C++ 网络爬虫实现

最近有个概念吵得很火，网络爬虫，但是基本都是用什么python或者JAVA写，貌似很少看到用c++写的，我在网上找了一个，看到其实还是很简单的算法

算法讲解：1.遍历资源网站

　　　　　2.获取html信息

　　　　   3.然后解析网址和图片url下载。

　　　　   4.递归调用搜索网址

BFS是最重要的处理：

 

       先是获取网页响应，保存到文本里面，然后找到其中的图片链接HTMLParse，

       下载所有图片DownLoadImg。

//广度遍历  
void BFS( const string & url ){  
	char * response;  
	int bytes;  
	// 获取网页的相应，放入response中。  
	if( !GetHttpResponse( url, response, bytes ) ){  
		cout << "The url is wrong! ignore." << endl;  
		return;  
	}  
	string httpResponse=response;  
	free( response );  
	string filename = ToFileName( url );  
	ofstream ofile( "./html/"+filename );  
	if( ofile.is_open() ){  
		// 保存该网页的文本内容  
		ofile << httpResponse << endl;  
		ofile.close();  
	}  
	vector<string> imgurls;  
	//解析该网页的所有图片链接，放入imgurls里面  
	HTMLParse( httpResponse,  imgurls, url );  

	//下载所有的图片资源  
	DownLoadImg( imgurls, url );  
}  

然后附上代码：

#include "stdafx.h"

//#include <Windows.h>  
#include <string>  
#include <iostream>  
#include <fstream>  
#include <vector>  
#include "winsock2.h"  
#include <time.h>  
#include <queue>  
#include <hash_set>  

#pragma comment(lib, "ws2_32.lib")   
using namespace std;  

#define DEFAULT_PAGE_BUF_SIZE 1048576  

queue<string> hrefUrl;  
hash_set<string> visitedUrl;  
hash_set<string> visitedImg;  
int depth=0;  
int g_ImgCnt=1;  

//解析URL，解析出主机名，资源名  
bool ParseURL( const string & url, string & host, string & resource){  
	if ( strlen(url.c_str()) > 2000 ) {  
		return false;  
	}  

	const char * pos = strstr( url.c_str(), "http://" );  
	if( pos==NULL ) pos = url.c_str();  
	else pos += strlen("http://");  
	if( strstr( pos, "/")==0 )  
		return false;  
	char pHost[100];  
	char pResource[2000];  
	sscanf( pos, "%[^/]%s", pHost, pResource );  
	host = pHost;  
	resource = pResource;  
	return true;  
}  

//使用Get请求，得到响应  
bool GetHttpResponse( const string & url, char * &response, int &bytesRead ){  
	string host, resource;  
	if(!ParseURL( url, host, resource )){  
		cout << "Can not parse the url"<<endl;  
		return false;  
	}  

	//建立socket  
	struct hostent * hp= gethostbyname( host.c_str() );  
	if( hp==NULL ){  
		cout<< "Can not find host address"<<endl;  
		return false;  
	}  

	SOCKET sock = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP);  
	if( sock == -1 || sock == -2 ){  
		cout << "Can not create sock."<<endl;  
		return false;  
	}  

	//建立服务器地址  
	SOCKADDR_IN sa;  
	sa.sin_family = AF_INET;  
	sa.sin_port = htons( 80 );  
	//char addr[5];  
	//memcpy( addr, hp->h_addr, 4 );  
	//sa.sin_addr.s_addr = inet_addr(hp->h_addr);  
	memcpy( &sa.sin_addr, hp->h_addr, 4 );  

	//建立连接  
	if( 0!= connect( sock, (SOCKADDR*)&sa, sizeof(sa) ) ){  
		cout << "Can not connect: "<< url <<endl;  
		closesocket(sock);  
		return false;  
	};  

	//准备发送数据  
	string request = "GET " + resource + " HTTP/1.1
Host:" + host + "
Connection:Close

";  

	//发送数据  
	if( SOCKET_ERROR ==send( sock, request.c_str(), request.size(), 0 ) ){  
		cout << "send error" <<endl;  
		closesocket( sock );  
		return false;  
	}  

	//接收数据  
	int m_nContentLength = DEFAULT_PAGE_BUF_SIZE;  
	char *pageBuf = (char *)malloc(m_nContentLength);  
	memset(pageBuf, 0, m_nContentLength);  

	bytesRead = 0;  
	int ret = 1;  
	cout <<"Read: ";  
	while(ret > 0){  
		ret = recv(sock, pageBuf + bytesRead, m_nContentLength - bytesRead, 0);  

		if(ret > 0)  
		{  
			bytesRead += ret;  
		}  

		if( m_nContentLength - bytesRead<100){  
			cout << "
Realloc memorry"<<endl;  
			m_nContentLength *=2;  
			pageBuf = (char*)realloc( pageBuf, m_nContentLength);       //重新分配内存  
		}  
		cout << ret <<" ";  
	}  
	cout <<endl;  

	pageBuf[bytesRead] = '';  
	response = pageBuf;  
	closesocket( sock );  
	return true;  
	//cout<< response <<endl;  
}  

//提取所有的URL以及图片URL  
void HTMLParse ( string & htmlResponse, vector<string> & imgurls, const string & host ){  
	//找所有连接，加入queue中  
	const char *p= htmlResponse.c_str();  
	char *tag="href="";  
	const char *pos = strstr( p, tag );  
	ofstream ofile("url.txt", ios::app);  
	while( pos ){  
		pos +=strlen(tag);  
		const char * nextQ = strstr( pos, """ );  
		if( nextQ ){  
			char * url = new char[ nextQ-pos+1 ];  
			//char url[100]; //固定大小的会发生缓冲区溢出的危险  
			sscanf( pos, "%[^"]", url);  
			string surl = url;  // 转换成string类型，可以自动释放内存  
			if( visitedUrl.find( surl ) == visitedUrl.end() ){  
				visitedUrl.insert( surl );  
				ofile << surl<<endl;  
				hrefUrl.push( surl );  
			}  
			pos = strstr(pos, tag );  
			delete [] url;  // 释放掉申请的内存  
		}  
	}  
	ofile << endl << endl;  
	ofile.close();  

	tag ="<img ";  
	const char* att1= "src="";  
	const char* att2="lazy-src="";  
	const char *pos0 = strstr( p, tag );  
	while( pos0 ){  
		pos0 += strlen( tag );  
		const char* pos2 = strstr( pos0, att2 );  
		if( !pos2 || pos2 > strstr( pos0, ">") ) {  
			pos = strstr( pos0, att1);  
			if(!pos) {  
				pos0 = strstr(att1, tag );  
				continue;  
			} else {  
				pos = pos + strlen(att1);  
			}  
		}  
		else {  
			pos = pos2 + strlen(att2);  
		}  

		const char * nextQ = strstr( pos, """);  
		if( nextQ ){  
			char * url = new char[nextQ-pos+1];  
			sscanf( pos, "%[^"]", url);  
			cout << url<<endl;  
			string imgUrl = url;  
			if( visitedImg.find( imgUrl ) == visitedImg.end() ){  
				visitedImg.insert( imgUrl );  
				imgurls.push_back( imgUrl );  
			}  
			pos0 = strstr(pos0, tag );  
			delete [] url;  
		}  
	}  
	cout << "end of Parse this html"<<endl;  
}  

//把URL转化为文件名  
string ToFileName( const string &url ){  
	string fileName;  
	fileName.resize( url.size());  
	int k=0;  
	for( int i=0; i<(int)url.size(); i++){  
		char ch = url[i];  
		if( ch!='\'&&ch!='/'&&ch!=':'&&ch!='*'&&ch!='?'&&ch!='"'&&ch!='<'&&ch!='>'&&ch!='|')  
			fileName[k++]=ch;  
	}  
	return fileName.substr(0,k) + ".txt";  
}  

//下载图片到img文件夹  
void DownLoadImg( vector<string> & imgurls, const string &url ){  

	//生成保存该url下图片的文件夹  
	string foldname = ToFileName( url );  
	foldname = "./img/"+foldname;  
	if(!CreateDirectory( foldname.c_str(),NULL ))  
		cout << "Can not create directory:"<< foldname<<endl;  
	char *image;  
	int byteRead;  
	for( int i=0; i<imgurls.size(); i++){  
		//判断是否为图片，bmp，jgp，jpeg，gif   
		string str = imgurls[i];  
		int pos = str.find_last_of(".");  
		if( pos == string::npos )  
			continue;  
		else{  
			string ext = str.substr( pos+1, str.size()-pos-1 );  
			if( ext!="bmp"&& ext!="jpg" && ext!="jpeg"&& ext!="gif"&&ext!="png")  
				continue;  
		}  
		//下载其中的内容  
		if( GetHttpResponse(imgurls[i], image, byteRead)){  
			if ( strlen(image) ==0 ) {  
				continue;  
			}  
			const char *p=image;  
			const char * pos = strstr(p,"

")+strlen("

");  
			int index = imgurls[i].find_last_of("/");  
			if( index!=string::npos ){  
				string imgname = imgurls[i].substr( index , imgurls[i].size() );  
				ofstream ofile( foldname+imgname, ios::binary );  
				if( !ofile.is_open() )  
					continue;  
				cout <<g_ImgCnt++<< foldname+imgname<<endl;  
				ofile.write( pos, byteRead- (pos-p) );  
				ofile.close();  
			}  
			free(image);  
		}  
	}  
}  



//广度遍历  
void BFS( const string & url ){  
	char * response;  
	int bytes;  
	// 获取网页的相应，放入response中。  
	if( !GetHttpResponse( url, response, bytes ) ){  
		cout << "The url is wrong! ignore." << endl;  
		return;  
	}  
	string httpResponse=response;  
	free( response );  
	string filename = ToFileName( url );  
	ofstream ofile( "./html/"+filename );  
	if( ofile.is_open() ){  
		// 保存该网页的文本内容  
		ofile << httpResponse << endl;  
		ofile.close();  
	}  
	vector<string> imgurls;  
	//解析该网页的所有图片链接，放入imgurls里面  
	HTMLParse( httpResponse,  imgurls, url );  

	//下载所有的图片资源  
	DownLoadImg( imgurls, url );  
}  

void main()  
{  
	//初始化socket，用于tcp网络连接  
	WSADATA wsaData;  
	if( WSAStartup(MAKEWORD(2,2), &wsaData) != 0 ){  
		return;  
	}  

	// 创建文件夹，保存图片和网页文本文件  
	CreateDirectory( "./img",0);  
	CreateDirectory("./html",0);  
	//string urlStart = "http://hao.360.cn/meinvdaohang.html";  

	// 遍历的起始地址  
	 string urlStart = "http://desk.zol.com.cn/bizhi/7018_87137_2.html";  
	//string urlStart = "http://item.taobao.com/item.htm?spm=a230r.1.14.19.sBBNbz&id=36366887850&ns=1#detail";  

	// 使用广度遍历  
	// 提取网页中的超链接放入hrefUrl中，提取图片链接，下载图片。  
	BFS( urlStart );  

	// 访问过的网址保存起来  
	visitedUrl.insert( urlStart );  

	while( hrefUrl.size()!=0 ){  
		string url = hrefUrl.front();  // 从队列的最开始取出一个网址  
		cout << url << endl;  
		BFS( url );                   // 遍历提取出来的那个网页，找它里面的超链接网页放入hrefUrl，下载它里面的文本，图片  
		hrefUrl.pop();                 // 遍历完之后，删除这个网址  
	}  
	WSACleanup();  
	return;  
}