[libcurl]_[初级]_[使用libcurl库做简单软件更新解决方案]

来源：互联网发布：mysql按月分区表编辑：程序博客网时间：2024/04/28 02:49

场景：

1.软件需要更新版本时，通过读取配置好的xml文件获得软件最新的版本信息。

2.因为访问网络可能造成延迟，所以不能阻碍界面操作，所以还得用工作线程进行操作。

3.使用expat库做xml分析,curl库下载xml数据流，两个都是跨平台的库，使用也比较方便。

libcurl: http://curl.haxx.se/

expat: http://expat.sourceforge.net/

pthread: http://sources.redhat.com/pthreads-win32/

1.要分析的xml文件

http://www.w3school.com.cn/example/xmle/note.xml

<?xml version="1.0" encoding="ISO-8859-1"?><note><to>George</to><from>John</from><heading>Reminder</heading><body>Don't forget the meeting!</body></note>

2. test_curl.cpp文件

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <string>#include <iostream>#include "curl/curl.h"#include "expat.h"#include "pthread.h"#include "windows.h"using namespace std;#define XML_FMT_INT_MOD "l"static bool bodyStart = false;static void StartElementHandler(void *userData,const XML_Char *name,                                const XML_Char **atts){    if(!strcmp("body",name))    {            bodyStart = true;    }}static void EndElementHandler(void *userData,const XML_Char *name){    if(!strcmp("body",name))    {        bodyStart = false;    }}static void CharacterDataHandler(void *userData,const XML_Char *s,                                 int len){    if(bodyStart && s)    {        string str(s,len);        cout << "inner Text: " << str << endl;    }}class DownloadManger{    public:    static DownloadManger* GetInstance()    {        if(!download_manger_)        {            download_manger_ = new DownloadManger();        }        return download_manger_;    }    ~DownloadManger()    {        download_manger_ = NULL;        curl_global_cleanup();    }    typedef size_t (*WriteMemoryCallback)(void *contents, size_t size,         size_t nmemb, void *userp);    int Process(const char* url,WriteMemoryCallback callback_func,void* userdata)    {        CURL *curl_handle = curl_easy_init();        curl_easy_setopt(curl_handle, CURLOPT_URL, url);        curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, callback_func);        curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, userdata);        curl_easy_setopt(curl_handle, CURLOPT_USERAGENT, "test-agent/1.0");        curl_easy_perform(curl_handle);        curl_easy_cleanup(curl_handle);                return 0;        }    private:    static DownloadManger* download_manger_;    DownloadManger()    {        curl_global_init(CURL_GLOBAL_ALL);    }};DownloadManger* DownloadManger::download_manger_ = NULL;static size_t DownloadCallback(void *contents, size_t size,     size_t nmemb, void *userp){    size_t realsize = size * nmemb;    XML_Parser parser = (XML_Parser)userp;      if (XML_Parse(parser, (char*) contents, realsize, 0) == XML_STATUS_ERROR)    {        fprintf(stderr, "%s at line %" XML_FMT_INT_MOD "u \n",                XML_ErrorString(XML_GetErrorCode(parser)),                XML_GetCurrentLineNumber(parser));        return 0;    }    return realsize;}XML_Parser CreateExpatParser(){    XML_Parser parser = XML_ParserCreate(NULL);    XML_SetUserData(parser, NULL);    XML_SetElementHandler(parser, &StartElementHandler,&EndElementHandler);    {        XML_SetCharacterDataHandler(parser,&CharacterDataHandler);    }    return parser;}void FreeExpatParser(XML_Parser parser){    XML_Parse(parser, (char*) 0, 0, 1);    XML_ParserFree(parser);}void * noMutexStartPthread(void * arg){    DWORD id = GetCurrentThreadId();    cout << "current thread id is: " << id << endl;    DownloadManger* manager = (DownloadManger*)arg;    XML_Parser parser = CreateExpatParser();    manager->Process("http://www.w3school.com.cn/example/xmle/note.xml",        &DownloadCallback,parser);    FreeExpatParser(parser);}int main(void){    DWORD id = GetCurrentThreadId();    cout << "main thread id is: " << id << endl;    DownloadManger* manager = DownloadManger::GetInstance();    pthread_t t1;    pthread_create(&t1, NULL, noMutexStartPthread, manager);    pthread_detach(t1);    pthread_t t2;    pthread_create(&t2, NULL, noMutexStartPthread, manager);    pthread_detach(t2);        int i = 0;    while(i < 10)    {        cout << "." << endl;        Sleep(1000);        ++i;    }    delete manager;    return 0;}

3.Makefile文件:

CP="cp"test_curl.exe:test_curl.o${CP} C:/Users/apple/Desktop/curl/curl-7.28.1/lib/.libs/libcurl-4.dll .${CP} E:/software/Lib/file/xml-expat-2.0.1/win32/release/share/libexpat-1.dll .${CP} E:/software/Lib/thread/pthreads-w32-2-8-0/win32/release/share/pthreadGC2.dll .g++ -o test_curl.exe test_curl.o -L/E/software/Lib/thread/pthreads-w32-2-8-0/win32/release/share -lpthreadGC2 -LC:/Users/apple/Desktop/curl/curl-7.28.1/lib/.libs -lcurl-4 -LE:/software/Lib/file/xml-expat-2.0.1/win32/release/share -lexpattest_curl.o:test_curl.cppg++ -I/E/software/Lib/thread/pthreads-w32-2-8-0/win32/release/share/include -IE:/software/Lib/file/xml-expat-2.0.1/win32/release/share/include -IC:/Users/apple/Desktop/curl/curl-7.28.1/include -c test_curl.cpp -o test_curl.o

4.运行结果:

main thread id is: 8004current thread id is: 4856.current thread id is: 6988inner Text: Don't forget the meeting!...inner Text: Don't forget the meeting!......