sha2: fix missing documentation on compression functions (#266)

Adds docs, tests all features in CI, and adds doc_cfg setup for docs.rs.

.github/workflows/sha2.yml

@@ -70,6 +70,7 @@ jobs:
       - run: cargo test --target ${{ matrix.target }} --release --no-default-features
       - run: cargo test --target ${{ matrix.target }} --release
       - run: cargo test --target ${{ matrix.target }} --release --features asm
+      - run: cargo test --target ${{ matrix.target }} --release --all-features
 
   # macOS tests
   macos:

sha2/Cargo.toml

@@ -39,3 +39,6 @@ compress = [] # Expose compress function
 force-soft = [] # Force software implementation
 asm-aarch64 = ["asm"] # DEPRECATED: use `asm` instead
 
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]

sha2/src/lib.rs

@@ -53,6 +53,7 @@
 //! [2]: https://github.com/RustCrypto/hashes
 
 #![no_std]
+#![cfg_attr(docsrs, feature(doc_cfg))]
 #![doc(
     html_logo_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg",
     html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg"

sha2/src/sha256.rs

@@ -163,6 +163,11 @@ cfg_if::cfg_if! {
     }
 }
 
+/// Raw SHA-256 compression function.
+///
+/// This is a low-level "hazmat" API which provides direct access to the core
+/// functionality of SHA-256.
+#[cfg_attr(docsrs, doc(cfg(feature = "compress")))]
 pub fn compress256(state: &mut [u32; 8], blocks: &[GenericArray<u8, U64>]) {
     // SAFETY: GenericArray<u8, U64> and [u8; 64] have
     // exactly the same memory layout

sha2/src/sha512.rs

@@ -241,6 +241,11 @@ cfg_if::cfg_if! {
     }
 }
 
+/// Raw SHA-512 compression function.
+///
+/// This is a low-level "hazmat" API which provides direct access to the core
+/// functionality of SHA-512.
+#[cfg_attr(docsrs, doc(cfg(feature = "compress")))]
 pub fn compress512(state: &mut [u64; 8], blocks: &[GenericArray<u8, U128>]) {
     // SAFETY: GenericArray<u8, U128> and [u8; 128] have
     // exactly the same memory layout