Module combinator

List of parsers and combinators

Note: this list is meant to provide a nicer way to find a parser than reading through the documentation on docs.rs. Function combinators are organized in module so they are a bit easier to find.

Basic elements

Those are used to take a series of tokens for the lowest level elements of your grammar, like, “here is a dot”, or “here is an big endian integer”.

combinator	usage	input	new input	output	comment
one_of	one_of(['a', 'b', 'c'])	"abc"	"bc"	Ok('a')	Matches one of the provided set of tokens (works with non ASCII characters too)
none_of	none_of(['a', 'b', 'c'])	"xyab"	"yab"	Ok('x')	Matches anything but one of the provided set of tokens
literal	"hello"	"hello world"	" world"	Ok("hello")	Recognizes a specific suite of characters or bytes (see also Caseless)
take	take(4)	"hello"	"o"	Ok("hell")	Takes a specific number of bytes or characters
take_while	take_while(0.., is_alphabetic)	"abc123"	"123"	Ok("abc")	Returns the longest slice of bytes or characters for which the provided set of tokens matches.
take_till	take_till(0.., is_alphabetic)	"123abc"	"abc"	Ok("123")	Returns a slice of bytes or characters until the provided set of tokens matches. This is the reverse behaviour from take_while: take_till(f) is equivalent to take_while(0.., |c| !f(c))
take_until	take_until(0.., "world")	"Hello world"	"world"	Ok("Hello ")	Returns a slice of bytes or characters until the provided literal is found.

Choice combinators

combinator	usage	input	new input	output	comment
alt	alt(("ab", "cd"))	"cdef"	"ef"	Ok("cd")	Try a list of parsers and return the result of the first successful one
dispatch	-	-	-	-	match for parsers
permutation	permutation(("ab", "cd", "12"))	"cd12abc"	"c"	Ok(("ab", "cd", "12"))	Succeeds when all its child parser have succeeded, whatever the order

Sequence combinators

combinator	usage	input	new input	output	comment
(...) (tuples)	("ab", "XY", take(1))	"abXYZ!"	"!"	Ok(("ab", "XY", "Z"))	Parse a series of values
seq!	seq!(_: '(', take(2), _: ')')	"(ab)cd"	"cd"	Ok("ab")	Parse a series of values, discarding those you specify
delimited	delimited('(', take(2), ')')	"(ab)cd"	"cd"	Ok("ab")	Parse three values, discarding the first and third value
preceded	preceded("ab", "XY")	"abXYZ"	"Z"	Ok("XY")	Parse two values, discarding the first value
terminated	terminated("ab", "XY")	"abXYZ"	"Z"	Ok("ab")	Parse two values, discarding the second value
separated_pair	separated_pair("hello", ',', "world")	"hello,world!"	"!"	Ok(("hello", "world"))	Parse three values, discarding the middle value

Applying a parser multiple times

combinator	usage	input	new input	output	comment
repeat	repeat(1..=3, "ab")	"ababc"	"c"	Ok(vec!["ab", "ab"])	Applies the parser between m and n times (n included) and returns the list of results in a Vec
repeat_till	repeat_till(0.., "ab", "ef")	"ababefg"	"g"	Ok((vec!["ab", "ab"], "ef"))	Applies the first parser until the second applies. Returns a tuple containing the list of results from the first in a Vec and the result of the second
separated	separated(1..=3, "ab", ",")	"ab,ab,ab."	"."	Ok(vec!["ab", "ab", "ab"])	Applies the parser and separator between m and n times (n included) and returns the list of results in a Vec
Repeat::fold	repeat(1..=2, be_u8).fold(|| 0, |acc, item| acc + item)	[1, 2, 3]	[3]	Ok(3)	Applies the parser between m and n times (n included) and folds the list of return value

Partial related

• eof: Returns its input if it is at the end of input data
• Parser::complete_err: Replaces an Incomplete returned by the child parser with an Backtrack

Modifiers

• cond: Conditional combinator. Wraps another parser and calls it if the condition is met
• Parser::flat_map: method to map a new parser from the output of the first parser, then apply that parser over the rest of the input
• Parser::value: method to replace the result of a parser
• Parser::default_value: method to replace the result of a parser
• Parser::void: method to discard the result of a parser
• Parser::map: method to map a function on the result of a parser
• Parser::and_then: Applies a second parser over the output of the first one
• Parser::verify_map: Maps a function returning an Option on the output of a parser
• Parser::try_map: Maps a function returning a Result on the output of a parser
• Parser::parse_to: Apply std::str::FromStr to the output of the parser
• not: Returns a result only if the embedded parser returns Backtrack or Incomplete. Does not consume the input
• opt: Make the underlying parser optional
• peek: Returns a result without consuming the input
• Parser::take: If the child parser was successful, return the consumed input as the produced value
• Parser::with_taken: If the child parser was successful, return a tuple of the consumed input and the produced output.
• Parser::span: If the child parser was successful, return the location of the consumed input as the produced value
• Parser::with_span: If the child parser was successful, return a tuple of the location of the consumed input and the produced output.
• Parser::verify: Returns the result of the child parser if it satisfies a verification function

Error management and debugging

• cut_err: Commit the parse result, disallowing alternative parsers from being attempted
• backtrack_err: Attempts a parse, allowing alternative parsers to be attempted despite use of cut_err
• Parser::context: Add context to the error if the parser fails
• trace: Print the parse state with the debug feature flag
• todo(): Placeholder parser

Remaining combinators

• empty: Succeed, consuming no input
• fail: Inversion of empty. Always fails.
• Parser::by_ref: Allow moving &mut impl Parser into other parsers

Text parsing

• any: Matches one token

• tab: Matches a tab character \t

• crlf: Recognizes the string \r\n

• line_ending: Recognizes an end of line (both \n and \r\n)

• newline: Matches a newline character \n

• till_line_ending: Recognizes a string of any char except \r or \n

• rest: Return the remaining input

• alpha0: Recognizes zero or more lowercase and uppercase alphabetic characters: [a-zA-Z]. alpha1 does the same but returns at least one character

• alphanumeric0: Recognizes zero or more numerical and alphabetic characters: [0-9a-zA-Z]. alphanumeric1 does the same but returns at least one character

• space0: Recognizes zero or more spaces and tabs. space1 does the same but returns at least one character

• multispace0: Recognizes zero or more spaces, tabs, carriage returns and line feeds. multispace1 does the same but returns at least one character

• digit0: Recognizes zero or more numerical characters: [0-9]. digit1 does the same but returns at least one character

• hex_digit0: Recognizes zero or more hexadecimal numerical characters: [0-9A-Fa-f]. hex_digit1 does the same but returns at least one character

• oct_digit0: Recognizes zero or more octal characters: [0-7]. oct_digit1 does the same but returns at least one character

• float: Parse a floating point number in a byte string

• dec_int: Decode a variable-width, decimal signed integer

• dec_uint: Decode a variable-width, decimal unsigned integer

• hex_uint: Decode a variable-width, hexadecimal integer

• take_escaped: Recognize the input slice with escaped characters

• escaped_transform: Parse escaped characters, unescaping them

Character test functions

Use these functions with a combinator like take_while:

• AsChar::is_alpha: Tests if byte is ASCII alphabetic: [A-Za-z]
• AsChar::is_alphanum: Tests if byte is ASCII alphanumeric: [A-Za-z0-9]
• AsChar::is_dec_digit: Tests if byte is ASCII digit: [0-9]
• AsChar::is_hex_digit: Tests if byte is ASCII hex digit: [0-9A-Fa-f]
• AsChar::is_oct_digit: Tests if byte is ASCII octal digit: [0-7]
• AsChar::is_space: Tests if byte is ASCII space or tab: [ \t]
• AsChar::is_newline: Tests if byte is ASCII newline: [\n]

Binary format parsing

• length_repeat Gets a number from the first parser, then applies the second parser that many times
• length_take: Gets a number from the first parser, then takes a subslice of the input of that size, and returns that subslice
• length_and_then: Gets a number from the first parser, takes a subslice of the input of that size, then applies the second parser on that subslice. If the second parser returns Incomplete, length_value will return an error

Integers

Parsing integers from binary formats can be done in two ways: With parser functions, or combinators with configurable endianness.

• configurable endianness: i16, i32, i64, u16, u32, u64 are combinators that take as argument a winnow::binary::Endianness, like this: i16(endianness). If the parameter is winnow::binary::Endianness::Big, parse a big endian i16 integer, otherwise a little endian i16 integer.
• fixed endianness: The functions are prefixed by be_ for big endian numbers, and by le_ for little endian numbers, and the suffix is the type they parse to. As an example, be_u32 parses a big endian unsigned integer stored in 32 bits.
  • be_f32, be_f64: Big endian floating point numbers
  • le_f32, le_f64: Little endian floating point numbers
  • be_i8, be_i16, be_i24, be_i32, be_i64, be_i128: Big endian signed integers
  • be_u8, be_u16, be_u24, be_u32, be_u64, be_u128: Big endian unsigned integers
  • le_i8, le_i16, le_i24, le_i32, le_i64, le_i128: Little endian signed integers
  • le_u8, le_u16, le_u24, le_u32, le_u64, le_u128: Little endian unsigned integers

Bit stream parsing

• bits: Transforms the current input type (byte slice &[u8]) to a bit stream on which bit specific parsers and more general combinators can be applied
• bytes: Transforms its bits stream input back into a byte slice for the underlying parser
• take: Take a set number of bits
• pattern: Check if a set number of bits matches a pattern
• bool: Match any one bit

Modules

impls

Opaque implementations of Parser

Macros

dispatch

match for parsers

seq

Initialize a struct or tuple out of a sequences of parsers

Structs

ParserIterator

Main structure associated to iterator.

Repeat

Customizable Parser implementation for repeat

Traits

Alt

Helper trait for the alt() combinator.

Permutation

Helper trait for the permutation() combinator.

Functions

alt

Pick the first successful parser

backtrack_err

Transforms an ErrMode::Cut (unrecoverable) to ErrMode::Backtrack (recoverable)

cond

Calls the parser if the condition is met.

cut_err

Transforms an ErrMode::Backtrack (recoverable) to ErrMode::Cut (unrecoverable)

delimited

Sequence three parsers, only returning the output of the second.

empty

Succeed, consuming no input

eof

Match the end of the Stream

fail

A parser which always fails.

fill

Repeats the embedded parser, filling the given slice with results.

iterator

Repeats the embedded parser, lazily returning the results

not

Succeeds if the child parser returns an error.

opt

Apply a Parser, producing None on ErrMode::Backtrack.

peek

Apply the parser without advancing the input.

permutation

Applies a list of parsers in any order.

preceded

Sequence two parsers, only returning the output from the second.

repeat

Accumulate the output of a parser into a container, like Vec

repeat_till

Accumulate the output of parser f into a container, like Vec, until the parser g produces a result.

separated

Accumulate the output of a parser, interleaved with sep

separated_foldl1

Alternates between two parsers, merging the results (left associative)

separated_foldr1

Alternates between two parsers, merging the results (right associative)

separated_pair

Sequence three parsers, only returning the values of the first and third.

terminated

Sequence two parsers, only returning the output of the first.

todo

A placeholder for a not-yet-implemented Parser

trace

Trace the execution of the parser