1 files changed, 52 insertions, 0 deletions
diff --git a/crypto/src/asn1/ConstructedBitStream.cs b/crypto/src/asn1/ConstructedBitStream.cs
index 49f54fc1b..f089dac75 100644
--- a/crypto/src/asn1/ConstructedBitStream.cs
+++ b/crypto/src/asn1/ConstructedBitStream.cs
@@ -33,6 +33,9 @@ namespace Org.BouncyCastle.Asn1
         {
             Streams.ValidateBufferArguments(buffer, offset, count);
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+            return Read(buffer.AsSpan(offset, count));
+#else
             if (count < 1)
                 return 0;
 
@@ -75,8 +78,57 @@ namespace Org.BouncyCastle.Asn1
                     m_currentStream = m_currentParser.GetBitStream();
                 }
             }
+#endif
         }
 
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public override int Read(Span<byte> buffer)
+        {
+            if (buffer.IsEmpty)
+                return 0;
+
+            if (m_currentStream == null)
+            {
+                if (!m_first)
+                    return 0;
+
+                m_currentParser = GetNextParser();
+                if (m_currentParser == null)
+                    return 0;
+
+                m_first = false;
+                m_currentStream = m_currentParser.GetBitStream();
+            }
+
+            int totalRead = 0;
+
+            for (;;)
+            {
+                int numRead = m_currentStream.Read(buffer[totalRead..]);
+
+                if (numRead > 0)
+                {
+                    totalRead += numRead;
+
+                    if (totalRead == buffer.Length)
+                        return totalRead;
+                }
+                else
+                {
+                    m_padBits = m_currentParser.PadBits;
+                    m_currentParser = GetNextParser();
+                    if (m_currentParser == null)
+                    {
+                        m_currentStream = null;
+                        return totalRead;
+                    }
+
+                    m_currentStream = m_currentParser.GetBitStream();
+                }
+            }
+        }
+#endif
+
         public override int ReadByte()
         {
             if (m_currentStream == null)