <any US-ASCII character (octets 0 - 127)>
// CTL = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
// CR = <US-ASCII CR, carriage return (13)>
// LF = <US-ASCII LF, linefeed (10)>
// SP = <US-ASCII SP, space (32)>
// HT = <US-ASCII HT, horizontal-tab (9)>
// <"> = <US-ASCII double-quote mark (34)>
// CRLF = CR LF
// LWS = [CRLF] 1*( SP | HT )
// TEXT = <any OCTET except CTLs, but including LWS>
// separators = "(" | ")" | "<" | ">" | "@" | "," | ";" | ":" | "\" | <">
// | "/" | "[" | "]" | "?" | "=" | "{" | "}" | SP | HT
// token = 1*<any CHAR except CTLs or separators>
// qdtext = <any TEXT except <">>
for c := 0; c < 256; c++ {
var t octetType
isCtl := c <= 31 || c == 127
isChar := 0 <= c && c <= 127
isSeparator := strings.IndexRune(" \t\"(),/:;<=>?@[]\\{}", rune(c)) >= 0
if strings.IndexRune(" \t\r\n", rune(c)) >= 0 {
t |= isSpace
}
if isChar && !isCtl && !isSeparator {
t |= isToken
}
octetTypes[c] = t
}
}
// Copy returns a shallow copy of the header.
func Copy(header http.Header) http.Header {
h := make(http.Header)
for k, vs := range header {
h[k] = vs
}
return h
}
var timeLayouts = []string{"Mon, 02 Jan 2006 15:04:05 GMT", time.RFC850, time.ANSIC}
// ParseTime parses the header as time. The zero value is returned if the
// header is not present or there is an error parsing the
// header.
func ParseTime(header http.Header, key string) time.Time {
if s := header.Get(key); s != "" {
for _, layout := range timeLayouts {
if t, err := time.Parse(layout, s); err == nil {
return t.UTC()
}
}
}
return time.Time{}
}
// ParseList parses a comma separated list of values. Commas are ignored in
// quoted strings. Quoted values are not unescaped or unquoted. Whitespace is
// trimmed.
func ParseList(header http.Header, key string) []string {
var result []string
for _, s := range header[http.CanonicalHeaderKey(key)] {
begin := 0
end := 0
escape := false
quote := false
for i := 0; i < len(s); i++ {
b := s[i]
switch {
case escape:
escape = false
end = i + 1
case quote:
switch b {
case '\\':
escape = true
case '"':
quote = false
}
end = i + 1
case b == '"':
quote = true
end = i + 1
case octetTypes[b]&isSpace != 0:
if begin == end {
begin = i + 1
end = begin
}
case b == ',':
if begin < end {
result = append(result, s[begin:end])
}
begin = i + 1
end = begin
default:
end = i + 1
}
}
if begin < end {
result = append(result, s[begin:end])
}
}
return result
}
// ParseValueAndParams parses a comma separated list of values with optional
// semicolon separated name-value pairs. Content-Type and Content-Disposition
// headers are in this format.
func ParseValueAndParams(header http.Header, key string) (value string, params map[string]string) {
params = make(map[string]string)
s := header.Get(key)
value, s = expectTokenSlash(s)
if value == "" {
return
}
value = strings.ToLower(value)
s = skipSpace(s)
for strings.HasPrefix(s, ";") {
var pkey string
pkey, s = expectToken(skipSpace(s[1:]))
if pkey == "" {
return
}
if !strings.HasPrefix(s, "=") {
return
}
var pvalue string
pvalue, s = expectTokenOrQuoted(s[1:])
if pvalue == "" {
return
}
pkey = strings.ToLower(pkey)
params[pkey] = pvalue
s = skipSpace(s)
}
return
}
type AcceptSpec struct {
Value string
Q float64
}
// ParseAccept parses Accept* headers.
func ParseAccept(header http.Header, key string) (specs []AcceptSpec) {
loop:
for _, s := range header[key] {
for {
var spec AcceptSpec
spec.Value, s = expectTokenSlash(s)
if spec.Value == "" {
continue loop
}
spec.Q = 1.0
s = skipSpace(s)
if strings.HasPrefix(s, ";") {
s = skipSpace(s[1:])
if !strings.HasPrefix(s, "q=") {
continue loop
}
spec.Q, s = expectQuality(s[2:])
if spec.Q < 0.0 {
continue loop
}
}
specs = append(specs, spec)
s = skipSpace(s)
if !strings.HasPrefix(s, ",") {
continue loop
}
s = skipSpace(s[1:])
}
}
return
}
func skipSpace(s string) (rest string) {
i := 0
for ; i < len(s); i++ {
if octetTypes[s[i]]&isSpace == 0 {
break
}
}
return s[i:]
}
func expectToken(s string) (token, rest string) {
i := 0
for ; i < len(s); i++ {
if octetTypes[s[i]]&isToken == 0 {
break
}
}
return s[:i], s[i:]
}
func expectTokenSlash(s string) (token, rest string) {
i := 0
for ; i < len(s); i++ {
b := s[i]
if (octetTypes[b]&isToken == 0) && b != '/' {
break
}
}
return s[:i], s[i:]
}
func expectQuality(s string) (q float64, rest string) {
switch {
case len(s) == 0:
return -1, ""
case s[0] == '0':
q = 0
case s[0] == '1':
q = 1
default:
return -1, ""
}
s = s[1:]
if !strings.HasPrefix(s, ".") {
return q, s
}
s = s[1:]
i := 0
n := 0
d := 1
for ; i < len(s); i++ {
b := s[i]
if b < '0' || b > '9' {
break
}
n = n*10 + int(b) - '0'
d *= 10
}
return q + float64(n)/float64(d), s[i:]
}
func expectTokenOrQuoted(s string) (value string, rest string) {
if !strings.HasPrefix(s, "\"") {
return expectToken(s)
}
s = s[1:]
for i := 0; i < len(s); i++ {
switch s[i] {
case '"':
return s[:i], s[i+1:]
case '\\':
p := make([]byte, len(s)-1)
j := copy(p, s[:i])
escape := true
for i = i + 1; i < len(s); i++ {
b := s[i]
switch {
case escape:
escape = false
p[j] = b
j += 1
case b == '\\':
escape = true
case b == '"':
return string(p[:j]), s[i+1:]
default:
p[j] = b
j += 1
}
}
return "", ""
}
}
return "", ""
}