如何使用C++下载网络资源

ToddSong

已于 2025-03-01 15:08:41 修改

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分类专栏：网络开发文章标签：网络 c++ null internet path url

于 2011-08-15 00:07:17 首次发布

本文链接：https://blog.youkuaiyun.com/newMFCer/article/details/6687093

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如何使用C++下载网络资源，其实只需要三个函数就可以搞定。他们分别是
①InternetOpen() 用来配置下载方式
②InternetOpenUrl() 打开要下载的资源
③InternetReadFile() 读取资源

下面就是一个函数用来实现网络下载功能

int DownFile1(char *url,char *path)
{
	HINTERNET hConn    = InternetOpen(NULL,INTERNET_OPEN_TYPE_PRECONFIG,NULL,NULL,0/*INTERNET_FLAG_ASYNC*/);	
	HINTERNET hIntFile = InternetOpenUrl(hConn,url,NULL,0,0,0);
	if(NULL == hIntFile) {
          /*使用函数就这里麻烦，释放要一大堆代码，等会上一个用类的方法*/
               InternetCloseHandle(hIntFile);
               InternetCloseHandle(hConn);
               return 0;
        }
	DWORD hasRead=0,hasWrite;
	HANDLE LocalFile = CreateFile(path,GENERIC_WRITE,0,NULL,CREATE_ALWAYS,0,NULL);
	unsigned char buff[1024]={0};
	BOOL hr = 0;
	hr = InternetReadFile(hIntFile,buff,sizeof(buff)-1,&hasRead);
	while(hasRead!=0&&hr)
	{
			WriteFile(LocalFile,buff,hasRead,&hasWrite,NULL);
			memset(buff,0x00,sizeof(buff));
			hr = InternetReadFile(hIntFile,buff,sizeof(buff)-1,&hasRead);
	}
	if(LocalFile) CloseHandle(LocalFile);
	if(hIntFile)  InternetCloseHandle(hIntFile);
	if(hConn)			InternetCloseHandle(hConn);
 	return 1;
}

就像上面说的那样，如果函数中间出现失败的话，那么会出现一大堆代码去释放资源，所以下面来个用OOP思想实现的代码

DownFile::DownFile()
{
 	m_hConn      = NULL;
	m_hInetFile  = NULL;
  m_hLocalFile = NULL;
}
DownFile::~DownFile()
{
	if(m_hLocalFile) CloseHandle(m_hLocalFile);
	if(m_hInetFile)  InternetCloseHandle(m_hInetFile);
	if(m_hConn)  InternetCloseHandle(m_hConn);	
}
int DownFile::Start(char *url,char *path)
{
	
		this->m_hConn      = InternetOpen(NULL,INTERNET_OPEN_TYPE_PRECONFIG,NULL,NULL,0);
		this->m_hInetFile  = InternetOpenUrl(this->m_hConn,url,NULL,0,0,0);
		if(NULL == this->m_hInetFile) return 0;
			/*
			*面向对象的好处就在这，如果使用函数的话，
			*就像DownFile1()在这里要释放一大堆资源，
			*而面向对象就不用管了，全交给析构函数
			*/
		this->m_hLocalFile = CreateFile(path,GENERIC_WRITE,0,NULL,CREATE_ALWAYS,0,NULL);
		if(NULL == this->m_hLocalFile) return 0;
		DWORD hasRead = 0,hasWrite;
		BOOL hr = 0;
		char buff[1024]={0};
		hr = InternetReadFile(this->m_hInetFile,buff,sizeof(buff)-1,&hasRead);
		while(0!=hasRead && hr)
		{
			WriteFile(this->m_hLocalFile,buff,hasRead,&hasWrite,NULL);	
			memset(buff,0x00,sizeof(buff));
			hr = InternetReadFile(this->m_hInetFile,buff,sizeof(buff)-1,&hasRead);			
		}
		return 1;
		
}