nom/

lib.rs

//! # nom, eating data byte by byte
//!
//! nom is a parser combinator library with a focus on safe parsing,
//! streaming patterns, and as much as possible zero copy.
//!
//! ## Example
//!
//! ```rust
//! use nom::{
//!   IResult,
//!   bytes::complete::{tag, take_while_m_n},
//!   combinator::map_res,
//!   sequence::tuple};
//!
//! #[derive(Debug,PartialEq)]
//! pub struct Color {
//!   pub red:     u8,
//!   pub green:   u8,
//!   pub blue:    u8,
//! }
//!
//! fn from_hex(input: &str) -> Result<u8, std::num::ParseIntError> {
//!   u8::from_str_radix(input, 16)
//! }
//!
//! fn is_hex_digit(c: char) -> bool {
//!   c.is_digit(16)
//! }
//!
//! fn hex_primary(input: &str) -> IResult<&str, u8> {
//!   map_res(
//!     take_while_m_n(2, 2, is_hex_digit),
//!     from_hex
//!   )(input)
//! }
//!
//! fn hex_color(input: &str) -> IResult<&str, Color> {
//!   let (input, _) = tag("#")(input)?;
//!   let (input, (red, green, blue)) = tuple((hex_primary, hex_primary, hex_primary))(input)?;
//!
//!   Ok((input, Color { red, green, blue }))
//! }
//!
//! fn main() {
//!   assert_eq!(hex_color("#2F14DF"), Ok(("", Color {
//!     red: 47,
//!     green: 20,
//!     blue: 223,
//!   })));
//! }
//! ```
//!
//! The code is available on [Github](https://github.com/Geal/nom)
//!
//! There are a few [guides](https://github.com/Geal/nom/tree/main/doc) with more details
//! about [how to write parsers](https://github.com/Geal/nom/blob/main/doc/making_a_new_parser_from_scratch.md),
//! or the [error management system](https://github.com/Geal/nom/blob/main/doc/error_management.md).
//! You can also check out the [recipes] module that contains examples of common patterns.
//!
//! **Looking for a specific combinator? Read the
//! ["choose a combinator" guide](https://github.com/Geal/nom/blob/main/doc/choosing_a_combinator.md)**
//!
//! If you are upgrading to nom 5.0, please read the
//! [migration document](https://github.com/Geal/nom/blob/main/doc/upgrading_to_nom_5.md).
//!
//! ## Parser combinators
//!
//! Parser combinators are an approach to parsers that is very different from
//! software like [lex](https://en.wikipedia.org/wiki/Lex_(software)) and
//! [yacc](https://en.wikipedia.org/wiki/Yacc). Instead of writing the grammar
//! in a separate syntax and generating the corresponding code, you use very small
//! functions with very specific purposes, like "take 5 bytes", or "recognize the
//! word 'HTTP'", and assemble them in meaningful patterns like "recognize
//! 'HTTP', then a space, then a version".
//! The resulting code is small, and looks like the grammar you would have
//! written with other parser approaches.
//!
//! This gives us a few advantages:
//!
//! - The parsers are small and easy to write
//! - The parsers components are easy to reuse (if they're general enough, please add them to nom!)
//! - The parsers components are easy to test separately (unit tests and property-based tests)
//! - The parser combination code looks close to the grammar you would have written
//! - You can build partial parsers, specific to the data you need at the moment, and ignore the rest
//!
//! Here is an example of one such parser, to recognize text between parentheses:
//!
//! ```rust
//! use nom::{
//!   IResult,
//!   sequence::delimited,
//!   // see the "streaming/complete" paragraph lower for an explanation of these submodules
//!   character::complete::char,
//!   bytes::complete::is_not
//! };
//!
//! fn parens(input: &str) -> IResult<&str, &str> {
//!   delimited(char('('), is_not(")"), char(')'))(input)
//! }
//! ```
//!
//! It defines a function named `parens` which will recognize a sequence of the
//! character `(`, the longest byte array not containing `)`, then the character
//! `)`, and will return the byte array in the middle.
//!
//! Here is another parser, written without using nom's combinators this time:
//!
//! ```rust
//! use nom::{IResult, Err, Needed};
//!
//! # fn main() {
//! fn take4(i: &[u8]) -> IResult<&[u8], &[u8]>{
//!   if i.len() < 4 {
//!     Err(Err::Incomplete(Needed::new(4)))
//!   } else {
//!     Ok((&i[4..], &i[0..4]))
//!   }
//! }
//! # }
//! ```
//!
//! This function takes a byte array as input, and tries to consume 4 bytes.
//! Writing all the parsers manually, like this, is dangerous, despite Rust's
//! safety features. There are still a lot of mistakes one can make. That's why
//! nom provides a list of functions to help in developing parsers.
//!
//! With functions, you would write it like this:
//!
//! ```rust
//! use nom::{IResult, bytes::streaming::take};
//! fn take4(input: &str) -> IResult<&str, &str> {
//!   take(4u8)(input)
//! }
//! ```
//!
//! A parser in nom is a function which, for an input type `I`, an output type `O`
//! and an optional error type `E`, will have the following signature:
//!
//! ```rust,compile_fail
//! fn parser(input: I) -> IResult<I, O, E>;
//! ```
//!
//! Or like this, if you don't want to specify a custom error type (it will be `(I, ErrorKind)` by default):
//!
//! ```rust,compile_fail
//! fn parser(input: I) -> IResult<I, O>;
//! ```
//!
//! `IResult` is an alias for the `Result` type:
//!
//! ```rust
//! use nom::{Needed, error::Error};
//!
//! type IResult<I, O, E = Error<I>> = Result<(I, O), Err<E>>;
//!
//! enum Err<E> {
//!   Incomplete(Needed),
//!   Error(E),
//!   Failure(E),
//! }
//! ```
//!
//! It can have the following values:
//!
//! - A correct result `Ok((I,O))` with the first element being the remaining of the input (not parsed yet), and the second the output value;
//! - An error `Err(Err::Error(c))` with `c` an error that can be built from the input position and a parser specific error
//! - An error `Err(Err::Incomplete(Needed))` indicating that more input is necessary. `Needed` can indicate how much data is needed
//! - An error `Err(Err::Failure(c))`. It works like the `Error` case, except it indicates an unrecoverable error: We cannot backtrack and test another parser
//!
//! Please refer to the ["choose a combinator" guide](https://github.com/Geal/nom/blob/main/doc/choosing_a_combinator.md) for an exhaustive list of parsers.
//! See also the rest of the documentation [here](https://github.com/Geal/nom/blob/main/doc).
//!
//! ## Making new parsers with function combinators
//!
//! nom is based on functions that generate parsers, with a signature like
//! this: `(arguments) -> impl Fn(Input) -> IResult<Input, Output, Error>`.
//! The arguments of a combinator can be direct values (like `take` which uses
//! a number of bytes or character as argument) or even other parsers (like
//! `delimited` which takes as argument 3 parsers, and returns the result of
//! the second one if all are successful).
//!
//! Here are some examples:
//!
//! ```rust
//! use nom::IResult;
//! use nom::bytes::complete::{tag, take};
//! fn abcd_parser(i: &str) -> IResult<&str, &str> {
//!   tag("abcd")(i) // will consume bytes if the input begins with "abcd"
//! }
//!
//! fn take_10(i: &[u8]) -> IResult<&[u8], &[u8]> {
//!   take(10u8)(i) // will consume and return 10 bytes of input
//! }
//! ```
//!
//! ## Combining parsers
//!
//! There are higher level patterns, like the **`alt`** combinator, which
//! provides a choice between multiple parsers. If one branch fails, it tries
//! the next, and returns the result of the first parser that succeeds:
//!
//! ```rust
//! use nom::IResult;
//! use nom::branch::alt;
//! use nom::bytes::complete::tag;
//!
//! let mut alt_tags = alt((tag("abcd"), tag("efgh")));
//!
//! assert_eq!(alt_tags(&b"abcdxxx"[..]), Ok((&b"xxx"[..], &b"abcd"[..])));
//! assert_eq!(alt_tags(&b"efghxxx"[..]), Ok((&b"xxx"[..], &b"efgh"[..])));
//! assert_eq!(alt_tags(&b"ijklxxx"[..]), Err(nom::Err::Error((&b"ijklxxx"[..], nom::error::ErrorKind::Tag))));
//! ```
//!
//! The **`opt`** combinator makes a parser optional. If the child parser returns
//! an error, **`opt`** will still succeed and return None:
//!
//! ```rust
//! use nom::{IResult, combinator::opt, bytes::complete::tag};
//! fn abcd_opt(i: &[u8]) -> IResult<&[u8], Option<&[u8]>> {
//!   opt(tag("abcd"))(i)
//! }
//!
//! assert_eq!(abcd_opt(&b"abcdxxx"[..]), Ok((&b"xxx"[..], Some(&b"abcd"[..]))));
//! assert_eq!(abcd_opt(&b"efghxxx"[..]), Ok((&b"efghxxx"[..], None)));
//! ```
//!
//! **`many0`** applies a parser 0 or more times, and returns a vector of the aggregated results:
//!
//! ```rust
//! # #[cfg(feature = "alloc")]
//! # fn main() {
//! use nom::{IResult, multi::many0, bytes::complete::tag};
//! use std::str;
//!
//! fn multi(i: &str) -> IResult<&str, Vec<&str>> {
//!   many0(tag("abcd"))(i)
//! }
//!
//! let a = "abcdef";
//! let b = "abcdabcdef";
//! let c = "azerty";
//! assert_eq!(multi(a), Ok(("ef",     vec!["abcd"])));
//! assert_eq!(multi(b), Ok(("ef",     vec!["abcd", "abcd"])));
//! assert_eq!(multi(c), Ok(("azerty", Vec::new())));
//! # }
//! # #[cfg(not(feature = "alloc"))]
//! # fn main() {}
//! ```
//!
//! Here are some basic combinators available:
//!
//! - **`opt`**: Will make the parser optional (if it returns the `O` type, the new parser returns `Option<O>`)
//! - **`many0`**: Will apply the parser 0 or more times (if it returns the `O` type, the new parser returns `Vec<O>`)
//! - **`many1`**: Will apply the parser 1 or more times
//!
//! There are more complex (and more useful) parsers like `tuple`, which is
//! used to apply a series of parsers then assemble their results.
//!
//! Example with `tuple`:
//!
//! ```rust
//! # fn main() {
//! use nom::{error::ErrorKind, Needed,
//! number::streaming::be_u16,
//! bytes::streaming::{tag, take},
//! sequence::tuple};
//!
//! let mut tpl = tuple((be_u16, take(3u8), tag("fg")));
//!
//! assert_eq!(
//!   tpl(&b"abcdefgh"[..]),
//!   Ok((
//!     &b"h"[..],
//!     (0x6162u16, &b"cde"[..], &b"fg"[..])
//!   ))
//! );
//! assert_eq!(tpl(&b"abcde"[..]), Err(nom::Err::Incomplete(Needed::new(2))));
//! let input = &b"abcdejk"[..];
//! assert_eq!(tpl(input), Err(nom::Err::Error((&input[5..], ErrorKind::Tag))));
//! # }
//! ```
//!
//! But you can also use a sequence of combinators written in imperative style,
//! thanks to the `?` operator:
//!
//! ```rust
//! # fn main() {
//! use nom::{IResult, bytes::complete::tag};
//!
//! #[derive(Debug, PartialEq)]
//! struct A {
//!   a: u8,
//!   b: u8
//! }
//!
//! fn ret_int1(i:&[u8]) -> IResult<&[u8], u8> { Ok((i,1)) }
//! fn ret_int2(i:&[u8]) -> IResult<&[u8], u8> { Ok((i,2)) }
//!
//! fn f(i: &[u8]) -> IResult<&[u8], A> {
//!   // if successful, the parser returns `Ok((remaining_input, output_value))` that we can destructure
//!   let (i, _) = tag("abcd")(i)?;
//!   let (i, a) = ret_int1(i)?;
//!   let (i, _) = tag("efgh")(i)?;
//!   let (i, b) = ret_int2(i)?;
//!
//!   Ok((i, A { a, b }))
//! }
//!
//! let r = f(b"abcdefghX");
//! assert_eq!(r, Ok((&b"X"[..], A{a: 1, b: 2})));
//! # }
//! ```
//!
//! ## Streaming / Complete
//!
//! Some of nom's modules have `streaming` or `complete` submodules. They hold
//! different variants of the same combinators.
//!
//! A streaming parser assumes that we might not have all of the input data.
//! This can happen with some network protocol or large file parsers, where the
//! input buffer can be full and need to be resized or refilled.
//!
//! A complete parser assumes that we already have all of the input data.
//! This will be the common case with small files that can be read entirely to
//! memory.
//!
//! Here is how it works in practice:
//!
//! ```rust
//! use nom::{IResult, Err, Needed, error::{Error, ErrorKind}, bytes, character};
//!
//! fn take_streaming(i: &[u8]) -> IResult<&[u8], &[u8]> {
//!   bytes::streaming::take(4u8)(i)
//! }
//!
//! fn take_complete(i: &[u8]) -> IResult<&[u8], &[u8]> {
//!   bytes::complete::take(4u8)(i)
//! }
//!
//! // both parsers will take 4 bytes as expected
//! assert_eq!(take_streaming(&b"abcde"[..]), Ok((&b"e"[..], &b"abcd"[..])));
//! assert_eq!(take_complete(&b"abcde"[..]), Ok((&b"e"[..], &b"abcd"[..])));
//!
//! // if the input is smaller than 4 bytes, the streaming parser
//! // will return `Incomplete` to indicate that we need more data
//! assert_eq!(take_streaming(&b"abc"[..]), Err(Err::Incomplete(Needed::new(1))));
//!
//! // but the complete parser will return an error
//! assert_eq!(take_complete(&b"abc"[..]), Err(Err::Error(Error::new(&b"abc"[..], ErrorKind::Eof))));
//!
//! // the alpha0 function recognizes 0 or more alphabetic characters
//! fn alpha0_streaming(i: &str) -> IResult<&str, &str> {
//!   character::streaming::alpha0(i)
//! }
//!
//! fn alpha0_complete(i: &str) -> IResult<&str, &str> {
//!   character::complete::alpha0(i)
//! }
//!
//! // if there's a clear limit to the recognized characters, both parsers work the same way
//! assert_eq!(alpha0_streaming("abcd;"), Ok((";", "abcd")));
//! assert_eq!(alpha0_complete("abcd;"), Ok((";", "abcd")));
//!
//! // but when there's no limit, the streaming version returns `Incomplete`, because it cannot
//! // know if more input data should be recognized. The whole input could be "abcd;", or
//! // "abcde;"
//! assert_eq!(alpha0_streaming("abcd"), Err(Err::Incomplete(Needed::new(1))));
//!
//! // while the complete version knows that all of the data is there
//! assert_eq!(alpha0_complete("abcd"), Ok(("", "abcd")));
//! ```
//! **Going further:** Read the [guides](https://github.com/Geal/nom/tree/main/doc),
//! check out the [recipes]!
#![cfg_attr(not(feature = "std"), no_std)]
#![cfg_attr(feature = "cargo-clippy", allow(clippy::doc_markdown))]
#![cfg_attr(feature = "docsrs", feature(doc_cfg))]
#![cfg_attr(feature = "docsrs", feature(extended_key_value_attributes))]
#![deny(missing_docs)]
#[cfg_attr(nightly, warn(rustdoc::missing_doc_code_examples))]
#[cfg(feature = "alloc")]
#[macro_use]
extern crate alloc;
#[cfg(doctest)]
extern crate doc_comment;

#[cfg(doctest)]
doc_comment::doctest!("../README.md");

/// Lib module to re-export everything needed from `std` or `core`/`alloc`. This is how `serde` does
/// it, albeit there it is not public.
#[cfg_attr(nightly, allow(rustdoc::missing_doc_code_examples))]
pub mod lib {
  /// `std` facade allowing `std`/`core` to be interchangeable. Reexports `alloc` crate optionally,
  /// as well as `core` or `std`
  #[cfg(not(feature = "std"))]
  #[cfg_attr(nightly, allow(rustdoc::missing_doc_code_examples))]
  /// internal std exports for no_std compatibility
  pub mod std {
    #[doc(hidden)]
    #[cfg(not(feature = "alloc"))]
    pub use core::borrow;

    #[cfg(feature = "alloc")]
    #[doc(hidden)]
    pub use alloc::{borrow, boxed, string, vec};

    #[doc(hidden)]
    pub use core::{cmp, convert, fmt, iter, mem, ops, option, result, slice, str};

    /// internal reproduction of std prelude
    #[doc(hidden)]
    pub mod prelude {
      pub use core::prelude as v1;
    }
  }

  #[cfg(feature = "std")]
  #[cfg_attr(nightly, allow(rustdoc::missing_doc_code_examples))]
  /// internal std exports for no_std compatibility
  pub mod std {
    #[doc(hidden)]
    pub use std::{
      alloc, borrow, boxed, cmp, collections, convert, fmt, hash, iter, mem, ops, option, result,
      slice, str, string, vec,
    };

    /// internal reproduction of std prelude
    #[doc(hidden)]
    pub mod prelude {
      pub use std::prelude as v1;
    }
  }
}

pub use self::bits::*;
pub use self::internal::*;
pub use self::traits::*;

pub use self::str::*;

#[macro_use]
mod macros;
#[macro_use]
pub mod error;

pub mod branch;
pub mod combinator;
mod internal;
pub mod multi;
pub mod sequence;
mod traits;

pub mod bits;
pub mod bytes;

pub mod character;

mod str;

pub mod number;

#[cfg(feature = "docsrs")]
#[cfg_attr(feature = "docsrs", cfg_attr(feature = "docsrs", doc = include_str!("../doc/nom_recipes.md")))]
pub mod recipes {}