RFC 8878, "Zstandard Compression and the 'application/zstd' Media Type", February 2021

Errata ID: 7297
Status: Reported
Type: Technical
Publication Format(s) : TEXT, PDF, HTML
Reported By: Felix Handte
Date Reported: 2023-01-03

Section 3.1.1.3.1.1 says:

Size_Format == 01:  4 streams.  Both Regenerated_Size and
   Compressed_Size use 10 bits (values 0-1023).
   Literals_Section_Header uses 3 bytes.

Size_Format == 10:  4 streams.  Both Regenerated_Size and
   Compressed_Size use 14 bits (values 0-16383).
   Literals_Section_Header uses 4 bytes.

Size_Format == 11:  4 streams.  Both Regenerated_Size and
   Compressed_Size use 18 bits (values 0-262143).
   Literals_Section_Header uses 5 bytes.

It should say:

Size_Format == 01:  4 streams.  Both Regenerated_Size and
   Compressed_Size use 10 bits (values 6-1023).
   Literals_Section_Header uses 3 bytes.

Size_Format == 10:  4 streams.  Both Regenerated_Size and
   Compressed_Size use 14 bits (values 6-16383).
   Literals_Section_Header uses 4 bytes.

Size_Format == 11:  4 streams.  Both Regenerated_Size and
   Compressed_Size use 18 bits (values 6-262143).
   Literals_Section_Header uses 5 bytes.

Notes:

The calculation for the size of the fourth stream, specified in section 3.1.1.3.1.6, will underflow if the total size of the literals in the block is less than 6 bytes. So the 4-stream mode cannot be used in blocks with fewer than 6 literals. (Nor should it be, since it is strictly less efficient for very small literal sections.)

The source for this errata is https://github.com/facebook/zstd/pull/3398.

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