[improv]改进SRMP多层通信的内存分配，Body>SRMP>WebSocket时，尽量一次性把内存分配到位。

NewLife.Core/Data/IPacket.cs

@@ -1,5 +1,6 @@
 using System.Buffers;
 using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
 using System.Runtime.InteropServices;
 using System.Text;
 using NewLife.Collections;
@@ -293,6 +294,32 @@ public static Boolean TryGetSpan(this IPacket pk, out Span<Byte> span)
         span = default;
         return false;
     }
+
+    /// <summary>尝试扩展头部，用于填充包头，减少内存分配</summary>
+    /// <param name="pk"></param>
+    /// <param name="size"></param>
+    /// <param name="newPacket"></param>
+    /// <returns></returns>
+    public static Boolean TryExpandHeader(this IPacket pk, Int32 size, [NotNullWhen(true)] out IPacket? newPacket)
+    {
+        newPacket = null;
+
+        if (pk is ArrayPacket ap && ap.Offset >= size)
+        {
+            newPacket = new ArrayPacket(ap.Buffer, ap.Offset - size, ap.Length + size) { Next = ap.Next };
+
+            return true;
+        }
+        else if (pk is OwnerPacket owner && owner.Offset >= size)
+        {
+            newPacket = new OwnerPacket(owner.Buffer, owner.Offset - size, owner.Length + size) { Next = owner.Next };
+            owner.Free();
+
+            return true;
+        }
+
+        return false;
+    }
 }
 
 /// <summary>所有权内存包。具有所有权管理，不再使用时释放</summary>
@@ -346,7 +373,7 @@ public OwnerPacket(Int32 length)
     /// <param name="offset"></param>
     /// <param name="length">长度</param>
     /// <exception cref="ArgumentOutOfRangeException"></exception>
-    private OwnerPacket(Byte[] buffer, Int32 offset, Int32 length)
+    public OwnerPacket(Byte[] buffer, Int32 offset, Int32 length)
     {
         if (offset < 0 || length < 0 || offset + length > buffer.Length)
             throw new ArgumentOutOfRangeException(nameof(length), "Length must be non-negative and less than or equal to the memory owner's length.");
@@ -502,6 +529,13 @@ Boolean IPacket.TryGetArray(out ArraySegment<Byte> segment)
         return false;
     }
 
+    /// <summary>释放所有权，不再使用</summary>
+    public void Free()
+    {
+        _buffer = null!;
+        Next = null;
+    }
+
     /// <summary>钉住内存</summary>
     /// <param name="elementIndex"></param>
     /// <returns></returns>

NewLife.Core/Http/WebSocketMessage.cs

@@ -1,4 +1,5 @@
 using System.Buffers.Binary;
+using System.Drawing;
 using System.Text;
 using NewLife.Buffers;
 using NewLife.Data;
@@ -132,6 +133,7 @@ public virtual IPacket ToPacket()
     {
         var body = Payload;
         var len = body == null ? 0 : body.Total;
+        var masks = MaskKey;
 
         // 特殊处理关闭消息
         if (len == 0 && Type == WebSocketMessageType.Close)
@@ -140,16 +142,29 @@ public virtual IPacket ToPacket()
             if (!StatusDescription.IsNullOrEmpty()) len += Encoding.UTF8.GetByteCount(StatusDescription);
         }
 
-        var rs = new OwnerPacket(1 + 1 + 8 + 4 + len);
+        //var rs = new OwnerPacket(1 + 1 + 8 + 4 + len);
+        var size = len switch
+        {
+            < 126 => 1 + 1,
+            < 0xFFFF => 1 + 1 + 2,
+            _ => 1 + 1 + 8,
+        };
+        if (masks != null) size += masks.Length;
+
+        if (body == null || !body.TryExpandHeader(size, out var rs))
+        {
+            if (Type == WebSocketMessageType.Close)
+                rs = new OwnerPacket(size + len);
+            else
+                rs = new OwnerPacket(size) { Next = body };
+        }
         var writer = new SpanWriter(rs.GetSpan())
         {
             IsLittleEndian = false
         };
 
         writer.WriteByte((Byte)(0x80 | (Byte)Type));
 
-        var masks = MaskKey;
-
         /*
          * 数据长度
          * len < 126    单字节表示长度
@@ -208,7 +223,11 @@ public virtual IPacket ToPacket()
         {
             // 注意body可能是链式数据包
             //writer.Write(body.GetSpan());
-            return rs.Slice(0, writer.Position).Append(body);
+
+            // 扩展得到的数据包，直接写入了头部，尾部数据不用拷贝也无需切片
+            return rs;
+
+            //return rs.Slice(0, writer.Position).Append(body);
         }
         else if (Type == WebSocketMessageType.Close)
         {

NewLife.Core/Messaging/DefaultMessage.cs

@@ -123,9 +123,7 @@ public override IPacket ToPacket()
 
         // 增加4字节头部，如果负载数据之前有足够空间则直接使用，否则新建数据包形成链式结构
         var size = len < 0xFFFF ? 4 : 8;
-        var pk = body is ArrayPacket ap && ap.Offset >= size
-            ? new ArrayPacket(ap.Buffer, ap.Offset - size, ap.Length + size) { Next = ap.Next }
-            : new ArrayPacket(new Byte[size]) { Next = body };
+        if (body == null || !body.TryExpandHeader(size, out var pk)) pk = new OwnerPacket(size) { Next = body };
 
         // 标记位
         var header = pk.GetSpan();

XUnitTest.Core/Http/WebSocketMessageTests.cs

@@ -1,4 +1,5 @@
 using System;
+using NewLife.Buffers;
 using NewLife.Data;
 using NewLife.Http;
 using NewLife.Messaging;
@@ -104,4 +105,49 @@ public void DefaultMessageOverWebsocket()
         Assert.Equal(dm.Sequence, dm2.Sequence);
         Assert.Equal(dm.Payload.ToHex(), dm2.Payload.ToHex());
     }
+
+    [Fact]
+    public void DefaultMessageOverWebsocket2()
+    {
+        var str = "Hello NewLife";
+        var buf = new Byte[8 + str.Length];
+        var src = new ArrayPacket(buf, 8, buf.Length - 8);
+        var writer = new SpanWriter(src.GetSpan());
+        writer.Write(str, -1);
+
+        var dm = new DefaultMessage
+        {
+            Flag = 0x01,
+            Sequence = 0xAB,
+            Payload = src
+        };
+        var pk = dm.ToPacket();
+        Assert.Null(pk.Next);
+
+        var msg = new WebSocketMessage
+        {
+            Type = WebSocketMessageType.Binary,
+            Payload = pk,
+        };
+
+        pk = msg.ToPacket();
+        Assert.Null(pk.Next);
+        Assert.Equal("821101AB0D0048656C6C6F204E65774C696665", pk.ToHex());
+
+        var msg2 = new WebSocketMessage();
+        var rs = msg2.Read(pk);
+        Assert.True(rs);
+
+        Assert.Equal(msg.Type, msg2.Type);
+        Assert.Equal(msg.Payload.ToHex(), msg2.Payload.ToHex());
+
+        var dm2 = new DefaultMessage();
+        rs = dm2.Read(msg2.Payload);
+        Assert.True(rs);
+
+        Assert.Equal(dm.Flag, dm2.Flag);
+        Assert.Equal(dm.Sequence, dm2.Sequence);
+        Assert.Equal(dm.Payload.ToHex(), dm2.Payload.ToHex());
+        Assert.Equal(str, dm2.Payload.ToStr());
+    }
 }