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Clarify that the presence of weight value 1 is required, and a lone implied 1 weight is invalid #3814

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Nov 24, 2023
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Clarify that the presence of weight value 1 is required, and a lone implied 1 weight is invalid #3814

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Clarify that the presence of a value with weight 1 is required
elasota Nov 9, 2023
ff0996d
Clarify that there must be at least 2 weights, i.e. encoding all weig…
elasota Nov 9, 2023
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4 changes: 3 additions & 1 deletion doc/zstd_compression_format.md
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Expand Up @@ -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.
Consequently, the `Weight` 1 is necessarily present.
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.
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