错误遍历IntPtr以构建结构数组

Question

我在从另一个struct的IntPtr构建一个struct数组时遇到问题。

我正在使用的Windows API返回此结构：

public struct DFS_INFO_9 {
    [MarshalAs(UnmanagedType.LPWStr)]
    public string EntryPath;
    [MarshalAs(UnmanagedType.LPWStr)]
    public string Comment;
    public DFS_VOLUME_STATE State;
    public UInt32 Timeout;
    public Guid Guid;
    public UInt32 PropertyFlags;
    public UInt32 MetadataSize;
    public UInt32 SdLengthReserved;
    public IntPtr pSecurityDescriptor;
    public UInt32 NumberOfStorages;
    public IntPtr Storage;
}

[DllImport("netapi32", CharSet = CharSet.Auto, SetLastError = true)]
public static extern int NetDfsEnum([MarshalAs(UnmanagedType.LPWStr)]string DfsName, int Level, int PrefMaxLen, out IntPtr Buffer, [MarshalAs(UnmanagedType.I4)]out int EntriesRead, [MarshalAs(UnmanagedType.I4)]ref int ResumeHandle);

我正在尝试获取IntPtr Storage引用的DFS_STORAGE_INFO_1数组。

这就是这种结构（如果重要的话）：

public struct DFS_STORAGE_INFO_1 {
    public DFS_STORAGE_STATE State;
    [MarshalAs(UnmanagedType.LPWStr)]
    public string ServerName;
    [MarshalAs(UnmanagedType.LPWStr)]
    public string ShareName;
    public IntPtr TargetPriority;
}

到目前为止，此代码一直在努力仅使用一个存储来获取DFS_INFO_9 ，但是在尝试DFS_INFO_9数组中的第二项时失败。

DFS_INFO_9 info = GetInfoFromWinApi();
List<DFS_STORAGE_INFO_1> Storages = new List<DFS_STORAGE_INFO_1>();
for (int i = 0; i < info.NumberOfStorages; i++) {
    IntPtr pStorage = new IntPtr(info.Storage.ToInt64() + i * Marshal.SizeOf(typeof(DFS_STORAGE_INFO_1)));
    DFS_STORAGE_INFO_1 storage = (DFS_STORAGE_INFO_1)Marshal.PtrToStructure(pStorage, typeof(DFS_STORAGE_INFO_1));
    Storages.Add(storage);
}

我收到一个FatalExecutionEngineError ，它吐出错误代码0x0000005（拒绝访问）。 我假设DFS_STORAGE_INFO_1的大小计算错误，导致元帅试图访问分配给该数组的内存之外的内存。 但这发生在i = 1 ，当时可能有7个存储要通过。 也许我的想法是有缺陷的，但我不知道该如何纠正。

Answer 1

DFS_STORAGE_INFO_1的实际定义是这样的：

public struct DFS_STORAGE_INFO_1 {
    public DFS_STORAGE_STATE State;
    [MarshalAs(UnmanagedType.LPWStr)]
    public string ServerName;
    [MarshalAs(UnmanagedType.LPWStr)]
    public string ShareName;
    DFS_TARGET_PRIORITY TargetPriority;
}

TargetPriority是一个结构， 在此定义：

public struct DFS_TARGET_PRIORITY {
    public DFS_TARGET_PRIORITY_CLASS TargetPriorityClass;
    public UInt16 TargetPriorityRank;
    public UInt16 Reserved;
}

public enum DFS_TARGET_PRIORITY_CLASS {
    DfsInvalidPriorityClass = -1,
    DfsSiteCostNormalPriorityClass = 0,
    DfsGlobalHighPriorityClass = 1,
    DfsSiteCostHighPriorityClass = 2,
    DfsSiteCostLowPriorityClass = 3,
    DfsGlobalLowPriorityClass = 4
}

至于FatalExecutionEngineError ，我认为结构DFS_STORAGE_INFO_1的大小计算不正确，因为定义不正确。 当尝试将指针转换为它们所引用的结构时，下一个索引是错误的，因为大小已关闭。 转换内存块时，它大概引用了不应访问的块，并引发“访问被拒绝（0x0000005）”错误。