This new setup is slighly better on `silesia.tar` :
Ratio : 3.649 -> 3.655
Speed : 11.9 MB/s -> 12.2 MB/s
At the cost of more memory : 24 MB -> 32 MB
The new memory budget is a reasonable interpolation between neighboring levels 12 and 14:
level 12 : 24 MB
level 13 : 32 MB (increased from 24 MB)
level 14 : 48 MB
Window size remains unaffected (4 MB)
* The block splitter missed a bounds check, so when the buffer is too small it
passes an erroneously large size to `ZSTD_entropyCompressSeqStore()`, which
can then write the compressed data past the end of the buffer. This is a new
regression in v1.5.0 when the block splitter is enabled. It is either enabled
explicitly, or implicitly when using the optimal parser and `ZSTD_compress2()`
or `ZSTD_compressStream*()`.
* `HUF_writeCTable_wksp()` omits a bounds check when calling
`HUF_compressWeights()`. If it is called with `dstCapacity == 0` it will pass
an erroneously large size to `HUF_compressWeights()`, which can then write
past the end of the buffer. This bug has been present for ages. However, I
believe that zstd cannot trigger the bug, because it never calls
`HUF_compress*()` with `dstCapacity == 0` because of [this check][1].
Credit to: Oss-Fuzz
[1]: 89127e5ee2/lib/compress/zstd_compress_literals.c (L100)
* Flatten ZSTD_row_getMatchMask
* Remove the SIMD abstraction layer.
* Add big endian support.
* Align `hashTags` within `tagRow` to a 16-byte boundary.
* Switch SSE2 to use aligned reads.
* Optimize scalar path using SWAR.
* Optimize neon path for `n == 32`
* Work around minor clang issue for NEON (https://bugs.llvm.org/show_bug.cgi?id=49577)
* replace memcpy with MEM_readST
* silence alignment warnings
* fix neon casts
* Update zstd_lazy.c
* unify simd preprocessor detection (#3)
* remove duplicate asserts
* tweak rotates
* improve endian detection
* add cast
there is a fun little catch-22 with gcc: result from pmovmskb has to be cast to uint32_t to avoid a zero-extension
but must be uint16_t to get gcc to generate a rotate instruction..
* more casts
* fix casts
better work-around for the (bogus) warning: unary minus on unsigned
Call `ZSTD_enforceMaxDist()` before each block with the beginning of the
block. This ensures that `lowLimit` is updated to `dictLimit` whenever
the ext-dict is out of range, so we can use prefix mode for speed.
This can cause non-determinism because prefix mode and ext-dict mode
match finders can return different results. It can also hurt speed
because ext-dict match finders are slower.
The scenario is:
1. Compress large data with a dictionary.
2. The dictionary goes out of bounds, so we invalidate it.
3. However, we still have `lowLimit < dictLimit`, since it is
never updated.
4. We will call the ext-dict match finder instead of the prefix one.
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.
* 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.
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`.
* 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`
