```
for f in $(find . \( -path ./.git -o -path ./tests/fuzz/corpora -o -path ./tests/regression/data-cache -o -path ./tests/regression/cache \) -prune -o -type f);
do
sed -i 's/\-2021/-present/' $f;
done
g co HEAD -- .github/workflows/dev-short-tests.yml # fix bad match
```
```
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
```
Currently this function actually reads the dict ID from the dictionary's
header, via `ZSTD_getDictID_fromDict()`. But during decompression the decomp-
ressor actually compares the dict ID in the frame header with the dict ID in
the DDict. Now of course the dict ID in the dictionary contents and the dict
ID in the DDict struct *should* be the same. But in cases of memory corrupt-
ion, where they can drift out of sync, it's misleading for this function to
read it again from the dict buffer rather then return the dict ID that will
actually be used.
Also doing it this way avoids rechecking the magic and so on and so it is a
tiny bit more efficient.
This commit avoids checking whether a hashtable write is safe in two of the
three match-found paths in `ZSTD_compressBlock_fast_noDict_generic`. This pro-
duces a ~0.5% speed-up in compression.
A comment in the code describes why we can skip this check in the other two
paths (the repcode check and the first match check in the unrolled loop).
A downside is that in the new position where we make this check, we have not
yet computed `mLength`. We therefore have to avoid writing *possibly* dangerous
positions, rather than the old check which only avoids writing *actually*
dangerous positions. This leads to a miniscule loss in ratio (remember that
this scenario can only been triggered in very negative levels or under incomp-
ressibility acceleration).
We previously triggered release artifact generation on release creation. We
sometimes observed that the action failed to run. I hypothesized that we were
hitting rate limiting or something. I just stumbled across [this documentat-
ion](https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#release), which says:
> Note: Workflows are not triggered for the `created`, `edited`, or `deleted`
> activity types for draft releases. When you create your release through the
> GitHub browser UI, your release may automatically be saved as a draft.
This must have been what was happening. This commit therefore changes the
trigger to the `published` activity. This should be more reliable.
This does have the unfortunate side effect that artifacts won't be generated
or attached until *after* the release has been published, which is what I was
trying to avoid by using the `created` activity. Oh well.
xxHash symbols are present in `libzstd.so`, but they are local and therefore
unavailable outside the lib. There are two possible solutions to the problem.
We could make those symbols global, or we could remove the dependency.
This commit chooses the latter approach. I suppose this comes at the cost of
code size / build time. I'm open to comments on whether this is a good thing
to do, especially since this will apply even when we are statically linking
everything.
This commit makes several changes:
1. It adds modules for the dictionary builder and errors headers.
2. It captures all of the macros that are used to configure these headers.
When the headers are imported as modules and one of these macros is defined
the compiler issues a warning that it needs to be defined on the CLI.
3. It promotes the modulemap file into the root of the lib directory.
Experimentation shows that clang's `-fimplicit-module-maps` will find the
modulemap when placed here, but not when it's put in a subdirectory.
Apparently, even when the assembly file is empty (because
`ZSTD_ENABLE_ASM_X86_64_BMI2` is false), it still is marked as possibly
needing an executable stack and so the whole library is marked as such. This
commit applies a simple patch for this problem by moving the noexecstack
indication outside the macro guard.
This commit builds on #2857.
This commit addresses #2963.
I couldn't find a good way to spread `ip0` and `ip1` apart when we accelerate
due to incompressible inputs. (The methods I tried slowed things down quite a
bit.)
Since we aren't splaying ip0 and ip1 apart (which would be like `0_1_2_3_`, as
opposed to the `01__23__` we were actually doing), it's a big ambitious to
increment `step` by 2. Instead, let's increment it by 1, which has the benefit
sliiightly improving compression. Speed remains pretty much unchanged.
The position updates are rewritten from `ip[N] = ip[N-1] + step` to be
`ip[N] = ip[N-2] + step`. This lets us only deal with the asymmetric spacing
of gaps at setup and then we only have to keep a single `step` variable.
This seems to work quite well on GCC and Clang!
This replicates the behavior of @terrelln's `ZSTD_fast` implementation. That
is, it always looks at adjacent pairs of positions, and only applies the
acceleration every other position. This produces a more fine-grained
acceleration.
I hadn't seen #2890, so I wrote my own version. I like this approach a little
better, since it does an explicit check for a regular file, rather than
passing a magic value.
Addresses #2874.
`lib/deprecated` is no longer built by zstd's bundled build files. However,
users may try to build these files when they import the source tree into
their own build systems. And if they have `-Wdeprecated-declarations` on,
this can produce warnings.
This PR migrates these files away from using deprecated declarations.
This addresses #2767.
PR #2850 attempted to fix a determinism bug that was uncovered by OSS-Fuzz. It
succeeded in addressing that source of non-determinism, but introduced a new
one: it was possible, when index reduction occurred, to map indices in the
window to the reserved value, which would cause them to be zeroed, potentially
altering parsing of the input.
This PR addresses this issue. It makes sure that the bottom of the window is
always `>= ZSTD_WINDOW_START_INDEX`.
I'm not sure if this makes #2850 redundant. I think it's probably still
valuable to have that protection as well.
Credit to OSS-Fuzz for discovering this issue.
Previously, if an index was equal to `reducerValue + 1`, it would get remapped
during index reduction to 1 i.e. `ZSTD_DUBT_UNSORTED_MARK`. This can affect the
parsing of the input slightly, by causing tree nodes to be nullified when they
otherwise wouldn't be. This hardly matters from a correctness or efficiency
perspective, but it does impact determinism.
So this commit changes index reduction to avoid mapping indices to collide with
`ZSTD_DUBT_UNSORTED_MARK`.
Since we're now hashing the position ahead even if we find a long match and
don't search that next position, we can write it back into the hashtable even
in long matches. This seems to cost us no speed, and improves compression
ratio slightly!
Aside from maybe a latency win in the loop, this means that when we find a
short match, we've already done the hash we need to check the next long match.
It's a bit strange, because this is hitting the dictionary special case where
the dictionary is contiguous with the input and still runs in the single-
segment path.
We should probably change that to hit the `extDict` path instead?
This removes the old `ZSTD_compressBlock_fast_generic()` and renames the new
`ZSTD_compressBlock_fast_generic_pipelined()` to replace it. This is
functionally a no-op.
Unrolling the loop to handle 2 positions in each iteration allows us to reduce
the frequency of some operations that don't need to happen at every position.
One such operation is the step calculation, which is a very rough heuristic
anyways. It's fine if we do this a position later. The other operation is the
repcode check. But since the repcode check already tries expanding back one
position, we're really not missing much of importance by only trying it every
other position.
This commit also slightly reorders some operations.
Amusingly, it seems to be a non-trivial performance hit to add in final
searches or even hash table insertions during cleanup. So let's not. It seems
to not make any meaningful difference in compression ratio.
W. Felix Handte