digest-io-async: initial commit

This introduces a new crate providing `HashReader`/`HashWriter`
wrappers implementing `AsyncRead`/`AsyncWrite`, mirroring `digest-io`'s
sync API.

This only implement the tokio's async API for now, and it is gated 
behind a `tokio` feature.

The intent is to fold it in `digest-io` when the
`AsyncReader`/`AsyncWriter` eventually make their way into `std`.

Author: baloo

.github/workflows/digest-io-async.yml

@@ -0,0 +1,48 @@
+name: digest-io-async
+
+on:
+  pull_request:
+      paths:
+        - "digest-io-async/**"
+        - "Cargo.*"
+  push:
+    branches: master
+
+permissions:
+  contents: read
+
+defaults:
+  run:
+    working-directory: digest-io-async
+
+env:
+  CARGO_INCREMENTAL: 0
+  RUSTFLAGS: "-Dwarnings"
+
+# Cancels CI jobs when new commits are pushed to a PR branch
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  minimal-versions:
+    uses: RustCrypto/actions/.github/workflows/minimal-versions.yml@master
+    with:
+        working-directory: ${{ github.workflow }}
+
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        rust:
+          - 1.85.0 # MSRV
+          - stable
+    steps:
+      - uses: actions/checkout@v7
+      - uses: RustCrypto/actions/cargo-cache@master
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ matrix.rust }}
+      - run: cargo test --no-default-features
+      - run: cargo test
+      - run: cargo test --all-features

Cargo.lock

@@ -9,6 +9,8 @@ members = [
     "ctutils",
     "cpufeatures",
     "dbl",
+    "digest-io",
+    "digest-io-async",
     "hex-literal",
     "inout",
     "sponge-cursor",

Cargo.toml

@@ -0,0 +1,8 @@
+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## Unreleased
+- Initial release