This new parameter makes it possible to call
streaming ZSTDMT with a single thread set
which is non blocking.
It makes it possible for the main thread to do other tasks in parallel
while the worker thread does compression.
Typically, for zstd cli, it means it can do I/O stuff.
Applied within fileio.c, this patch provides non-negligible gains during compression.
Tested on my laptop, with enwik9 (1000000000 bytes) : time zstd -f enwik9
With traditional single-thread blocking mode :
real 0m9.557s
user 0m8.861s
sys 0m0.538s
With new single-worker non blocking mode :
real 0m7.938s
user 0m8.049s
sys 0m0.514s
=> 20% faster
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).
in a new "custom memory allocator" paragraph
which is itself part of "memory management" category.
This makes it simpler to see the relation between the type and its usages.
ZSTD_updateTree() expected to be followed by a Bt match finder, which would update zc->nextToUpdate.
With the new optimal match finder, it's not necessarily the case : a match might be found during repcode or hash3, and stops there because it reaches sufficient_len, without even entering the binary tree.
Previous policy was to nonetheless update zc->nextToUpdate, but the current position would not be inserted, creating "holes" in the btree, aka positions that will no longer be searched.
Now, when current position is not inserted, zc->nextToUpdate is not update, expecting ZSTD_updateTree() to fill the tree later on.
Solution selected is that ZSTD_updateTree() takes care of properly setting zc->nextToUpdate,
so that it no longer depends on a future function to do this job.
It took time to get there, as the issue started with a memory sanitizer error.
The pb would have been easier to spot with a proper `assert()`.
So this patch add a few of them.
Additionnally, I discovered that `make test` does not enable `assert()` during CLI tests.
This patch enables them.
Unfortunately, these `assert()` triggered other (unrelated) bugs during CLI tests, mostly within zstdmt.
So this patch also fixes them.
- Changed packed structure for gcc memory access : memory sanitizer would complain that a read "might" reach out-of-bound position on the ground that the `union` is larger than the type accessed.
Now, to avoid this issue, each type is independent.
- ZSTD_CCtxParams_setParameter() : @return provides the value of parameter, clamped/fixed appropriately.
- ZSTDMT : changed constant name to ZSTDMT_JOBSIZE_MIN
- ZSTDMT : multithreading is automatically disabled when srcSize <= ZSTDMT_JOBSIZE_MIN, since only one thread will be used in this case (saves memory and runtime).
- ZSTDMT : nbThreads is automatically clamped on setting the value.
it was invoking ZSTD_initCStream_advanced() with pledgedSrcSize==0 and contentSizeFlag=1
which means "empty"
while the intention was to mean "unknown".
The contentSizeFlag==1 is new, it is a consequence of setting this value to 1 by default.
The solution selected here is to pass ZSTD_CONTENTSIZE_UNKNOWN to mean "unknown".
So contentSizeFlag remains set (it wasn't in previous versions).
to mean "pledgedSrcSize is not known at init time" instead of `0`.
Note that, a few prototypes created and documented with `0` to mean "unknown" still interpret "0" as unknown,
to avoid breaking 3rd party applications which depend on this behavior.
But this value is no longer recommended to mean "unknown".
In some future version, it might be possible to switch "0" to mean "empty",
as is already the case for several prototypes.
The advantage is that pledgedSrcSize field would have same behavior accross entire API,
making it easier to reason about.
Note that all concerned prototypes belong to the "experimental" API section.
srcSize is controlled at end of compression,
so if someone uses "0" to mean "unknown" while it effectively means "empty",
this is immediately caught by the compression function, which generates an error code : ZSTD_ERROR_srcSize_wrong
ZSTD_compressBound() works fine, but is only useful for dynamic allocation.
For static allocation, only a macro can provide the amount during compilation time.
It would previously exit when srcSize is unknown.
But in the case of custom parameters,
hLog and cLog can still be too large in comparison with windowLog.
Reduces maximum memory allocated during zstreamtest --newapi
* Maximum window size in 32-bit mode is 1GB, since allocations for 2GB fail
on my Mac.
* Maximum window size in 64-bit mode is 2GB, since that is the largest
power of 2 that works with the overflow prevention.
* Allow `--long=windowLog` to set the window log, along with
`--zstd=wlog=#`. These options also set the window size during
decompression, but don't override `--memory=#` if it is set.
* Present a helpful error message when the window size is too large during
decompression.
* The long range matcher defaults to a hash log 7 less than the window log,
which keeps it at 20 for window log 27.
* Keep the default long range matcher window size and the default maximum
window size at 27 for the API and CLI.
* Add tests that use the maximum window size and hash size for compression
and decompression.
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.
Yann Collet
Nick Terrell
Yann Collet
Stella Lau