Limit match length?

[ashra ivy]

Is there a way to limit the match lenght? For example to MINMATCH+15+255?

This would allow get rid of the loop for the length.

Cheers 42Bastian

[Yann Collet]

Unfortunately, when it comes to the existing reference implementation at github.com/lz4/lz4 ,
there is no build macro available to limit match length.

I can guess how such a limitation could simplify a tiny asm decoder implementation,
but this limitation would also come at the cost of both compression ratio and decompression speed for the "general" case.

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[ashra ivy]

I understand, but do you see any chance/a place where I could add such. Of course, some post-processing could check the compressed files and choose a simplified decompressor.

Anyway, thanks for the reply.

42Bastian

[Yann Collet]

Presuming you are mostly interested in the LZ4 HC variant, for asymmetric compression scenarios,

you could have a loot at the function `LZ4HC_encodeSequence()`,

at https://github.com/lz4/lz4/blob/v1.9.4/lib/lz4hc.c#L467 .

That's where a sequence (literals + match) is encoded in the LZ4 format.

You could use this one place to cut a long match into multiple smaller ones.

Only LZ4 HC variants would be impacted though.

[ashra ivy]

Thanks for the hint.

Though I think, this is too late to interfere.

But meanwhile I checked my decompressors and it won't save much to remove the loop.

Cheers