tests: Rename fuzz helpers back. (klauspost#931)

s2: Fix DecodeConcurrent deadlock on errors (klauspost#925)

When DecodeConcurrent encounters an error it can lock up in some cases.

Fix and add fuzz test for stream decoding.

Fixes klauspost#920

s2: Document and test how to peek the stream for skippable blocks (kl…

…auspost#918)

Co-authored-by: Klaus Post <[email protected]>

gzhttp: Allow overriding decompression on transport (klauspost#892)

This allows getting compressed data even if `Content-Encoding` is set.

Also allows decompression even if "Accept-Encoding" was not set by this client.

gzhttp: Fix missing content type on Close (klauspost#883)

If compression had not yet been triggered in Write, be sure to detect content type on Close.

Fixes klauspost#882

zstd: Fix corrupted output in "best" (klauspost#876)

* zstd: Fix corrupted output in "best"

Regression from klauspost#784 and followup klauspost#793

Fixes klauspost#875

A 0 offset backreference was possible when "improve" was successful twice in a row in the "skipBeginning" part, only finding 2 (previously unmatches) length 4 matches, but where start offset decreased by 2 in both cases.

This would result in output where the end offset would equal to the next 's', thereby doing a self-reference.

Add a general check in "improve" and just reject these. Will also guard against similar issues in the future.

This also hints at some potentially suboptimal hash indexing - but I will take that improvement separately.

Fuzz test set updated.

s2: Fix S2 best dictionary wrong encoding (klauspost#871)

A dictionary match one byte out of dictionary range was possible.

Recovery is possible. Send me a request if you find any content with this error in the [discussion](https://github.com/klauspost/compress/discussions/categories/general).

gzip: Copy bufio.Reader on Reset (klauspost#860)

The code already checks to see if the buffer can be reused, but since
it's not copied in the overwrite, a new buffer is allocated each time.

s2: add GetBufferCapacity() method (klauspost#832)

Add GetBufferCapacity() method. We are reusing readers with sync.Pool
and we'd like to avoid allocating memory for the default block size
since most of the inputs are smaller. To have a better estimate of how
big the lazy buffer should be, we are thinking about keeping in mind a
running average of the internal buffer capacities. This method would
allow us to implement that.

s2: Clean up matchlen assembly (klauspost#825)

* s2: Clean up matchlen assembly