Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+LZ4 - Library Files
+================================
+
+The `/lib` directory contains many files, but depending on project's objectives,
+not all of them are required.
+Limited systems may want to reduce the nb of source files to include
+as a way to reduce binary size and dependencies.
+
+Capabilities are added at the "level" granularity, detailed below.
+
+#### Level 1 : Minimal LZ4 build
+
+The minimum required is **`lz4.c`** and **`lz4.h`**,
+which provides the fast compression and decompression algorithms.
+They generate and decode data using the [LZ4 block format].
+
+
+#### Level 2 : High Compression variant
+
+For more compression ratio at the cost of compression speed,
+the High Compression variant called **lz4hc** is available.
+Add files **`lz4hc.c`** and **`lz4hc.h`**.
+This variant also compresses data using the [LZ4 block format],
+and depends on regular `lib/lz4.*` source files.
+
+
+#### Level 3 : Frame support, for interoperability
+
+In order to produce compressed data compatible with `lz4` command line utility,
+it's necessary to use the [official interoperable frame format].
+This format is generated and decoded automatically by the **lz4frame** library.
+Its public API is described in `lib/lz4frame.h`.
+In order to work properly, lz4frame needs all other modules present in `/lib`,
+including, lz4 and lz4hc, and also **xxhash**.
+So it's necessary to also include `xxhash.c` and `xxhash.h`.
+
+
+#### Level 4 : File compression operations
+
+As a helper around file operations,
+the library has been recently extended with `lz4file.c` and `lz4file.h`
+(still considered experimental at the time of this writing).
+These helpers allow opening, reading, writing, and closing files
+using transparent LZ4 compression / decompression.
+As a consequence, using `lz4file` adds a dependency on `<stdio.h>`.
+
+`lz4file` relies on `lz4frame` in order to produce compressed data
+conformant to the [LZ4 Frame format] specification.
+Consequently, to enable this capability,
+it's necessary to include all `*.c` and `*.h` files from `lib/` directory.
+
+
+#### 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 suggests, 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 exposed by the dynamic library by default.
+Should they be nonetheless needed, it's possible to force their publication
+by using build macros `LZ4_PUBLISH_STATIC_FUNCTIONS`
+and `LZ4F_PUBLISH_STATIC_FUNCTIONS`.
+
+
+#### Build macros
+
+The following build macro can be selected to adjust source code behavior at compilation time :
+
+- `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.
+  Reducing maximum distance will reduce opportunities for LZ4 to find matches,
+  hence will produce a worse compression ratio.
+  Setting a smaller max distance could allow compatibility with specific decoders with limited memory budget.
+  This build macro only influences the compressed output of the compressor.
+
+- `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.
+  This build macro offers another project-specific method
+  by defining `LZ4_DISABLE_DEPRECATE_WARNINGS` before including the LZ4 header files.
+
+- `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.
+
+- `LZ4_USER_MEMORY_FUNCTIONS` : replace calls to `<stdlib,h>`'s `malloc()`, `calloc()` and `free()`
+  by user-defined functions, which must be named `LZ4_malloc()`, `LZ4_calloc()` and `LZ4_free()`.
+  User functions must be available at link time.
+
+- `LZ4_STATIC_LINKING_ONLY_DISABLE_MEMORY_ALLOCATION` :
+  Remove support of dynamic memory allocation.
+  For more details, see description of this macro in `lib/lz4.c`.
+
+- `LZ4_FREESTANDING` : by setting this build macro to 1,
+  LZ4/HC removes dependencies on the C standard library,
+  including allocation functions and `memmove()`, `memcpy()`, and `memset()`.
+  This build macro is designed to help use LZ4/HC in restricted environments
+  (embedded, bootloader, etc).
+  For more details, see description of this macro in `lib/lz4.h`.
+
+
+
+#### 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:
+```
+cat lz4.c lz4hc.c lz4frame.c > lz4_all.c
+```
+(`cat` file order is important) then compile `lz4_all.c`.
+All `*.h` files present in `/lib` remain necessary to compile `lz4_all.c`.
+
+
+#### Windows : using MinGW+MSYS to create DLL
+
+DLL can be created using MinGW+MSYS with the `make liblz4` command.
+This command creates `dll\liblz4.dll` and the import library `dll\liblz4.lib`.
+To override the `dlltool` command when cross-compiling on Linux, just set the `DLLTOOL` variable. Example of cross compilation on Linux with mingw-w64 64 bits:
+```
+make BUILD_STATIC=no CC=x86_64-w64-mingw32-gcc DLLTOOL=x86_64-w64-mingw32-dlltool OS=Windows_NT
+```
+The import library is only required with Visual C++.
+The header files `lz4.h`, `lz4hc.h`, `lz4frame.h` and the dynamic library
+`dll\liblz4.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 LZ4 consists of a single `test-dll.c`
+file it should be linked with `dll\liblz4.dll`. For example:
+```
+    $(CC) $(CFLAGS) -Iinclude/ test-dll.c -o test-dll dll\liblz4.dll
+```
+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. 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
+
+[official interoperable frame format]: ../doc/lz4_Frame_format.md
+[LZ4 Frame format]: ../doc/lz4_Frame_format.md
+[LZ4 block format]: ../doc/lz4_Block_format.md
+
+
+#### License
+
+All source material within __lib__ directory are BSD 2-Clause licensed.
+See [LICENSE](LICENSE) for details.
+The license is also reminded at the top of each source file.