使用固定缓冲区将字节数组重新解释为托管结构

Question

我希望将字节数组重新解释为 C# 结构。我已经阅读了该问题的其他几个答案，大多数都是关于如何实现重新解释演员表。我已经确定了一种重新解释演员表的方法，但是在我的演员表中我得到的是单个字符而不是字符数组。

例如，我有以下对象：

    public unsafe struct Establish503
    {
        public static Establish503 ReinterpretCast(byte[] message)
        {
            GCHandle handle = GCHandle.Alloc(message, GCHandleType.Pinned);
            Establish503 theStruct = (Establish503)Marshal.PtrToStructure(handle.AddrOfPinnedObject(),
                typeof(Establish503));
            handle.Free();
            return theStruct;
        }

        public fixed char HMACSignature[32];
        public fixed char AccessKey[20];
        public fixed char TradingSystemName[30];
        public fixed char TradingSystemVersion[10];
        public fixed char TradingSystemVendor[10];
    }

由于某种原因，我没有一个字节数组，而是在一个数组应该有的地方有单个字符。为什么会这样？这是我的本地调试窗口：

如您所见，出于某种原因，它将所有字段视为char 而不是char[]。

如果这不是正确的方法，我还有什么需要注意的吗？我一直在调查Span<T>。

编辑：在与所选答案的作者 Oguz Ozgul 进一步讨论后，确定编组是最好的方法。一个后续问题是，我将如何处理嵌套结构？以下是我目前的做法。正如 Oguz 所提到的，对于在类之外定义且包含原始类型的结构，可以排除 Marshal 属性。然后这些结构可以用作另一个结构中的字段。我已经解决了定义嵌套结构的问题，类似于我定义非嵌套结构的方式。

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
    public struct OrderMassActionReport558
    {
        public const int templateId_ = 558;
        public const int blockSize_ = 103;

        public static OrderMassActionReport558 ReinterpretCast(byte[] message)
        {
            GCHandle handle = GCHandle.Alloc(message, GCHandleType.Pinned);
            OrderMassActionReport558 theStruct = (OrderMassActionReport558)
                Marshal.PtrToStructure(handle.AddrOfPinnedObject(), 
                typeof(OrderMassActionReport558));
            handle.Free();
            return theStruct;
        }

        [MarshalAs(UnmanagedType.U4)]
        public uInt32 seqNum;
        [MarshalAs(UnmanagedType.U8)]
        public uInt64 uUID;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
        private byte[] _senderID;
        public string senderID => System.Text.Encoding.ASCII.GetString(this._senderID);
        [MarshalAs(UnmanagedType.U8)]
        public uInt64 partyDetailsListReqID;
        [MarshalAs(UnmanagedType.U8)]
        public uInt64 transactTime;
        [MarshalAs(UnmanagedType.U8)]
        public uInt64 sendingTimeEpoch;
        [MarshalAs(UnmanagedType.U8)]
        public uInt64 orderRequestID;
        [MarshalAs(UnmanagedType.U8)]
        public uInt64 massActionReportID;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 6)]
        private byte[] _securityGroup;
        public string securityGroup => System.Text.Encoding.ASCII.GetString(this._securityGroup);
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)]
        private byte[] _location;
        public string location => System.Text.Encoding.ASCII.GetString(this._location);
        [MarshalAs(UnmanagedType.I4)]
        public Int32NULL securityID;
        [MarshalAs(UnmanagedType.U2)]
        public uInt16NULL delayDuration;
        [MarshalAs(UnmanagedType.U1)]
        public MassActionResponse massActionResponse;
        [MarshalAs(UnmanagedType.U1)]
        public ManualOrdIndReq manualOrderIndicator;
        [MarshalAs(UnmanagedType.U1)]
        public MassActionScope massActionScope;
        [MarshalAs(UnmanagedType.U1)]
        public uInt8 totalAffectedOrders;
        [MarshalAs(UnmanagedType.U1)]
        public BooleanFlag lastFragment;
        [MarshalAs(UnmanagedType.U1)]
        public uInt8NULL massActionRejectReason;
        [MarshalAs(UnmanagedType.U1)]
        public uInt8NULL marketSegmentID;
        [MarshalAs(UnmanagedType.U1)]
        public MassCxlReqTyp massCancelRequestType;
        [MarshalAs(UnmanagedType.U1)]
        public SideNULL side;
        [MarshalAs(UnmanagedType.U1)]
        public MassActionOrdTyp ordType;
        [MarshalAs(UnmanagedType.U1)]
        public MassCancelTIF timeInForce;
        [MarshalAs(UnmanagedType.U1)]
        public SplitMsg splitMsg;
        [MarshalAs(UnmanagedType.U1)]
        public BooleanNULL liquidityFlag;
        [MarshalAs(UnmanagedType.U1)]
        public BooleanFlag possRetransFlag;

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
        public struct NoAffectedOrdersEntry
        {
            public const int blockSize_ = 32;
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 20)]
            private byte[] _origCIOrdID;
            public string origCIOrdID => System.Text.Encoding.ASCII.GetString(this._origCIOrdID);
            public uInt64 AffectedOrderID;
            public uInt32 CxlQuantity;
        }
    }

Answer 1

这是因为只设置了 char 数组的第一个元素，其余元素为零（您可以在“内存”窗口中看到这一点）。

首先，尝试用原始二进制数据填充 char 数组会导致不希望的和不可预测的结果，除非我们可以指定确切的字符集。您可以在结构顶部看到 CharSet 设置为 Ansi，每个字符 1 个字节。

然后，您可以使用字符串而不是使用固定指针 char 数组，但按值和精确大小对它们进行编组。

如果这有帮助，请告诉我：

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
    public unsafe struct Establish503
    {
        public static Establish503 ReinterpretCast(byte[] message)
        {
            GCHandle handle = GCHandle.Alloc(message, GCHandleType.Pinned);
            Establish503 theStruct = (Establish503)Marshal.PtrToStructure(handle.AddrOfPinnedObject(),
                typeof(Establish503));
            handle.Free();
            return theStruct;
        }

        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
        public string HMACSignature;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 20)]
        public string AccessKey;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 30)]
        public string TradingSystemName;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 10)]
        public string TradingSystemVersion;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 10)]
        public string TradingSystemVendor;
    }  

更新 1：OP 还在下面的评论中提出了一个附加问题，因此更新了答案。

OP 想知道如果另一个具有 Int64 字段的结构嵌入到当前结构中会怎样。

首先，阅读：https://docs.microsoft.com/en-us/dotnet/framework/interop/default-marshaling-behavior#default-marshaling-for-value-types

所以我在源代码中添加了这个新结构：

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
    public struct Data
    {
        [MarshalAs(UnmanagedType.I8)]
        public long LongField;
    }

然后，将其嵌入到当前：

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
    public unsafe struct Establish503
    {
        public static Establish503 ReinterpretCast(byte[] message)
        {
            GCHandle handle = GCHandle.Alloc(message, GCHandleType.Pinned);
            Establish503 theStruct = (Establish503)Marshal.PtrToStructure(handle.AddrOfPinnedObject(),
                typeof(Establish503));
            handle.Free();
            return theStruct;
        }

        public Data DataStruct;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
        public string HMACSignature;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 20)]
        public string AccessKey;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 30)]
        public string TradingSystemName;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 10)]
        public string TradingSystemVersion;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 10)]
        public string TradingSystemVendor;
    }

最后，将它从非托管内存中封送回来：

        Establish503 establish503 = Establish503.ReinterpretCast(new byte[] { 
            1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 
            1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 
            1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 
            1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 
            1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 
            1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20
        });