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在Linux下实现COM组件

第七根弦 2016 年 3 月 1 日 Linux shell, UC 发表评论 (0)

COM组件是一种编程规范，它规定了软件编程的一般方法，虽然它由Microsoft公司制定和提出，但是它的规则也可以在Linux下使用，下面是在Linux下实现COM组件的方法。
—-参考《COM技术内幕》一书。
COM实现的技术，主要是C++的虚函数、多继承以及动态链接库(DLL)技术。

COM组件的实现：
类型定义文件type.h

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#ifndef TYPE_H
#define TYPE_H
 
typedef long            HRESULT;
typedef unsigned long   ULONG;
 
typedef struct _GUID
{
    unsigned long Data1;
    unsigned short Data2;
    unsigned short Data3;
    unsigned char Data4[8];
} GUID;
typedef GUID IID;
 
#define interface struct
 
#define E_NOINTERFACE 0x80004002L
#define S_OK  0
 
#endif // TYPE_H

GUID定义文件guids.h

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#include "type.h"
 
extern "C"
{
        extern const IID IID_IX =
                {0x32bb8320, 0xb41b, 0x11cf,
                {0xa6, 0xbb, 0x0, 0x80, 0xc7, 0xb2, 0xd6, 0x82}};
 
        extern const IID IID_IY =
                {0x32bb8321, 0xb41b, 0x11cf,
                {0xa6, 0xbb, 0x0, 0x80, 0xc7, 0xb2, 0xd6, 0x82}};
 
        extern const IID IID_IZ =
                {0x32bb8322, 0xb41b, 0x11cf,
                {0xa6, 0xbb, 0x0, 0x80, 0xc7, 0xb2, 0xd6, 0x82}};
 
        extern const IID IID_IUnknown =
                {0x32bb8323, 0xb41b, 0x11cf,
                {0xa6, 0xbb, 0x0, 0x80, 0xc7, 0xb2, 0xd6, 0x82}};
}

接口基类：IUnknown.h

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#ifndef IUNKNOWN_H
#define IUNKNOWN_H
 
#include "type.h"
 
interface IUnknown
{
        virtual HRESULT  QueryInterface(const IID& iid, void** ppv)=0;
        virtual ULONG    AddRef()=0;
        virtual ULONG    Release()=0;
};
 
#endif // IUNKNOWN_H

接口定义头文件iface.h

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#ifndef IFACE_H
#define IFACE_H
 
#include "IUnknown.h"
 
interface IX:IUnknown
{
        virtual void Fx()=0;
};
 
interface IY:IUnknown
{
        virtual void Fy()=0;
};
 
interface IZ:IUnknown
{
        virtual void Fz()=0;
};
 
extern "C"
{
        extern const IID IID_IX;
        extern const IID IID_IY;
        extern const IID IID_IZ;
}
 
#endif // IFACE_H

组件实现文件cmpnt1.cpp

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#include <iostream>
#include "type.h"
#include "iface.h"
#include "guids.h"
 
using namespace std;
 
bool operator==(const IID& guid1, const IID& guid2)
{
        if(guid1.Data1 != guid2.Data1)
                return false;
        if(guid1.Data2 != guid2.Data2)
                return false;
        if(guid1.Data3 != guid2.Data3)
                return false;
 
        for(int i = 0; i < 8; i++)
        {
                if(guid1.Data4[i] != guid2.Data4[i])
                        return false;
        }
 
        return true;
}
 
void trace1(const char* msg) { cout << "Component1:\t" << msg << endl; }
 
class CA:public IX
{
private:
        //IUnknown interface
        virtual HRESULT QueryInterface(const IID& iid, void** ppv);
        virtual ULONG   AddRef();
        virtual ULONG   Release();
 
        //IX interface
        virtual void Fx() { cout << "FX" << endl; }
 
public:
        //Constructor
        CA():m_cRef(0){}
 
        //Destructor
        ~CA(){ trace1("CA Destoryed by itself!"); }
 
private:
        long m_cRef;
};
 
HRESULT CA::QueryInterface(const IID& iid, void** ppv)
{
 
        if(iid == IID_IX)
        {
                trace1("Return Pointer to IX");
                *ppv = static_cast<IX*>(this);
        }
        else if(iid == IID_IUnknown)
        {
                trace1("Return Pointer to IUnknown");
                *ppv = static_cast<IUnknown*>(this);
        }
        else
        {
                trace1("Interface is not surpport!");
                *ppv = NULL;
                return E_NOINTERFACE;
        }
        reinterpret_cast<IUnknown*>(*ppv)->AddRef();
 
        return S_OK;
}
 
ULONG CA::AddRef()
{
        m_cRef++;
}
 
ULONG CA::Release()
{
        if((--m_cRef) == 0)
        {
                delete this;
                return 0;
        }
        return m_cRef;
}
 
extern "C" IUnknown* CreateInstance()
{
        IUnknown* pI = static_cast<IX*>(new CA);
        pI->AddRef();
        return pI;
}

创建组件
create.h

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#ifndef CREATE_H
#define CREATE_H
 
#include <iostream>
#include "IUnknown.h"
#include <dlfcn.h>
 
using namespace std;
 
struct CREATE
{
        void* handle;
        IUnknown* CallCreateInstance(char *name);
        void closeHandle();
};
 
#endif // CREATE_H

create.cpp

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#include "create.h"
#include <stdlib.h>
 
typedef IUnknown* (*CREATEFUNCPTR)();
 
IUnknown* CREATE::CallCreateInstance(char* name)
{
        CREATEFUNCPTR   CreateInstance;
        char*           error;
        IUnknown*       pUnknown;
 
        handle = dlopen(name , RTLD_LAZY);
 
        if(!handle)
        {
                cout << "Load lib " << name << " fail!" << endl;
                exit(1);
        }
 
        dlerror();
        *(void**)(&CreateInstance) = dlsym(handle, "CreateInstance");
        if ((error = dlerror()) != NULL)
        {
                cout << error << endl;
                exit(1);
        }
 
        pUnknown = CreateInstance();
 
//      dlclose(handle);
        return pUnknown;
}
 
void   CREATE::closeHandle()
{
        dlclose(handle);
}
 
bool operator==(const IID& guid1, const IID& guid2)
{
        if(guid1.Data1 != guid2.Data1)
                return false;
        if(guid1.Data2 != guid2.Data2)
                return false;
        if(guid1.Data3 != guid2.Data3)
                return false;
 
        for(int i = 0; i < 8; i++)
        {
                if(guid1.Data4[i] != guid2.Data4[i])
                        return false;
        }
 
        return true;
}

客户端实现client1.cpp

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#include <iostream>
#include <stdlib.h>
#include "iface.h"
#include "create.h"
#include "guids.h"
 
void trace(const char* msg) { cout << "Client1:\t" << msg << endl; }
 
int main(int argc, char** argv)
{
        HRESULT hr;
        char name[40];
        CREATE  create;
 
        cout << "Enter the file name of a component to use[lib***.so]:";
        cin >> name;
        cout << endl;
 
        trace("Get an IUnknown pointer.");
        IUnknown* pUnknown = create.CallCreateInstance(name);
        if(pUnknown == NULL)
        {
                trace("CallCreateInstance fail!");
                exit(1);
        }
 
        trace("Get Interface IX.");
 
        IX* pIX = NULL;
 
        hr = pUnknown->QueryInterface(IID_IX, (void**)&pIX);
 
        if(hr >= 0)
        {
                trace("Success get the IX.");
                pIX->Fx();
                pIX->Release();
        }
        else
        {
                trace("Counld not get the IX interface.");
}
        trace("Release the IUnknown interface.");
        pUnknown->Release();
 
        create.closeHandle();
        return 0;
}

CMakeLists.txt

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cmake_minimum_required(VERSION 2.6)
 
set(SRC_CLIENT
  client1.cpp
  create.cpp
)
 
add_executable(com_client ${SRC_CLIENT})
 
set_target_properties(com_client PROPERTIES INSTALL_RPATH "./libs")
#include_directories()
target_link_libraries(com_client
  dl
)
 
install(TARGETS com_client RUNTIME DESTINATION bin)
 
set(SRC_COM
  cmpnt1.cpp
)
add_library(cmpnt1 SHARED ${SRC_COM})
install(TARGETS cmpnt1 LIBRARY DESTINATION bin/libs)

也可以使用Makefile

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objects=cmpnt1.o client1.o create.o
 
all : libcmpnt1 client1
 
libcmpnt1 : cmpnt1.o
g++ -shared -Wl,-soname -O3 -o libcmpnt1.so cmpnt1.o
 
cmpnt1.o : guids.cpp iface.h  IUnknown.h  type.h
g++ -c -fPIC cmpnt1.cpp  -O3 -o cmpnt1.o
 
client1 : client1.o create.o
g++ -g -rdynamic -ldl -o client1 client1.o create.o -Wl,-rpath,.
 
client1.o :
g++ -g -c client1.cpp
 
create.o :
g++ -g -c create.cpp
 
.PYTHON : clean
clean :
rm -f ${objects}

运行时注意：需要保证当前的环境下环境变量LD_LIBRARY_PATH已经设置。
具体运行方法如下：

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[root@localhost cust_comp]# export LD_LIBRARY_PATH=.
[root@localhost cust_comp]# ./client1
Enter the file name of a component to use[lib***.so]:libcmpnt1.so
 
Client1:        Get an IUnknown pointer.
Client1:        Get Interface IX.
Component1:     Return Pointer to IX
Client1:        Success get the IX.
FX
Client1:        Release the IUnknown interface.
Component1:     CA Destoryed by itself!

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