X-Git-Url: https://notaz.gp2x.de/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=deps%2Flibchdr%2Fdeps%2Fzstd-1.5.5%2Fprograms%2FREADME.md;fp=deps%2Flibchdr%2Fdeps%2Fzstd-1.5.5%2Fprograms%2FREADME.md;h=1b9f47cbba9c0ef001ec60a3767944d82d4755ad;hb=648db22b0750712da893c306efcc8e4b2d3a4e3c;hp=0000000000000000000000000000000000000000;hpb=e2fb1389dc12376acb84e4993ed3b08760257252;p=pcsx_rearmed.git diff --git a/deps/libchdr/deps/zstd-1.5.5/programs/README.md b/deps/libchdr/deps/zstd-1.5.5/programs/README.md new file mode 100644 index 00000000..1b9f47cb --- /dev/null +++ b/deps/libchdr/deps/zstd-1.5.5/programs/README.md @@ -0,0 +1,302 @@ +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-]asyncio : use asynchronous IO (default: enabled) +--[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 chunks of size # (default: no chunking) + -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]: https://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`