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A Node module for generating byte field diagrams like this one. Inspired by the LaTeX bytefield package. Powered by a Clojure-based domain specific language (now built on top of SCI, the Small Clojure Interpreter).


Sample byte field diagram


This is published to npm, so you can install it for use in a Javascript project by running:

npm install bytefield-svg

Or you can install it globally for use anywhere by running:

npm install -g bytefield-svg

The language you use to create diagrams has its own documentation site.

Invoking from Javascript

Once installed, you can generate diagrams in your code like this:

const generate = require('bytefield-svg');

const source = `
;; Put your diagram DSL here, or read it from a file, or build it...
const diagram = generate(source);

By default, a full SVG file is generated, complete with XML version and namespaces. If you want to generate a simple <svg> tag which is suitable for embedding inside an HTML document, you can request that by calling generate like this:

// setup code omitted...
const diagram = generate(source, { "embedded": true });

Of course, you can do other things than writing the diagram to standard out. For a few more examples of usage, you can see the cli.js source in this project which implements the command-line interface, our next topic:

Invoking from the Command Line

This package also installs a command-line tool. If you have installed it globally, you can simply invoke it as bytefield-svg. If you have installed it locally, you can invoke it using npx bytefield-svg within your project.

With no arguments, the tool will read the diagram source from standard in, and write it to standard out. So you can generate the example diagram from this Read Me, as long as you have the test.edn file, by running:

bytefield-svg <test.edn >test.svg

You can also use the -s or --source command-line argument to specify that the tool should read from a named file rather than standard in, and -o or --output to write to a named file rather than standard out, which might be helpful in a scripting pipeline:

bytefield-svg --source test.edn --output test.svg

If you supply just a filename with no command-line flag, it is assumed to be the diagram source file.

Normally the output is a full SVG file, complete with XML version information and namespaces. If instead you want to generate a simple SVG tag which is suitable for embedding inside an HTML document, you can supply the -e or --embedded flag.

Invoking it with -h or --help displays this usage information.

-h, --help            Display this usage guide.
-s, --source string   File from which to read the diagram source, defaults to
                      standard in.
-o, --output string   File to which to write the SVG diagram, defaults to
                      standard out.
-e, --embedded        Emit a simple <svg> tag suitable for embedding in an
                      HTML document. (The default is to emit a full SVG file
                      with XML version and namespaces.)

Getting Help

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The DSL has been nicely validated by porting all of the LaTeX documents I needed it for to an Antora documentation site.

As that site suggests, this package’s main purpose is to act as an Asciidoctor extension, and in fact asciidoctor-bytefield has now been published to enable that.


To build a development build of bytefield-svg from source, clone the repository and make sure you have Node.js and the Clojure CLI tools installed, then from the top-level directory of your cloned repo run:

npm install
npm run build

This will create the file lib.js. At that point, you can generate the sample diagram by running:

node cli.js test.edn >test.svg

(The test.edn file is present in this project. It renders a diagram from the above-linked documentation site. With some well-designed helper functions in site’s own include file, the source for an even more attractive version of the diagram shrinks to this).

The DSL documentation is hosted on, and built out of the doc folder, which includes build instructions. (They are slightly more complex than if you were using asciidoctor-bytefield, because they want to build against the latest version of bytefield-svg in case they are demonstrating unreleased features that haven’t yet made it to the that extension.)

To check for outdated dependencies, you can run:

clojure -M:outdated


To cut a release, check for outdated dependencies as above, update the version in package.json, tag and push to GitHub, then run:

npm install
npm run release
npm publish


Deep Symmetry

Copyright © 2020–2023 Deep Symmetry, LLC

Distributed under the Eclipse Public License 2.0. By using this software in any fashion, you are agreeing to be bound by the terms of this license. You must not remove this notice, or any other, from this software.