Stream modernization

1 files changed, 56 insertions, 0 deletions

diff --git a/crypto/src/util/io/LimitedInputStream.cs b/crypto/src/util/io/LimitedInputStream.cs
new file mode 100644
index 000000000..d6616eff5
--- /dev/null
+++ b/crypto/src/util/io/LimitedInputStream.cs
@@ -0,0 +1,56 @@
+using Org.BouncyCastle.Utilities.Zlib;
+using System;
+using System.IO;
+
+namespace Org.BouncyCastle.Utilities.IO
+{
+    internal class LimitedInputStream
+        : BaseInputStream
+    {
+        private readonly Stream m_stream;
+        private long m_limit;
+
+        internal LimitedInputStream(Stream stream, long limit)
+        {
+            this.m_stream = stream;
+            this.m_limit = limit;
+        }
+
+        internal long CurrentLimit => m_limit;
+
+        public override int Read(byte[] buffer, int offset, int count)
+        {
+            int numRead = m_stream.Read(buffer, offset, count);
+            if (numRead > 0)
+            {
+                if ((m_limit -= numRead) < 0)
+                    throw new StreamOverflowException("Data Overflow");
+            }
+            return numRead;
+        }
+
+#if NETCOREAPP2_1_OR_GREATER || NETSTANDARD2_1_OR_GREATER
+        public override int Read(Span<byte> buffer)
+        {
+            int numRead = m_stream.Read(buffer);
+            if (numRead > 0)
+            {
+                if ((m_limit -= numRead) < 0)
+                    throw new StreamOverflowException("Data Overflow");
+            }
+            return numRead;
+        }
+#endif
+
+        public override int ReadByte()
+        {
+            int b = m_stream.ReadByte();
+            if (b >= 0)
+            {
+                if (--m_limit < 0)
+                    throw new StreamOverflowException("Data Overflow");
+            }
+            return b;
+        }
+    }
+}