111 lines
3.7 KiB
C#
111 lines
3.7 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Text;
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using System.Runtime.InteropServices;
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namespace EPocalipse.IFilter
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{
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[ComVisible(false)]
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[ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("00000001-0000-0000-C000-000000000046")]
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internal interface IClassFactory
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{
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void CreateInstance([MarshalAs(UnmanagedType.Interface)] object pUnkOuter, ref Guid refiid, [MarshalAs(UnmanagedType.Interface)] out object ppunk);
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void LockServer(bool fLock);
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}
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/// <summary>
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/// Utility class to get a Class Factory for a certain Class ID
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/// by loading the dll that implements that class
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/// </summary>
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internal static class ComHelper
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{
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//DllGetClassObject fuction pointer signature
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private delegate int DllGetClassObject(ref Guid ClassId, ref Guid InterfaceId, [Out, MarshalAs(UnmanagedType.Interface)] out object ppunk);
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//Some win32 methods to load\unload dlls and get a function pointer
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private class Win32NativeMethods
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{
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[DllImport("kernel32.dll", CharSet=CharSet.Ansi)]
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public static extern IntPtr GetProcAddress(IntPtr hModule, string lpProcName);
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[DllImport("kernel32.dll")]
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public static extern bool FreeLibrary(IntPtr hModule);
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[DllImport("kernel32.dll")]
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public static extern IntPtr LoadLibrary(string lpFileName);
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}
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/// <summary>
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/// Holds a list of dll handles and unloads the dlls
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/// in the destructor
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/// </summary>
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private class DllList
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{
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private List<IntPtr> _dllList=new List<IntPtr>();
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public void AddDllHandle(IntPtr dllHandle)
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{
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lock (_dllList)
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{
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_dllList.Add(dllHandle);
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}
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}
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~DllList()
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{
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foreach (IntPtr dllHandle in _dllList)
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{
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try
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{
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Win32NativeMethods.FreeLibrary(dllHandle);
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}
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catch { };
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}
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}
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}
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static DllList _dllList=new DllList();
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/// <summary>
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/// Gets a class factory for a specific COM Class ID.
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/// </summary>
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/// <param name="dllName">The dll where the COM class is implemented</param>
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/// <param name="filterPersistClass">The requested Class ID</param>
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/// <returns>IClassFactory instance used to create instances of that class</returns>
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internal static IClassFactory GetClassFactory(string dllName, string filterPersistClass)
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{
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//Load the class factory from the dll
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IClassFactory classFactory=GetClassFactoryFromDll(dllName, filterPersistClass);
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return classFactory;
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}
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private static IClassFactory GetClassFactoryFromDll(string dllName, string filterPersistClass)
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{
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//Load the dll
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IntPtr dllHandle=Win32NativeMethods.LoadLibrary(dllName);
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if (dllHandle==IntPtr.Zero)
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return null;
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//Keep a reference to the dll until the process\AppDomain dies
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_dllList.AddDllHandle(dllHandle);
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//Get a pointer to the DllGetClassObject function
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IntPtr dllGetClassObjectPtr=Win32NativeMethods.GetProcAddress(dllHandle, "DllGetClassObject");
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if (dllGetClassObjectPtr==IntPtr.Zero)
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return null;
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//Convert the function pointer to a .net delegate
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DllGetClassObject dllGetClassObject=(DllGetClassObject)Marshal.GetDelegateForFunctionPointer(dllGetClassObjectPtr, typeof(DllGetClassObject));
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//Call the DllGetClassObject to retreive a class factory for out Filter class
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Guid filterPersistGUID=new Guid(filterPersistClass);
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Guid IClassFactoryGUID=new Guid("00000001-0000-0000-C000-000000000046"); //IClassFactory class id
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Object unk;
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if (dllGetClassObject(ref filterPersistGUID, ref IClassFactoryGUID, out unk)!=0)
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return null;
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//Yippie! cast the returned object to IClassFactory
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return (unk as IClassFactory);
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}
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}
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}
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