A DEFLATE-based stream compression/decompression library

This library provides support for compression and decompression of DEFLATE-based streams:

• the DEFLATE format itself
• the zlib format
• gzip

These three formats are all closely related and largely only differ in their headers/footers. This crate has three types in each submodule for dealing with these three formats.

Implementation

In addition to supporting three formats, this crate supports several different backends, controlled through this crate's features:

• default, or rust_backend - this implementation uses the miniz_oxide crate which is a port of miniz.c to Rust. This feature does not require a C compiler, and only uses safe Rust code.

• zlib-rs - this implementation utilizes the zlib-rs crate, a Rust rewrite of zlib. This backend is the fastest, at the cost of some unsafe Rust code.

Several backends implemented in C are also available. These are useful in case you are already using a specific C implementation and need the result of compression to be bit-identical. See the crate's README for details on the available C backends.

The zlib-rs backend typically outperforms all the C implementations.

Organization

This crate consists mainly of three modules, read, write, and bufread. Each module contains a number of types used to encode and decode various streams of data.

All types in the write module work on instances of Write, whereas all types in the read module work on instances of Read and bufread works with BufRead. If you are decoding directly from a &[u8], use the bufread types.

use flate2::write::GzEncoder;
use flate2::Compression;
use std::io;
use std::io::prelude::*;

# fn main() { let _ = run(); }
# fn run() -> io::Result<()> {
let mut encoder = GzEncoder::new(Vec::new(), Compression::default());
encoder.write_all(b"Example")?;
# Ok(())
# }

Other various types are provided at the top-level of the crate for management and dealing with encoders/decoders. Also note that types which operate over a specific trait often implement the mirroring trait as well. For example a flate2::read::DeflateDecoder<T> also implements the Write trait if T: Write. That is, the "dual trait" is forwarded directly to the underlying object if available.

About multi-member Gzip files

While most gzip files one encounters will have a single member that can be read with the GzDecoder, there may be some files which have multiple members.

A GzDecoder will only read the first member of gzip data, which may unexpectedly provide partial results when a multi-member gzip file is encountered. GzDecoder is appropriate for data that is designed to be read as single members from a multi-member file. bufread::GzDecoder and write::GzDecoder also allow non-gzip data following gzip data to be handled.

The MultiGzDecoder on the other hand will decode all members of a gzip file into one consecutive stream of bytes, which hides the underlying members entirely. If a file contains non-gzip data after the gzip data, MultiGzDecoder will emit an error after decoding the gzip data. This behavior matches the gzip, gunzip, and zcat command line tools.