将char数组添加到C 中的字符串
Adding char array to string in c++
char site[];
scanf("%s", site);
send(sock,"GET / HTTP/1.1rnHost: " + site + "rnConnection: closernrn", strlen("GET / HTTP/1.1rnHost: " + site + "rnConnection: closernrn"),0);
这给了我错误:表达式必须具有积分或枚举类型。
我该如何修复?
正如其他答案中所述,您发布的代码是直接的。在C 中,您通常会喜欢std ::字符串到C-style Char Arrays and std :: cin到C - 风格的scanf()。更C 的方式看起来像这样
std::string input;
std::cin >> input;
std::string out = "GET / HTTP/1.1rnHost: " + input + "rnConnection: closernrn";
send(sock, out.c_str(), out.size(), 0);
尽管标记为C ,但代码是直接的。有两个问题:首先,site
是不完整的类型;您需要给它一个尺寸;其次,在C中,您不能仅仅与' '一起堵塞字符串。您需要使用strcat
:
char site[128];
char cmd[128];
scanf("%s", site);
strcpy(cmd, "GET / HTTP/1.1rnHost: ");
strcat(cmd, site);
strcat(cmd, "rnConnection: closernrn");
这不是对样式的认可(也不是 r n的东西),只是一个简单的代码块,它可以执行原始内容。
更改以下内容: "GET / HTTP/1.1rnHost: " + site + "rnConnection: closernrn", strlen("GET / HTTP/1.1rnHost: " + site + "rnConnection: closernrn"
:
(std::string() +"GET / HTTP/1.1rnHost: " + site + "rnConnection: closernrn", strlen("GET / HTTP/1.1rnHost: " + site + "rnConnection: closernrn").c_str()
绝对最小的更改使该行编译并执行您可能想要的事情。
操作员 在RAW C字符串上没有做任何您想做的事情。通过从std :: string()开始,添加RAW C字符串创建了新的std :: strings。然后,我们在末尾致电.c_str()返回到一个原始的C字符串,该c字符串至少持续到您调用完成功能为止。然后一切都清理了。
现在,您的代码还有其他问题。char site[]; scanf("%s", site);
调用了未定义的行为,因为编译器不知道site
数组应该有多大。即使您给site
尺寸(例如char site[100];
),这将是一个缓冲区跨流,等待发生 - 不建议使用scanf
。
读取字符串时,您要么需要一个将您阅读的量的函数限制为正在阅读的缓冲区,要么根据需要调整缓冲区以适合您正在阅读的内容。
请注意,我假设代码实际上是C ,如标记。
char site[];
此代码不合法。您的编译器应产生错误,例如:
main.cpp:5:10: error: definition of variable with array type needs an explicit size or an initializer
char site[];
^
因为在C 中,内置阵列具有固定大小,这是其类型的一部分。如果您想要一个可重大的数组,则应将std::vector
用于一般情况,而std::string
用于字符串。
scanf("%s", site);
如果char site[]
正在使用您的编译器,则可能会创建一个大小为零的数组,因此在其中读取任何内容会导致缓冲区溢出。
send(sock,"GET / HTTP/1.1rnHost: " + site + "rnConnection: closernrn", strlen("GET / HTTP/1.1rnHost: " + site + "rnConnection: closernrn"),0);
这应该导致沿着:
的线路发生另一个错误main.cpp:10:42: error: invalid operands to binary expression ('const char *' and 'char *')
send(sock,"GET / HTTP/1.1rnHost: " + site + "rnConnection: closernrn", strlen("GET / HTTP/1.1rnHost: " + site + "rnConnection: closernrn"),0);
~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~
在C 中,您不能简单地将数组添加在一起。同样,C 中的数组是固定尺寸的对象。但是,您可以将std::strings
添加在一起,也可以使用const char *
添加std::string
(因为STD :: String定义了自身和const char *
之间的operator+
)。
std::string site;
site = getURL(); // you'll have to implement this, including both getting the string from the user and validating that the user isn't entering in something tricky that will cause security problems
std::string query = "GET / HTTP/1.1rnHost: " + site + "rnConnection: closernrn";
send(sock, query.c_str(), query.size());
另一个GET
实现。
char *get_http= new char[256];
memset(get_http,' ', sizeof(get_http) );
strcpy(get_http,"GET / HTTP/1.1rnHost: ");
strcat(get_http,url);
strcat(get_http,"rnConnection: closernrn");
.
.
send(Socket,get_http, strlen(get_http),0 );
示例winsock控制台HTML浏览器代码:
#include <winsock2.h>
#include <windows.h>
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cctype>
#include <locale>
#pragma comment(lib,"ws2_32.lib")
using namespace std;
string website_HTML;
locale local;
//***************************
void get_Website(char *url );
//***************************
int main ()
{
get_Website("www.msn.com" );
for (size_t i=0; i<website_HTML.length(); ++i) website_HTML[i]= tolower(website_HTML[i],local);
cout <<website_HTML;
cout<<"nn";
return 0;
}
//***************************
void get_Website(char *url )
{
WSADATA wsaData;
SOCKET Socket;
SOCKADDR_IN SockAddr;
int lineCount=0;
int rowCount=0;
struct hostent *host;
char *get_http= new char[256];
memset(get_http,' ', sizeof(get_http) );
strcpy(get_http,"GET / HTTP/1.1rnHost: ");
strcat(get_http,url);
strcat(get_http,"rnConnection: closernrn");
if (WSAStartup(MAKEWORD(2,2), &wsaData) != 0)
{
cout << "WSAStartup failed.n";
system("pause");
//return 1;
}
Socket=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
host = gethostbyname(url);
SockAddr.sin_port=htons(80);
SockAddr.sin_family=AF_INET;
SockAddr.sin_addr.s_addr = *((unsigned long*)host->h_addr);
cout << "Connecting to "<< url<<" ...n";
if(connect(Socket,(SOCKADDR*)(&SockAddr),sizeof(SockAddr)) != 0)
{
cout << "Could not connect";
system("pause");
//return 1;
}
cout << "Connected.n";
send(Socket,get_http, strlen(get_http),0 );
char buffer[10000];
int nDataLength;
while ((nDataLength = recv(Socket,buffer,10000,0)) > 0)
{
int i = 0;
while (buffer[i] >= 32 || buffer[i] == 'n' || buffer[i] == 'r')
{
website_HTML+=buffer[i];
i += 1;
}
}
closesocket(Socket);
WSACleanup();
delete[] get_http;
}