Linearly back off the frequency of overflow correction based on the
number of times the `ZSTD_window_t` has been overflow corrected. This
will still allow the fuzzer to quickly find overflow correction bugs,
while also keeping good speed for larger inputs.
Additionally, the `nbOverflowCorrections` variable can be useful for
debugging coredumps, since we can inspect the `ZSTD_CCtx` to see if
overflow correction has happened yet.
I've verified this fixes the timeouts in OSS-Fuzz (176 seconds -> 6
seconds). I've also verified that fuzzers and `fuzzer` and `zstreamtest`
still catch the row-hash overflow correction bug.
The FAQ covers the questions asked in Issue #2566. It first covers why
you would want to use a dictionary, then what a dictionary is, and
finally it tells you how to train a dictionary, and clarifies some of
the parameters.
There is definitely more that could be said about some of the advanced
trainers, but this should be a good start.
This flag forces zstd to always load the prefix in ext-dict mode, even
if it happens to be contiguous, to force determinism. It also applies to
dictionaries that are re-processed.
A determinism test case is also added, which fails without
`ZSTD_c_deterministicRefPrefix` and passes with it set.
Question: Should this be the default behavior? It isn't in this PR.
* Take `params` by const reference in `ZSTD_resetCCtx_internal()`.
* Add `simpleApiParams` to the CCtx and use them in the simple API
functions, instead of creating those parameters on the stack.
I think this is a good direction to move in, because we shouldn't need
to worry about adding parameters to `ZSTD_CCtx_params`, since it should
always be on the heap (unless they become absoultely gigantic).
Some `ZSTD_CCtx_params` are still on the stack in the CDict functions,
but I've left them for now, because it was a little more complex, and we
don't use those functions in stack-constrained currently.
Dictionaries larger than `ZSTD_CHUNKSIZE_MAX` used to have to be loaded
in multiple segments. Instead, when we detect large dictionaries, ensure
that we reset the context's indicies. Then, for dictionaries larger than
`ZSTD_CURRENT_MAX - 1`, only load the suffix of the dictionary. Finally,
enable DDS for large dictionaries, since we no longer load in multiple
segments.
This simplifes the dictionary loading code, and reduces opportunities
for non-determinism to slip in.
LDM does especially poorly on repetitive data when that data's hash happens
to have `(hash & stopMask) == 0`. Either because the `stopMask == 0` or
random chance. Optimize this case by skipping over repetitive patterns.
The detection is very simplistic, but should catch most of the offending
cases.
```
head -c 1G /dev/zero | perf stat -- ./zstd -1 -o /dev/null -v --zstd=ldmHashRateLog=1 --long
21.187881087 seconds time elapsed
head -c 1G /dev/zero | perf stat -- ./zstd -1 -o /dev/null -v --zstd=ldmHashRateLog=1 --long
1.149707921 seconds time elapsed
```
Switch from `-T0` to the default `-T1` which significantly reduces
memory usage for level 19 when there are many cores. This fixes
32-bit issues of running out of address space.
Fixes#2603.
* Fix overflow correction when `windowLog < cycleLog`. Previously, we
got the correction wrong in this case, and our chain tables and binary
trees would be corrupted. Now, we work as long as `maxDist` is a power
of two, by adding `MAX(maxDist, cycleSize)` to our indices.
* When `ZSTD_WINDOW_OVERFLOW_CORRECT_FREQUENTLY` is defined to non-zero
run overflow correction as frequently as allowed without impacting
compression ratio.
* Enable `ZSTD_WINDOW_OVERFLOW_CORRECT_FREQUENTLY` in `fuzzer` and
`zstreamtest` as well as all the OSS-Fuzz fuzzers. This has a 5-10%
speed penalty at most, which seems reasonable.
`zstd_errors.h` and `zdict.h` are public headers, so they deserve to be
in the root `lib/` directory with `zstd.h`, not mixed in with our private
headers.
Replace kernel-style comments with regular comments.
E.g.
```
/** Before */
/* After */
/**
* Before
*/
/*
* After
*/
/***********************************
* Before
***********************************/
/* *********************************
* After
***********************************/
```
Instead of providing a default no-op implementation, check the symbols
for `NULL` before accessing them. Providing a default implementation
doesn't reliably work with dynamic linking. Depending on link order the
default implementations may not be overridden. By skipping the default
implementation, all link order issues are resolved. If the symbols
aren't provided the weak function will be `NULL`.
* Switch to yearless copyright per FB policy
* Fix up SPDX-License-Identifier lines in `contrib/linux-kernel` sources
* Add zstd copyright/license header to the `contrib/linux-kernel` sources
* Update the `tests/test-license.py` to check for yearless copyright
* Improvements to `tests/test-license.py`
* Check `contrib/linux-kernel` in `tests/test-license.py`
* Move `counting` to a struct in `FSE_decompress_wksp_body()`
* Fix error code in `FSE_decompress_wksp_body()`
* Rename a variable in `HUF_ReadDTableX2_Workspace`
Expose the zstd headers in `include/linux` to avoid struct duplication.
This makes the member names not follow Kernel style guidelines, and
exposes the zstd symbols. But, the LMKL reviewers are okay with that.
Fixes the update from PR #2508. I had accidentally forgotten to rebuild
the library, and the regression test suite isn't hooked up to the new
fancy build system yet.
I've double checked that the results are deterministic.
9f327c02fd changed the compression method
for LDM, so the results are slightly different.
I've re-tested LDM on some larger inputs and everything seems fine.
These ratio changes just seem to be noise. There is generally a 0.01%
swing in ratio, sometimes better sometimes worse, but never large.
* Fix compiler version regex, which was broken for multi-digit
versions.
* Fix compiler detection for gcc.
* Disable `pointer-overflow` instead of `integer-overflow` for gcc
versions newer than 8.0.0.
The simple compression functions are intended to ignore the advanced
parameters, but they were accidentally using them. All the
`ZSTD_parameters` were set correctly, but any extra parameters were
used as-is. E.g. `ZSTD_c_format`.
This PR makes all the simple single-pass functions listed below ignore
the advanced parameters, as intended.
* `ZSTD_compressCCtx()`
* `ZSTD_compress_usingDict()`
* `ZSTD_compress_usingCDict()`
* `ZSTD_compress_advanced()`
* `ZSTD_compress_usingCDict_advanced()`
It also adds a test case that ensures that each of these functions
ignore the advanced parameters.
Forward the correct compressionLevel to the appliedParams in all cases.
It was already correct for the advanced API, so only the old single-pass
functions needed to be fixed.
This compression level is unused by the library, but is set so that the
tracing framework can consume it.
The most common information that you want to track between begin() and
end() is the timestamp of the begin function, so you can measure the
duration of the (de)compression call. Allow the tracing library to put
this information inside the `ZSTD_TraceCtx`, so it doesn't need to keep
a global map in this case. If a single uint64_t is not enough, the
tracing library can return a unique identifier (like the context
pointer) instead, and use it as a key in a map.
This keeps the simple case simple.
This program takes a file with concatenated zstd frames and splits the
file up by frame. E.g. if `dir.zst` has 4 frames:
```
> ./recover_directory dir.zst recovery/file
Recovering 4 files...
Recovered recovery/file0
Recovered recovery/file1
Recovered recovery/file2
Recovered recovery/file3
Complete
```
Treat ZSTD_getCParams() and ZSTD_adjustCParams() in the same way
we treat streaming compression. Choose parameters based on the
dictionary size + source size, and assume the source size is small
if unkown. But, don't shrink the window log down in
ZSTD_adjustCParams_internal().
Fixes#2442.
1. When creating a dictionary keep the same behavior as before.
Assume the source size is 513 bytes when adjusting parameters.
2. When calling ZSTD_getCParams() or ZSTD_adjustCParams() keep
the same behavior as before.
3. When attaching a dictionary keep the same behavior of ignoring
the dictionary size. When streaming this will select the
largest parameters and not adjust them down. But, the CDict
will use the correctly sized parameters, which seems like the
right tradeoff.
4. When not attaching a dictionary (either forced not to, or
using a prefix dictionary) we select parameters based on the
dictionary size + source size, and assume the source size is
small, which is the same behavior as before. But, now we don't
adjust the window log (and hash and chain log) down when the
source size is unknown.
When the source size is unknown all cdicts should attach, except
when the user disables attaching, or `forceWindow` is used. This
means that when streaming with a CDict we end up in the good case
where we get small CDict parameters, and large source parameters.
TODO: Add a streaming + dictionary regression test case.
* Add a test that runs without a pledgedSrcSize and with a dictionary.
* Add github.tar data with uses the github dictionary while compressing
github.tar, instead of each file individually.
The pkgconfig file generation didn't correctly escape the paths. It both
quoted and escaped spaces with `\`, which doesn't work. The fix is to
remove the quoting.
Comment and refactor `HUF_buildCTable()` and the helper functions
it calls as I read and understand the code. Hopefully this refactor
makes the code a bit more clear.
