Add Crc32

Author: jzebedee

src/LibDeflate/Checksums/Crc32.cs

@@ -0,0 +1,23 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace LibDeflate.Checksums
+{
+    using static Imports.Checksums;
+
+    public struct Crc32
+    {
+        private uint _currentCrc;
+
+        public uint Hash => _currentCrc;
+
+        public void Append(ReadOnlySpan<byte> input)
+            => _currentCrc = AppendCore(_currentCrc, input);
+
+        public uint Compute(ReadOnlySpan<byte> input)
+            => _currentCrc = AppendCore(0, input);
+
+        private static uint AppendCore(uint crc, ReadOnlySpan<byte> input)
+            => libdeflate_crc32(crc, MemoryMarshal.GetReference(input), (nuint)input.Length);
+    }
+}