扩充的BNF（Backus-Naur Form）

name = definition

空格的价值：HTTP/1.1 的消息头域值可以折叠成多行，但紧接着的被折叠行由空格（SP）或水平制表（HT）折叠标记开始。所有的线性空白（LWS）包括被折叠行的折叠标记（空格SP或水平制表键HT），具有同SP一样的语义。

"literal" 大小写不明感

rule1 | rule2    匹配当中的任一个

(rule1 rule2)    将其看作一个整体

*rule    允许0到无限个规则

<n>*<m>(rule)    允许n到m次规则

[rule]    *1rule

Nrule    <n>(rule)        <n>*<n>(rule)

#rule    eg: 1#element等同为 ( *LWS element *( *LWS "," *LWS element ))

;    注释

 

OCTET = <any 8-bit sequence of data>

CHAR = <any US-ASCII character (octets 0 - 127)>

UPALPHA = <any US-ASCII uppercase letter "A".."Z">

LOALPHA = <any US-ASCII lowercase letter "a".."z">

ALPHA = UPALPHA | LOALPHA

DIGIT = <any US-ASCII digit "0".."9">

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    任何协议元素的行尾标志

LWS = [CRLF] 1*(SP | HT)    线性空白

TEXT = <除CTLs以外的任意OCTET，但包括LWS>

HEX = "A" | "B" | "C" | "D" | "E" | "F" | "a" | "b" | "c" | "d" | "e" | "f" | DIGIT

separators（分割符） = "(" | ")" | "<" | ">" | "@" | "," | ";" | ":" | """ | <"> | "/" | "[" | "]" | "?" | "=" | "{" | "}" | SP | HT

token（标记） = 1*<除CTLs与分割符以外的任意CHAR>

comment = "(" *( ctext | quoted-pair | comment ) ")"    注释

ctext = <除"(" 和 ")"以外的任意TEXT >    注释文本

quoted-string = ( <"> *(qdtext | quoted-pair ) <"> )

qdtext = <any TEXT except <">>

quoted-pair = "\" CHAR