Add parameterized CRC-32 and CRC-64 by bartonjs · Pull Request #124117 · dotnet/runtime

bartonjs · 2026-02-07T00:58:35Z

Add parameterized CRC-32 and CRC-64. Currently, they are just done as
byte-by-byte table lookup, except for the Crc32 and Crc64 parameter
sets, which defer to the already-optimized implementations, and CRC-32/C,
which uses x86 and ARM intrinsics.

Generalized vectorization will be done as a followup.

Fixes #123164.

byte-by-byte table lookup, except for the `Crc32` and `Crc64` parameter sets, which defer to the already-optimized implementations, and CRC-32/C, which uses x86 and ARM intrinsics. Generalized vectorization will be done as a followup.

dotnet-policy-service · 2026-02-07T00:59:17Z

Tagging subscribers to this area: @dotnet/area-system-io-hashing, @bartonjs, @vcsjones
See info in area-owners.md if you want to be subscribed.

Copilot

Pull request overview

Adds support for computing CRC-32 and CRC-64 using caller-specified parameter sets, while keeping the existing optimized implementations for the default CRC-32 / CRC-64 variants (and CRC-32C via intrinsics where available). This expands System.IO.Hashing to cover additional CRC variants requested in #123164.

Changes:

Introduce Crc32ParameterSet / Crc64ParameterSet types with factory creation and a small set of well-known presets (e.g., CRC-32, CRC-32C, CRC-64, CRC-64/NVME).
Add parameterized overloads/constructors on Crc32 and Crc64 that accept a parameter set, and route hashing through the parameter set implementation.
Add extensive new test coverage for parameterized CRC-32/CRC-64 variants and known-answer tests for well-known parameter sets.

Reviewed changes

Copilot reviewed 22 out of 22 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc32.cs	Adds `Crc32ParameterSet` constructor/property and parameterized Hash/TryHash/HashToUInt32 overloads; routes computation through parameter set.
src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc64.cs	Adds `Crc64ParameterSet` constructor/property and parameterized Hash/TryHash/HashToUInt64 overloads; routes computation through parameter set.
src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc32ParameterSet.cs	Introduces core CRC-32 parameter set type (properties, Create, finalization, byte-order write).
src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc32ParameterSet.Table.cs	Implements table-based CRC-32 update for reflected and forward modes.
src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc32ParameterSet.WellKnown.cs	Adds well-known CRC-32 and CRC-32C parameter sets, including intrinsic-based CRC-32C path.
src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc64ParameterSet.cs	Introduces core CRC-64 parameter set type (properties, Create, finalization, byte-order write).
src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc64ParameterSet.Table.cs	Implements table-based CRC-64 update for reflected and forward modes.
src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc64ParameterSet.WellKnown.cs	Adds well-known CRC-64 (ECMA-182) and CRC-64/NVME parameter sets.
src/libraries/System.IO.Hashing/src/System.IO.Hashing.csproj	Adds new parameter set sources to the build.
src/libraries/System.IO.Hashing/ref/System.IO.Hashing.cs	Updates the public reference surface for new parameter set types and overloads.
src/libraries/System.IO.Hashing/tests/System.IO.Hashing.Tests.csproj	Includes new test sources for parameterized CRC testing.
src/libraries/System.IO.Hashing/tests/Crc32Tests.cs	Adds argument-null validation tests for new CRC-32 parameterSet overloads/ctor.
src/libraries/System.IO.Hashing/tests/Crc32ParameterSetTests.cs	Adds known-answer tests for several CRC-32 parameter sets.
src/libraries/System.IO.Hashing/tests/Crc32Tests_Parameterized.cs	Adds parameterized driver-based test framework for CRC-32 parameter sets.
src/libraries/System.IO.Hashing/tests/Crc32Tests_ParameterSet_Crc32.cs	Adds CRC-32 parameter set driver + singleton/value tests.
src/libraries/System.IO.Hashing/tests/Crc32Tests_ParameterSet_Crc32C.cs	Adds CRC-32C parameter set driver + singleton/value tests.
src/libraries/System.IO.Hashing/tests/Crc32Tests_ParameterSet_Custom.cs	Adds custom CRC-32 parameter set drivers using `Create(...)`.
src/libraries/System.IO.Hashing/tests/Crc64ParameterSetTests.cs	Adds known-answer tests for several CRC-64 parameter sets.
src/libraries/System.IO.Hashing/tests/Crc64Tests_Parameterized.cs	Adds parameterized driver-based test framework for CRC-64 parameter sets.
src/libraries/System.IO.Hashing/tests/Crc64Tests_Parameterized_Crc64.cs	Adds CRC-64 parameter set driver + singleton/value tests.
src/libraries/System.IO.Hashing/tests/Crc64Tests_Parameterized_Custom.cs	Adds a custom CRC-64 parameter set driver using `Create(...)`.
src/libraries/System.IO.Hashing/tests/Crc64Tests_Parameterized_Nvme.cs	Adds CRC-64/NVME parameter set driver + singleton/value tests.

Copilot · 2026-02-07T01:08:31Z

src/libraries/System.IO.Hashing/tests/Crc64Tests_Parameterized.cs

+        [Theory]
+        [MemberData(nameof(TestCases))]
+        public void VerifyHashToUInt32(TestCase testCase)
+        {
+            var alg = new Crc64(s_parameterSet);
+            alg.Append(testCase.Input);
+            AssertEqualHashNumber(testCase.OutputHex, alg.GetCurrentHashAsUInt64(), littleEndian: s_parameterSet.ReflectValues);
+            AssertEqualHashNumber(testCase.OutputHex, Crc64.HashToUInt64(s_parameterSet, testCase.Input), littleEndian: s_parameterSet.ReflectValues);
+        }


Test name VerifyHashToUInt32 is misleading here: it validates GetCurrentHashAsUInt64() and Crc64.HashToUInt64(...). Rename the test method to VerifyHashToUInt64 to match what it's asserting.

Copilot · 2026-02-07T01:08:32Z

src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc64.cs

+        public Crc64(Crc64ParameterSet parameterSet)
+            : base(Size)
+        {
+            ArgumentNullException.ThrowIfNull(parameterSet);
+
+            ParameterSet = parameterSet;
+            _crc = parameterSet.InitialValue;
        }


New APIs add ArgumentNullException.ThrowIfNull(parameterSet) in the Crc64(Crc64ParameterSet) ctor and parameterized Hash/TryHash/HashToUInt64 overloads, but there are no unit tests asserting these null checks (unlike Crc32Tests.ParameterSetIsRequired). Add coverage for Crc64 to ensure the exceptions (and bytesWritten behavior for TryHash) are validated.

Copilot · 2026-02-07T01:08:32Z

src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc32ParameterSet.WellKnown.cs

+        private static Crc32ParameterSet MakeCrc32CParameterSet()
+        {
+#if NET
+            if (System.Runtime.Intrinsics.X86.Sse.IsSupported || System.Runtime.Intrinsics.Arm.Crc32.IsSupported)


MakeCrc32CParameterSet checks X86.Sse.IsSupported, but the SSE CRC32C instruction requires SSE4.2 (X86.Sse42.IsSupported). On x86 machines with SSE but without SSE4.2, this will return Crc32CParameterSet, then UpdateIntrinsic falls into the ARM path and will assert/call unsupported intrinsics. Change the capability check to use Sse42.IsSupported (and keep the ARM check as-is).

Suggested change

if (System.Runtime.Intrinsics.X86.Sse.IsSupported || System.Runtime.Intrinsics.Arm.Crc32.IsSupported)

if (System.Runtime.Intrinsics.X86.Sse42.IsSupported || System.Runtime.Intrinsics.Arm.Crc32.IsSupported)

Copilot · 2026-02-07T01:08:32Z

src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc32ParameterSet.WellKnown.cs

+
+                    foreach (byte value in remainingBytes)
+                    {
+                        crc = System.Runtime.Intrinsics.Arm.Crc32.Arm64.ComputeCrc32C(crc, value);


In the ARM fallback, the per-byte loop calls Arm.Crc32.Arm64.ComputeCrc32C(crc, value) where value is a byte. This ends up using the 64-bit (8-byte) CRC instruction with an implicit conversion to ulong, which produces an incorrect CRC (it effectively processes 8 bytes, not 1). Use Arm.Crc32.ComputeCrc32C(crc, value) for the remaining bytes.

Suggested change

crc = System.Runtime.Intrinsics.Arm.Crc32.Arm64.ComputeCrc32C(crc, value);

crc = System.Runtime.Intrinsics.Arm.Crc32.ComputeCrc32C(crc, value);

Copilot · 2026-02-07T01:08:33Z

src/libraries/System.IO.Hashing/src/System/IO/Hashing/Crc32.cs

+        /// <summary>Computes the CRC-32 hash of the provided data, using the ITU-T V.42 / IEEE 802.3 parameters.</summary>
+        /// <param name="parameterSet">The parameters to use for the CRC computation.</param>
        /// <param name="source">The data to hash.</param>
        /// <returns>The computed CRC-32 hash.</returns>
+        /// <exception cref="ArgumentNullException">
+        ///   <paramref name="parameterSet"/> is <see langword="null"/>.
+        /// </exception>


The XML doc for HashToUInt32(Crc32ParameterSet parameterSet, ReadOnlySpan<byte> source) says it uses the ITU-T V.42 / IEEE 802.3 parameters, but this overload computes using the provided parameterSet. Update the <summary> to describe that it uses the specified parameter set (the default-parameter summary above is already correct).

bartonjs added 2 commits February 6, 2026 16:31

Remove support for refIn!=refOut

f4b8a5e

bartonjs added the area-System.IO.Hashing label Feb 7, 2026

Copilot AI review requested due to automatic review settings February 7, 2026 00:58

dotnet-policy-service bot assigned bartonjs Feb 7, 2026

Copilot started reviewing on behalf of bartonjs February 7, 2026 00:59 View session

Copilot AI reviewed Feb 7, 2026

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build-analysis bot mentioned this pull request Feb 7, 2026

Tests failing on tvos with "The app 'net.dot.System.Runtime.Tests' terminated with signal 11" #124072

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Add parameterized CRC-32 and CRC-64#124117

Add parameterized CRC-32 and CRC-64#124117
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	if (System.Runtime.Intrinsics.X86.Sse.IsSupported \|\| System.Runtime.Intrinsics.Arm.Crc32.IsSupported)
	if (System.Runtime.Intrinsics.X86.Sse42.IsSupported \|\| System.Runtime.Intrinsics.Arm.Crc32.IsSupported)

	crc = System.Runtime.Intrinsics.Arm.Crc32.Arm64.ComputeCrc32C(crc, value);
	crc = System.Runtime.Intrinsics.Arm.Crc32.ComputeCrc32C(crc, value);

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