changed workspace parameter convention
to always provide workspaceSize,
so that size can be explicitly checked.
Also, use more enum to make the meaning of some parameters more explicit.
fix#1385
decompressing into NULL was an automatic error.
It is now allowed, as long as the content of the frame is empty.
Seems to simplify things for `arrow`.
Maybe some other projects rely on this behavior ?
fix#1379
decodecorpus was generating one extraneous byte when `nbSeq==0`.
This is disallowed by the specification.
The reference decoder was just skipping the extraneous byte.
It is now stricter, and flag such situation as an error.
and slightly refactored affected function.
Honestly, the formula calculating variance should get a second reviewing round,
it's not clear if it's correct.
We could allocate up to 2^28 bytes of memory when using 2 threads with
window log = 24. Now, we limit it to 2^26 bytes of memory when not running
big tests.
I chose max window log = 22 since that is the maximum source size when
big tests are disabled. Hopefully this will be enough to reduce or
eliminate the test failures.
experimental function ZSTD_compressBlock() is designed for very small data in mind,
for situation where saving the ~12 bytes of frame header can actually make a difference.
Some systems though may have to deal with small and large data entangled.
If it's larger than a block (> 128KB), compressBlock() cannot compress them in one round.
That's why it's possible to compress in multiple rounds.
This is a chain of compressed blocks.
Some users push this capability to the limit, encoding gigantic chain of blocks.
On crossing the 4GB limit, some internal overflow occurs.
This fix moves the overflow correction mechanism higher in the call chain,
so that it's applied also to gigantic chains of blocks.
Added a test case in fuzzer.c, which crashes before the fix, and pass now.
