contrib/lz4/lib/README.md in extlz4-0.3.1 vs contrib/lz4/lib/README.md in extlz4-0.3.2

- old
+ new

@@ -33,25 +33,26 @@ #### Advanced / Experimental API Definitions which are not guaranteed to remain stable in future versions, are protected behind macros, such as `LZ4_STATIC_LINKING_ONLY`. -As the name implies, these definitions can only be invoked +As the name strongly implies, these definitions should only be invoked in the context of static linking ***only***. Otherwise, dependent application may fail on API or ABI break in the future. -The associated symbols are also not present in dynamic library by default. +The associated symbols are also not exposed by the dynamic library by default. Should they be nonetheless needed, it's possible to force their publication -by using build macro `LZ4_PUBLISH_STATIC_FUNCTIONS`. +by using build macros `LZ4_PUBLISH_STATIC_FUNCTIONS` +and `LZ4F_PUBLISH_STATIC_FUNCTIONS`. #### Build macros -The following build macro can be selected at compilation time : +The following build macro can be selected to adjust source code behavior at compilation time : -- `LZ4_FAST_DEC_LOOP` : this triggers the optimized decompression loop. - This loops works great on x86/x64 cpus, and is automatically enabled on this platform. - It's possible to enable or disable it manually, by passing `LZ4_FAST_DEC_LOOP=1` or `0` to the preprocessor. +- `LZ4_FAST_DEC_LOOP` : this triggers a speed optimized decompression loop, more powerful on modern cpus. + This loop works great on `x86`, `x64` and `aarch64` cpus, and is automatically enabled for them. + It's also possible to enable or disable it manually, by passing `LZ4_FAST_DEC_LOOP=1` or `0` to the preprocessor. For example, with `gcc` : `-DLZ4_FAST_DEC_LOOP=1`, and with `make` : `CPPFLAGS+=-DLZ4_FAST_DEC_LOOP=1 make lz4`. - `LZ4_DISTANCE_MAX` : control the maximum offset that the compressor will allow. Set to 65535 by default, which is the maximum value supported by lz4 format. @@ -63,14 +64,30 @@ - `LZ4_DISABLE_DEPRECATE_WARNINGS` : invoking a deprecated function will make the compiler generate a warning. This is meant to invite users to update their source code. Should this be a problem, it's generally possible to make the compiler ignore these warnings, for example with `-Wno-deprecated-declarations` on `gcc`, or `_CRT_SECURE_NO_WARNINGS` for Visual Studio. - Another method is to define `LZ4_DISABLE_DEPRECATE_WARNINGS` - before including the LZ4 header files. + This build macro offers another project-specific method + by defining `LZ4_DISABLE_DEPRECATE_WARNINGS` before including the LZ4 header files. +- `LZ4_USER_MEMORY_FUNCTIONS` : replace calls to <stdlib>'s `malloc`, `calloc` and `free` + by user-defined functions, which must be called `LZ4_malloc()`, `LZ4_calloc()` and `LZ4_free()`. + User functions must be available at link time. +- `LZ4_FORCE_SW_BITCOUNT` : by default, the compression algorithm tries to determine lengths + by using bitcount instructions, generally implemented as fast single instructions in many cpus. + In case the target cpus doesn't support it, or compiler intrinsic doesn't work, or feature bad performance, + it's possible to use an optimized software path instead. + This is achieved by setting this build macros . + In most cases, it's not expected to be necessary, + but it can be legitimately considered for less common platforms. + +- `LZ4_ALIGN_TEST` : alignment test ensures that the memory area + passed as argument to become a compression state is suitably aligned. + This test can be disabled if it proves flaky, by setting this value to 0. + + #### Amalgamation lz4 source code can be amalgamated into a single file. One can combine all source code into `lz4_all.c` by using following command: ``` @@ -100,10 +117,10 @@ The compiled executable will require LZ4 DLL which is available at `dll\liblz4.dll`. #### Miscellaneous -Other files present in the directory are not source code. There are : +Other files present in the directory are not source code. They are : - `LICENSE` : contains the BSD license text - `Makefile` : `make` script to compile and install lz4 library (static and dynamic) - `liblz4.pc.in` : for `pkg-config` (used in `make install`) - `README.md` : this file