From: Yann Collet Date: Sun, 31 Dec 2017 14:50:00 +0000 (+0100) Subject: updated /lib documentation X-Git-Tag: v1.3.4~1^2~97 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2eff2171366239a129c35aae4cd610661770e812;p=thirdparty%2Fzstd.git updated /lib documentation --- diff --git a/lib/README.md b/lib/README.md index df136c486..8a13b4e3d 100644 --- a/lib/README.md +++ b/lib/README.md @@ -2,16 +2,19 @@ Zstandard library files ================================ The __lib__ directory is split into several sub-directories, -in order to make it easier to select or exclude specific features. +in order to make it easier to select or exclude 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). +`Makefile` script is provided, supporting all standard [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 in default system directories +`libzstd` default scope includes compression, decompression, dictionary building, +and decoding support for legacy formats >= v0.4.0. + #### API @@ -27,29 +30,37 @@ Optional advanced features are exposed via : - `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. + These APIs are not "stable", their definition may change in the future. + As a consequencem, it 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. + - 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` . + 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 legacy zstd formats, starting from `v0.1.0`. + This module depends on `lib/common` and `lib/decompress`. + To enable this feature, it's required to define `ZSTD_LEGACY_SUPPORT` during compilation. + Typically, with `gcc`, add argument `-DZSTD_LEGACY_SUPPORT=1`. + Using higher number limits versions supported. + For example, `ZSTD_LEGACY_SUPPORT=2` means : "support legacy formats >= v0.2.0". + `ZSTD_LEGACY_SUPPORT=3` means : "support legacy formats >= v0.3.0", and so on. + Starting v0.8.0, all versions of `zstd` produce frames compliant with specification. + As a consequence, `ZSTD_LEGACY_SUPPORT=8` (or more) doesn't trigger legacy support. + Also, `ZSTD_LEGACY_SUPPORT=0` means "do __not__ support legacy formats". + Once enabled, this capability is transparently triggered within decompression functions. + It's also possible to invoke directly legacy API, as exposed in `lib/legacy/zstd_legacy.h`. + Each version also provides an additional dedicated set of advanced API. + For example, advanced API for version `v0.4` is exposed in `lib/legacy/zstd_v04.h` . + Note : `lib/legacy` only supports _decoding_ legacy formats. #### Multithreading support @@ -57,19 +68,16 @@ Optional advanced features are exposed via : 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) +- on POSIX systems : compile with pthread (`-pthread` compilation flag for `gcc`) 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. +Multithreading capabilities are exposed +via [advanced API `ZSTD_compress_generic()` defined in `lib/zstd.h`](https://github.com/facebook/zstd/blob/dev/lib/zstd.h#L919). +This API is still considered experimental, +but is expected to become "stable" at some point in the future. #### Windows : using MinGW+MSYS to create DLL @@ -92,7 +100,6 @@ The compiled executable will require ZSTD DLL which is available at `dll\libzstd 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`.