A streaming compression/decompression library DEFLATE-based streams in Rust.

This crate by default uses the miniz_oxide crate, a port of miniz.c to pure Rust. This crate also supports other backends, such as the widely available zlib library or the high-performance zlib-ng library.

Supported formats:

• deflate
• zlib
• gzip

# Cargo.toml
[dependencies]
flate2 = "1.0"

This crate supports the current and previous stable versions of the Rust compiler. For example, if the current stable is 1.80, this crate supports 1.80 and 1.79.

Other compiler versions may work, but failures may not be treated as a flate2 bug.

The Cargo.toml file specifies a rust-version for which builds of the current version passed at some point. This value is indicative only, and may change at any time.

The rust-version is a best-effort measured value and is different to the MSRV. The rust-version can be incremented by a PR in order to pass tests, as long as the MSRV continues to hold. When the rust-version increases, the next release should be a minor version, to allow any affected users to pin to a previous minor version.

use std::io::prelude::*;
use flate2::Compression;
use flate2::write::ZlibEncoder;
fn main() {
    let mut e = ZlibEncoder::new(Vec::new(), Compression::default());
    e.write_all(b"foo");
    e.write_all(b"bar");
    let compressed_bytes = e.finish();
}

use std::io::prelude::*;
use flate2::read::GzDecoder;
fn main() {
    let mut d = GzDecoder::new("...".as_bytes());
    let mut s = String::new();
    d.read_to_string(&mut s).unwrap();
    println!("{}", s);
}

The default miniz_oxide backend has the advantage of only using safe Rust.

If you want maximum performance while still benefiting from a Rust implementation at the cost of some unsafe, you can use zlib-rs:

[dependencies]
flate2 = { version = "1.0.17", features = ["zlib-rs"], default-features = false }

While zlib-rs is the fastest overall, the zlib-ng C library can be slightly faster in certain cases:

[dependencies]
flate2 = { version = "1.0.17", features = ["zlib-ng"], default-features = false }

Note that the "zlib-ng" feature works even if some other part of your crate graph depends on zlib.

However, if you're already using another C or Rust library that depends on zlib, and you want to avoid including both zlib and zlib-ng, you can use that for Rust code as well:

[dependencies]
flate2 = { version = "1.0.17", features = ["zlib"], default-features = false }

Or, if you have C or Rust code that depends on zlib and you want to use zlib-ng via libz-sys in zlib-compat mode, use:

[dependencies]
flate2 = { version = "1.0.17", features = ["zlib-ng-compat"], default-features = false }

Note that when using the "zlib-ng-compat" feature, if any crate in your dependency graph explicitly requests stock zlib, or uses libz-sys directly without default-features = false, you'll get stock zlib rather than zlib-ng. See the libz-sys README for details. To avoid that, use the "zlib-ng" feature instead.

For compatibility with previous versions of flate2, the Cloudflare optimized version of zlib is available, via the cloudflare_zlib feature. It's not as fast as zlib-ng, but it's faster than stock zlib. It requires an x86-64 CPU with SSE 4.2 or ARM64 with NEON & CRC. It does not support 32-bit CPUs at all and is incompatible with mingw. For more information check the crate documentation. Note that cloudflare_zlib will cause breakage if any other crate in your crate graph uses another version of zlib/libz.

This project is licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or https://opensource.org/licenses/MIT)

at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.