Add no_std and WASM support

This commit adds comprehensive no_std compatibility while maintaining 100%
backward compatibility with existing std-based code.

Key changes:
- Add optional `std` feature (enabled by default)
- Add `alloc` and `cache` features for heap allocation in no_std
- Use spin crate for no_std synchronization (Once, RwLock, Mutex)
- Use hashbrown for no_std HashMap when cache feature enabled
- Fix UB in algorithm.rs (potential out-of-bounds read)
- Fix Miri memory leaks in software fallback caching
- Add dual-path feature detection (runtime with std, compile-time without)
- Add comprehensive test coverage (tests/no_std_tests.rs, tests/wasm_tests.rs)
- Add CI workflows for embedded (ARM, RISC-V) and WASM targets
- Update all modules to use core/alloc primitives where appropriate

Tested on:
- Embedded: thumbv7em, thumbv8m, riscv32
- WASM: wasm32-unknown-unknown, wasm32-wasip1, wasm32-wasip2
- All existing x86/x86_64/aarch64 targets
- Miri validation passes (no memory leaks)

Author: loadingalias

.github/workflows/tests.yml

@@ -146,4 +146,83 @@ jobs:
         run: cargo miri nextest run --all-features -j${{ steps.cores.outputs.count }}
       - name: Run Miri tests (serial)
         if: steps.cores.outputs.use_nextest == 'false'
-        run: cargo miri test --all-features
+        run: cargo miri test --all-features
+
+  test-no-std:
+    name: Test no_std
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        target:
+          - thumbv7em-none-eabihf  # ARM Cortex-M4F/M7F
+          - thumbv8m.main-none-eabihf  # ARM Cortex-M33/M35P
+          - riscv32imac-unknown-none-elf  # RISC-V 32-bit
+        rust-toolchain:
+          - "1.81" # minimum for this crate
+          - "stable"
+          - "nightly"
+    steps:
+      - uses: actions/checkout@v4 # not pinning to commit hash since this is a GitHub action, which we trust
+      - uses: actions-rust-lang/setup-rust-toolchain@9d7e65c320fdb52dcd45ffaa68deb6c02c8754d9 # v1.12.0
+        with:
+          toolchain: ${{ matrix.rust-toolchain }}
+          target: ${{ matrix.target }}
+          components: rustfmt, clippy
+          cache-key: ${{ matrix.target }}-${{ matrix.rust-toolchain }}
+      - name: Check no_std (no features)
+        run: cargo check --target ${{ matrix.target }} --no-default-features --features panic-handler --lib
+      - name: Check no_std with alloc
+        run: cargo check --target ${{ matrix.target }} --no-default-features --features alloc,panic-handler --lib
+      - name: Check no_std with cache
+        run: cargo check --target ${{ matrix.target }} --no-default-features --features cache,panic-handler --lib
+      - name: Run no_std tests (on host with std test harness)
+        run: cargo test --test no_std_tests
+
+  test-wasm:
+    name: Test WASM
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        include:
+          # WASM 1.0/2.0 (32-bit) - all toolchains
+          - target: wasm32-unknown-unknown
+            rust-toolchain: "1.81"
+          - target: wasm32-unknown-unknown
+            rust-toolchain: "stable"
+          - target: wasm32-unknown-unknown
+            rust-toolchain: "nightly"
+          # WASI preview 1 (32-bit) - all toolchains
+          - target: wasm32-wasip1
+            rust-toolchain: "1.81"
+          - target: wasm32-wasip1
+            rust-toolchain: "stable"
+          - target: wasm32-wasip1
+            rust-toolchain: "nightly"
+          # WASI preview 2 (32-bit) - nightly only (experimental)
+          - target: wasm32-wasip2
+            rust-toolchain: "nightly"
+          # Note: wasm64-unknown-unknown removed - not consistently available in nightly
+    steps:
+      - uses: actions/checkout@v4 # not pinning to commit hash since this is a GitHub action, which we trust
+      - uses: actions-rust-lang/setup-rust-toolchain@9d7e65c320fdb52dcd45ffaa68deb6c02c8754d9 # v1.12.0
+        with:
+          toolchain: ${{ matrix.rust-toolchain }}
+          target: ${{ matrix.target }}
+          components: rustfmt, clippy
+          cache-key: ${{ matrix.target }}-${{ matrix.rust-toolchain }}
+      - name: Check WASM (no features)
+        run: cargo check --target ${{ matrix.target }} --no-default-features --features panic-handler --lib
+      - name: Check WASM with alloc
+        run: cargo check --target ${{ matrix.target }} --no-default-features --features alloc,panic-handler --lib
+      - name: Check WASM with cache
+        run: cargo check --target ${{ matrix.target }} --no-default-features --features cache,panic-handler --lib
+      - name: Build WASM release
+        run: cargo build --target ${{ matrix.target }} --no-default-features --features alloc,panic-handler --lib --release
+      - name: Run WASM tests (on host with std test harness)
+        run: cargo test --test wasm_tests
+      - if: ${{ matrix.target == 'wasm32-unknown-unknown' && matrix.rust-toolchain == 'stable' }}
+        name: Install wasm-pack
+        run: curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh
+      - if: ${{ matrix.target == 'wasm32-unknown-unknown' && matrix.rust-toolchain == 'stable' }}
+        name: Build WASM package with wasm-pack
+        run: wasm-pack build --target web --no-default-features --features alloc,panic-handler

.gitignore

@@ -4,4 +4,4 @@
 .idea
 .DS_Store
 .git
-.vscode
+.vscode

Cargo.lock

@@ -23,19 +23,26 @@ bench = true
 
 [dependencies]
 crc = "3"
-digest = {  version = "0.10", features = ["alloc"] }
+digest = { version = "0.10", optional = true, default-features = false, features = ["alloc"] }
 
 # will be removed once Rust 1.89 is the minimum supported version
 rustversion = "1.0"
 
 # constrain indexmap (transitive) to a version compatible with Rust 1.81.0
 indexmap = { version = ">=2.11.0, <2.12.0", optional = true }
 
+# no_std support
+# spin is always required for no_std builds (feature detection synchronization)
+spin = { version = "0.10.0", default-features = false, features = ["once", "rwlock", "mutex", "spin_mutex"] }
+# hashbrown is only needed when caching is enabled in no_std
+hashbrown = { version = "0.16.0", optional = true }
+
 [dev-dependencies]
 criterion = "0.7"
 cbindgen = "0.29"
 rand = "0.9"
 regex = "1.12"
+wasm-bindgen-test = "0.3"
 
 # lto=true has a big improvement in performance
 [profile.release]
@@ -62,12 +69,16 @@ required-features = ["cli"]
 [[bench]]
 name = "benchmark"
 harness = false
+required-features = ["std"]
 
 [features]
-default = ["std"]
-std = []
+default = ["std", "panic-handler"]
+std = ["alloc"] # std implies alloc is available
 cli = ["std"]
-alloc = []
+alloc = ["digest"] # marker feature for heap allocation support
+cache = ["alloc", "hashbrown"] # caching requires alloc + hashbrown HashMap
+ffi = ["std"]
+panic-handler = [] # Provides panic handler for no_std library checks (disable in binaries)
 
 # the features below are deprecated, aren't in use, and will be removed in the next MAJOR version (v2)
 vpclmulqdq = [] # deprecated, VPCLMULQDQ stabilized in Rust 1.89.0
@@ -87,4 +98,4 @@ rustdoc-args = ["--cfg", "docsrs"]
 [[test]]
 name = "checksum_integration_tests"
 path = "tests/checksum_integration_tests.rs"
-required-features = ["cli"]
+required-features = ["cli"]

Cargo.toml

@@ -59,11 +59,8 @@ fn create_aligned_data(input: &[u8]) -> Vec<u8> {
     // Size of our target alignment structure
     let align_size = std::mem::size_of::<[[u64; 4]; 2]>(); // 64 bytes
 
-    // Create a vector with padding to ensure we can find a properly aligned position
-    let mut padded = Vec::with_capacity(input.len() + align_size);
-
-    // Fill with zeros initially to reach needed capacity
-    padded.resize(input.len() + align_size, 0);
+    // Create a zero-filled vector with padding to ensure we can find a properly aligned position
+    let mut padded = vec![0; input.len() + align_size];
 
     // Find the first address that satisfies our alignment
     let start_addr = padded.as_ptr() as usize;
@@ -87,7 +84,7 @@ fn bench_crc32(c: &mut Criterion) {
     );
 
     for (size_name, size) in SIZES {
-        let buf = create_aligned_data(&*random_data(*size));
+        let buf = create_aligned_data(&random_data(*size));
 
         let (part1, rest) = buf.split_at(buf.len() / 4);
         let (part2, rest) = rest.split_at(rest.len() / 3);
@@ -115,10 +112,10 @@ fn bench_crc32(c: &mut Criterion) {
                 b.iter(|| {
                     black_box({
                         let mut digest = crc_fast::Digest::new(*algorithm);
-                        digest.update(&part1);
-                        digest.update(&part2);
-                        digest.update(&part3);
-                        digest.update(&part4);
+                        digest.update(part1);
+                        digest.update(part2);
+                        digest.update(part3);
+                        digest.update(part4);
                         digest.finalize()
                     })
                 })
@@ -137,7 +134,7 @@ fn bench_crc64(c: &mut Criterion) {
     let mut group = c.benchmark_group("CRC-64");
 
     for (size_name, size) in SIZES {
-        let buf = create_aligned_data(&*random_data(*size));
+        let buf = create_aligned_data(&random_data(*size));
 
         let (part1, rest) = buf.split_at(buf.len() / 4);
         let (part2, rest) = rest.split_at(rest.len() / 3);
@@ -165,10 +162,10 @@ fn bench_crc64(c: &mut Criterion) {
                 b.iter(|| {
                     black_box({
                         let mut digest = crc_fast::Digest::new(*algorithm);
-                        digest.update(&part1);
-                        digest.update(&part2);
-                        digest.update(&part3);
-                        digest.update(&part4);
+                        digest.update(part1);
+                        digest.update(part2);
+                        digest.update(part3);
+                        digest.update(part4);
                         digest.finalize()
                     })
                 })