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05dffe43a7
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Yann Collet 05dffe43a7 Fixed Btree update 
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.
2017-11-16 12:18:56 -08:00
..
common Fixed Btree update 2017-11-16 12:18:56 -08:00
compress Fixed Btree update 2017-11-16 12:18:56 -08:00
decompress Allow skippable frames of any size 2017-11-01 13:07:26 -07:00
deprecated fixed zbufftest 2017-10-19 14:06:02 -07:00
dictBuilder [libzstd] pthread function prefixed with ZSTD_ 2017-09-27 11:48:48 -07:00
dll fixed a bunch of headers after license change (#825) 2017-08-31 11:24:54 -07:00
legacy updated license header 2017-09-08 00:09:23 -07:00
.gitignore makes it possible to compile libzstd in single-thread mode without zstdmt_compress.c (#819) 2017-09-11 14:09:34 -07:00
BUCK Update BUCK files 2017-10-25 12:47:57 -07:00
libzstd.pc.in updated pkg config file 2016-11-30 11:06:58 -08:00
Makefile makes it possible to compile libzstd in single-thread mode without zstdmt_compress.c (#819) 2017-09-11 14:09:34 -07:00
README.md programs/Makefile : better support for GNU conventions 2017-09-06 16:53:59 -07:00
zstd.h Fixed Btree update 2017-11-16 12:18:56 -08:00

README.md

Zstandard library files

The lib directory is split into several sub-directories, in order to make it easier to select or exclude specific features.

Building

Makefile script is provided, supporting the standard set of commands, directories, and variables (see https://www.gnu.org/prep/standards/html_node/Command-Variables.html).

  • make : generates both static and dynamic libraries
  • make install : install libraries in default system directories

API

Zstandard's stable API is exposed within lib/zstd.h.

Advanced API

Optional advanced features are exposed via :

  • lib/common/zstd_errors.h : translates size_t function results into an ZSTD_ErrorCode, for accurate error handling.
  • ZSTD_STATIC_LINKING_ONLY : if this macro is defined before including zstd.h, it unlocks access to advanced experimental API, exposed in second part of zstd.h. These APIs shall never be used with dynamic library ! They are not "stable", their definition may change in the future. Only static linking is allowed.

Modular build

  • Directory lib/common is always required, for all variants.
  • Compression source code lies in lib/compress
  • Decompression source code lies in lib/decompress
  • It's possible to include only compress or only decompress, they don't depend on each other.
  • lib/dictBuilder : makes it possible to generate dictionaries from a set of samples. The API is exposed in lib/dictBuilder/zdict.h. This module depends on both lib/common and lib/compress .
  • lib/legacy : source code to decompress older zstd formats, starting from v0.1. This module depends on lib/common and lib/decompress. To enable this feature, it's necessary to define ZSTD_LEGACY_SUPPORT = 1 during compilation. Typically, with gcc, add argument -DZSTD_LEGACY_SUPPORT=1. Using higher number limits the number of version supported. For example, ZSTD_LEGACY_SUPPORT=2 means : "support legacy formats starting from v0.2+". The API is exposed in lib/legacy/zstd_legacy.h. Each version also provides a (dedicated) set of advanced API. For example, advanced API for version v0.4 is exposed in lib/legacy/zstd_v04.h .

Multithreading support

Multithreading is disabled by default when building with make. Enabling multithreading requires 2 conditions :

  • set macro ZSTD_MULTITHREAD
  • on POSIX systems : compile with pthread (-pthread compilation flag for gcc for example)

Both conditions are automatically triggered by invoking make lib-mt target. Note that, when linking a POSIX program with a multithreaded version of libzstd, it's necessary to trigger -pthread flag during link stage.

Multithreading capabilities are exposed via :

  • private API lib/compress/zstdmt_compress.h. Symbols defined in this header are currently exposed in libzstd, hence usable. Note however that this API is planned to be locked and remain strictly internal in the future.
  • advanced API ZSTD_compress_generic(), defined in lib/zstd.h, experimental section. This API is still considered experimental, but is designed to be labelled "stable" at some point in the future. It's the recommended entry point for multi-threading operations.

Windows : using MinGW+MSYS to create DLL

DLL can be created using MinGW+MSYS with the make libzstd command. This command creates dll\libzstd.dll and the import library dll\libzstd.lib. The import library is only required with Visual C++. The header file zstd.h and the dynamic library dll\libzstd.dll are required to compile a project using gcc/MinGW. The dynamic library has to be added to linking options. It means that if a project that uses ZSTD consists of a single test-dll.c file it should be linked with dll\libzstd.dll. For example:

    gcc $(CFLAGS) -Iinclude/ test-dll.c -o test-dll dll\libzstd.dll

The compiled executable will require ZSTD DLL which is available at dll\libzstd.dll.

Deprecated API

Obsolete API on their way out are stored in directory lib/deprecated. At this stage, it contains older streaming prototypes, in lib/deprecated/zbuff.h. Presence in this directory is temporary. These prototypes will be removed in some future version. Consider migrating code towards supported streaming API exposed in zstd.h.

Miscellaneous

The other files are not source code. There are :

  • LICENSE : contains the BSD license text
  • Makefile : make script to build and install zstd library (static and dynamic)
  • BUCK : support for buck build system (https://buckbuild.com/)
  • libzstd.pc.in : for pkg-config (used in make install)
  • README.md : this file