Add `SHA512Checksum` helper

src/BizHawk.Common/checksums/CRC32Checksum.cs

@@ -6,6 +6,7 @@ namespace BizHawk.Common
 	/// <seealso cref="MD5Checksum"/>
 	/// <seealso cref="SHA1Checksum"/>
 	/// <seealso cref="SHA256Checksum"/>
+	/// <seealso cref="SHA512Checksum"/>
 	public static class CRC32Checksum
 	{
 		/// <remarks>in bits</remarks>

src/BizHawk.Common/checksums/MD5Checksum.cs

@@ -9,6 +9,7 @@ namespace BizHawk.Common
 	/// <seealso cref="CRC32Checksum"/>
 	/// <seealso cref="SHA1Checksum"/>
 	/// <seealso cref="SHA256Checksum"/>
+	/// <seealso cref="SHA512Checksum"/>
 	public static class MD5Checksum
 	{
 		/// <remarks>in bits</remarks>

src/BizHawk.Common/checksums/SHA1Checksum.cs

@@ -11,6 +11,7 @@ namespace BizHawk.Common
 	/// <seealso cref="CRC32Checksum"/>
 	/// <seealso cref="MD5Checksum"/>
 	/// <seealso cref="SHA256Checksum"/>
+	/// <seealso cref="SHA512Checksum"/>
 	public static class SHA1Checksum
 	{
 		/// <remarks>in bits</remarks>

src/BizHawk.Common/checksums/SHA256Checksum.cs

@@ -9,6 +9,7 @@ namespace BizHawk.Common
 	/// <seealso cref="CRC32Checksum"/>
 	/// <seealso cref="MD5Checksum"/>
 	/// <seealso cref="SHA1Checksum"/>
+	/// <seealso cref="SHA512Checksum"/>
 	public static class SHA256Checksum
 	{
 		/// <remarks>in bits</remarks>

src/BizHawk.Common/checksums/SHA512Checksum.cs

@@ -0,0 +1,58 @@
+using System.Diagnostics;
+using System.Security.Cryptography;
+
+using BizHawk.Common.BufferExtensions;
+
+namespace BizHawk.Common
+{
+	/// <summary>uses <see cref="SHA512"/> implementation from BCL</summary>
+	/// <seealso cref="CRC32Checksum"/>
+	/// <seealso cref="MD5Checksum"/>
+	/// <seealso cref="SHA1Checksum"/>
+	/// <seealso cref="SHA256Checksum"/>
+	public static class SHA512Checksum
+	{
+		/// <remarks>in bits</remarks>
+		internal const int EXPECTED_LENGTH = 512;
+
+		internal const string PREFIX = "SHA512";
+
+#if NET7_0_OR_GREATER
+		public static byte[] Compute(ReadOnlySpan<byte> data)
+			=> SHA512.HashData(data);
+#else
+		private static SHA512? _sha512Impl;
+
+		private static SHA512 SHA512Impl
+		{
+			get
+			{
+				if (_sha512Impl == null)
+				{
+					_sha512Impl = SHA512.Create();
+					Debug.Assert(_sha512Impl.CanReuseTransform && _sha512Impl.HashSize is EXPECTED_LENGTH, "nonstandard implementation?");
+				}
+				return _sha512Impl;
+			}
+		}
+
+		public static byte[] Compute(byte[] data)
+			=> SHA512Impl.ComputeHash(data);
+
+		public static string ComputeDigestHex(byte[] data)
+			=> Compute(data).BytesToHexString();
+
+		public static string ComputePrefixedHex(byte[] data)
+			=> $"{PREFIX}:{ComputeDigestHex(data)}";
+
+		public static byte[] Compute(ReadOnlySpan<byte> data)
+			=> Compute(data.ToArray());
+#endif
+
+		public static string ComputeDigestHex(ReadOnlySpan<byte> data)
+			=> Compute(data).BytesToHexString();
+
+		public static string ComputePrefixedHex(ReadOnlySpan<byte> data)
+			=> $"{PREFIX}:{ComputeDigestHex(data)}";
+	}
+}