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.
When ZSTD_e_end directive is provided,
the question is not only "are internal buffers completely flushed",
it is also "is current frame completed".
In some rare cases,
it was possible for internal buffers to be completely flushed,
triggering a @return == 0,
but frame was not completed as it needed a last null-size block to mark the end,
resulting in an unfinished frame.
added some test
also updated relevant doc
+ fixed a mistake in `lz4` symlink support :
lz4 utility doesn't remove source files by default (like zstd, but unlike gzip).
The symlink must behave the same.
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.
it still fallbacks to single-thread blocking invocation
when input is small (<1job)
or when invoking ZSTDMT_compress(), which is blocking.
Also : fixed a bug in new block-granular compression routine.
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).
we want the dictionary table to be fully sorted,
not just lazily filled.
Dictionary loading is a bit more intensive,
but it saves cpu cycles for match search during compression.
