CHOC: "Classy Header Only Classes" ¹

A random grab-bag of header-only, dependency-free C++ classes.

When you start trying to write a C++ project of any size, you'll soon start finding gaping holes in what the C++ standard library provides. To fill them, you'll end up either writing lots of helper functions yourself, or trawling the web for awful 3rd-party libraries which come with all kinds of baggage like messy build requirements, scads of stupid compiler warnings, awkward licenses, etc.

I got tired of re-implementing many of the same little helper classes and functions in different projects, so CHOC is an attempt at preventing future wheel-reinvention, by providing some commonly-needed things in a format that makes it as frictionless as possible for anyone to use this code in any kind of project.

So with that goal in mind, the rules for everything in CHOC are:

• It's strictly header-only. Just #include the file you want, and you're done. Nothing needs adding to your build system to use any of this stuff.
• It's all permissively ISC licensed. It should pass silently under the noses of even the most zealous legal teams.
• Each file is as self-contained as possible. If you only need a couple of these classes, you should be able to cherry-pick at most a few CHOC headers into your project and not need to drag the whole repo along.
• Clean, consistent, concise, modern C++. Not too simple. Not too over-generic or fancy. Easy to skim-read and find what you're looking for. Self-documenting where possible, with decent comments.

Basically CHOC is aimed at people (like me) who just want to use some decent library code without also spending their afternoon fighting CMake or looking up the right compiler flags to make the dratted thing work.

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Highlights

The library is getting quite big now! Some of its many delights include:

Miscellaneous

• A tiny platform-detection header.
• A fast, round-trip-accurate float/double to string converter.
• Some headers which will disable and reenable warnings for times when you have to include messy 3rd-party code in your otherwise faultless codebase.
• The world's simplest unit test framework. I mainly wrote this so that CHOC can self-host its own unit-tests without any external dependencies, but have found it surprisingly useful for something that's about 100 lines of code.
• Cross-platform dynamic library loading.
• A tempting-but-probably-perilous in-memory DLL loader which can load a DLL from memory instead of a file (Windows only).
• Various maths and bit-twiddling bits and bobs.
• A system for easily adding and collecting all the open-source licenses that your project uses into a single string for displaying to a user (for license compliance).
• A one-file header-only encapsulation of zlib, exposing std::iostream compatible classes for compressing and decompressing data.
• A Zip file reader and decompressor class.
• A HTTP and WebSocket server class. Life is too short to learn how boost::beast works and write all the boilerplate required just to serve some content and talk down a web-socket, so this class hides all the horribleness behind a very simple API.

Text and Files

• Utterly basic string stuff like trimming, splitting, joining, comparisons, etc. For god's sake, I shouldn't need to write my own library just to trim a string...
• Some more esoteric string utilities like pretty-printing durations and sizes, URI encoding, etc.
• Some UTF8 validation and iteration classes.
• Some file utilities to provide single-function-call ways to do obvious things like loading a file's content, or saving a string into a file, creating self-deleting temp files, etc.
• A file watcher class for monitoring changes to a file or folder.
• A CodePrinter class to help creating indented code listings.
• A HTML generator for creating a tree of DOM objects and generating HTML text for it
• A text table generator, which can take an array of strings and tabulate it to align the columns nicely.
• A file wildcard matcher. I claim this is the cleanest possible implementation of this algorithm - I challenge you to prove me wrong!
• A simple command-line argumment helper which simplifies a lot of basic command-line arg parsing tasks.

Containers

• A span class to fill the gap until we can finally use std::span.
• Some type and value classes which can represent typed values, but also build them dynamically, serialise them to a compact binary format (or as JSON).
• A handy SmallVector class which offers a std::vector interface but has pre-allocated internal storage.
• Everyone hates COM, but sometimes you need some COM helper classes to hide the ugliness.

Memory

• One of those aligned memory block classes that you always end up needing for some reason.
• A fast memory pool allocator.
• Helpers for reading writing data with different endianness.
• Some integer compression and zigzag encoding functions.
• A base64 encoder/decoder.
• An implementation of the xxHash very-fast-but-pretty-secure hash algorithm.

GUI

• Some bare-bones message loop control functions.

• A timer class for cross-platform message loop timer callbacks.

• The world's most hassle-free single-header WebView class!

  This lets you create an embedded browser view (either as a desktop window or added to an existing window), and interact with it by invoking javascript code and binding callback C++ functions to be called by javascript. Something that makes this particularly special compared to other web-view libraries is that on Windows, it provides the modern Edge browser without you needing to install extra SDKs to compile it, and without any need to link or redistribute the Microsoft loader DLLs - it's literally a dependency-free single-header Edge implementation. (Internally, some absolutely hideous shenanegans are involved to make this possible!)

  To try it out, if you compile the choc/tests project and run it with the command-line arg "webview", it pops up an example page and shows how to do some event-handling.

Javascript and JSON

• A cross-engine Javascript API, with implementations for V8, QuickJS and Duktape!

  Both QuickJS and Duktape have been squashed into single-file header-only implementations, so are trivially easy to add to any project. V8 unfortunately requires you to link to their enormous static libraries, but obviously provides optimum performance. All these engines are abstracted behind the same choc::javascript::Context base-class, and you can choose to use any combination of engines interchangeably (or simultaneously) in your project.

• A JSON parser that uses choc::value::Value objects.

Audio

• Some audio buffer classes for managing blocks of multi-channel sample data. These can flexibly handle both owned buffers and non-owned views in either packed/interleaved or separate-channel formats.
• Utility classes for handling MIDI messages, MIDI sequences and MIDI files.
• An AudioFileFormat system for reading/writing audio files, with support for WAV, FLAC, Ogg-Vorbis, and read-only support for MP3. Hopefully more formats will get added in due course.
• Some basic audio utilities like simple oscillators.
• A sinc interpolator
• A MIDI/audio block sync mechanism.
• Functions for packing/unpacking integer sample data to floats.

Threading

• Some threading helpers such as a thread-safe functor, a task thread and spin-lock
• A range of atomic FIFOs, and a handy variable size object FIFO for handling queues of heterogenous objects without locking.
• A lock-free dirty list for efficiently queueing up objects that need some attention.

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Hopefully some people will find some of these things useful! If you like it, please tell your friends! If you think you're up to contributing, that's great, but be aware that anything other than an utterly immaculate pull request will be given short shrift :)

-- Jules

Footnotes

1. ...or maybe "Clean Header-Only Classes" ...or "Cuddly Header-Only Classes"... It's just a backronym, so feel free to pick whatever C-word feels right to you. I may change the word occasionally on a whim, just to cause annoying diffs in the codebase. ↩