spec update : require minimum nb of literals for 4-streams mode #3398
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felixhandte
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Dec 22, 2022
Yes, that would be a good follow up. |
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Reported by @shulib : the specification for 4-streams mode doesn't work when the amount of literals to compress is 5 bytes. Extending it, it also doesn't work for sizes 1 or 2. This patch updates the specification and the implementation to require a minimum of 6 literals to trigger or accept the 4-streams mode. The impact is expected to be a no-op : the 4-streams mode is never triggered for such small quantity of literals anyway, since it would be wasteful (it costs ~7.3 bytes more than single-stream mode). An informal lower limit is set at ~256 bytes, so the technical minimum is very far from this limit. This is just meant for completeness of the specification.
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Reported by @shulib :
the specification for 4-streams mode
doesn't work when the amount of literals to compress is 5 bytes. Extending it, it also doesn't work for sizes 1 or 2.
This patch updates the specification and the implementation to require a minimum of 6 literals to trigger or accept the 4-streams mode.
The impact is expected to be none over the ecosystem :
the 4-streams mode is never triggered for such small quantity of literals anyway, since it would be wasteful (it costs ~7.3 bytes more than single-stream mode). An informal lower limit is set at ~256 bytes,
so the technical minimum is very far from this limit.
On the other side, the decoder was already protected against scenario, and would already fail cleanly if presented with such request.
This is just meant for completeness of the specification.
Fix #3316