From 1843d914ed51a4d9819e3d6247fce5696a7ba35b Mon Sep 17 00:00:00 2001
From: feyris-tan <4116042+feyris-tan@users.noreply.github.com>
Date: Thu, 28 May 2026 22:28:19 +0200
Subject: [PATCH] Refactor ATSC PLP Parser to use Span<byte> instead of byte[]

---
 .../Atsc/A322/AtscPlpBasebandParser.cs        | 49 ++++++++++++++-----
 .../A324/BasebandPacketDataStreamReceiver.cs  |  5 +-
 2 files changed, 40 insertions(+), 14 deletions(-)

diff --git a/skyscraper8/Atsc/A322/AtscPlpBasebandParser.cs b/skyscraper8/Atsc/A322/AtscPlpBasebandParser.cs
index 5141b51..263a4a2 100644
--- a/skyscraper8/Atsc/A322/AtscPlpBasebandParser.cs
+++ b/skyscraper8/Atsc/A322/AtscPlpBasebandParser.cs
@@ -13,10 +13,9 @@ namespace skyscraper8.Atsc.A322
 {
 	internal class AtscPlpBasebandParser
 	{
-		internal void PushBbframe(byte[] payload)
+		internal void PushBbframe(Span<byte> payload)
 		{
-			MemoryStream ms = new MemoryStream(payload);
-			byte a = ms.ReadUInt8();
+			byte a = payload[0];
 			bool mode = ((a >> 7) & 0x01) != 0;
 			int pointer = (a & 0x7f);
 			int addToPointer;
@@ -29,7 +28,7 @@ namespace skyscraper8.Atsc.A322
 			else
 			{
 				addToPointer = 2;
-				byte b = ms.ReadUInt8();
+				byte b = payload[1];
 				pointer |= (((b >> 2) & 0x3F) << 7);
 				OfiDescription ofi = (OfiDescription)(b & 0x3);
 				switch (ofi)
@@ -37,29 +36,45 @@ namespace skyscraper8.Atsc.A322
 					case OfiDescription.NoExtensionMode:
 						break;
 					case OfiDescription.LongExtensionMode:
-						byte lc = ms.ReadUInt8();
+						byte lc = payload[2];
 						addToPointer++;
 						int extType = (lc >> 5) & 0x7;
 						int extLen = (lc) & 0x1F;
-						byte ld = ms.ReadUInt8();
+						byte ld = payload[3];
 						addToPointer++;
 						extLen |= (((ld) & 0xFF) << 5);
 						// see A322-2026-04-Physical-Layer-Protocol.pdf, Table 5.2
 						//0 = counter
 						//7 = padding
-						byte[] extensionFiled = ms.ReadBytes(extLen);
+						Span<byte> extensionField = payload.Slice(4, extLen);
 						addToPointer += extLen;
-						if (extType != 7)
-						{
-							throw new NotImplementedException(String.Format("ATSC 3.0 BBFRAME Padding Type {0} not yet implemented.", extType));
-						}
+						HandleExtension(true, extType, extensionField);
+						break;
+					case OfiDescription.ShortExtensionMode:
+						byte lc2 = payload[2];
+						addToPointer++;
+						int extType2 = (lc2 >> 5) & 0x07;
+						int extLen2 = (lc2) & 0x1f;
+
+						Span<byte> extensionField2 = payload.Slice(4, extLen2);
+						addToPointer += extLen2;
+						HandleExtension(false, extType2, extensionField2);
 						break;
 					default:
 						throw new NotImplementedException(String.Format("{0} is not yet implemented in the ATSC 3.0 BBFrame Parser.", ofi));
 				}
 			}
 
-			while (ms.GetAvailableBytes() > 0)
+			Span<byte> bbHeaderStripped = payload.Slice(addToPointer);
+			if (pointer + 4 > bbHeaderStripped.Length)
+			{
+				Console.WriteLine("BBFRame, offset: {0}, less than four bytes left.", pointer);
+			}
+			else
+			{
+				Console.WriteLine("BBFRame, offset: {0}, first bytes: 0x{1:X2}{2:X2}{3:X2}{4:X2}", pointer, bbHeaderStripped[pointer], bbHeaderStripped[pointer + 1], bbHeaderStripped[pointer + 2], bbHeaderStripped[pointer + 3]);
+			}
+			/*while (ms.GetAvailableBytes() > 0)
 			{
 				switch(stateMachineState)
 				{
@@ -169,7 +184,17 @@ namespace skyscraper8.Atsc.A322
 					default:
 						throw new NotImplementedException(String.Format("ATSC PLP Baseband Parser State machine state #{0}", stateMachineState));
 				}
+			}*/
+		}
+
+		private void HandleExtension(bool isLongExtension, int extType, Span<byte> extensionField)
+		{
+			if (extType == 7)
+			{
+				//Padding
+				return;
 			}
+			throw new NotImplementedException();
 		}
 
 		private void DeliverPacket(AlpPacket? currentAlpPacket, byte[]? neededBuffer)
diff --git a/skyscraper8/Atsc/A324/BasebandPacketDataStreamReceiver.cs b/skyscraper8/Atsc/A324/BasebandPacketDataStreamReceiver.cs
index 812c6b9..53cdb25 100644
--- a/skyscraper8/Atsc/A324/BasebandPacketDataStreamReceiver.cs
+++ b/skyscraper8/Atsc/A324/BasebandPacketDataStreamReceiver.cs
@@ -94,7 +94,8 @@ namespace skyscraper8.Atsc.A324
 			}
 			else if (plp <= 63)
 			{
-				HandlePlp(plp, rtpPacket.RtpPayload);
+				Span<byte> rtpPayloadSpan = new Span<byte>(rtpPacket.RtpPayload);
+				HandlePlp(plp, rtpPayloadSpan);
 				return;
 			}
 		}
@@ -149,7 +150,7 @@ namespace skyscraper8.Atsc.A324
 		}
 
 		private AtscPlpBasebandParser[] plps;
-		private void HandlePlp(ushort plp, byte[] rtpPayload)
+		private void HandlePlp(ushort plp, Span<byte> rtpPayload)
 		{
 			if (plps == null)
 			{