Bun cannot zip data larger than 160,000 bytes

[nakasyou]

How to reproduce

1. clone https://github.com/nakasyou/bun-fflate-160000
2. run bun i
3. run bun run index.ts

The problem

When executing the zip function in Bun, it fails with the following log message when its length is 160,000 or more:

294 |       newDat.set(dat, dict.length);
295 |       dat = newDat;
296 |       st.w = dict.length;
297 |     }
298 |   }
299 |   return dflt(dat, opt.level == null ? 6 : opt.level, opt.mem == null ? st.l ? Math.ceil(Math.max(8, Math.min(13, Math.log(dat.length))) * 1.5) : 20 : 12 + opt.mem, pre, post, st);
                                                                                                                                 ^
TypeError: undefined is not an object (evaluating 'dat.length')
      at dopt (blob:a2b1f5c8-43da-413b-86ed-bbfba16ce28f:299:124)
      at deflateSync (blob:a2b1f5c8-43da-413b-86ed-bbfba16ce28f:301:10)
      at onmessage (blob:a2b1f5c8-43da-413b-86ed-bbfba16ce28f:305:16)
      at blob:a2b1f5c8-43da-413b-86ed-bbfba16ce28f:306:80

The zipSync function and Node.js do not produce an error.

[atty303]

I encountered this with inflate. It maybe relate to oven-sh/bun#25860.

Because Bun can resolve both Node’s worker_threads and the browser Worker APIs in the same runtime, fflate’s environment detection can pick the Node worker build (node-worker.ts) even though it’s being used in a “Web Worker-like” context. So you observe what looks like a “double onmessage run”.