Restoring authorship annotation for <thegeorg@yandex-team.ru>. Commit 1 of 2.

1 files changed, 299 insertions, 299 deletions

diff --git a/contrib/libs/zstd/programs/README.md b/contrib/libs/zstd/programs/README.md
index 5570f90c3b..aaff49db5f 100644
--- a/contrib/libs/zstd/programs/README.md
+++ b/contrib/libs/zstd/programs/README.md
@@ -1,301 +1,301 @@
-Command Line Interface for Zstandard library
-============================================
-
-Command Line Interface (CLI) can be created using the `make` command without any additional parameters.
-There are however other Makefile targets that create different variations of CLI:
-- `zstd` : default CLI supporting gzip-like arguments; includes dictionary builder, benchmark, and supports decompression of legacy zstd formats
-- `zstd_nolegacy` : Same as `zstd` but without support for legacy zstd formats
-- `zstd-small` : CLI optimized for minimal size; no dictionary builder, no benchmark, and no support for legacy zstd formats
-- `zstd-compress` : version of CLI which can only compress into zstd format
-- `zstd-decompress` : version of CLI which can only decompress zstd format
-
-
-### Compilation variables
-`zstd` scope can be altered by modifying the following `make` variables :
-
-- __HAVE_THREAD__ : multithreading is automatically enabled when `pthread` is detected.
-  It's possible to disable multithread support, by setting `HAVE_THREAD=0`.
-  Example : `make zstd HAVE_THREAD=0`
-  It's also possible to force multithread support, using `HAVE_THREAD=1`.
-  In which case, linking stage will fail if neither `pthread` nor `windows.h` library can be found.
-  This is useful to ensure this feature is not silently disabled.
-
-- __ZSTD_LEGACY_SUPPORT__ : `zstd` can decompress files compressed by older versions of `zstd`.
-  Starting v0.8.0, all versions of `zstd` produce frames compliant with the [specification](../doc/zstd_compression_format.md), and are therefore compatible.
-  But older versions (< v0.8.0) produced different, incompatible, frames.
-  By default, `zstd` supports decoding legacy formats >= v0.4.0 (`ZSTD_LEGACY_SUPPORT=4`).
-  This can be altered by modifying this compilation variable.
-  `ZSTD_LEGACY_SUPPORT=1` means "support all formats >= v0.1.0".
-  `ZSTD_LEGACY_SUPPORT=2` means "support all formats >= v0.2.0", and so on.
-  `ZSTD_LEGACY_SUPPORT=0` means _DO NOT_ support any legacy format.
-  if `ZSTD_LEGACY_SUPPORT >= 8`, it's the same as `0`, since there is no legacy format after `7`.
-  Note : `zstd` only supports decoding older formats, and cannot generate any legacy format.
-
-- __HAVE_ZLIB__ : `zstd` can compress and decompress files in `.gz` format.
-  This is ordered through command `--format=gzip`.
-  Alternatively, symlinks named `gzip` or `gunzip` will mimic intended behavior.
-  `.gz` support is automatically enabled when `zlib` library is detected at build time.
-  It's possible to disable `.gz` support, by setting `HAVE_ZLIB=0`.
-  Example : `make zstd HAVE_ZLIB=0`
-  It's also possible to force compilation with zlib support, using `HAVE_ZLIB=1`.
-  In which case, linking stage will fail if `zlib` library cannot be found.
-  This is useful to prevent silent feature disabling.
-
-- __HAVE_LZMA__ : `zstd` can compress and decompress files in `.xz` and `.lzma` formats.
-  This is ordered through commands `--format=xz` and `--format=lzma` respectively.
-  Alternatively, symlinks named `xz`, `unxz`, `lzma`, or `unlzma` will mimic intended behavior.
-  `.xz` and `.lzma` support is automatically enabled when `lzma` library is detected at build time.
-  It's possible to disable `.xz` and `.lzma` support, by setting `HAVE_LZMA=0`.
-  Example : `make zstd HAVE_LZMA=0`
-  It's also possible to force compilation with lzma support, using `HAVE_LZMA=1`.
-  In which case, linking stage will fail if `lzma` library cannot be found.
-  This is useful to prevent silent feature disabling.
-
-- __HAVE_LZ4__ : `zstd` can compress and decompress files in `.lz4` formats.
-  This is ordered through commands `--format=lz4`.
-  Alternatively, symlinks named `lz4`, or `unlz4` will mimic intended behavior.
-  `.lz4` support is automatically enabled when `lz4` library is detected at build time.
-  It's possible to disable `.lz4` support, by setting `HAVE_LZ4=0` .
-  Example : `make zstd HAVE_LZ4=0`
-  It's also possible to force compilation with lz4 support, using `HAVE_LZ4=1`.
-  In which case, linking stage will fail if `lz4` library cannot be found.
-  This is useful to prevent silent feature disabling.
-
-- __ZSTD_NOBENCH__ : `zstd` cli will be compiled without its integrated benchmark module.
-  This can be useful to produce smaller binaries.
-  In this case, the corresponding unit can also be excluded from compilation target.
-
-- __ZSTD_NODICT__ : `zstd` cli will be compiled without support for the integrated dictionary builder.
-  This can be useful to produce smaller binaries.
-  In this case, the corresponding unit can also be excluded from compilation target.
-
-- __ZSTD_NOCOMPRESS__ : `zstd` cli will be compiled without support for compression.
-  The resulting binary will only be able to decompress files.
-  This can be useful to produce smaller binaries.
-  A corresponding `Makefile` target using this ability is `zstd-decompress`.
-
-- __ZSTD_NODECOMPRESS__ : `zstd` cli will be compiled without support for decompression.
-  The resulting binary will only be able to compress files.
-  This can be useful to produce smaller binaries.
-  A corresponding `Makefile` target using this ability is `zstd-compress`.
-
-- __BACKTRACE__ : `zstd` can display a stack backtrace when execution
-  generates a runtime exception. By default, this feature may be
-  degraded/disabled on some platforms unless additional compiler directives are
-  applied. When triaging a runtime issue, enabling this feature can provide
-  more context to determine the location of the fault.
-  Example : `make zstd BACKTRACE=1`
-
-
-### Aggregation of parameters
-CLI supports aggregation of parameters i.e. `-b1`, `-e18`, and `-i1` can be joined into `-b1e18i1`.
-
-
-### Symlink shortcuts
-It's possible to invoke `zstd` through a symlink.
-When the name of the symlink has a specific value, it triggers an associated behavior.
-- `zstdmt` : compress using all cores available on local system.
-- `zcat` : will decompress and output target file using any of the supported formats. `gzcat` and `zstdcat` are also equivalent.
-- `gzip` : if zlib support is enabled, will mimic `gzip` by compressing file using `.gz` format, removing source file by default (use `--keep` to preserve). If zlib is not supported, triggers an error.
-- `xz` : if lzma support is enabled, will mimic `xz` by compressing file using `.xz` format, removing source file by default (use `--keep` to preserve). If xz is not supported, triggers an error.
-- `lzma` : if lzma support is enabled, will mimic `lzma` by compressing file using `.lzma` format, removing source file by default (use `--keep` to preserve). If lzma is not supported, triggers an error.
-- `lz4` : if lz4 support is enabled, will mimic `lz4` by compressing file using `.lz4` format. If lz4 is not supported, triggers an error.
-- `unzstd` and `unlz4` will decompress any of the supported format.
-- `ungz`, `unxz` and `unlzma` will do the same, and will also remove source file by default (use `--keep` to preserve).
-
-
-### Dictionary builder in Command Line Interface
-Zstd offers a training mode, which can be used to tune the algorithm for a selected
-type of data, by providing it with a few samples. The result of the training is stored
-in a file selected with the `-o` option (default name is `dictionary`),
-which can be loaded before compression and decompression.
-
-Using a dictionary, the compression ratio achievable on small data improves dramatically.
-These compression gains are achieved while simultaneously providing faster compression and decompression speeds.
-Dictionary work if there is some correlation in a family of small data (there is no universal dictionary).
-Hence, deploying one dictionary per type of data will provide the greater benefits.
-Dictionary gains are mostly effective in the first few KB. Then, the compression algorithm
-will rely more and more on previously decoded content to compress the rest of the file.
-
-Usage of the dictionary builder and created dictionaries with CLI:
-
-1. Create the dictionary : `zstd --train PathToTrainingSet/* -o dictionaryName`
-2. Compress with the dictionary: `zstd FILE -D dictionaryName`
-3. Decompress with the dictionary: `zstd --decompress FILE.zst -D dictionaryName`
-
-
-### Benchmark in Command Line Interface
-CLI includes in-memory compression benchmark module for zstd.
-The benchmark is conducted using given filenames. The files are read into memory and joined together.
-It makes benchmark more precise as it eliminates I/O overhead.
-Multiple filenames can be supplied, as multiple parameters, with wildcards,
-or names of directories can be used as parameters with `-r` option.
-
-The benchmark measures ratio, compressed size, compression and decompression speed.
-One can select compression levels starting from `-b` and ending with `-e`.
-The `-i` parameter selects minimal time used for each of tested levels.
-
-
-### Usage of Command Line Interface
-The full list of options can be obtained with `-h` or `-H` parameter:
-```
-Usage :
-      zstd [args] [FILE(s)] [-o file]
-
-FILE    : a filename
-          with no FILE, or when FILE is - , read standard input
-Arguments :
- -#     : # compression level (1-19, default: 3)
- -d     : decompression
- -D DICT: use DICT as Dictionary for compression or decompression
- -o file: result stored into `file` (only 1 output file)
- -f     : overwrite output without prompting, also (de)compress links
---rm    : remove source file(s) after successful de/compression
- -k     : preserve source file(s) (default)
- -h/-H  : display help/long help and exit
-
-Advanced arguments :
- -V     : display Version number and exit
+Command Line Interface for Zstandard library 
+============================================ 
+ 
+Command Line Interface (CLI) can be created using the `make` command without any additional parameters. 
+There are however other Makefile targets that create different variations of CLI: 
+- `zstd` : default CLI supporting gzip-like arguments; includes dictionary builder, benchmark, and supports decompression of legacy zstd formats 
+- `zstd_nolegacy` : Same as `zstd` but without support for legacy zstd formats 
+- `zstd-small` : CLI optimized for minimal size; no dictionary builder, no benchmark, and no support for legacy zstd formats 
+- `zstd-compress` : version of CLI which can only compress into zstd format 
+- `zstd-decompress` : version of CLI which can only decompress zstd format 
+ 
+ 
+### Compilation variables 
+`zstd` scope can be altered by modifying the following `make` variables : 
+ 
+- __HAVE_THREAD__ : multithreading is automatically enabled when `pthread` is detected. 
+  It's possible to disable multithread support, by setting `HAVE_THREAD=0`. 
+  Example : `make zstd HAVE_THREAD=0` 
+  It's also possible to force multithread support, using `HAVE_THREAD=1`. 
+  In which case, linking stage will fail if neither `pthread` nor `windows.h` library can be found. 
+  This is useful to ensure this feature is not silently disabled. 
+ 
+- __ZSTD_LEGACY_SUPPORT__ : `zstd` can decompress files compressed by older versions of `zstd`. 
+  Starting v0.8.0, all versions of `zstd` produce frames compliant with the [specification](../doc/zstd_compression_format.md), and are therefore compatible. 
+  But older versions (< v0.8.0) produced different, incompatible, frames. 
+  By default, `zstd` supports decoding legacy formats >= v0.4.0 (`ZSTD_LEGACY_SUPPORT=4`). 
+  This can be altered by modifying this compilation variable. 
+  `ZSTD_LEGACY_SUPPORT=1` means "support all formats >= v0.1.0". 
+  `ZSTD_LEGACY_SUPPORT=2` means "support all formats >= v0.2.0", and so on. 
+  `ZSTD_LEGACY_SUPPORT=0` means _DO NOT_ support any legacy format. 
+  if `ZSTD_LEGACY_SUPPORT >= 8`, it's the same as `0`, since there is no legacy format after `7`. 
+  Note : `zstd` only supports decoding older formats, and cannot generate any legacy format. 
+ 
+- __HAVE_ZLIB__ : `zstd` can compress and decompress files in `.gz` format. 
+  This is ordered through command `--format=gzip`. 
+  Alternatively, symlinks named `gzip` or `gunzip` will mimic intended behavior. 
+  `.gz` support is automatically enabled when `zlib` library is detected at build time. 
+  It's possible to disable `.gz` support, by setting `HAVE_ZLIB=0`. 
+  Example : `make zstd HAVE_ZLIB=0` 
+  It's also possible to force compilation with zlib support, using `HAVE_ZLIB=1`. 
+  In which case, linking stage will fail if `zlib` library cannot be found. 
+  This is useful to prevent silent feature disabling. 
+ 
+- __HAVE_LZMA__ : `zstd` can compress and decompress files in `.xz` and `.lzma` formats. 
+  This is ordered through commands `--format=xz` and `--format=lzma` respectively. 
+  Alternatively, symlinks named `xz`, `unxz`, `lzma`, or `unlzma` will mimic intended behavior. 
+  `.xz` and `.lzma` support is automatically enabled when `lzma` library is detected at build time. 
+  It's possible to disable `.xz` and `.lzma` support, by setting `HAVE_LZMA=0`. 
+  Example : `make zstd HAVE_LZMA=0` 
+  It's also possible to force compilation with lzma support, using `HAVE_LZMA=1`. 
+  In which case, linking stage will fail if `lzma` library cannot be found. 
+  This is useful to prevent silent feature disabling. 
+ 
+- __HAVE_LZ4__ : `zstd` can compress and decompress files in `.lz4` formats. 
+  This is ordered through commands `--format=lz4`. 
+  Alternatively, symlinks named `lz4`, or `unlz4` will mimic intended behavior. 
+  `.lz4` support is automatically enabled when `lz4` library is detected at build time. 
+  It's possible to disable `.lz4` support, by setting `HAVE_LZ4=0` . 
+  Example : `make zstd HAVE_LZ4=0` 
+  It's also possible to force compilation with lz4 support, using `HAVE_LZ4=1`. 
+  In which case, linking stage will fail if `lz4` library cannot be found. 
+  This is useful to prevent silent feature disabling. 
+ 
+- __ZSTD_NOBENCH__ : `zstd` cli will be compiled without its integrated benchmark module. 
+  This can be useful to produce smaller binaries. 
+  In this case, the corresponding unit can also be excluded from compilation target. 
+ 
+- __ZSTD_NODICT__ : `zstd` cli will be compiled without support for the integrated dictionary builder. 
+  This can be useful to produce smaller binaries. 
+  In this case, the corresponding unit can also be excluded from compilation target. 
+ 
+- __ZSTD_NOCOMPRESS__ : `zstd` cli will be compiled without support for compression. 
+  The resulting binary will only be able to decompress files. 
+  This can be useful to produce smaller binaries. 
+  A corresponding `Makefile` target using this ability is `zstd-decompress`. 
+ 
+- __ZSTD_NODECOMPRESS__ : `zstd` cli will be compiled without support for decompression. 
+  The resulting binary will only be able to compress files. 
+  This can be useful to produce smaller binaries. 
+  A corresponding `Makefile` target using this ability is `zstd-compress`. 
+ 
+- __BACKTRACE__ : `zstd` can display a stack backtrace when execution 
+  generates a runtime exception. By default, this feature may be 
+  degraded/disabled on some platforms unless additional compiler directives are 
+  applied. When triaging a runtime issue, enabling this feature can provide 
+  more context to determine the location of the fault. 
+  Example : `make zstd BACKTRACE=1` 
+ 
+ 
+### Aggregation of parameters 
+CLI supports aggregation of parameters i.e. `-b1`, `-e18`, and `-i1` can be joined into `-b1e18i1`. 
+ 
+ 
+### Symlink shortcuts 
+It's possible to invoke `zstd` through a symlink. 
+When the name of the symlink has a specific value, it triggers an associated behavior. 
+- `zstdmt` : compress using all cores available on local system. 
+- `zcat` : will decompress and output target file using any of the supported formats. `gzcat` and `zstdcat` are also equivalent. 
+- `gzip` : if zlib support is enabled, will mimic `gzip` by compressing file using `.gz` format, removing source file by default (use `--keep` to preserve). If zlib is not supported, triggers an error. 
+- `xz` : if lzma support is enabled, will mimic `xz` by compressing file using `.xz` format, removing source file by default (use `--keep` to preserve). If xz is not supported, triggers an error. 
+- `lzma` : if lzma support is enabled, will mimic `lzma` by compressing file using `.lzma` format, removing source file by default (use `--keep` to preserve). If lzma is not supported, triggers an error. 
+- `lz4` : if lz4 support is enabled, will mimic `lz4` by compressing file using `.lz4` format. If lz4 is not supported, triggers an error. 
+- `unzstd` and `unlz4` will decompress any of the supported format. 
+- `ungz`, `unxz` and `unlzma` will do the same, and will also remove source file by default (use `--keep` to preserve). 
+ 
+ 
+### Dictionary builder in Command Line Interface 
+Zstd offers a training mode, which can be used to tune the algorithm for a selected 
+type of data, by providing it with a few samples. The result of the training is stored 
+in a file selected with the `-o` option (default name is `dictionary`), 
+which can be loaded before compression and decompression. 
+ 
+Using a dictionary, the compression ratio achievable on small data improves dramatically. 
+These compression gains are achieved while simultaneously providing faster compression and decompression speeds. 
+Dictionary work if there is some correlation in a family of small data (there is no universal dictionary). 
+Hence, deploying one dictionary per type of data will provide the greater benefits. 
+Dictionary gains are mostly effective in the first few KB. Then, the compression algorithm 
+will rely more and more on previously decoded content to compress the rest of the file. 
+ 
+Usage of the dictionary builder and created dictionaries with CLI: 
+ 
+1. Create the dictionary : `zstd --train PathToTrainingSet/* -o dictionaryName` 
+2. Compress with the dictionary: `zstd FILE -D dictionaryName` 
+3. Decompress with the dictionary: `zstd --decompress FILE.zst -D dictionaryName` 
+ 
+ 
+### Benchmark in Command Line Interface 
+CLI includes in-memory compression benchmark module for zstd. 
+The benchmark is conducted using given filenames. The files are read into memory and joined together. 
+It makes benchmark more precise as it eliminates I/O overhead. 
+Multiple filenames can be supplied, as multiple parameters, with wildcards, 
+or names of directories can be used as parameters with `-r` option. 
+ 
+The benchmark measures ratio, compressed size, compression and decompression speed. 
+One can select compression levels starting from `-b` and ending with `-e`. 
+The `-i` parameter selects minimal time used for each of tested levels. 
+ 
+ 
+### Usage of Command Line Interface 
+The full list of options can be obtained with `-h` or `-H` parameter: 
+``` 
+Usage : 
+      zstd [args] [FILE(s)] [-o file] 
+ 
+FILE    : a filename 
+          with no FILE, or when FILE is - , read standard input 
+Arguments : 
+ -#     : # compression level (1-19, default: 3) 
+ -d     : decompression 
+ -D DICT: use DICT as Dictionary for compression or decompression 
+ -o file: result stored into `file` (only 1 output file) 
+ -f     : overwrite output without prompting, also (de)compress links 
+--rm    : remove source file(s) after successful de/compression 
+ -k     : preserve source file(s) (default) 
+ -h/-H  : display help/long help and exit 
+ 
+Advanced arguments : 
+ -V     : display Version number and exit 
  -c     : write to standard output (even if it is the console)
- -v     : verbose mode; specify multiple times to increase verbosity
- -q     : suppress warnings; specify twice to suppress errors too
---no-progress : do not display the progress counter
- -r     : operate recursively on directories
---filelist FILE : read list of files to operate upon from FILE
---output-dir-flat DIR : processed files are stored into DIR
---output-dir-mirror DIR : processed files are stored into DIR respecting original directory structure
---[no-]check : during compression, add XXH64 integrity checksum to frame (default: enabled). If specified with -d, decompressor will ignore/validate checksums in compressed frame (default: validate).
---      : All arguments after "--" are treated as files
-
-Advanced compression arguments :
---ultra : enable levels beyond 19, up to 22 (requires more memory)
---long[=#]: enable long distance matching with given window log (default: 27)
---fast[=#]: switch to very fast compression levels (default: 1)
---adapt : dynamically adapt compression level to I/O conditions
+ -v     : verbose mode; specify multiple times to increase verbosity 
+ -q     : suppress warnings; specify twice to suppress errors too 
+--no-progress : do not display the progress counter 
+ -r     : operate recursively on directories 
+--filelist FILE : read list of files to operate upon from FILE 
+--output-dir-flat DIR : processed files are stored into DIR 
+--output-dir-mirror DIR : processed files are stored into DIR respecting original directory structure 
+--[no-]check : during compression, add XXH64 integrity checksum to frame (default: enabled). If specified with -d, decompressor will ignore/validate checksums in compressed frame (default: validate). 
+--      : All arguments after "--" are treated as files 
+ 
+Advanced compression arguments : 
+--ultra : enable levels beyond 19, up to 22 (requires more memory) 
+--long[=#]: enable long distance matching with given window log (default: 27) 
+--fast[=#]: switch to very fast compression levels (default: 1) 
+--adapt : dynamically adapt compression level to I/O conditions 
 --patch-from=FILE : specify the file to be used as a reference point for zstd's diff engine
- -T#    : spawns # compression threads (default: 1, 0==# cores)
- -B#    : select size of each job (default: 0==automatic)
---single-thread : use a single thread for both I/O and compression (result slightly different than -T1)
---rsyncable : compress using a rsync-friendly method (-B sets block size)
---exclude-compressed: only compress files that are not already compressed
---stream-size=# : specify size of streaming input from `stdin`
---size-hint=# optimize compression parameters for streaming input of approximately this size
---target-compressed-block-size=# : generate compressed block of approximately targeted size
---no-dictID : don't write dictID into header (dictionary compression only)
---[no-]compress-literals : force (un)compressed literals
---format=zstd : compress files to the .zst format (default)
---format=gzip : compress files to the .gz format
---format=xz : compress files to the .xz format
---format=lzma : compress files to the .lzma format
---format=lz4 : compress files to the .lz4 format
-
-Advanced decompression arguments :
- -l     : print information about zstd compressed files
---test  : test compressed file integrity
- -M#    : Set a memory usage limit for decompression
---[no-]sparse : sparse mode (default: disabled)
-
-Dictionary builder :
---train ## : create a dictionary from a training set of files
---train-cover[=k=#,d=#,steps=#,split=#,shrink[=#]] : use the cover algorithm with optional args
---train-fastcover[=k=#,d=#,f=#,steps=#,split=#,accel=#,shrink[=#]] : use the fast cover algorithm with optional args
---train-legacy[=s=#] : use the legacy algorithm with selectivity (default: 9)
- -o DICT : DICT is dictionary name (default: dictionary)
---maxdict=# : limit dictionary to specified size (default: 112640)
---dictID=# : force dictionary ID to specified value (default: random)
-
-Benchmark arguments :
- -b#    : benchmark file(s), using # compression level (default: 3)
- -e#    : test all compression levels successively from -b# to -e# (default: 1)
- -i#    : minimum evaluation time in seconds (default: 3s)
- -B#    : cut file into independent blocks of size # (default: no block)
- -S     : output one benchmark result per input file (default: consolidated result)
---priority=rt : set process priority to real-time
-```
-
-### Passing parameters through Environment Variables
-There is no "generic" way to pass "any kind of parameter" to `zstd` in a pass-through manner.
-Using environment variables for this purpose has security implications.
-Therefore, this avenue is intentionally restricted and only supports `ZSTD_CLEVEL` and `ZSTD_NBTHREADS`.
-
-`ZSTD_CLEVEL` can be used to modify the default compression level of `zstd`
-(usually set to `3`) to another value between 1 and 19 (the "normal" range).
-
-`ZSTD_NBTHREADS` can be used to specify a number of threads
-that `zstd` will use for compression, which by default is `1`.
-This functionality only exists when `zstd` is compiled with multithread support.
-`0` means "use as many threads as detected cpu cores on local system".
-The max # of threads is capped at `ZSTDMT_NBWORKERS_MAX`,
-which is either 64 in 32-bit mode, or 256 for 64-bit environments.
-
-This functionality can be useful when `zstd` CLI is invoked in a way that doesn't allow passing arguments.
-One such scenario is `tar --zstd`.
-As `ZSTD_CLEVEL` and `ZSTD_NBTHREADS` only replace the default compression level
-and number of threads respectively, they can both be overridden by corresponding command line arguments:
-`-#` for compression level and `-T#` for number of threads.
-
-
-### Long distance matching mode
-The long distance matching mode, enabled with `--long`, is designed to improve
-the compression ratio for files with long matches at a large distance (up to the
-maximum window size, `128 MiB`) while still maintaining compression speed.
-
-Enabling this mode sets the window size to `128 MiB` and thus increases the memory
-usage for both the compressor and decompressor. Performance in terms of speed is
-dependent on long matches being found. Compression speed may degrade if few long
-matches are found. Decompression speed usually improves when there are many long
-distance matches.
-
-Below are graphs comparing the compression speed, compression ratio, and
-decompression speed with and without long distance matching on an ideal use
-case: a tar of four versions of clang (versions `3.4.1`, `3.4.2`, `3.5.0`,
-`3.5.1`) with a total size of `244889600 B`. This is an ideal use case as there
-are many long distance matches within the maximum window size of `128 MiB` (each
-version is less than `128 MiB`).
-
-Compression Speed vs Ratio | Decompression Speed
----------------------------|---------------------
-![Compression Speed vs Ratio](https://raw.githubusercontent.com/facebook/zstd/v1.3.3/doc/images/ldmCspeed.png "Compression Speed vs Ratio") | ![Decompression Speed](https://raw.githubusercontent.com/facebook/zstd/v1.3.3/doc/images/ldmDspeed.png "Decompression Speed")
-
-| Method | Compression ratio | Compression speed | Decompression speed  |
-|:-------|------------------:|-------------------------:|---------------------------:|
-| `zstd -1`  | `5.065`    | `284.8 MB/s`  | `759.3 MB/s`  |
-| `zstd -5`  | `5.826`    | `124.9 MB/s`  | `674.0 MB/s`  |
-| `zstd -10` | `6.504`    | `29.5 MB/s`   | `771.3 MB/s`  |
-| `zstd -1 --long` | `17.426` | `220.6 MB/s` | `1638.4 MB/s` |
-| `zstd -5 --long` | `19.661` | `165.5 MB/s` | `1530.6 MB/s` |
-| `zstd -10 --long`| `21.949` |  `75.6 MB/s` | `1632.6 MB/s` |
-
-On this file, the compression ratio improves significantly with minimal impact
-on compression speed, and the decompression speed doubles.
-
-On the other extreme, compressing a file with few long distance matches (such as
-the [Silesia compression corpus]) will likely lead to a deterioration in
-compression speed (for lower levels) with minimal change in compression ratio.
-
-The below table illustrates this on the [Silesia compression corpus].
-
-[Silesia compression corpus]: http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia
-
-| Method | Compression ratio | Compression speed | Decompression speed  |
-|:-------|------------------:|------------------:|---------------------:|
-| `zstd -1`        | `2.878` | `231.7 MB/s`      | `594.4 MB/s`   |
-| `zstd -1 --long` | `2.929` | `106.5 MB/s`      | `517.9 MB/s`   |
-| `zstd -5`        | `3.274` | `77.1 MB/s`       | `464.2 MB/s`   |
-| `zstd -5 --long` | `3.319` | `51.7 MB/s`       | `371.9 MB/s`   |
-| `zstd -10`       | `3.523` | `16.4 MB/s`       | `489.2 MB/s`   |
-| `zstd -10 --long`| `3.566` | `16.2 MB/s`       | `415.7 MB/s`   |
-
-
-### zstdgrep
-
-`zstdgrep` is a utility which makes it possible to `grep` directly a `.zst` compressed file.
-It's used the same way as normal `grep`, for example :
-`zstdgrep pattern file.zst`
-
-`zstdgrep` is _not_ compatible with dictionary compression.
-
-To search into a file compressed with a dictionary,
-it's necessary to decompress it using `zstd` or `zstdcat`,
-and then pipe the result to `grep`. For example  :
-`zstdcat -D dictionary -qc -- file.zst | grep pattern`
+ -T#    : spawns # compression threads (default: 1, 0==# cores) 
+ -B#    : select size of each job (default: 0==automatic) 
+--single-thread : use a single thread for both I/O and compression (result slightly different than -T1) 
+--rsyncable : compress using a rsync-friendly method (-B sets block size) 
+--exclude-compressed: only compress files that are not already compressed 
+--stream-size=# : specify size of streaming input from `stdin` 
+--size-hint=# optimize compression parameters for streaming input of approximately this size 
+--target-compressed-block-size=# : generate compressed block of approximately targeted size 
+--no-dictID : don't write dictID into header (dictionary compression only) 
+--[no-]compress-literals : force (un)compressed literals 
+--format=zstd : compress files to the .zst format (default) 
+--format=gzip : compress files to the .gz format 
+--format=xz : compress files to the .xz format 
+--format=lzma : compress files to the .lzma format 
+--format=lz4 : compress files to the .lz4 format 
+ 
+Advanced decompression arguments : 
+ -l     : print information about zstd compressed files 
+--test  : test compressed file integrity 
+ -M#    : Set a memory usage limit for decompression 
+--[no-]sparse : sparse mode (default: disabled) 
+ 
+Dictionary builder : 
+--train ## : create a dictionary from a training set of files 
+--train-cover[=k=#,d=#,steps=#,split=#,shrink[=#]] : use the cover algorithm with optional args 
+--train-fastcover[=k=#,d=#,f=#,steps=#,split=#,accel=#,shrink[=#]] : use the fast cover algorithm with optional args 
+--train-legacy[=s=#] : use the legacy algorithm with selectivity (default: 9) 
+ -o DICT : DICT is dictionary name (default: dictionary) 
+--maxdict=# : limit dictionary to specified size (default: 112640) 
+--dictID=# : force dictionary ID to specified value (default: random) 
+ 
+Benchmark arguments : 
+ -b#    : benchmark file(s), using # compression level (default: 3) 
+ -e#    : test all compression levels successively from -b# to -e# (default: 1) 
+ -i#    : minimum evaluation time in seconds (default: 3s) 
+ -B#    : cut file into independent blocks of size # (default: no block) 
+ -S     : output one benchmark result per input file (default: consolidated result) 
+--priority=rt : set process priority to real-time 
+``` 
+ 
+### Passing parameters through Environment Variables 
+There is no "generic" way to pass "any kind of parameter" to `zstd` in a pass-through manner. 
+Using environment variables for this purpose has security implications. 
+Therefore, this avenue is intentionally restricted and only supports `ZSTD_CLEVEL` and `ZSTD_NBTHREADS`. 
+ 
+`ZSTD_CLEVEL` can be used to modify the default compression level of `zstd` 
+(usually set to `3`) to another value between 1 and 19 (the "normal" range). 
+ 
+`ZSTD_NBTHREADS` can be used to specify a number of threads 
+that `zstd` will use for compression, which by default is `1`. 
+This functionality only exists when `zstd` is compiled with multithread support. 
+`0` means "use as many threads as detected cpu cores on local system". 
+The max # of threads is capped at `ZSTDMT_NBWORKERS_MAX`, 
+which is either 64 in 32-bit mode, or 256 for 64-bit environments. 
+ 
+This functionality can be useful when `zstd` CLI is invoked in a way that doesn't allow passing arguments. 
+One such scenario is `tar --zstd`. 
+As `ZSTD_CLEVEL` and `ZSTD_NBTHREADS` only replace the default compression level 
+and number of threads respectively, they can both be overridden by corresponding command line arguments: 
+`-#` for compression level and `-T#` for number of threads. 
+ 
+ 
+### Long distance matching mode 
+The long distance matching mode, enabled with `--long`, is designed to improve 
+the compression ratio for files with long matches at a large distance (up to the 
+maximum window size, `128 MiB`) while still maintaining compression speed. 
+ 
+Enabling this mode sets the window size to `128 MiB` and thus increases the memory 
+usage for both the compressor and decompressor. Performance in terms of speed is 
+dependent on long matches being found. Compression speed may degrade if few long 
+matches are found. Decompression speed usually improves when there are many long 
+distance matches. 
+ 
+Below are graphs comparing the compression speed, compression ratio, and 
+decompression speed with and without long distance matching on an ideal use 
+case: a tar of four versions of clang (versions `3.4.1`, `3.4.2`, `3.5.0`, 
+`3.5.1`) with a total size of `244889600 B`. This is an ideal use case as there 
+are many long distance matches within the maximum window size of `128 MiB` (each 
+version is less than `128 MiB`). 
+ 
+Compression Speed vs Ratio | Decompression Speed 
+---------------------------|--------------------- 
+![Compression Speed vs Ratio](https://raw.githubusercontent.com/facebook/zstd/v1.3.3/doc/images/ldmCspeed.png "Compression Speed vs Ratio") | ![Decompression Speed](https://raw.githubusercontent.com/facebook/zstd/v1.3.3/doc/images/ldmDspeed.png "Decompression Speed") 
+ 
+| Method | Compression ratio | Compression speed | Decompression speed  | 
+|:-------|------------------:|-------------------------:|---------------------------:| 
+| `zstd -1`  | `5.065`    | `284.8 MB/s`  | `759.3 MB/s`  | 
+| `zstd -5`  | `5.826`    | `124.9 MB/s`  | `674.0 MB/s`  | 
+| `zstd -10` | `6.504`    | `29.5 MB/s`   | `771.3 MB/s`  | 
+| `zstd -1 --long` | `17.426` | `220.6 MB/s` | `1638.4 MB/s` | 
+| `zstd -5 --long` | `19.661` | `165.5 MB/s` | `1530.6 MB/s` | 
+| `zstd -10 --long`| `21.949` |  `75.6 MB/s` | `1632.6 MB/s` | 
+ 
+On this file, the compression ratio improves significantly with minimal impact 
+on compression speed, and the decompression speed doubles. 
+ 
+On the other extreme, compressing a file with few long distance matches (such as 
+the [Silesia compression corpus]) will likely lead to a deterioration in 
+compression speed (for lower levels) with minimal change in compression ratio. 
+ 
+The below table illustrates this on the [Silesia compression corpus]. 
+ 
+[Silesia compression corpus]: http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia 
+ 
+| Method | Compression ratio | Compression speed | Decompression speed  | 
+|:-------|------------------:|------------------:|---------------------:| 
+| `zstd -1`        | `2.878` | `231.7 MB/s`      | `594.4 MB/s`   | 
+| `zstd -1 --long` | `2.929` | `106.5 MB/s`      | `517.9 MB/s`   | 
+| `zstd -5`        | `3.274` | `77.1 MB/s`       | `464.2 MB/s`   | 
+| `zstd -5 --long` | `3.319` | `51.7 MB/s`       | `371.9 MB/s`   | 
+| `zstd -10`       | `3.523` | `16.4 MB/s`       | `489.2 MB/s`   | 
+| `zstd -10 --long`| `3.566` | `16.2 MB/s`       | `415.7 MB/s`   | 
+ 
+ 
+### zstdgrep 
+ 
+`zstdgrep` is a utility which makes it possible to `grep` directly a `.zst` compressed file. 
+It's used the same way as normal `grep`, for example : 
+`zstdgrep pattern file.zst` 
+ 
+`zstdgrep` is _not_ compatible with dictionary compression. 
+ 
+To search into a file compressed with a dictionary, 
+it's necessary to decompress it using `zstd` or `zstdcat`, 
+and then pipe the result to `grep`. For example  : 
+`zstdcat -D dictionary -qc -- file.zst | grep pattern`