reported by @let-def.
It's actually a bug in ZSTD_compressBegin_usingCDict()
which would pass a wrong pledgedSrcSize value (0 instead of ZSTD_CONTENTSIZE_UNKNOWN)
resulting in wrong window size, resulting in downsized seqStore,
resulting in segfault when writing into the seqStore later in the process.
Added a test in fuzzer to cover this use case (fails before the patch).
The overflow protection is broken when the window log is `> (3U << 29)`, so 31.
It doesn't work when `current` isn't around `1U << windowLog` ahead of `lowLimit`,
and the the assertion `current > newCurrent` fails. This happens when the same
context is used many times over, but with a large window log, like in zstdmt.
Fix it by triggering correction based on `nextSrc - base` instead of `lowLimit`.
The added test fails before the patch, and passes after.
negative compression level trade compression ratio for more compression speed.
They turn off huffman compression of literals,
and use row 0 as baseline with a stepSize = -cLevel.
added associated test in fuzzer
also added : new advanced parameter ZSTD_p_literalCompression
This makes it easier to explain that nbWorkers=0 --> single-threaded mode,
while nbWorkers=1 --> asynchronous mode (one mode thread on top of the "main" caller thread).
No need for an additional asynchronous mode flag.
nbWorkers>=2 works the same as nbThreads>=2 previously.
ZSTD_create?Dict() is required to produce a ?Dict* return type
because `free()` does not accept a `const type*` argument.
If it wasn't for this restriction, I would have preferred to create a `const ?Dict*` object
to emphasize the fact that, once created, a dictionary never changes
(hence can be shared concurrently until the end of its lifetime).
There is no such limitation with initStatic?Dict() :
as stated in the doc, there is no corresponding free() function,
since `workspace` is provided, hence allocated, externally,
it can only be free() externally.
Which means, ZSTD_initStatic?Dict() can return a `const ZSTD_?Dict*` pointer.
Tested with `make all`, to catch initStatic's users,
which, incidentally, also updated zstd.h documentation.
Pathological samples may result in literal section being incompressible.
This case is now detected,
and literal distribution is replaced by one that can be written into the dictionary.
constants in zstd.h should not depend on MIN() macro which existence is not guaranteed.
Added a test to check the specific constants.
The test is a bit too specific.
But I have found no way to control a more generic "are all macro already defined" condition,
especially as this is a valid construction (the missing macro might be defined later, intentionnally).
ZSTD_compress() and friends would treat an empty input as an unknown size
when selecting parameters. Thus, they would drastically overallocate the
context. Tell ZSTD_getParams() that the source size is 1 when it is empty.
adding check at end of single-pass ZSTD_decompressFrame().
Check within ZSTD_decompressContinue() was already added in a previous patch : b3f33ccfb3b4fcc73df82126fd5ecfb751268fc6
supporting function for bufferless streaming API (ZSTD_decompressContinue())
makes it possible to correctly size a round buffer for decoding using this API.
also : added field blockSizeMax within ZSTD_frameHeader,
as it's a necessary information to know when to restart at beginning of decoding buffer.
