added IDigestFactory

Author: dghgit

crypto/src/crypto/IDigestFactory.cs

@@ -0,0 +1,24 @@
+namespace Org.BouncyCastle.Crypto
+{
+    /// <summary>
+    /// Base interface for operator factories that create stream-based digest calculators.
+    /// </summary>
+    /// <typeparam name="A">The algorithm details/parameter type for the digest factory.</typeparam>
+    public interface IDigestFactory<out A>
+	{
+		/// <summary>The algorithm details object for calculators made by this factory.</summary>
+		A AlgorithmDetails { get ; }
+
+		/// <summary>Return the size of the digest associated with this factory.</summary>
+		/// <returns>The length of the digest produced by this calculators from this factory in bytes.</returns>
+		int DigestLength { get; }
+
+		/// <summary>
+		/// Create a stream calculator for the digest associated with this factory. The stream
+		/// calculator is used for the actual operation of entering the data to be digested
+		/// and producing the digest block.
+		/// </summary>
+		/// <returns>A calculator producing an IBlockResult with the final digest in it.</returns>
+		IStreamCalculator<IBlockResult> CreateCalculator();
+	}
+}