C#总结(五)动态加载C++动态链接库

C#静态加载C++动态链接库,这个之前的文章里面,都有介绍,请看之前的文章,https://www.cnblogs.com/zhangweizhong/p/8119340.html 。

然而很多时候,Dll库的目录可能是变化的,或是有些场景,需要根据具体的情况,来动态加载这些Dll库。这样使用静态调用的方式就很不方便,C#中我们经常通过配置动态的调用托管Dll,那么是不是也可以这样动态调用C++动态链接呢?
只要通过LoadLibrary, GetProcess, FreeLibrary这几个函数是可以动态调用动态链接的(它们包含在kernel32.dll中)。

 

动态加载的方式:

HMODULE WINAPI LoadLibrary ( LPCTSTR lpFileName):载入指定的动态链接库,并将它映射到当前进程使用的地址空间。一旦载入,即可访问库内保存的资源

GetProcAddress (HMODULE hModule, LPCSTR lpProcName):GetProcAddress函数检索指定的动态链接库(DLL)中的输出库函数地址。 如果函数调用成功,返回值是DLL中的输出函数地址。 如果函数调用失败,返回值是NULL。调用函数GetLastError ,得到具体的错误信息。

 

FreeLibrary ( In HMODULE hModule)  :释放指定的动态链接库,它们早先是用LoadLibrary API函数装载的。

实现
1. 将kernel32中的几个方法封装成本地调用类 DLLWrapper 

 

 

using System;
using System.IO;
using System.Runtime.InteropServices;

namespace Irisking.Basic.Util
{
    /// 
    /// DLLWrapper
    /// 
    internal class DLLWrapper
    {
        [DllImport("kernel32.dll")]
        private static extern uint GetLastError();


        /// 
        /// API LoadLibraryEx
        /// 
        /// 
        /// 
        /// 
        /// 
        [DllImport("kernel32.dll", EntryPoint = "LoadLibraryEx", SetLastError = true)]
        private static extern int LoadLibraryEx(string lpFileName, IntPtr hReservedNull, LoadLibraryFlags dwFlags);

        /// 
        /// API GetProcAddress
        /// 
        /// 
        /// 
        /// 
        [DllImport("Kernel32", EntryPoint = "GetProcAddress", SetLastError = true)]
        public static extern int GetProcAddress(int handle, string funcname);

        /// 
        ///  API FreeLibrary
        /// 
        /// 
        /// 
        [DllImport("Kernel32", EntryPoint = "FreeLibrary", SetLastError = true)]
        private static extern int FreeLibrary(int handle);

        ///
        /// 通过非托管函数名转换为对应的委托 , by jingzhongrong
        ///
        /// 通过 LoadLibrary 获得的 DLL 句柄 
        /// 非托管函数名 
        /// 对应的委托类型 
        /// 委托实例,可强制转换为适当的委托类型 
        public static Delegate GetFunctionAddress(int dllModule, string functionName, Type t)
        {
            int address = GetProcAddress(dllModule, functionName);
            if (address == 0)
                return null;
            else
                return Marshal.GetDelegateForFunctionPointer(new IntPtr(address), t);
        }

        ///
        /// 将表示函数地址的 intPtr 实例转换成对应的委托
        ///
        public static Delegate GetDelegateFromIntPtr(IntPtr address, Type t)
        {
            if (address == IntPtr.Zero)
                return null;
            else
                return Marshal.GetDelegateForFunctionPointer(address, t);
        }

        ///
        /// 将表示函数地址的 int  转换成对应的委托
        ///
        public static Delegate GetDelegateFromIntPtr(int address, Type t)
        {
            if (address == 0)
                return null;
            else
                return Marshal.GetDelegateForFunctionPointer(new IntPtr(address), t);
        }

        /// 
        /// 加载sdk
        /// 
        /// 
        /// 
        public static int LoadSDK(string lpFileName)
        {
            if (File.Exists(lpFileName))
            {
                var hReservedNull = IntPtr.Zero;
                var dwFlags = LoadLibraryFlags.LOAD_WITH_ALTERED_SEARCH_PATH;

                var result = LoadLibraryEx(lpFileName, hReservedNull, dwFlags);

                var errCode = GetLastError();
                LogHelper.Info($"LoadSDK Result:{result}, ErrorCode: {errCode}");
               
                return result;
            }
            return 0;
        }

        /// 
        /// 释放sdk
        /// 
        /// 
        /// 
        public static int ReleaseSDK(int handle)
        {
            try
            {
                if (handle > 0)
                {
                    LogHelper.Info($"FreeLibrary handle:{handle}");
                    var result = FreeLibrary(handle);
                    var errCode = GetLastError();
                    LogHelper.Info($"FreeLibrary Result:{result}, ErrorCode: {errCode}");
                    return 0;
                }
                return -1;
            }
            catch (Exception ex)
            {
                LogHelper.Error(ex);
                return -1;
            }
        }
    }

    /// 
    /// LoadLibraryFlags
    /// 
    public enum LoadLibraryFlags : uint
    {
        /// 
        /// DONT_RESOLVE_DLL_REFERENCES
        /// 
        DONT_RESOLVE_DLL_REFERENCES = 0x00000001,

        /// 
        /// LOAD_IGNORE_CODE_AUTHZ_LEVEL
        /// 
        LOAD_IGNORE_CODE_AUTHZ_LEVEL = 0x00000010,

        /// 
        /// LOAD_LIBRARY_AS_DATAFILE
        /// 
        LOAD_LIBRARY_AS_DATAFILE = 0x00000002,

        /// 
        /// LOAD_LIBRARY_AS_DATAFILE_EXCLUSIVE
        /// 
        LOAD_LIBRARY_AS_DATAFILE_EXCLUSIVE = 0x00000040,

        /// 
        /// LOAD_LIBRARY_AS_IMAGE_RESOURCE
        /// 
        LOAD_LIBRARY_AS_IMAGE_RESOURCE = 0x00000020,

        /// 
        /// LOAD_LIBRARY_SEARCH_APPLICATION_DIR
        /// 
        LOAD_LIBRARY_SEARCH_APPLICATION_DIR = 0x00000200,

        /// 
        /// LOAD_LIBRARY_SEARCH_DEFAULT_DIRS
        /// 
        LOAD_LIBRARY_SEARCH_DEFAULT_DIRS = 0x00001000,

        /// 
        /// LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR
        /// 
        LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR = 0x00000100,

        /// 
        /// LOAD_LIBRARY_SEARCH_SYSTEM32
        /// 
        LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800,

        /// 
        /// LOAD_LIBRARY_SEARCH_USER_DIRS
        /// 
        LOAD_LIBRARY_SEARCH_USER_DIRS = 0x00000400,

        /// 
        /// LOAD_WITH_ALTERED_SEARCH_PATH
        /// 
        LOAD_WITH_ALTERED_SEARCH_PATH = 0x00000008
    }
}

 

 

 

 

2. 使用DLLWrapper类动态读取C++Dll,获得函数指针,并且将指针封装成C#中的委托。原因很简单,C#中已经不能使用指针了,如下:

 

通过如上例子,我们可以在C#中动态或者静态的调用C++写的代码了。

 

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