Compute zstd compress bound

[tomyl]

Hi,

Is it possible to compute a compress bound for zstd? Something like https://pkg.go.dev/github.com/DataDog/zstd?utm_source=godoc#CompressBound

CompressBound returns the worst case size needed for a destination buffer, which can be used to preallocate a destination buffer or select a previously allocated buffer from a pool.

Thanks,
Tommy

[klauspost]

Should be feasible. It will probably be more complex than this with non-default window/block sizes.

You can use a similar function to get a very reasonable buffer size.

Moving to Feature/Idea category.

[tomyl]

You can use a similar function to get a very reasonable buffer size.

Which function is that? Actually I think it's sufficient for me to know how large the destination slice needs to be in order to avoid allocations. I suppose len(src) + zstd.HeaderMaxSize should be safe? Hmm no. If I compress 4194304 (4MiB) of random data I get 4194509 bytes back.

[klauspost]

I was thinking you could use the CompressBound, but it doesn't account for the frame header.

Let me see if I can do something that is closer.

[klauspost]

#691

[tomyl]

Nice, thanks! Works well for me.