字節[]數組結構與可變長度數組

Question

我收到來自套接字的字節數組和字節的結構只是一個固定寬度的字符串的大型字符數組。在某些情況下，最後一個字段是動態的（而不是固定的長度），我試圖將字節編組爲一個結構。我讀過可變長字符數組需要是IntPtr，但我還沒有想出如何用剩餘的字節對它進行編組。我也讀過一些文章，可能需要第二種結構，但仍然無法弄清楚如何正確編組。

這裏有一個這樣的site

什麼是應對結構變長字符數組的正確方法？

的結構：

[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 
} 

功能：

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; 
     } 
    } 
} 

這工作 - 但現在Marshal.SizeOf（headerObj）說，這是小於它確實是，當我試圖將其轉換回一個byte []數組。除此之外，這個解決方案有什麼問題嗎？

[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; 
} 

Answer 1

只是不要試圖讓你的C＃聲明完全匹配數據包格式。你會喜歡這個：

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

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

現在它變得簡單。您可以名帥一舉頭，只是複製任何額外的字節存在：

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; 
} 

並修改數據包類，您認爲合適，你可能想添加了一堆的屬性來處理的char [ ]。