Expose GRFilter's methods that accept a cached stream reader (#1186)

* Expose methods that accept a cached stream reader

This allows to use call match the same filter against a different set of elements without requiring to re-read the filter data, which it really expensive.

* CR suggestions

NBitcoin.Tests/Bip158_tests.cs

@@ -79,10 +79,13 @@ public void BuildFilterAndMatchValues()
 				.Build();
 
 			var testKey = key.ToBytes().SafeSubarray(0, 16);
+			var reader = filter.GetNewGRStreamReader();
+
 			// The filter should match all the values that were added.
 			foreach (var name in names)
 			{
 				Assert.True(filter.Match(name, testKey));
+				Assert.True(filter.Match(name, testKey, reader));
 			}
 
 			// The filter should NOT match any extra value.
@@ -445,9 +448,10 @@ public void RealScriptPubKeyFilterTest()
 			var filter = builder.Build();
 
 			var keyMatch = key.ToBytes().SafeSubarray(0, 16);
+			var reader = filter.GetNewGRStreamReader();
 			foreach (var script in scripts)
 			{
-				var match = filter.MatchAny(new[] { script.ToBytes() }, keyMatch);
+				var match = filter.Match(script.ToBytes(), keyMatch, reader);
 				Assert.True(match);
 			}
 		}

NBitcoin/BIP158/BitStream.cs

@@ -1,5 +1,5 @@
 using System;
-using System.Collections;
+using System.Collections.Generic;
 
 namespace NBitcoin
 {
@@ -170,7 +170,6 @@ private void EnsureCapacity()
 		}
 	}
 
-
 	internal class GRCodedStreamWriter
 	{
 		private readonly BitStream _stream;
@@ -204,22 +203,54 @@ public void Write(ulong value)
 		}
 	}
 
-	internal class GRCodedStreamReader
+	public class CachedGRCodedStreamReader : GRCodedStreamReader
+	{
+		private readonly List<ulong> _cachedValues;
+		private int _position;
+
+		internal CachedGRCodedStreamReader(BitStream stream, byte p, ulong lastValue) : base(stream, p, lastValue)
+		{
+			_cachedValues = new List<ulong>(10_000);
+			_position = 0;
+		}
+
+		public override bool TryRead(out ulong value)
+		{
+			if (_position >= _cachedValues.Count)
+			{
+				if (!base.TryRead(out var readValue))
+				{
+					value = 0;
+					return false;
+				}
+				_cachedValues.Add(readValue);
+			}
+			value = _cachedValues[_position++];
+			return true;
+		}
+
+		internal override void ResetPosition()
+		{
+			_position = 0;
+		}
+	}
+
+	public class GRCodedStreamReader
 	{
 		private readonly BitStream _stream;
 		private readonly byte _p;
 		private readonly ulong _modP;
 		private ulong _lastValue;
 
-		public GRCodedStreamReader(BitStream stream, byte p, ulong lastValue)
+		internal GRCodedStreamReader(BitStream stream, byte p, ulong lastValue)
 		{
 			_stream = stream;
 			_p = p;
 			_modP = (1UL << p);
 			_lastValue = lastValue;
 		}
 
-		public bool TryRead(out ulong value)
+		public virtual bool TryRead(out ulong value)
 		{
 			if (TryReadUInt64(out var readedValue))
 			{
@@ -233,6 +264,8 @@ public bool TryRead(out ulong value)
 			return false;
 		}
 
+		internal virtual void ResetPosition () {}
+
 		private bool TryReadUInt64(out ulong value)
 		{
 			value = 0U;

NBitcoin/BIP158/GolombRiceFilter.cs

@@ -156,10 +156,23 @@ public uint256 GetHeader(uint256 previousHeader)
 		/// <param name="key">Key used for hashing the data elements.</param>
 		/// <returns>true if the element is in the filter, otherwise false.</returns>
 		public bool Match(byte[] data, byte[] key)
+		{
+			var reader = new GRCodedStreamReader(new BitStream(Data), P, 0);
+			return Match(data, key, reader);
+		}
+
+		/// <summary>
+		/// Checks if the value passed is in the filter.
+		/// </summary>
+		/// <param name="data">Data element to check in the filter.</param>
+		/// <param name="key">Key used for hashing the data elements.</param>
+		/// <param name="reader">Golomb-Rice stream reader.</param>
+		/// <returns>true if the element is in the filter, otherwise false.</returns>
+		public bool Match(byte[] data, byte[] key, GRCodedStreamReader reader)
 		{
 			if (data == null)
 				throw new ArgumentNullException(nameof(data));
-			return MatchAny(new[] { data }, 1, key);
+			return MatchAny(new[] { data }, 1, key, reader);
 		}
 
 		/// <summary>
@@ -170,7 +183,8 @@ public bool Match(byte[] data, byte[] key)
 		/// <returns>true if at least one of the elements is in the filter, otherwise false.</returns>
 		public bool MatchAny(byte[][] data, byte[] key)
 		{
-			return MatchAny(data, data.Length, key);
+			var reader = new GRCodedStreamReader(new BitStream(Data), P, 0);
+			return MatchAny(data, data.Length, key, reader);
 		}
 
 		/// <summary>
@@ -180,20 +194,33 @@ public bool MatchAny(byte[][] data, byte[] key)
 		/// <param name="key">Key used for hashing the data elements.</param>
 		/// <returns>true if at least one of the elements is in the filter, otherwise false.</returns>
 		public bool MatchAny(IEnumerable<byte[]> data, byte[] key)
+		{
+			var reader = new GRCodedStreamReader(new BitStream(Data), P, 0);
+			return MatchAny(data, key, reader);
+		}
+
+		/// <summary>
+		/// Checks if any of the provided elements is in the filter.
+		/// </summary>
+		/// <param name="data">Data elements to check in the filter.</param>
+		/// <param name="key">Key used for hashing the data elements.</param>
+		/// <param name="reader">Golomb-Rice stream reader.</param>
+		/// <returns>true if at least one of the elements is in the filter, otherwise false.</returns>
+		public bool MatchAny(IEnumerable<byte[]> data, byte[] key, GRCodedStreamReader reader)
 		{
 			if (data == null)
 				throw new ArgumentNullException(nameof(data));
 			if (data is byte[][] dataArray)
 			{
-				return MatchAny(dataArray, dataArray.Length, key);
+				return MatchAny(dataArray, dataArray.Length, key, reader);
 			}
 			else if (data is ICollection<byte[]> dataCollection)
 			{
-				return MatchAny(dataCollection, dataCollection.Count, key);
+				return MatchAny(dataCollection, dataCollection.Count, key, reader);
 			}
 			else
 			{
-				return MatchAny(data, data.Count(), key);
+				return MatchAny(data, data.Count(), key, reader);
 			}
 		}
 
@@ -203,7 +230,19 @@ public bool MatchAny(IEnumerable<byte[]> data, byte[] key)
 		/// <param name="data">Data elements to check in the filter.</param>
 		/// <param name="key">Key used for hashing the data elements.</param>
 		/// <returns>true if at least one of the elements is in the filter, otherwise false.</returns>
-		internal bool MatchAny(IEnumerable<byte[]> data, int dataCount, byte[] key)
+		internal bool MatchAny(IEnumerable<byte[]> data, int dataCount, byte[] key, GRCodedStreamReader reader)
+		{
+			try
+			{
+				return InternalMatchAny(data, dataCount, key, reader);
+			}
+			finally
+			{
+				reader.ResetPosition();
+			}
+		}
+
+		private bool InternalMatchAny(IEnumerable<byte[]> data, int dataCount, byte[] key, GRCodedStreamReader sr)
 		{
 			if (data == null || dataCount == 0)
 				throw new ArgumentException("data can not be null or empty array.", nameof(data));
@@ -212,9 +251,6 @@ internal bool MatchAny(IEnumerable<byte[]> data, int dataCount, byte[] key)
 
 			var hs = ConstructHashedSet(P, N, M, key, data, dataCount);
 
-			var bitStream = new BitStream(Data);
-			var sr = new GRCodedStreamReader(bitStream, P, 0);
-
 			while(sr.TryRead(out var val))
 			{
 				var dataIndex = 0;
@@ -255,6 +291,15 @@ public override string ToString()
 			return NBitcoin.DataEncoders.Encoders.Hex.EncodeData(ToBytes());
 		}
 
+		/// <summary>
+		/// Create a cached Golomb-Rice stream reader.
+		/// </summary>
+		/// <returns>A new cached Golomb-Rice stream reader instance</returns>
+		public CachedGRCodedStreamReader GetNewGRStreamReader()
+		{
+			return new CachedGRCodedStreamReader(new BitStream(Data), P, 0);
+		}
+
 		internal static ulong FastReduction(ulong value, ulong nhi, ulong nlo)
 		{
 			// First, we'll spit the item we need to reduce into its higher and lower bits.