Rust nom

Welcome to Nominomicon; a guide to using the Nom parser for great good. This guide will give you an introduction rust nom the theory and practice of using Nom.

Its goal is to provide tools to build safe parsers without compromising the speed or memory consumption. To that end, it uses extensively Rust's strong typing and memory safety to produce fast and correct parsers, and provides functions, macros and traits to abstract most of the error prone plumbing. Hexadecimal color parser:. Compared to the usual handwritten C parsers, nom parsers are just as fast, free from buffer overflow vulnerabilities, and handle common patterns for you:. While nom was made for binary format at first, it soon grew to work just as well with text formats.

Rust nom

This tutorial is a guide to parsing with nom. It covers the basics of parsing and how to use nom to parse a string into a data structure. We will cover a variety of different examples ranging from parsing simple CSS like syntax to a full blown Markdown parser. If you would like to get involved in an open source project and like Rust crates, we welcome your contributions to the r3bl-open-core repo. For more information on general Rust type system design functional approach rather than object oriented , please take a look at this paper by Will Crichton demonstrating Typed Design Patterns with Rust. This tutorial takes a hands on approach to learning nom. However, the resources listed below are very useful for learning nom. Think of them as a reference guide and deep dive into how the nom library works. You can write small functions that parse a specific part of your input, and then combine them to build a parser that parses the whole input. Roughly the way it works is that you tell nom how to parse a bunch of bytes in a way that matches some pattern that is valid for your data.

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There are a few guides with more details about how to write parsers , or the error management system. You can also check out the recipes module that contains examples of common patterns. Looking for a specific combinator? If you are upgrading to nom 5. Parser combinators are an approach to parsers that is very different from software like lex and yacc.

There are a few guides with more details about the design of nom macros , how to write parsers , or the error management system. Looking for a specific combinator? Read the "choose a combinator" guide. If you are upgrading to nom 5. Parser combinators are an approach to parsers that is very different from software like lex and 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. 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. 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.

Rust nom

Nom , documented here is a parser library for Rust which is well worth the initial time investment. Likewise, for configuration files use dedicated parsers like ini or toml. But if the text is not regular, or some made-up format, then you need to scan that text without writing a lot of tedious string-processing code. The suggested go-to is often regex , but regexes can be frustratingly opaque when sufficiently involved. Nom provides a way to parse text which is just as powerful and can be built up by combining simpler parsers.

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Branches Tags. So many1! The idea is to build up expressions from the bottom up. Useful functions to calculate the offset between slices and show a hexdump of a slice. Creates a parse error from a nom::ErrorKind , the position in the input and the next error in the parsing tree. The resulting code is small, and looks like the grammar you would have written with other parser approaches. You can build up your complicated parsers from simpler parsers, which you can test individually. Nom knows that "bye" may be followed by a name and wants us to give it more data. The match values are combined into a single value, using a binary operator. Its goal is to provide tools to build safe parsers without compromising the speed or memory consumption.

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Expressions consist of terms , which are added or subtracted. Parsing Arithmetic Expressions With the necessary background established, we can do simple arithmetic expressions. Folders and files Name Name Last commit message. Rust parser combinator framework License MIT license. Errors are a key part of it being able to apply a variety of different parsers to the same input. Note that you can use whitespace here to make the parser function easier to read:! If the child parser returns an error, opt will still succeed and return None:. Notice that it was straightforward to combine an existing parser for greetings with a parser that picks up names, and then it was easy to make that name optional. We're going to need floating-point asserts here, and there's a crate for that. Combining Parsers Let's continue the greeting example and imagine that a greeting consists of "hi" or "bye", plus a name. Generalized workflow Build a Markdown parser Introduction This tutorial is a guide to parsing with nom. By just wrapping the tag! Skip to content.