Question about seekable format and checksums

[rorosen]

The seek table of the seekable format has an optional Checksum field for every frame, where the least 32 bit of the xxh64 hash of the uncompressed frame data are stored. However, the Content_Checksum field of a zstd frame seems to have the same purpose. I there a reason for the seekable format not to use the Content_Checksum field with ZSTD_c_checksumFlag?

Also, how should I understand the contrib directory, especially the seekable format? Should I take it more as a proof of concept of seekable compression with zstd or more like a feature? I'm just asking out of curiosity.