Re: [PATCH RFC 1/9] lib/lz4: import upstream LZ4 sources verbatim

[Sergey Senozhatsky]

On (26/09/25 13:27), Michal Wilczynski wrote:
[..]

> +void LZ4_resetStream_fast(LZ4_stream_t* ctx) {
> +    LZ4_prepareTable(&(ctx->internal_donotuse), 0, byU32);
> +}

[..]

> +void LZ4_attach_dictionary(LZ4_stream_t* workingStream, const LZ4_stream_t* dictionaryStream)
> +{
> +    const LZ4_stream_t_internal* dictCtx = (dictionaryStream == NULL) ? NULL :
> +        &(dictionaryStream->internal_donotuse);
> +
> +    DEBUGLOG(4, "LZ4_attach_dictionary (%p, %p, size %u)",
> +             workingStream, dictionaryStream,
> +             dictCtx != NULL ? dictCtx->dictSize : 0);
> +
> +    if (dictCtx != NULL) {
> +        /* If the current offset is zero, we will never look in the
> +         * external dictionary context, since there is no value a table
> +         * entry can take that indicate a miss. In that case, we need
> +         * to bump the offset to something non-zero.
> +         */
> +        if (workingStream->internal_donotuse.currentOffset == 0) {
> +            workingStream->internal_donotuse.currentOffset = 64 KB;
> +        }
> +
> +        /* Don't actually attach an empty dictionary.
> +         */
> +        if (dictCtx->dictSize == 0) {
> +            dictCtx = NULL;
> +        }
> +    }
> +    workingStream->internal_donotuse.dictCtx = dictCtx;
> +}

Just a side note,
there is a bunch of new helpful API added in this release.  Currently,
we do some memcpy hacks to avoid re-init of lz4 C/D-dict in zram, but
once this series lands I'll be happy to send some trivial EXPORT_SYMBOL
patches so that zram (and other lz4 users) can use standard lz4 dict
API instead of hacks.