1//! A DEFLATE-based stream compression/decompression library
2//!
3//! This library provides support for compression and decompression of
4//! DEFLATE-based streams:
5//!
6//! * the DEFLATE format itself
7//! * the zlib format
8//! * gzip
9//!
10//! These three formats are all closely related and largely only differ in their
11//! headers/footers. This crate has three types in each submodule for dealing
12//! with these three formats.
13//!
14//! # Implementation
15//!
16//! In addition to supporting three formats, this crate supports several different
17//! backends, controlled through this crate's features:
18//!
19//! * `default`, or `rust_backend` - this implementation uses the `miniz_oxide`
20//! crate which is a port of `miniz.c` to Rust. This feature does not
21//! require a C compiler, and only uses safe Rust code.
22//!
23//! * `zlib-rs` - this implementation utilizes the `zlib-rs` crate, a Rust rewrite of zlib.
24//! This backend is the fastest, at the cost of some `unsafe` Rust code.
25//!
26//! Several backends implemented in C are also available.
27//! These are useful in case you are already using a specific C implementation
28//! and need the result of compression to be bit-identical.
29//! See the crate's README for details on the available C backends.
30//!
31//! The `zlib-rs` backend typically outperforms all the C implementations.
32//!
33//! # Organization
34//!
35//! This crate consists mainly of three modules, [`read`], [`write`], and
36//! [`bufread`]. Each module contains a number of types used to encode and
37//! decode various streams of data.
38//!
39//! All types in the [`write`] module work on instances of [`Write`][write],
40//! whereas all types in the [`read`] module work on instances of
41//! [`Read`][read] and [`bufread`] works with [`BufRead`][bufread]. If you
42//! are decoding directly from a `&[u8]`, use the [`bufread`] types.
43//!
44//! ```
45//! use flate2::write::GzEncoder;
46//! use flate2::Compression;
47//! use std::io;
48//! use std::io::prelude::*;
49//!
50//! # fn main() { let _ = run(); }
51//! # fn run() -> io::Result<()> {
52//! let mut encoder = GzEncoder::new(Vec::new(), Compression::default());
53//! encoder.write_all(b"Example")?;
54//! # Ok(())
55//! # }
56//! ```
57//!
58//!
59//! Other various types are provided at the top-level of the crate for
60//! management and dealing with encoders/decoders. Also note that types which
61//! operate over a specific trait often implement the mirroring trait as well.
62//! For example a `flate2::read::DeflateDecoder<T>` *also* implements the
63//! `Write` trait if `T: Write`. That is, the "dual trait" is forwarded directly
64//! to the underlying object if available.
65//!
66//! # About multi-member Gzip files
67//!
68//! While most `gzip` files one encounters will have a single *member* that can be read
69//! with the [`GzDecoder`], there may be some files which have multiple members.
70//!
71//! A [`GzDecoder`] will only read the first member of gzip data, which may unexpectedly
72//! provide partial results when a multi-member gzip file is encountered. `GzDecoder` is appropriate
73//! for data that is designed to be read as single members from a multi-member file. `bufread::GzDecoder`
74//! and `write::GzDecoder` also allow non-gzip data following gzip data to be handled.
75//!
76//! The [`MultiGzDecoder`] on the other hand will decode all members of a `gzip` file
77//! into one consecutive stream of bytes, which hides the underlying *members* entirely.
78//! If a file contains non-gzip data after the gzip data, MultiGzDecoder will
79//! emit an error after decoding the gzip data. This behavior matches the `gzip`,
80//! `gunzip`, and `zcat` command line tools.
81//!
82//! [`read`]: read/index.html
83//! [`bufread`]: bufread/index.html
84//! [`write`]: write/index.html
85//! [read]: https://doc.rust-lang.org/std/io/trait.Read.html
86//! [write]: https://doc.rust-lang.org/std/io/trait.Write.html
87//! [bufread]: https://doc.rust-lang.org/std/io/trait.BufRead.html
88//! [`GzDecoder`]: read/struct.GzDecoder.html
89//! [`MultiGzDecoder`]: read/struct.MultiGzDecoder.html
90#![doc(html_root_url = "https://docs.rs/flate2/0.2")]
91#![deny(missing_docs)]
92#![deny(missing_debug_implementations)]
93#![allow(trivial_numeric_casts)]
94#![cfg_attr(test, deny(warnings))]
95#![cfg_attr(docsrs, feature(doc_auto_cfg))]
96
97#[cfg(not(feature = "any_impl",))]
98compile_error!("You need to choose a zlib backend");
99
100pub use crate::crc::{Crc, CrcReader, CrcWriter};
101pub use crate::gz::GzBuilder;
102pub use crate::gz::GzHeader;
103pub use crate::mem::{Compress, CompressError, Decompress, DecompressError, Status};
104pub use crate::mem::{FlushCompress, FlushDecompress};
105
106mod bufreader;
107mod crc;
108mod deflate;
109mod ffi;
110mod gz;
111mod mem;
112mod zio;
113mod zlib;
114
115/// Types which operate over [`Read`] streams, both encoders and decoders for
116/// various formats.
117///
118/// Note that the `read` decoder types may read past the end of the compressed
119/// data while decoding. If the caller requires subsequent reads to start
120/// immediately following the compressed data wrap the `Read` type in a
121/// [`BufReader`] and use the `BufReader` with the equivalent decoder from the
122/// `bufread` module and also for the subsequent reads.
123///
124/// [`Read`]: https://doc.rust-lang.org/std/io/trait.Read.html
125/// [`BufReader`]: https://doc.rust-lang.org/std/io/struct.BufReader.html
126pub mod read {
127 pub use crate::deflate::read::DeflateDecoder;
128 pub use crate::deflate::read::DeflateEncoder;
129 pub use crate::gz::read::GzDecoder;
130 pub use crate::gz::read::GzEncoder;
131 pub use crate::gz::read::MultiGzDecoder;
132 pub use crate::zlib::read::ZlibDecoder;
133 pub use crate::zlib::read::ZlibEncoder;
134}
135
136/// Types which operate over [`Write`] streams, both encoders and decoders for
137/// various formats.
138///
139/// [`Write`]: https://doc.rust-lang.org/std/io/trait.Write.html
140pub mod write {
141 pub use crate::deflate::write::DeflateDecoder;
142 pub use crate::deflate::write::DeflateEncoder;
143 pub use crate::gz::write::GzDecoder;
144 pub use crate::gz::write::GzEncoder;
145 pub use crate::gz::write::MultiGzDecoder;
146 pub use crate::zlib::write::ZlibDecoder;
147 pub use crate::zlib::write::ZlibEncoder;
148}
149
150/// Types which operate over [`BufRead`] streams, both encoders and decoders for
151/// various formats.
152///
153/// [`BufRead`]: https://doc.rust-lang.org/std/io/trait.BufRead.html
154pub mod bufread {
155 pub use crate::deflate::bufread::DeflateDecoder;
156 pub use crate::deflate::bufread::DeflateEncoder;
157 pub use crate::gz::bufread::GzDecoder;
158 pub use crate::gz::bufread::GzEncoder;
159 pub use crate::gz::bufread::MultiGzDecoder;
160 pub use crate::zlib::bufread::ZlibDecoder;
161 pub use crate::zlib::bufread::ZlibEncoder;
162}
163
164fn _assert_send_sync() {
165 fn _assert_send_sync<T: Send + Sync>() {}
166
167 _assert_send_sync::<read::DeflateEncoder<&[u8]>>();
168 _assert_send_sync::<read::DeflateDecoder<&[u8]>>();
169 _assert_send_sync::<read::ZlibEncoder<&[u8]>>();
170 _assert_send_sync::<read::ZlibDecoder<&[u8]>>();
171 _assert_send_sync::<read::GzEncoder<&[u8]>>();
172 _assert_send_sync::<read::GzDecoder<&[u8]>>();
173 _assert_send_sync::<read::MultiGzDecoder<&[u8]>>();
174 _assert_send_sync::<write::DeflateEncoder<Vec<u8>>>();
175 _assert_send_sync::<write::DeflateDecoder<Vec<u8>>>();
176 _assert_send_sync::<write::ZlibEncoder<Vec<u8>>>();
177 _assert_send_sync::<write::ZlibDecoder<Vec<u8>>>();
178 _assert_send_sync::<write::GzEncoder<Vec<u8>>>();
179 _assert_send_sync::<write::GzDecoder<Vec<u8>>>();
180}
181
182/// When compressing data, the compression level can be specified by a value in
183/// this struct.
184#[derive(Copy, Clone, PartialEq, Eq, Debug)]
185pub struct Compression(u32);
186
187impl Compression {
188 /// Creates a new description of the compression level with an explicitly
189 /// specified integer.
190 ///
191 /// The integer here is typically on a scale of 0-9 where 0 means "no
192 /// compression" and 9 means "take as long as you'd like".
193 ///
194 /// ### Backend differences
195 ///
196 /// The [`miniz_oxide`](https://crates.io/crates/miniz_oxide) backend for flate2
197 /// does not support level 0 or `Compression::none()`. Instead it interprets them
198 /// as the default compression level, which is quite slow.
199 /// `Compression::fast()` should be used instead.
200 ///
201 /// `miniz_oxide` also supports a non-compliant compression level 10.
202 /// It is even slower and may result in higher compression, but
203 /// **only miniz_oxide will be able to read the data** compressed with level 10.
204 /// Do **not** use level 10 if you need other software to be able to read it!
205 pub const fn new(level: u32) -> Compression {
206 Compression(level)
207 }
208
209 /// No compression is to be performed, this may actually inflate data
210 /// slightly when encoding.
211 pub const fn none() -> Compression {
212 Compression(0)
213 }
214
215 /// Optimize for the best speed of encoding.
216 pub const fn fast() -> Compression {
217 Compression(1)
218 }
219
220 /// Optimize for the size of data being encoded.
221 pub const fn best() -> Compression {
222 Compression(9)
223 }
224
225 /// Returns an integer representing the compression level, typically on a
226 /// scale of 0-9. See [`new`](Self::new) for details about compression levels.
227 pub fn level(&self) -> u32 {
228 self.0
229 }
230}
231
232impl Default for Compression {
233 fn default() -> Compression {
234 Compression(6)
235 }
236}
237
238#[cfg(test)]
239fn random_bytes() -> impl Iterator<Item = u8> {
240 use rand::Rng;
241 use std::iter;
242
243 iter::repeat(()).map(|_| rand::rng().random())
244}
245