将byte[]数组转换为具有可变长度数组的结构体

Question

将byte[]数组转换为具有可变长度数组的结构体

13

我正在从套接字接收一个字节数组，这些字节的结构只是一个固定宽度字符串的大型字符数组。在某些情况下，最后一个字段是动态的（而不是固定长度），我正在尝试将字节编组为一个结构体。我已经读到可变长度的char数组需要使用IntPtr，但我还没有弄清楚如何用剩余的字节进行编组。我也在一些文章中读到可能需要第二个结构体，但仍然无法正确地进行编组。

以下是其中一个网站。

如何正确处理结构体中的可变长度char数组？

该结构体：

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct Header
{
    #region private member fields

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
    private char[] _f1;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
    private char[] _f2;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
    private char[] _f3;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
    private char[] _f4;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
    private char[] _f5;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
    private char[] _f6;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 4)]
    private char[] _f7;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 12)]
    private char[] _f8;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 32)]
    private char[] _f9;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 16)]
    private char[] _f10;

    // how would this get filled with a char[] array from the byte array?
    public IntPtr VariableLengthData;

    #endregion
}

这个函数：

public static Header FromArray(byte[] array)
{
    IntPtr buff = IntPtr.Zero;

    try
    {
        int objsize = Marshal.SizeOf(typeof(Header));
        buff = Marshal.AllocHGlobal(objsize);
        Marshal.Copy(array, 0, buff, objsize);
        var result = (Header)Marshal.PtrToStructure(buff, typeof(HostHeader));

        // the variable length data needs to be filled in somehow
        // but also note that an extra 4 bytes was added to the size
        // of the struct with the IntPtr
        if(objsize < array.Length)
        {
            Marshal.Copy(array, array.Length - objsize, result.VariableLengthData, array.Length - objsize);
        }

        return result;
    }
    finally
    {
        if (buff != IntPtr.Zero)
        {
            Marshal.FreeHGlobal(buff);
            buff = IntPtr.Zero;
        }
    }
}

这个方案有效 - 但现在当我尝试将其转换回byte[]数组时，Marshal.SizeOf（headerObj）说它比实际小。除此之外，这个方案还有什么问题吗？

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct Header
{
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)] 
    public char[] Field1;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)] 
    public char[] Field2;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 8)] 
    public char[] Field3;

    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 1)]
    public char[] Field4;
}

public static Header DeserializeHeader(byte[] data)
{
    int objsize = Marshal.SizeOf(typeof(Header));
    IntPtr buff = Marshal.AllocHGlobal(objsize);
    Marshal.Copy(data, 0, buff, objsize);
    var header = (Header)Marshal.PtrToStructure(buff, typeof(Header));
    Marshal.FreeHGlobal(buff);

    // resize Field4 to hold all the remaining bytes
    if(objsize < data.Length)
    {
        header.Field4 = Encoding.ASCII.GetChars(data, objsize - header.Field4.Length, data.Length - objsize - header.Field4.Length);
    }
    return header;
}

- Chris Gessler

你应该重新表述并提出一个实际问题。 - Mihai Caracostea

array+160 是您数据的其余部分。Encoding.ASCII.GetString(array,160,array.Length-160) - EZI

@EZI - 正确。如果字节数组大于160，则其余部分均为可变长度字段。 - Chris Gessler

1个回答

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- Hans Passant · Accepted Answer

不要过分努力让你的C#声明与数据包格式完全匹配。最好是这样:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
public class Header {
    //....
}

public class Packet {
    public Header Header;
    public byte[] VariableLengthData;
}

现在变得简单了。你可以一举措置标题，并复制任何额外的字节。

static unsafe Packet FromArray(byte[] data) {
    var hdrsize = Marshal.SizeOf(typeof(Header));
    if (data.Length < hdrsize) throw new ArgumentException();
    Packet result = new Packet();
    // Marshal the header
    fixed (byte* pdata = &data[0]) {
        result.Header = (Header)Marshal.PtrToStructure(new IntPtr(pdata), typeof(Header)); 
    }
    // Copy the rest
    var varsize = data.Length - hdrsize;
    result.VariableLengthData = new byte[varsize];
    Array.Copy(data, hdrsize, result.VariableLengthData, 0, varsize);
    return result;
}

根据您的需要修改Packet类，您可能需要添加一些属性来处理char[]。