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diff --git a/src/zstd/lib/README.md b/src/zstd/lib/README.md new file mode 100644 index 00000000..df136c48 --- /dev/null +++ b/src/zstd/lib/README.md @@ -0,0 +1,108 @@ +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](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 |