Nick Terrell [Thu, 12 Jan 2023 02:14:40 +0000 (18:14 -0800)]
Add support for in-place decompression
* Add a function and macro ZSTD_decompressionMargin() that computes the
decompression margin for in-place decompression. The function computes
a tight margin that works in all cases, and the macro computes an upper
bound that will only work if flush isn't used.
* When doing in-place decompression, make sure that our output buffer
doesn't overlap with the input buffer. This ensures that we don't
decide to use the portion of the output buffer that overlaps the input
buffer for temporary memory, like for literals.
* Add a simple unit test.
* Add in-place decompression to the simple_round_trip and
stream_round_trip fuzzers. This should help verify that our margin stays
correct.
Yann Collet [Wed, 11 Jan 2023 23:11:51 +0000 (15:11 -0800)]
fix root cause of #3416
A minor change in 5434de0 changed a `<=` into a `<`,
and as an indirect consequence allowed compression attempt of literals when there are only 6 literals to compress
(previous limit was effectively 7 literals).
This is not in itself a problem, as the threshold is merely an heuristic,
but it emerged a bug that has always been there, and was just never triggered so far due to the previous limit.
This bug would make the literal compressor believes that all literals are the same symbol,
but for the exact case where nbLiterals==6, plus a pretty wild combination of other limit conditions,
this outcome could be false, resulting in data corruption.
Replaced the blind heuristic by an actual test for all limit cases,
so that even if the threshold is changed again in the future,
the detection of RLE mode will remain reliable.
Daniel Kutenin [Tue, 10 Jan 2023 15:33:50 +0000 (15:33 +0000)]
Fix fuzzing with ZSTD_MULTITHREAD
At Google we fuzz zstd without ZSTD_MULTITHREAD but we want inputs to be as much as reproducible. It allows us to test new fuzzing methods for our fuzz team internally and have more horsepower to find bugs
Yann Collet [Thu, 22 Dec 2022 00:21:29 +0000 (16:21 -0800)]
update levels.sh test
comparing level 19 to level 22 and expecting a stricter better result from level 22
is not that guaranteed,
because level 19 and 22 are very close to each other,
especially for small files,
so any noise in the final compression result
result in failing this test.
Level 22 could be compared to something much lower, like level 15,
But level 19 is required anyway, because there is a clamping test which depends on it.
Yann Collet [Wed, 21 Dec 2022 22:58:53 +0000 (14:58 -0800)]
improve compression ratio of small alphabets
fix #3328
In situations where the alphabet size is very small,
the evaluation of literal costs from the Optimal Parser is initially incorrect.
It takes some time to converge, during which compression is less efficient.
This is especially important for small files,
because there will not be enough data to converge,
so most of the parsing is selected based on incorrect metrics.
After this patch, the scenario ##3328 gets fixed,
delivering the expected 29 bytes compressed size (smallest known compressed size).
Yann Collet [Wed, 28 Dec 2022 07:40:34 +0000 (23:40 -0800)]
New xp library symbol : ZSTD_CCtx_setCParams()
Inspired by #3395,
offer a new capability to set all parameters defined in a ZSTD_compressionParameters structure
with a single symbol invocation
to improve user code brevity.
Yann Collet [Thu, 22 Dec 2022 19:30:15 +0000 (11:30 -0800)]
spec update : require minimum nb of literals for 4-streams mode
Reported by @shulib :
the specification for 4-streams mode
doesn't work when the amount of literals to compress is 5 bytes.
Extending it, it also doesn't work for sizes 1 or 2.
This patch updates the specification and the implementation
to require a minimum of 6 literals to trigger or accept the 4-streams mode.
The impact is expected to be a no-op :
the 4-streams mode is never triggered for such small quantity of literals anyway,
since it would be wasteful (it costs ~7.3 bytes more than single-stream mode).
An informal lower limit is set at ~256 bytes,
so the technical minimum is very far from this limit.
This is just meant for completeness of the specification.
Nick Terrell [Thu, 22 Dec 2022 01:48:24 +0000 (17:48 -0800)]
[tests] Remove deprecated function from longmatch.c test
Thanks to @eli-schwartz for pointing it out!
We should maybe consider adding a helper function for applying
`ZSTD_parameters` and `ZSTD_compressionParameters` to a context.
That would aid the transition to the new API in situations like this.
Nick Terrell [Thu, 22 Dec 2022 01:21:09 +0000 (17:21 -0800)]
[cli-tests] Add --set-exact-output to update the expected output
`./run.py --set-exact-output` will update `stdout.expect` and
`stderr.expect` to match the expected output. This doesn't apply to
outputs which use `.glob` or `.ignore`.
The one that isn't pinned is the OSS-Fuzz builder and runner. They don't
offer tagged releases. I could pin to the current master commit, but I'm not
sure how desirable that is.
```
for f in $(find . \( -path ./.git -o -path ./tests/fuzz/corpora \) -prune -o -type f);
do
sed -i 's/Facebook, Inc\./Meta Platforms, Inc. and affiliates./' $f;
done
```
Nick Terrell [Mon, 19 Dec 2022 20:23:29 +0000 (12:23 -0800)]
[pzstd] Fixes for Windows build
* Add `Portability.h` to fix min/max issues.
* Fix conversion warnings
* Assert that windowLog <= 23, which is currently always the case.
This could be loosened, but we aren't looking to add new functionality.
Fixes on top of PR #3375 by @eli-schwartz, which added Windows CI for contrib & programs.
Yonatan Komornik [Sat, 17 Dec 2022 02:24:02 +0000 (18:24 -0800)]
Fix race condition in the Windows thread / pthread translation layer
When spawning a Windows thread we have small worker wrapper function that translates
between the interfaces of Windows and POSIX threads.
This wrapper is given a pointer that might get stale before the worker starts running,
resulting in UB and crashes.
This commit adds synchronization so that we know the wrapper has finished reading the data
it needs before we allow the main thread to resume execution.
Yonatan Komornik [Fri, 16 Dec 2022 00:11:56 +0000 (16:11 -0800)]
Fixes two bugs in the Windows thread / pthread translation layer
1. If threads are resized the threads' `ZSTD_pthread_t` might move
while the worker still holds a pointer into it (see more details in #3120).
2. The join operation was waiting for a thread and then return its `thread.arg`
as a return value, but since the `ZSTD_pthread_t thread` was passed by value it
would have a stale `arg` that wouldn't match the thread's actual return value.
This fix changes the `ZSTD_pthread_join` API and removes support for returning
a value. This means that we are diverging from the `pthread_join` API and this
is no longer just an alias.
In the future, if needed, we could return a Windows thread's return value using
`GetExitCodeThread`, but as this path wouldn't be excised in any case, it's
preferable to not add it right now.
projects / thirdparty / zstd.git / log
