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Clarify that there must be at least 2 weights, i.e. encoding all weights as 0 is invalid

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elasota 2023-11-08 23:46:37 -05:00 committed by Nick Terrell
parent dc84e35138
commit 05059e5a48
1 changed files with 3 additions and 1 deletions
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doc/zstd_compression_format.md
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@ -1252,7 +1252,9 @@ Number_of_Bits = Weight ? (Max_Number_of_Bits + 1 - Weight) : 0
```
When a literal value is not present, it receives a `Weight` of 0.
The least frequent symbol receives a `Weight` of 1.
If no symbol has a `Weight` of 1, then the data is considered corrupted.
If no literal has a `Weight` of 1, then the data is considered corrupted.
If there are not at least two literals with non-zero `Weight`, then the data
is considered corrupted.
The most frequent symbol receives a `Weight` anywhere between 1 and 11 (max).
The last symbol's `Weight` is deduced from previously retrieved Weights,
by completing to the nearest power of 2. It's necessarily non 0.