Vendor things

third-party/vendor/digest/README.md

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+# RustCrypto: Digest Algorithm Traits
+
+[![crate][crate-image]][crate-link]
+[![Docs][docs-image]][docs-link]
+![Apache2/MIT licensed][license-image]
+![Rust Version][rustc-image]
+[![Project Chat][chat-image]][chat-link]
+[![Build Status][build-image]][build-link]
+
+Traits which describe functionality of [cryptographic hash functions][0], a.k.a.
+digest algorithms.
+
+See [RustCrypto/hashes][1] for implementations which use this trait.
+
+[Documentation][docs-link]
+
+## Minimum Supported Rust Version
+
+Rust **1.41** or higher.
+
+Minimum supported Rust version can be changed in the future, but it will be
+done with a minor version bump.
+
+## SemVer Policy
+
+- All on-by-default features of this library are covered by SemVer
+- MSRV is considered exempt from SemVer as noted above
+
+## Usage
+
+Let us demonstrate how to use crates in this repository using Sha256 as an
+example.
+
+First add the `sha2` crate to your `Cargo.toml`:
+
+```toml
+[dependencies]
+sha2 = "0.10"
+```
+
+`sha2` and other crates re-export `digest` crate and `Digest` trait for
+convenience, so you don't have to add `digest` crate as an explicit dependency.
+
+Now you can write the following code:
+
+```rust
+use sha2::{Sha256, Digest};
+
+let mut hasher = Sha256::new();
+let data = b"Hello world!";
+hasher.update(data);
+// `input` can be called repeatedly and is generic over `AsRef<[u8]>`
+hasher.update("String data");
+// Note that calling `finalize()` consumes hasher
+let hash = hasher.finalize();
+println!("Result: {:x}", hash);
+```
+
+In this example `hash` has type [`GenericArray<u8, U64>`][2], which is a generic
+alternative to `[u8; 64]`.
+
+Alternatively you can use chained approach, which is equivalent to the previous
+example:
+
+```rust
+let hash = Sha256::new()
+    .chain_update(b"Hello world!")
+    .chain_update("String data")
+    .finalize();
+
+println!("Result: {:x}", hash);
+```
+
+If the whole message is available you also can use convenience `digest` method:
+
+```rust
+let hash = Sha256::digest(b"my message");
+println!("Result: {:x}", hash);
+```
+
+### Hashing `Read`-able objects
+
+If you want to hash data from [`Read`][3] trait (e.g. from file) you can rely on
+implementation of [`Write`][4] trait (requires enabled-by-default `std` feature):
+
+```rust
+use sha2::{Sha256, Digest};
+use std::{fs, io};
+
+let mut file = fs::File::open(&path)?;
+let mut hasher = Sha256::new();
+let n = io::copy(&mut file, &mut hasher)?;
+let hash = hasher.finalize();
+
+println!("Path: {}", path);
+println!("Bytes processed: {}", n);
+println!("Hash value: {:x}", hash);
+```
+
+### Generic code
+
+You can write generic code over `Digest` (or other traits from `digest` crate)
+trait which will work over different hash functions:
+
+```rust
+use digest::Digest;
+
+// Toy example, do not use it in practice!
+// Instead use crates from: https://github.com/RustCrypto/password-hashing
+fn hash_password<D: Digest>(password: &str, salt: &str, output: &mut [u8]) {
+    let mut hasher = D::new();
+    hasher.update(password.as_bytes());
+    hasher.update(b"$");
+    hasher.update(salt.as_bytes());
+    output.copy_from_slice(hasher.finalize().as_slice())
+}
+
+let mut buf1 = [0u8; 32];
+let mut buf2 = [0u8; 64];
+
+hash_password::<sha2::Sha256>("my_password", "abcd", &mut buf1);
+hash_password::<sha2::Sha512>("my_password", "abcd", &mut buf2);
+```
+
+If you want to use hash functions with trait objects, use `digest::DynDigest`
+trait.
+
+## License
+
+Licensed under either of:
+
+ * [Apache License, Version 2.0](http://www.apache.org/licenses/LICENSE-2.0)
+ * [MIT license](http://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
+dual licensed as above, without any additional terms or conditions.
+
+[//]: # (badges)
+
+[crate-image]: https://img.shields.io/crates/v/digest.svg
+[crate-link]: https://crates.io/crates/digest
+[docs-image]: https://docs.rs/digest/badge.svg
+[docs-link]: https://docs.rs/digest/
+[license-image]: https://img.shields.io/badge/license-Apache2.0/MIT-blue.svg
+[rustc-image]: https://img.shields.io/badge/rustc-1.41+-blue.svg
+[chat-image]: https://img.shields.io/badge/zulip-join_chat-blue.svg
+[chat-link]: https://rustcrypto.zulipchat.com/#narrow/stream/260041-hashes
+[build-image]: https://github.com/RustCrypto/traits/workflows/digest/badge.svg?branch=master&event=push
+[build-link]: https://github.com/RustCrypto/traits/actions?query=workflow%3Adigest
+
+[//]: # (general links)
+
+[0]: https://en.wikipedia.org/wiki/Cryptographic_hash_function
+[1]: https://github.com/RustCrypto/hashes
+[2]: https://docs.rs/generic-array
+[3]: https://doc.rust-lang.org/std/io/trait.Read.html
+[4]: https://doc.rust-lang.org/std/io/trait.Write.html
+[5]: https://en.wikipedia.org/wiki/Hash-based_message_authentication_code
+[6]: https://github.com/RustCrypto/MACs