ABNF parser written in TypeScript

This package is designed to allow easy usage of ABNF grammars in a javascript environment. This package can:

• Compile ABNF grammars into a JSON grammar format
• Take the JSON grammar and use it to parse text
• Read text from the parse tree returned

Example usage

A very simple example of creating a grammar to read numbers with optional decimal points:

import { AbnfCompiler, AbnfParser, AbnfReader, toCharArray } from "abnf-js";

// Create a simple grammar
const grammarText = `number = 1*%x30-39 [ decimal ]\ndecimal = "." 1*%x30-39\n`;

// And a simple test string and convert it to a Uint16Array with the toCharArray helper provided
const text = toCharArray("615.485932053165");

// Create a compiler and use it to build a GrammarRuleSet
const compiler = new AbnfCompiler(grammarText);
const grammar = compiler.build();

// Create a parser and parse the text to return a ParseTree
const parser = new AbnfParser(grammar, "number");
const results = parser.parse(text);

// Results will be `false` on error, or a `ParseTree` on success
if (results) {
    // Create a reader with the results to extract text
    const reader = new AbnfReader(text, results);
    // Read the "decimal" rule from the "number" rule.
    console.log(reader.get("decimal").read());
}

Compiling grammars to reduce overhead

It's fairly easy to compile a grammar using the CLI and npx. An example of compiling the ScramGrammar, including the core ABNF grammar is as follows:

npx abnf-js -n ScramGrammar --input scram.abnf --output - -d CoreGrammar

This will output a TypeScript file that exports an AbnfGrammarRuleSet which can be used with this library. Most of this is JSON with some wrappers for type declarations. You can then use the resulting grammar by passing it to AbnfParser and AbnfReader:

import { AbnfParser, AbnfReader, toCharArray } from "abnf-js";
import ScramGrammar from "./ScramGrammar.js";

const text = toCharArray("c=biws,r=fyko+d2lbbFgONRv9qkxdawL3rfcNHYJY1ZVvWVs7j,ext=test,p=v0X8v3Bz2T0CJGbJQyF0X+HI4Ts=");

const parser = new AbnfParser(ScramGrammar, "client-final-message");
const results = parser.parse(text);

if (results) {
    const reader = new AbnfReader(text, results);
    console.log(reader.get("proof").read());
}

Troubleshooting compiling grammars

Grammars can fail for numerous reasons. Common issues are:

• File uses LF for new lines, ABNF grammars specify CRLF new lines
• Whitespace at the end of the file, end of file must be a CRLF