From 75ef73619db51c97a242b0e9c165838854534694 Mon Sep 17 00:00:00 2001
From: Peter Dettman <peter.dettman@bouncycastle.org>
Date: Thu, 19 May 2022 16:38:12 +0700
Subject: Add previewing of pending output records

---
 crypto/src/tls/ByteQueue.cs   |  8 ++++++++
 crypto/src/tls/TlsProtocol.cs | 22 ++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/crypto/src/tls/ByteQueue.cs b/crypto/src/tls/ByteQueue.cs
index e39e797dd..45bec8be4 100644
--- a/crypto/src/tls/ByteQueue.cs
+++ b/crypto/src/tls/ByteQueue.cs
@@ -149,6 +149,14 @@ namespace Org.BouncyCastle.Tls
             return TlsUtilities.ReadInt32(m_databuf, m_skipped);
         }
 
+        public int ReadUint16(int skip)
+        {
+            if (m_available < skip + 2)
+                throw new InvalidOperationException("Not enough data to read");
+
+            return TlsUtilities.ReadUint16(m_databuf, m_skipped + skip);
+        }
+
         /// <summary>Remove some bytes from our data from the beginning.</summary>
         /// <param name="i">How many bytes to remove.</param>
         public void RemoveData(int i)
diff --git a/crypto/src/tls/TlsProtocol.cs b/crypto/src/tls/TlsProtocol.cs
index 57b452f60..c30c253e1 100644
--- a/crypto/src/tls/TlsProtocol.cs
+++ b/crypto/src/tls/TlsProtocol.cs
@@ -1074,6 +1074,28 @@ namespace Org.BouncyCastle.Tls
             return SafePreviewRecordHeader(recordHeader);
         }
 
+        public virtual int PreviewOutputRecord()
+        {
+            if (m_blocking)
+                throw new InvalidOperationException("Cannot use PreviewOutputRecord() in blocking mode!");
+
+            ByteQueue buffer = m_outputBuffer.Buffer;
+            int available = buffer.Available;
+            if (available < 1)
+                return 0;
+
+            if (available >= RecordFormat.FragmentOffset)
+            {
+                int length = buffer.ReadUint16(RecordFormat.LengthOffset);
+                int recordSize = RecordFormat.FragmentOffset + length;
+
+                if (available >= recordSize)
+                    return recordSize;
+            }
+
+            throw new InvalidOperationException("Can only use PreviewOutputRecord() for record-aligned output.");
+        }
+
         /// <exception cref="IOException"/>
         public virtual RecordPreview PreviewOutputRecord(int applicationDataSize)
         {
-- 
cgit 1.4.1