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
```
Any stable API entry point introduced after v1.0
should be documented with its minimum version number.
Since PR fixes this requirement
updating mostly new entry points since v1.4.0
and newly introduced ones for future v1.5.0.
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`.
If build_dir is set the zstd build complains about md5sum not being found.
Fix this by checking if build_dir is set before checking and using the hash tool
just like in lib/Makefile .
* Perform 64-byte alignment of wksp tables and aligneds internally
* Clean up cwskp_finalize() function to only do two allocs
* Refactor aligned/buffer reservation code, remove ASAN req for alignment reservations
* Change from allocating 128 bytes always to allocating only buffer space as needed for tables/aligned
* Back out aligned/table reservation order restriction
* Add stricter bounds for new/resized wksps, fix comment in zstd_cwksp.h
* Do not emit last partitions of blocks as RLE/uncompressed
* Fix repcode updates within block splitter
* Add a entropytables confirm function, redo ZSTD_confirmRepcodesAndEntropyTables() for better function signature
* Add a repcode updater to block splitter, no longer need to force emit compressed blocks
* 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`
