memset(p, 0, sizeof p);转换为c代码
时间: 2024-02-17 08:02:50 浏览: 24
这段代码已经是C语言代码了,没有必要再进行转换。这是一个使用了C标准库函数的代码,其中p是一个指针变量,用于指向需要清零的内存空间。sizeof p表示p所指向的数据类型的大小,这个大小是编译时确定的。最后,调用memset函数将p所指向的内存空间全部置为0。可以将这段代码放在函数中,以便在需要时调用。例如:
```
#include <string.h>
void clear_mem(void *p, size_t size) {
memset(p, 0, size);
}
int main() {
int arr[10];
clear_mem(arr, sizeof arr);
// 现在arr中的所有元素都被设置为0
return 0;
}
```
在这个例子中,我们定义了一个clear_mem函数,用于清零任何指针所指向的内存空间。然后,在main函数中,我们声明了一个包含10个int类型元素的数组arr,并将它传递给clear_mem函数,以确保它的所有元素都被设置为0。
相关问题
linux C语言实现将域名转换为IP地址
在 Linux C 语言中,可以使用 getaddrinfo 函数将域名转换为 IP 地址。
具体实现步骤如下:
1. 引入头文件:
```
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
```
2. 定义 getaddrinfo() 函数所需的结构体:
```
struct addrinfo hints, *res;
int status;
char ipstr[INET6_ADDRSTRLEN];
```
3. 初始化 hints 结构体:
```
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC; // AF_INET 或 AF_INET6 均可
hints.ai_socktype = SOCK_STREAM; // TCP
```
4. 调用 getaddrinfo() 函数:
```
status = getaddrinfo("www.example.com", NULL, &hints, &res);
```
其中 "www.example.com" 是需要转换的域名。
5. 遍历返回的地址列表,并将其转换为 IP 地址:
```
struct addrinfo *p;
void *addr;
for(p = res; p != NULL; p = p->ai_next) {
if (p->ai_family == AF_INET) { // IPv4
struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr;
addr = &(ipv4->sin_addr);
} else { // IPv6
struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr;
addr = &(ipv6->sin6_addr);
}
// 将 IP 地址转换为字符串
inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr);
}
```
其中,inet_ntop() 函数将 IP 地址转换为字符串形式,ipstr 变量即为转换后的 IP 地址。
6. 释放内存:
```
freeaddrinfo(res);
```
完整代码如下:
```
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main() {
struct addrinfo hints, *res;
int status;
char ipstr[INET6_ADDRSTRLEN];
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
status = getaddrinfo("www.example.com", NULL, &hints, &res);
if (status != 0) {
fprintf(stderr, "getaddrinfo error: %s\n", gai_strerror(status));
exit(1);
}
struct addrinfo *p;
void *addr;
for(p = res; p != NULL; p = p->ai_next) {
if (p->ai_family == AF_INET) { // IPv4
struct sockaddr_in *ipv4 = (struct sockaddr_in *)p->ai_addr;
addr = &(ipv4->sin_addr);
} else { // IPv6
struct sockaddr_in6 *ipv6 = (struct sockaddr_in6 *)p->ai_addr;
addr = &(ipv6->sin6_addr);
}
inet_ntop(p->ai_family, addr, ipstr, sizeof ipstr);
printf("IP address: %s\n", ipstr);
}
freeaddrinfo(res);
return 0;
}
```
IPv4客户端和IPv6服务器端通信的c语言代码demo
以下是一个简单的示例代码,展示了如何使用C语言在IPv4客户端和IPv6服务器端之间进行通信:
IPv4客户端代码:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#define PORT "8080"
int main(int argc, char *argv[]) {
int sockfd;
struct addrinfo hints, *servinfo, *p;
int rv;
char s[INET6_ADDRSTRLEN];
char buf[1024];
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
if ((rv = getaddrinfo("localhost", PORT, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
// loop through all the results and connect to the first we can
for (p = servinfo; p != NULL; p = p->ai_next) {
if ((sockfd = socket(p->ai_family, p->ai_socktype,
p->ai_protocol)) == -1) {
perror("client: socket");
continue;
}
if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
close(sockfd);
perror("client: connect");
continue;
}
break; // if we get here, we must have connected successfully
}
if (p == NULL) {
fprintf(stderr, "client: failed to connect\n");
return 2;
}
inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr),
s, sizeof s);
printf("client: connecting to %s\n", s);
freeaddrinfo(servinfo); // all done with this structure
while (1) {
printf("Enter message to send: ");
fgets(buf, sizeof(buf), stdin);
if (send(sockfd, buf, strlen(buf), 0) == -1) {
perror("send");
exit(1);
}
printf("Waiting for server response...\n");
int numbytes;
if ((numbytes = recv(sockfd, buf, sizeof(buf), 0)) == -1) {
perror("recv");
exit(1);
}
buf[numbytes] = '\0';
printf("Server response: %s\n", buf);
}
close(sockfd);
return 0;
}
```
IPv6服务器端代码:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#define PORT "8080"
void *get_in_addr(struct sockaddr *sa) {
if (sa->sa_family == AF_INET) {
return &(((struct sockaddr_in*)sa)->sin_addr);
}
return &(((struct sockaddr_in6*)sa)->sin6_addr);
}
int main(void) {
int sockfd, new_fd; // listen on sock_fd, new connection on new_fd
struct addrinfo hints, *servinfo, *p;
struct sockaddr_storage their_addr; // connector's address information
socklen_t sin_size;
int yes = 1;
char s[INET6_ADDRSTRLEN];
char buf[1024];
int rv;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE; // use my IP
if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
// loop through all the results and bind to the first we can
for (p = servinfo; p != NULL; p = p->ai_next) {
if ((sockfd = socket(p->ai_family, p->ai_socktype,
p->ai_protocol)) == -1) {
perror("server: socket");
continue;
}
if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes,
sizeof(int)) == -1) {
perror("setsockopt");
exit(1);
}
if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
close(sockfd);
perror("server: bind");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "server: failed to bind\n");
return 2;
}
freeaddrinfo(servinfo); // all done with this structure
if (listen(sockfd, 10) == -1) {
perror("listen");
exit(1);
}
printf("server: waiting for connections...\n");
while (1) { // main accept() loop
sin_size = sizeof their_addr;
new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
if (new_fd == -1) {
perror("accept");
continue;
}
inet_ntop(their_addr.ss_family,
get_in_addr((struct sockaddr *)&their_addr),
s, sizeof s);
printf("server: got connection from %s\n", s);
while (1) {
int numbytes;
if ((numbytes = recv(new_fd, buf, sizeof(buf), 0)) == -1) {
perror("recv");
exit(1);
}
if (numbytes == 0) {
printf("Connection closed\n");
break;
}
buf[numbytes] = '\0';
printf("Client message: %s", buf);
if (send(new_fd, buf, numbytes, 0) == -1) {
perror("send");
exit(1);
}
}
close(new_fd); // parent doesn't need this
}
return 0;
}
```
注意:在IPv6服务器端代码中,我们使用了一个名为`get_in_addr()`的函数,它将IPv4和IPv6地址转换为通用的地址格式。在IPv4情况下,它返回`sin_addr`字段,而在IPv6情况下,它返回`sin6_addr`字段。