ABNF Parser
Introduction
ABNF Parser
What is ABNF ?
BNF is the most common tool to define computer language in computer field.
BNF or Extended BNF (EBNF) can define languages including C language, Pascal language and Java language.
The Augmented BNF (ABNF – another kind of BNF), due to its simple but powerful features,
has become the most commonly used definition tool for textual descriptive language on the internet.
ABNF is adopted as the standardized definition for textual descriptive language in most areas of the Internet.
In the RFC documents collection of IETF (The Internet Engineering Task Force), RFC2234 is a special instruction
describing ABNF specification and its core rules.
ABNF itself can be defined by ABNF. The defined syntax of its core rule is:
rulelist = 1*(rule / (*c-wsp c-nl))
rule = rulename defined-as elements c-nl; continues if next line starts; with white space
rulename = ALPHA *(ALPHA / DIGIT / "-")
defined-as = *c-wsp ("=" / "=/") *c-wsp; basic rules definition and; incremental alternatives
elements = alternation *c-wsp
c-wsp = WSP / (c-nl WSP)
c-nl = comment / CRLF; comment or newline
comment = ";" *(WSP / VCHAR) CRLF
alternation = concatenation *(*c-wsp "/" *c-wsp concatenation)
concatenation = repetition *(1*c-wsp repetition)
repetition = [repeat] element
repeat = 1*DIGIT / (*DIGIT "*" *DIGIT)
element = rulename / group / option / char-val / num-val / prose-val
group = "(" *c-wsp alternation *c-wsp ")"
option = "[" *c-wsp alternation *c-wsp "]"
char-val = DQUOTE *(%x20-21 / %x23-7E) DQUOTE; quoted string of SP and VCHAR without DQUOTE
num-val = "%" (bin-val / dec-val / hex-val)
bin-val = "b" 1*BIT [1*("." 1*BIT) / ("-" 1*BIT)]; series of concatenated bit values; or single ONEOF range
dec-val = "d" 1*DIGIT [1*("." 1*DIGIT) / ("-" 1*DIGIT)]
hex-val = "x" 1*HEXDIG [1*("." 1*HEXDIG) / ("-" 1*HEXDIG)]
prose-val = "<" *(%x20-3D / %x3F-7E) ">"; bracketed string of SP and VCHAR without angles; prose description, to be used as last resort
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
BIT = "0" / "1"
CHAR = %x01-7F; any 7-bit US-ASCII character, excluding NUL
CR = %x0D; carriage return
CRLF = CR LF; Internet standard newline
CTL = %x00-1F / %x7F; controls
DIGIT = %x30-39; 0-9
DQUOTE = %x22;" (Double Quote)
HEXDIG = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
HTAB = %x09; horizontal tab
LF = %x0A; linefeed
LWSP = *(WSP / CRLF WSP); linear white space (past newline)
OCTET = %x00-FF; 8 bits of data
SP = %x20; space
VCHAR = %x21-7E; visible (printing) characters
WSP = SP / HTAB; white space
rule = rulename defined-as elements c-nl; continues if next line starts; with white space
rulename = ALPHA *(ALPHA / DIGIT / "-")
defined-as = *c-wsp ("=" / "=/") *c-wsp; basic rules definition and; incremental alternatives
elements = alternation *c-wsp
c-wsp = WSP / (c-nl WSP)
c-nl = comment / CRLF; comment or newline
comment = ";" *(WSP / VCHAR) CRLF
alternation = concatenation *(*c-wsp "/" *c-wsp concatenation)
concatenation = repetition *(1*c-wsp repetition)
repetition = [repeat] element
repeat = 1*DIGIT / (*DIGIT "*" *DIGIT)
element = rulename / group / option / char-val / num-val / prose-val
group = "(" *c-wsp alternation *c-wsp ")"
option = "[" *c-wsp alternation *c-wsp "]"
char-val = DQUOTE *(%x20-21 / %x23-7E) DQUOTE; quoted string of SP and VCHAR without DQUOTE
num-val = "%" (bin-val / dec-val / hex-val)
bin-val = "b" 1*BIT [1*("." 1*BIT) / ("-" 1*BIT)]; series of concatenated bit values; or single ONEOF range
dec-val = "d" 1*DIGIT [1*("." 1*DIGIT) / ("-" 1*DIGIT)]
hex-val = "x" 1*HEXDIG [1*("." 1*HEXDIG) / ("-" 1*HEXDIG)]
prose-val = "<" *(%x20-3D / %x3F-7E) ">"; bracketed string of SP and VCHAR without angles; prose description, to be used as last resort
ALPHA = %x41-5A / %x61-7A ; A-Z / a-z
BIT = "0" / "1"
CHAR = %x01-7F; any 7-bit US-ASCII character, excluding NUL
CR = %x0D; carriage return
CRLF = CR LF; Internet standard newline
CTL = %x00-1F / %x7F; controls
DIGIT = %x30-39; 0-9
DQUOTE = %x22;" (Double Quote)
HEXDIG = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"
HTAB = %x09; horizontal tab
LF = %x0A; linefeed
LWSP = *(WSP / CRLF WSP); linear white space (past newline)
OCTET = %x00-FF; 8 bits of data
SP = %x20; space
VCHAR = %x21-7E; visible (printing) characters
WSP = SP / HTAB; white space
