Avoid some allocations around MPInteger

5 files changed, 60 insertions, 46 deletions

diff --git a/crypto/src/bcpg/BcpgInputStream.cs b/crypto/src/bcpg/BcpgInputStream.cs
index 5aa7ae306..7a19a90dd 100644
--- a/crypto/src/bcpg/BcpgInputStream.cs
+++ b/crypto/src/bcpg/BcpgInputStream.cs
@@ -62,22 +62,26 @@ namespace Org.BouncyCastle.Bcpg
 			return Streams.ReadAll(this);
 		}
 
-		public void ReadFully(
-            byte[]	buffer,
-            int		off,
-            int		len)
+		public void ReadFully(byte[] buffer, int offset, int count)
         {
-			if (Streams.ReadFully(this, buffer, off, len) < len)
+			if (Streams.ReadFully(this, buffer, offset, count) < count)
 				throw new EndOfStreamException();
         }
 
-		public void ReadFully(
-            byte[] buffer)
+		public void ReadFully(byte[] buffer)
         {
             ReadFully(buffer, 0, buffer.Length);
         }
 
-		/// <summary>Returns the next packet tag in the stream.</summary>
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public void ReadFully(Span<byte> buffer)
+        {
+            if (Streams.ReadFully(this, buffer) < buffer.Length)
+                throw new EndOfStreamException();
+        }
+#endif
+
+        /// <summary>Returns the next packet tag in the stream.</summary>
         public PacketTag NextPacketTag()
         {
             if (!next)
diff --git a/crypto/src/bcpg/ECDHPublicBCPGKey.cs b/crypto/src/bcpg/ECDHPublicBCPGKey.cs
index dc225e31e..05c34ba8b 100644
--- a/crypto/src/bcpg/ECDHPublicBCPGKey.cs
+++ b/crypto/src/bcpg/ECDHPublicBCPGKey.cs
@@ -14,15 +14,18 @@ namespace Org.BouncyCastle.Bcpg
         private SymmetricKeyAlgorithmTag symAlgorithmId;
 
         /// <param name="bcpgIn">The stream to read the packet from.</param>
-        public ECDHPublicBcpgKey(
-            BcpgInputStream bcpgIn)
+        public ECDHPublicBcpgKey(BcpgInputStream bcpgIn)
             : base(bcpgIn)
         {
             int length = bcpgIn.ReadByte();
-            byte[] kdfParameters =  new byte[length];
-            if (kdfParameters.Length != 3)
-                throw new InvalidOperationException("kdf parameters size of 3 expected.");
+            if (length != 3)
+                throw new InvalidOperationException("KDF parameters size of 3 expected.");
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+            Span<byte> kdfParameters = stackalloc byte[length];
+#else
+            byte[] kdfParameters = new byte[length];
+#endif
             bcpgIn.ReadFully(kdfParameters);
 
             reserved = kdfParameters[0];
@@ -75,7 +78,7 @@ namespace Org.BouncyCastle.Bcpg
 
         private void VerifyHashAlgorithm()
         {
-            switch ((HashAlgorithmTag)hashFunctionId)
+            switch (hashFunctionId)
             {
             case HashAlgorithmTag.Sha256:
             case HashAlgorithmTag.Sha384:
@@ -88,7 +91,7 @@ namespace Org.BouncyCastle.Bcpg
 
         private void VerifySymmetricKeyAlgorithm()
         {
-            switch ((SymmetricKeyAlgorithmTag)symAlgorithmId)
+            switch (symAlgorithmId)
             {
             case SymmetricKeyAlgorithmTag.Aes128:
             case SymmetricKeyAlgorithmTag.Aes192:
diff --git a/crypto/src/bcpg/ECPublicBCPGKey.cs b/crypto/src/bcpg/ECPublicBCPGKey.cs
index 4733ee6c9..560c6ad05 100644
--- a/crypto/src/bcpg/ECPublicBCPGKey.cs
+++ b/crypto/src/bcpg/ECPublicBCPGKey.cs
@@ -26,7 +26,7 @@ namespace Org.BouncyCastle.Bcpg
             DerObjectIdentifier oid,
             ECPoint point)
         {
-            this.point = new BigInteger(1, point.GetEncoded(false));
+            this.point = MPInteger.ToMpiBigInteger(point);
             this.oid = oid;
         }
 
diff --git a/crypto/src/bcpg/MPInteger.cs b/crypto/src/bcpg/MPInteger.cs
index 441407244..2f564b00c 100644
--- a/crypto/src/bcpg/MPInteger.cs
+++ b/crypto/src/bcpg/MPInteger.cs
@@ -1,59 +1,66 @@
 using System;
-using System.IO;
 
 using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Math.EC;
 
 namespace Org.BouncyCastle.Bcpg
 {
 	/// <remarks>A multiple precision integer</remarks>
-    public class MPInteger
+    public sealed class MPInteger
         : BcpgObject
     {
-        private readonly BigInteger val;
+        private readonly BigInteger m_val;
 
-        public MPInteger(
-            BcpgInputStream bcpgIn)
+        public MPInteger(BcpgInputStream bcpgIn)
         {
 			if (bcpgIn == null)
-				throw new ArgumentNullException("bcpgIn");
+				throw new ArgumentNullException(nameof(bcpgIn));
 
-			int length = (bcpgIn.ReadByte() << 8) | bcpgIn.ReadByte();
-            byte[] bytes = new byte[(length + 7) / 8];
+			int lengthInBits = (bcpgIn.ReadByte() << 8) | bcpgIn.ReadByte();
+            int lengthInBytes = (lengthInBits + 7) / 8;
 
-            bcpgIn.ReadFully(bytes);
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+            if (lengthInBytes <= 512)
+            {
+                Span<byte> span = stackalloc byte[lengthInBytes];
+                bcpgIn.ReadFully(span);
+                m_val = new BigInteger(1, span);
+                return;
+            }
+#endif
 
-            this.val = new BigInteger(1, bytes);
+            byte[] bytes = new byte[lengthInBytes];
+            bcpgIn.ReadFully(bytes);
+            m_val = new BigInteger(1, bytes);
         }
 
-		public MPInteger(
-            BigInteger val)
+		public MPInteger(BigInteger val)
         {
 			if (val == null)
-				throw new ArgumentNullException("val");
+				throw new ArgumentNullException(nameof(val));
 			if (val.SignValue < 0)
-				throw new ArgumentException("Values must be positive", "val");
+				throw new ArgumentException("Values must be positive", nameof(val));
 
-			this.val = val;
+			m_val = val;
         }
 
-		public BigInteger Value
+        public BigInteger Value => m_val;
+
+        public override void Encode(BcpgOutputStream bcpgOut)
         {
-            get { return val; }
+            bcpgOut.WriteShort((short)m_val.BitLength);
+            bcpgOut.Write(m_val.ToByteArrayUnsigned());
         }
 
-        public override void Encode(
-            BcpgOutputStream bcpgOut)
+        internal static BigInteger ToMpiBigInteger(ECPoint point)
         {
-			bcpgOut.WriteShort((short) val.BitLength);
-			bcpgOut.Write(val.ToByteArrayUnsigned());
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+            Span<byte> encoding = stackalloc byte[point.GetEncodedLength(false)];
+            point.EncodeTo(false, encoding);
+            return new BigInteger(1, encoding);
+#else
+            return new BigInteger(1, point.GetEncoded(false));
+#endif
         }
-
-		internal static void Encode(
-			BcpgOutputStream	bcpgOut,
-			BigInteger			val)
-		{
-			bcpgOut.WriteShort((short) val.BitLength);
-			bcpgOut.Write(val.ToByteArrayUnsigned());
-		}
     }
 }
diff --git a/crypto/src/openpgp/PgpEncryptedDataGenerator.cs b/crypto/src/openpgp/PgpEncryptedDataGenerator.cs
index f086aaf75..a86dce42d 100644
--- a/crypto/src/openpgp/PgpEncryptedDataGenerator.cs
+++ b/crypto/src/openpgp/PgpEncryptedDataGenerator.cs
@@ -146,7 +146,7 @@ namespace Org.BouncyCastle.Bcpg.OpenPgp
                 byte[] paddedSessionData = PgpPad.PadSessionData(sessionInfo, sessionKeyObfuscation);
 
                 byte[] C = w.Wrap(paddedSessionData, 0, paddedSessionData.Length);
-                byte[] VB = new MPInteger(new BigInteger(1, ephPub.Q.GetEncoded(false))).GetEncoded();
+                byte[] VB = new MPInteger(MPInteger.ToMpiBigInteger(ephPub.Q)).GetEncoded();
 
                 byte[] rv = new byte[VB.Length + 1 + C.Length];