zlib-sync-rust

High-performance sync Zlib inflater for Node.js, built with Rust (napi-rs).

A simple, fast, and synchronous zlib-stream decoder, designed for use cases like Discord Gateway compression, or any application needing zlib-stream inflation without async streams or event handling.

🚀 Features

• ✅ Synchronous interface – No on('data') handling
• ✅ Streaming decompression – Keeps state across push() calls
• ✅ Auto stream-reset on end – Works well for multiple stream chunks (e.g. Discord)
• ✅ Rust + napi-rs – Fast, portable, and memory-safe
• ✅ Supports both CommonJS and ESM
• ✅ Same usage style as zlib-sync but written in Rust
• ✅ Prebuilt binaries for major platforms – No need to compile or install build tools

📦 Install

npm install zlib-sync-rust

🔧 Usage

Basic Example

CJS

const { Inflater } = require('zlib-sync-rust');

const inflater = new Inflater();

// Push compressed data chunk by chunk (zlib-stream)
const out1 = inflater.push(chunk1);
const out2 = inflater.push(chunk2);
const out3 = inflater.push(chunk3);
const result = Buffer.concat([out1, out2, out3]);
console.log(result.toString());

ESM

import { Inflater } from 'zlib-sync-rust';

const inflater = new Inflater();

const out = inflater.push(zlibStreamChunk);
console.log(out.toString());

🔍 API

new Inflater()

Creates a new zlib-stream inflater instance.

inflater.push(input: Buffer, flush?: boolean): Buffer

| Parameter | Type | Default | Description | | --------- | --------- | -------- | -------------------------------------- | | input | Buffer | Required | The compressed zlib stream chunk | | flush | boolean | false | Whether to finalize the current stream |

• If flush is false (default), it keeps streaming.
• If flush is true, it signals the end of a zlib stream.
• When a stream ends (via flush: true or stream end marker), internal state is auto-reset for the next stream.

inflater.reset(): void

Manually reset the internal inflater state. This is optional in most use cases, but may be useful when:

• You detect the end of a zlib stream manually (e.g. Discord's 0x00 00 ff ff marker)
• You want to force discard current stream state between data chunks

inflater.reset(); // Ready for a new zlib stream

⚠️ Streaming Strategy Notes

• This inflater supports both:

  • Single continuous zlib streams (e.g. a file split into parts)
  • Multiple independent zlib streams (e.g. Discord's message framing)

• When used with Discord Gateway:

  • Discord sends separate zlib streams, each ending with 0x00 00 ff ff
  • You should call .reset() after detecting this marker
  • Do not call with flush: true unless you know the entire stream is present

⚡ Why?

Node's native zlib is event-based and not friendly for some low-level protocols like Discord's zlib-stream compression. This library gives you a sync-friendly, stateful inflater with Rust-level performance.

🚀 Prebuilt binaries

zlib-sync-rust provides prebuilt .node binaries for major platforms:

• Windows
• Linux

No need for node-gyp or build tools. Install and use directly.

This uses @napi-build/cli.

🧰 License

MIT © 2025 Yuki