dlopen、dlsym和dlclose的使用

因为项目需求，需要集成一个第三方的方案。但是第三方只给我们release 了一个so 库+函数说明；现在需要调用到so 库中的函数。。

先给出一些函数的定义

       #include <dlfcn.h>       void *dlopen(const char *filename, int flag);       char *dlerror(void);       void *dlsym(void *handle, const char *symbol);       int dlclose(void *handle);       //Link with -ldl.

这里需要注意亮点

1、加上头文件#inclue<dlfcn.h>

2、编译的时候加上 -ldl选项

下面是生成动态供调用的so库代码

#include<stdio.h>#include<unistd.h>#include<sys/types.h>//#define bool intvoid *getValue(char *param,int intparam){    printf("%s-->%d,param=%s,intparam=%d\n",__FUNCTION__,__LINE__,param,intparam);    return 0;}void *getValue1(char *param,int intparam,int isReturnAddress){    printf("%s-->%d,param=%s,intparam=%d,isReturnAddress=%d\n",__FUNCTION__,__LINE__,param,intparam,isReturnAddress);    if(isReturnAddress>0){        return 1;    }else{        return 0;    }}void * InitEffect(unsigned char bitsPerSample,unsigned char numChannels,unsigned char dataIsInterleaved,unsigned int sampleRate){    printf("%s-->%d\n",__FUNCTION__,__LINE__);}void *ReinitEffect(unsigned char bitsPerSample,unsigned char numChannels,unsigned char dataIsInterleaved,unsigned int sampleRate){    printf("%s-->%d\n",__FUNCTION__,__LINE__);}int Process(void* inBuffer,void* outBuffer,void *mePtr,unsigned short num_frames){    printf("%s-->%d\n",__FUNCTION__,__LINE__);}int SetParam(void *mPtr,int paramId,void* paramVal){    printf("%s-->%d\n",__FUNCTION__,__LINE__);}int GetParam(void *mPtr,int paramId){    printf("%s-->%d\n",__FUNCTION__,__LINE__);}int Deallocate(void * mePtr){    printf("%s-->%d\n",__FUNCTION__,__LINE__);}void * GetSpecBufAddress(void *mePtr,int *bufLength){    printf("%s-->%d\n",__FUNCTION__,__LINE__);}

编译生成 so库

gcc -fPIC -shared -o test.so test.c

务必注意-fPIC编译选择

测试使用so库的代码

#include<stdio.h>#include<unistd.h>#include<sys/types.h>#include <dlfcn.h>typedef void* (*TCT_InitEffect)(unsigned char,unsigned char,unsigned char,unsigned int);typedef void* (*TCT_ReinitEffect)(unsigned char,unsigned char,unsigned char,unsigned int);typedef int (*TCT_Process)(void*,void*,void *,unsigned short);typedef int (*TCT_SetParam)(void*,int,void*);typedef int (*TCT_GetParam)(void*,int);typedef int (*TCT_Deallocate)(void*);typedef int (*TCT_GetSpecBufAddress)(void *mePtr,int *bufLength);typedef void* (*tct_getValue)(char*,int);typedef void* (*tct_getValue1)(char*,int,int);int main(int argc, char **argv) {    //open the .so library    void* handle = dlopen("./test.so", RTLD_LAZY);    //get function pointer from dlsym    tct_getValue getValue = (tct_getValue)dlsym(handle, "getValue");    tct_getValue1 getValue1 = (tct_getValue1)dlsym(handle, "getValue1");    TCT_InitEffect Harman_InitEffect = (TCT_InitEffect)dlsym(handle, "InitEffect");    TCT_ReinitEffect Harman_ReinitEffect = (TCT_ReinitEffect)dlsym(handle, "ReinitEffect");    TCT_Process Harman_Process = (TCT_Process)dlsym(handle, "Process");    TCT_SetParam Harman_SetParam = (TCT_SetParam)dlsym(handle, "SetParam");    TCT_GetParam Harman_GetParam = (TCT_GetParam)dlsym(handle, "GetParam");    TCT_Deallocate Harman_Deallocate = (TCT_Deallocate)dlsym(handle, "Deallocate");    TCT_GetSpecBufAddress Harman_GetSpecBufAddress = (TCT_GetSpecBufAddress)dlsym(handle, "GetSpecBufAddress");    //call function    Harman_InitEffect(1,1,1,1);    Harman_ReinitEffect(1,1,1,1);    Harman_Process(1,1,1,1);    Harman_SetParam(1,1,1);    Harman_GetParam(1,1);    Harman_Deallocate(1);    Harman_GetSpecBufAddress(1,1);    getValue("getValuexxxxxxx",1);    int xxx = getValue1("getValue1",1,0);    printf("main function return from getVaule1 =%d\n",xxx);    //dlclose handle    dlclose(handle);    return 0;}

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编译生成可执行文件

gcc hello.c  -o hello -ldl

这里需要加入-ldl编译选项

执行 

./hello

运行结果

InitEffect-->21ReinitEffect-->24Process-->28SetParam-->31GetParam-->34Deallocate-->37GetSpecBufAddress-->40getValue-->7,param=getValuexxxxxxx,intparam=1getValue1-->12,param=getValue1,intparam=1,isReturnAddress=0main function return from getVaule1 =0