ffast

The fast (and dangerous 🐉) node.js FFI library

Introduction

This is an initial Proof of Concept for surfacing all the lower level bindings necessary into JS-land so we can generate FFI wrappers from JS itself, without any dependencies on third party non-JS libraries like libffi or libtcc.

This should run on node.js current and LTS on Linux x64/arm64 and macos arm64. It has been tested on Raspberry Pi 3B+ which has a Cortex A53 and works fine there. It will also probably work on older versions of node.js but will need to be rebuilt for older versions of V8 that node.js embeds. Please report on issues you find.

It currently supports (with bugs and pretty much zero safety) passing any integer types, strings and pointers. float support and struct passing will be coming a little later. There are benchmarks coming soon that will show how to do callbacks from C/C++ to JS too.

It should be pretty easy to add a lot of libraries to this using the bindings definitions that already exist for the lo runtime. It should also be possible to run this on Bun if there is some work done on Bun side to add symbols for the V8 fastcall api's (which won't have any effect on Bun/JSC).

Windows support should not be a lot of work (famous last words!).

Right now assumption is 64-bit platforms only.

🐉🐉🐉 Beware! 🐉🐉🐉 There are many dragons here. This is surfacing a lot of dangerous things into JS-land which break things like JavaScript memory safety. It should be possible to wrap this in an internal module and hide the unsafe things away, but further research needs to be done on that front. The goal rn is to see how fast we can go with few if any guardrails. We can then measure the overhead any safety features we add have on the baseline implementation.

Support

OS	Arch	Supported	Planned
linux	x64	✅
linux	arm64	✅
macos	x64		✔️
macos	arn64	✅
windows	x64		✔️
windows	x64		✔️
android	arm64		✔️

Building

Requirements

• curl
• make
• a C compiler toolchain to compile the benchmark shared library
• a C++ compiler toolchain to compile the bindings
• node LTS (v22.13.1) or Current (v23.7.0) with npm and node-gyp

Makefile

$ make help
bench/bench.so                 build the shared library for the benchmarks
bench                          run the benchmark
src/v8-fast-api-calls.h        download the v8 fast api headers for current node/v8 version
src/ffast.cc                   generate the ffast node binding source
node_modules/.bin/node-gyp     install node-gyp locally
build/Release/ffast.node       build the ffast binding
library                        build the ffast binding
clean                          clean all the build artifacts except node_modules
cleanall                       clean everything including node_modules and package-lock.json

## build everything and run the benchmarks
$ make cleanall bench