Marshal.PtrToStructure抛出AccessViolationException

Question

我有这个结构:

    [StructLayout(LayoutKind.Sequential)]
    public struct IS
    {
    public UInt32 ID; 
    public UInt32 Quality; 
    public UInt32 Flags;
    public UInt32 Flags2;     
    public UInt32 ContainerSlots; 
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 10)]
    public Int32[] ItemStatType;  
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 10)]
    public UInt32[] ItemStatValue;    
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 10)]
    public Int32[] ItemStatUnk1;    
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 10)]
    public Int32[] ItemStatUnk2;       
    public UInt32 ScalingStatDistribution; 
    public UInt32 DamageType;      
    public UInt32 Delay;      
    public float RangedModRange;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)]
    public Int32[] SpellId;          
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)]
    public Int32[] SpellTrigger;       
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)]
    public Int32[] SpellCharges;  
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)]
    public Int32[] SpellCooldown;   
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)]
    public Int32[] SpellCategory;     
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)]
    public Int32[] SpellCategoryCooldown;
    public UInt32 Bonding; 
    public string Name;       
    public string Name2;                  
    public string Name3;         
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)]
    public UInt32[] Color;  
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)]
    public UInt32[] Content;
};

我正在尝试从文件中读取字节并struct使用Marshal和GCHandle 将这些字节复制到上面,我的代码如下:

reader = BinaryReader.FromFile(fileName);
m_rows = new List<IS>();
int size = Marshal.SizeOf(typeof(IS));
if(reader.BaseStream.Length < size)
  return;
byte[] buffer = new byte[size];
buffer = reader.ReadBytes(size);
GCHandle handle = GCHandle.Alloc(buffer, GCHandleType.Pinned);
m_rows.Add((IS)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(IS)));
handle.Free();

但我得到了一个 AccessViolationException : attempt to read or write protected memory

我不知道为什么抛出这个异常.

Answer 1

我没有立即看到这个错误并写了一个小测试程序来重现这个问题.使用二进制搜索来查找问题,重复注释一半字段,直到我将其缩小到:

[StructLayout(LayoutKind.Sequential)]
public struct IS {
    public string Name;
}

这不起作用,pinvoke marshaller假定字符串的默认封送来自C字符串,char*.这不可能纠正您从文件中读取的数据,它永远不会包含有效的指针.尝试取消引用指针时会触发AccessViolation.

问题中没有任何提示可以猜测字符串是如何实际序列化到文件中的.在正常的方法是:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct IS {
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 42)]
    public string Name;
};

如有必要,请使用十六进制查看器来确定SizeConst的正确值.如果编码异常(不是系统默认页面),则必须将其声明为byte []并使用正确的编码进行转换.