Marshalling a Linked List
-
09-09-2019 - |
Question
Apologies for duplicate posting.
Hi
I am having trouble marshalling a linked list from a DLL.
------C++ Structure and Function--------
struct localeInfo {
WCHAR countryName[BUFFER_SIZE];
WCHAR localeName[BUFFER_SIZE];
localeInfo *next;
}
int GetSystemLocales(localeInfo **ppList);
-----------C# Declarations-----------
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
private struct LocaleInfo {
public string countryName;
public string localeName;
public IntPtr next;
};
[DllImport("systemLocales.dll")]
private static extern int GetSystemLocales(ref IntPtr ppList);
int main()
{
var pListHead = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(IntPtr)));
try
{
GetSystemLocales(ref pListHead);
var deref1(IntPtr)Marshal.PtrToStructure(pListHead, typeof(IntPtr));
var deref2 = (LocaleInfo)Marshal.PtrToStructure(deref1, typeof(LocaleInfo));
}
finally
{
Marshal.FreeHGlobal(pListHead);
}
}
I get an FatalExecutionEngine Exception at deref2 declaration. I can't figure out how to get the linked list back and access its contents.
Here is the C++ code that I wrote to get the linked list. I want something similar to work in C#.
localeInfo *pHead = NULL;
localeInfo *pTemp;
GetSystemLocales(&pHead);
for(pTemp = pHead; pTemp!=NULL; pTemp = pTemp->next)
{
wprintf(L"Display Name : %s (%s) \n", pTemp->countryName, pTemp->localeName);
}
Solution
try this:
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
private struct LocaleInfo {
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = BUFFER_SIZE)]
public string countryName;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = BUFFER_SIZE)]
public string localeName;
public IntPtr next;
};
OTHER TIPS
I answered on your other question along these lines. Shay's struct
definition is part of it, but I've corrected Main
also.
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
private struct LocaleInfo
{
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = BUFFER_SIZE)]
public string countryName;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = BUFFER_SIZE)]
public string localeName;
public IntPtr next;
};
[DllImport("systemLocales.dll")]
private static extern int GetSystemLocales(ref IntPtr ppList);
static void Main()
{
IntPtr pList = IntPtr.Zero;
GetSystemLocales(ref pList);
while (pList != IntPtr.Zero)
{
var info = (LocaleInfo)Marshal.PtrToStructure(pList, typeof(LocaleInfo));
Console.WriteLine("Display Name : {0} ({1}) ", info.countryName, info.localeName);
Marshal.FreeHGlobal(pList);
pList = info.next;
}
}
You ought to close the other question really - I only noticed by luck that you had posted this one too.
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