<p align="center"><img src="https://raw.githubusercontent.com/facebook/zstd/dev/doc/images/zstd_logo86.png" alt="Zstandard"></p>
__Zstandard__, or `zstd` as short version, is a fast lossless compression algorithm,
targeting real-time compression scenarios at zlib-level and better compression ratios.
It's backed by a very fast entropy stage, provided by [Huff0 and FSE library](https://github.com/Cyan4973/FiniteStateEntropy).
Zstandard's format is stable and documented in [RFC8878](https://datatracker.ietf.org/doc/html/rfc8878). Multiple independent implementations are already available.
This repository represents the reference implementation, provided as an open-source dual [BSD](LICENSE) and [GPLv2](COPYING) licensed **C** library,
and a command line utility producing and decoding `.zst`, `.gz`, `.xz` and `.lz4` files.
Should your project require another programming language,
a list of known ports and bindings is provided on [Zstandard homepage](https://facebook.github.io/zstd/#other-languages).
**Development branch status:**
[![Build Status][travisDevBadge]][travisLink]
[![Build status][CircleDevBadge]][CircleLink]
[![Build status][CirrusDevBadge]][CirrusLink]
[![Fuzzing Status][OSSFuzzBadge]][OSSFuzzLink]
[travisDevBadge]: https://api.travis-ci.com/facebook/zstd.svg?branch=dev "Continuous Integration test suite"
[travisLink]: https://travis-ci.com/facebook/zstd
[CircleDevBadge]: https://circleci.com/gh/facebook/zstd/tree/dev.svg?style=shield "Short test suite"
[CircleLink]: https://circleci.com/gh/facebook/zstd
[CirrusDevBadge]: https://api.cirrus-ci.com/github/facebook/zstd.svg?branch=dev
[CirrusLink]: https://cirrus-ci.com/github/facebook/zstd
[OSSFuzzBadge]: https://oss-fuzz-build-logs.storage.googleapis.com/badges/zstd.svg
[OSSFuzzLink]: https://bugs.chromium.org/p/oss-fuzz/issues/list?sort=-opened&can=1&q=proj:zstd
## Benchmarks
For reference, several fast compression algorithms were tested and compared
on a desktop running Ubuntu 20.04 (`Linux 5.11.0-41-generic`),
with a Core i7-9700K CPU @ 4.9GHz,
using [lzbench], an open-source in-memory benchmark by @inikep
compiled with [gcc] 9.3.0,
on the [Silesia compression corpus].
[lzbench]: https://github.com/inikep/lzbench
[Silesia compression corpus]: https://sun.aei.polsl.pl//~sdeor/index.php?page=silesia
[gcc]: https://gcc.gnu.org/
| Compressor name | Ratio | Compression| Decompress.|
| --------------- | ------| -----------| ---------- |
| **zstd 1.5.1 -1** | 2.887 | 530 MB/s | 1700 MB/s |
| [zlib] 1.2.11 -1 | 2.743 | 95 MB/s | 400 MB/s |
| brotli 1.0.9 -0 | 2.702 | 395 MB/s | 450 MB/s |
| **zstd 1.5.1 --fast=1** | 2.437 | 600 MB/s | 2150 MB/s |
| **zstd 1.5.1 --fast=3** | 2.239 | 670 MB/s | 2250 MB/s |
| quicklz 1.5.0 -1 | 2.238 | 540 MB/s | 760 MB/s |
| **zstd 1.5.1 --fast=4** | 2.148 | 710 MB/s | 2300 MB/s |
| lzo1x 2.10 -1 | 2.106 | 660 MB/s | 845 MB/s |
| [lz4] 1.9.3 | 2.101 | 740 MB/s | 4500 MB/s |
| lzf 3.6 -1 | 2.077 | 410 MB/s | 830 MB/s |
| snappy 1.1.9 | 2.073 | 550 MB/s | 1750 MB/s |
[zlib]: https://www.zlib.net/
[lz4]: https://lz4.github.io/lz4/
The negative compression levels, specified with `--fast=#`,
offer faster compression and decompression speed
at the cost of compression ratio (compared to level 1).
Zstd can also offer stronger compression ratios at the cost of compression speed.
Speed vs Compression trade-off is configurable by small increments.
Decompression speed is preserved and remains roughly the same at all settings,
a property shared by most LZ compression algorithms, such as [zlib] or lzma.
The following tests were run
on a server running Linux Debian (`Linux version 4.14.0-3-amd64`)
with a Core i7-6700K CPU @ 4.0GHz,
using [lzbench], an open-source in-memory benchmark by @inikep
compiled with [gcc] 7.3.0,
on the [Silesia compression corpus].
Compression Speed vs Ratio | Decompression Speed
---------------------------|--------------------
![Compression Speed vs Ratio](doc/images/CSpeed2.png "Compression Speed vs Ratio") | ![Decompression Speed](doc/images/DSpeed3.png "Decompression Speed")
A few other algorithms can produce higher compression ratios at slower speeds, falling outside of the graph.
For a larger picture including slow modes, [click on this link](doc/images/DCspeed5.png).
## The case for Small Data compression
Previous charts provide results applicable to typical file and stream scenarios (several MB). Small data comes with different perspectives.
The smaller the amount of data to compress, the more difficult it is to compress. This problem is common to all compression algorithms, and reason is, compression algorithms learn from past data how to compress future data. But at the beginning of a new data set, there is no "past" to build upon.
To solve this situation, Zstd offers a __training mode__, which can be used to tune the algorithm for a selected type of data.
Training Zstandard is achieved by providing it with a few samples (one file per sample). The result of this training is stored in a file called "dictionary", which must be loaded before compression and decompression.
Using this dictionary, the compression ratio achievable on small data improves dramatically.
The following example uses the `github-users` [sample set](https://github.com/facebook/zstd/releases/tag/v1.1.3), created from [github public API](https://developer.github.com/v3/users/#get-all-users).
It consists of roughly 10K records weighing about 1KB each.
Compression Ratio | Compression Speed | Decompression Speed
------------------|-------------------|--------------------
![Compression Ratio](doc/images/dict-cr.png "Compression Ratio") | ![Compression Speed](doc/images/dict-cs.png "Compression Speed") | ![Decompression Speed](doc/images/dict-ds.png "Decompression Speed")
These compression gains are achieved while simultaneously providing _faster_ compression and decompression speeds.
Training works if there is some correlation in a family of small data samples. The more data-specific a dictionary is, the more efficient it is (there is no _universal dictionary_).
Hence, deploying one dictionary per type of data will provide the greatest benefits.
Dictionary gains are mostly effective in the first few KB. Then, the compression algorithm will gradually use previously decoded content to better compress the rest of the file.
### Dictionary compression How To:
1. Create the dictionary
`zstd --train FullPathToTrainingSet/* -o dictionaryName`
2. Compress with dictionary
`zstd -D dictionaryName FILE`
3. Decompress with dictionary
`zstd -D dictionaryName --decompress FILE.zst`
## Build instructions
`make` is the officially maintained build system of this project.
All other build systems are "compatible" and 3rd-party maintained,
they may feature small differences in advanced options.
When your system allows it, prefer using `make` to build `zstd` and `libzstd`.
### Makefile
If your system is compatible with standard `make` (or `gmake`),
invoking `make` in root directory will generate `zstd` cli in root directory.
It will also create `libzstd` into `lib/`.
Other available options include:
- `make install` : create and install zstd cli, library and man pages
- `make check` : create and run `zstd`, test its behavior on local platform
The `Makefile` follows the [GNU Standard Makefile conventions](https://www.gnu.org/prep/standards/html_node/Makefile-Conventions.html),
allowing staged install, standard flags, directory variables and command variables.
For advanced use cases, specialized compilation flags which control binary generation
are documented in [`lib/README.md`](lib/README.md#modular-build) for the `libzstd` library
and in [`programs/README.md`](programs/README.md#compilation-variables) for the `zstd` CLI.
### cmake
A `cmake` project generator is provided within `build/cmake`.
It can generate Makefiles or other
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curl 命令行工具,进行测试 nacos 的 openA (333个子文件)
libcrypto.a 3.35MB
libcurl.a 1.44MB
libzstd.a 867KB
libssl.a 673KB
libngtcp2.a 442KB
libssh2.a 409KB
libnghttp2.a 286KB
libnghttp3.a 243KB
libbrotlicommon.a 131KB
libz.a 119KB
libpsl.a 66KB
libbrotlidec.a 55KB
libngtcp2_crypto_quictls.a 40KB
libcurl.dll.a 16KB
http2-upload.c 8KB
http2-serverpush.c 7KB
chkspeed.c 7KB
smtp-tls.c 6KB
http2-download.c 6KB
smtp-ssl.c 6KB
smtp-mime.c 6KB
smtp-authzid.c 5KB
post-callback.c 5KB
multi-legacy.c 5KB
http2-pushinmemory.c 5KB
sendrecv.c 5KB
smtp-mail.c 5KB
externalsocket.c 5KB
simplessl.c 5KB
smtp-multi.c 5KB
ftpupload.c 4KB
anyauthput.c 4KB
ftpuploadresume.c 4KB
10-at-a-time.c 4KB
debug.c 4KB
multi-debugcallback.c 4KB
ftp-wildcard.c 4KB
cookie_interface.c 4KB
sftpuploadresume.c 4KB
ftpuploadfrommem.c 4KB
imap-append.c 4KB
postit2-formadd.c 4KB
httpput.c 4KB
imap-tls.c 4KB
hsts-preload.c 3KB
pop3-tls.c 3KB
multi-app.c 3KB
httpput-postfields.c 3KB
postit2.c 3KB
websocket.c 3KB
multi-formadd.c 3KB
postinmemory.c 3KB
sftpget.c 3KB
imap-ssl.c 3KB
getinmemory.c 3KB
pop3-ssl.c 3KB
progressfunc.c 3KB
multi-post.c 3KB
ftpgetinfo.c 3KB
ftpsget.c 3KB
fileupload.c 3KB
imap-store.c 3KB
sepheaders.c 3KB
https.c 3KB
multi-double.c 3KB
smtp-vrfy.c 3KB
ftpget.c 3KB
smtp-expn.c 3KB
connect-to.c 3KB
shared-connection-cache.c 3KB
ftpgetresp.c 3KB
headerapi.c 3KB
url2file.c 2KB
imap-copy.c 2KB
imap-search.c 2KB
getredirect.c 2KB
imap-multi.c 2KB
pop3-multi.c 2KB
sslbackend.c 2KB
httpcustomheader.c 2KB
multi-single.c 2KB
certinfo.c 2KB
imap-authzid.c 2KB
pop3-authzid.c 2KB
persistent.c 2KB
websocket-cb.c 2KB
pop3-dele.c 2KB
parseurl.c 2KB
pop3-stat.c 2KB
urlapi.c 2KB
imap-examine.c 2KB
pop3-top.c 2KB
pop3-noop.c 2KB
imap-list.c 2KB
imap-lsub.c 2KB
imap-delete.c 2KB
imap-create.c 2KB
pop3-uidl.c 2KB
http-post.c 2KB
imap-noop.c 2KB
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