149 lines
6.9 KiB
Markdown
149 lines
6.9 KiB
Markdown
Zstandard library files
|
|
================================
|
|
|
|
The __lib__ directory is split into several sub-directories,
|
|
in order to make it easier to select or exclude features.
|
|
|
|
|
|
#### Building
|
|
|
|
`Makefile` script is provided, supporting [Makefile conventions](https://www.gnu.org/prep/standards/html_node/Makefile-Conventions.html#Makefile-Conventions),
|
|
including commands variables, staged install, directory variables and standard targets.
|
|
- `make` : generates both static and dynamic libraries
|
|
- `make install` : install libraries and headers in target system directories
|
|
|
|
`libzstd` default scope is pretty large, including compression, decompression, dictionary builder,
|
|
and support for decoding legacy formats >= v0.5.0.
|
|
The scope can be reduced on demand (see paragraph _modular build_).
|
|
|
|
|
|
#### Multithreading support
|
|
|
|
Multithreading is disabled by default when building with `make`.
|
|
Enabling multithreading requires 2 conditions :
|
|
- set build macro `ZSTD_MULTITHREAD` (`-DZSTD_MULTITHREAD` for `gcc`)
|
|
- for POSIX systems : compile with pthread (`-pthread` compilation flag for `gcc`)
|
|
|
|
Both conditions are automatically applied when invoking `make lib-mt` target.
|
|
|
|
When linking a POSIX program with a multithreaded version of `libzstd`,
|
|
note that it's necessary to request the `-pthread` flag during link stage.
|
|
|
|
Multithreading capabilities are exposed
|
|
via the [advanced API defined in `lib/zstd.h`](https://github.com/facebook/zstd/blob/v1.3.8/lib/zstd.h#L592).
|
|
|
|
|
|
#### 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 a `ZSTD_ErrorCode`, for accurate error handling.
|
|
|
|
- `ZSTD_STATIC_LINKING_ONLY` : if this macro is defined _before_ including `zstd.h`,
|
|
it unlocks access to the experimental API,
|
|
exposed in the second part of `zstd.h`.
|
|
All definitions in the experimental APIs are unstable,
|
|
they may still change in the future, or even be removed.
|
|
As a consequence, experimental definitions shall ___never be used with dynamic library___ !
|
|
Only static linking is allowed.
|
|
|
|
|
|
#### Modular build
|
|
|
|
It's possible to compile only a limited set of features within `libzstd`.
|
|
The file structure is designed to make this selection manually achievable for any build system :
|
|
|
|
- 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` : makes it possible to decompress legacy zstd formats, starting from `v0.1.0`.
|
|
This module depends on `lib/common` and `lib/decompress`.
|
|
To enable this feature, define `ZSTD_LEGACY_SUPPORT` during compilation.
|
|
Specifying a number limits versions supported to that version onward.
|
|
For example, `ZSTD_LEGACY_SUPPORT=2` means : "support legacy formats >= v0.2.0".
|
|
Conversely, `ZSTD_LEGACY_SUPPORT=0` means "do __not__ support legacy formats".
|
|
By default, this build macro is set as `ZSTD_LEGACY_SUPPORT=5`.
|
|
Decoding supported legacy format is a transparent capability triggered within decompression functions.
|
|
It's also allowed to invoke legacy API directly, exposed in `lib/legacy/zstd_legacy.h`.
|
|
Each version does also provide its own set of advanced API.
|
|
For example, advanced API for version `v0.4` is exposed in `lib/legacy/zstd_v04.h` .
|
|
|
|
- While invoking `make libzstd`, it's possible to define build macros
|
|
`ZSTD_LIB_COMPRESSION, ZSTD_LIB_DECOMPRESSION`, `ZSTD_LIB_DICTBUILDER`,
|
|
and `ZSTD_LIB_DEPRECATED` as `0` to forgo compilation of the corresponding features.
|
|
This will also disable compilation of all dependencies
|
|
(eg. `ZSTD_LIB_COMPRESSION=0` will also disable dictBuilder).
|
|
|
|
- There are some additional build macros that can be used to minify the decoder.
|
|
|
|
Zstandard often has more than one implementation of a piece of functionality,
|
|
where each implementation optimizes for different scenarios. For example, the
|
|
Huffman decoder has complementary implementations that decode the stream one
|
|
symbol at a time or two symbols at a time. Zstd normally includes both (and
|
|
dispatches between them at runtime), but by defining `HUF_FORCE_DECOMPRESS_X1`
|
|
or `HUF_FORCE_DECOMPRESS_X2`, you can force the use of one or the other, avoiding
|
|
compilation of the other. Similarly, `ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT`
|
|
and `ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG` force the compilation and use of
|
|
only one or the other of two decompression implementations. The smallest
|
|
binary is achieved by using `HUF_FORCE_DECOMPRESS_X1` and
|
|
`ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT`.
|
|
|
|
For squeezing the last ounce of size out, you can also define
|
|
`ZSTD_NO_INLINE`, which disables inlining, and `ZSTD_STRIP_ERROR_STRINGS`,
|
|
which removes the error messages that are otherwise returned by
|
|
`ZSTD_getErrorName`.
|
|
|
|
- While invoking `make libzstd`, the build macro `ZSTD_LEGACY_MULTITHREADED_API=1`
|
|
will expose the deprecated `ZSTDMT` API exposed by `zstdmt_compress.h` in
|
|
the shared library, which is now hidden by default.
|
|
|
|
|
|
#### 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`.
|
|
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 :
|
|
|
|
- `BUCK` : support for `buck` build system (https://buckbuild.com/)
|
|
- `Makefile` : `make` script to build and install zstd library (static and dynamic)
|
|
- `README.md` : this file
|
|
- `dll/` : resources directory for Windows compilation
|
|
- `libzstd.pc.in` : script for `pkg-config` (used in `make install`)
|