This is forked and this repo is authoritative for the fork.

The methodology used to generate this CL is documented in
https://crbug.com/1098010#c95.

No-Try: true
Bug: 1098010
Change-Id: I4698084a28dda86210e9dba6ddac76c13377e687
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3921823


Auto-Submit: Avi Drissman <avi@chromium.org>
Reviewed-by: Adam Langley <agl@chromium.org>
Commit-Queue: Adam Langley <agl@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1051972}
NOKEYCHECK=True
GitOrigin-RevId: 9fc44ce454cc889b603900ccd14b7024ea2c284c

In zlib, hash_size is 1 << s->hash_bits or 65536 (at most) at maximum
memory level which makes the Assert(hash_size == (ush)hash_size) fail
at maximum zlib memory level (issue 1321435).

Fix this incorrect Assert: test that hash_size is bounded viz., 1<<16
at most, and 1<<8 at least.

Bug: 1316541, 1321435
Change-Id: Id1d28b1901905dcfdb889fcd5d3cdbc2a3d478a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3617306


Commit-Queue: Adenilson Cavalcanti <cavalcantii@chromium.org>
Reviewed-by: Adenilson Cavalcanti <cavalcantii@chromium.org>
Cr-Commit-Position: refs/heads/main@{#998237}
NOKEYCHECK=True
GitOrigin-RevId: 0e8968867160101c6726e979fae136b560e54def

If USE_ZLIB_RABIN_KARP_ROLLING_HASH build-time option is defined, use
the Rabin-Karp hash. This disables CRC SIMD hashing on ARM and Intel,
which will degrade compression speed.

However, the compressed output matches canonical zlib output, for the
same input, and that should resolve ASOP OTA issue 1316541.

To ensure the Rabin-Karp hash is used correctly in chromium zlib, the
first step is to go back to using canonical fill_window(). To do this
combine the ARM NEON and Intel SSE2 slide_hash() routines in a common
framework called slide_hash_simd(). Remove fill_window_sse.c and undo
deflate_read_buf() rename: name it back to canonical read_buf().

Change insert_string(): by default it uses CRC32C hashes on all ports
(ARM, Intel) so add code comments to state that. If Rabin-Karp hashes
are enabled, disable CRC32C hashes.

Add a new deflate internal state variable chromium_zlib_hash, used to
detect which type of hashing is enabled (Rabin-Karp, CRC32C). Set the
state variable in deflateInit2_ after cpu_check_features() detection,
with #ifdef guards matching the #ifdef logic of insert_string().

Change canonical fill_window() to insert hashes into {hash,prev} hash
chains based on hash type (Rabin-Karp, CRC32C). Prior to this change,
the ARM port was inserting Rabin-Karp hashes into hash chains even if
CRC32 hashing was active when s->insert was > 0.

Change longest_match() and deflate_fast(): update them to use the new
deflate state variable chromium_zlib_hash.

Compression performance degrades when Rabin-Karp hashing is used, but
is unchanged when CRC32C hashing is enabled (chromium zlib default).

Compat: if Rabin-Karp hashing is enabled, zlib-bench --check built as normal and against canonical zlib 1.2.11, produce the same compressed output for the snappy corpora for gzip,zlib,raw types and compression levels 1..9.

Bug: 1316541
Change-Id: I0d5ee6240f0b7eac4653d60a29d459d994c3871f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3596671


Reviewed-by: Chris Blume <cblume@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Adenilson Cavalcanti <cavalcantii@chromium.org>
Cr-Commit-Position: refs/heads/main@{#998062}
NOKEYCHECK=True
GitOrigin-RevId: 2bd100e46361a459b41a29212ea8f97a4837a06c