封装read、write、accept、connect函数，实现超时操作。

学习linux网络编程的时候，看视频学习，封装了一些可以直接拿来用的函数，方便以后查找。

/**
 * read_timeout - 读超时检测函数，不含读操作
 *@fd: 文件描述符
 *@wait_seconds: 等待超时秒数，如果为0表示不检测超时
 * 成功（未超时）返回0，失败返回-1，超时返回-1并且errno = ETIMEDOUT
 */
int read_timeout(int fd, unsigned int wait_seconds)
{
int ret = 0;
if (wait_seconds > 0)
{
fd_set read_fdset;
struct timeval timeout;


FD_ZERO(&read_fdset);
FD_SET(fd, &read_fdset);


timeout.tv_sec = wait_seconds;
timeout.tv_usec = 0;
do
{
ret = select(fd + 1, &read_fdset, NULL, NULL, &timeout);
} while (ret < 0 && errno == EINTR);


if (ret == 0)
{
ret = -1;
errno = ETIMEDOUT;
}
else if (ret == 1)
ret = 0;
}


return ret;
}

/**
 * write_timeout - 读超时检测函数，不含写操作
 * @fd: 文件描述符
 * @wait_seconds: 等待超时秒数，如果为0表示不检测超时
 * 成功（未超时）返回0，失败返回-1，超时返回-1并且errno = ETIMEDOUT
 */
int write_timeout(int fd, unsigned int wait_seconds)
{
int ret = 0;
if (wait_seconds > 0)
{
fd_set write_fdset;
struct timeval timeout;


FD_ZERO(&write_fdset);
FD_SET(fd, &write_fdset);


timeout.tv_sec = wait_seconds;
timeout.tv_usec = 0;
do
{
ret = select(fd + 1, NULL, NULL, &write_fdset, &timeout);
} while (ret < 0 && errno == EINTR);


if (ret == 0)
{
ret = -1;
errno = ETIMEDOUT;
}
else if (ret == 1)
ret = 0;
}


return ret;
}

/**
 * accept_timeout - 带超时的accept
 * @fd: 套接字
 * @addr: 输出参数，返回对方地址
 * @wait_seconds: 等待超时秒数，如果为0表示正常模式
 * 成功（未超时）返回已连接套接字，超时返回-1并且errno = ETIMEDOUT
 */
int accept_timeout(int fd, struct sockaddr_in *addr, unsigned int wait_seconds)
{
int ret;
socklen_t addrlen = sizeof(struct sockaddr_in);


if (wait_seconds > 0)
{
fd_set accept_fdset;
struct timeval timeout;
FD_ZERO(&accept_fdset);
FD_SET(fd, &accept_fdset);
timeout.tv_sec = wait_seconds;
timeout.tv_usec = 0;
do
{
ret = select(fd + 1, &accept_fdset, NULL, NULL, &timeout);
} while (ret < 0 && errno == EINTR);
if (ret == -1)
return -1;
else if (ret == 0)
{
errno = ETIMEDOUT;
return -1;
}
}


if (addr != NULL)
ret = accept(fd, (struct sockaddr*)addr, &addrlen);
else
ret = accept(fd, NULL, NULL);
/* if (ret == -1)
ERR_EXIT("accept");
*/


return ret;
}


/**
 * connect_timeout - connect
 * @fd: 套接字
 * @addr: 要连接的对方地址
 * @wait_seconds: 等待超时秒数，如果为0表示正常模式
 * 成功（未超时）返回0，失败返回-1，超时返回-1并且errno = ETIMEDOUT
 */
int connect_timeout(int fd, struct sockaddr_in *addr, unsigned int wait_seconds)
{
int ret;
socklen_t addrlen = sizeof(struct sockaddr_in);


if (wait_seconds > 0)
activate_nonblock(fd);


ret = connect(fd, (struct sockaddr*)addr, addrlen);
if (ret < 0 && errno == EINPROGRESS)
{
//printf("AAAAA\n");
fd_set connect_fdset;
struct timeval timeout;
FD_ZERO(&connect_fdset);
FD_SET(fd, &connect_fdset);
timeout.tv_sec = wait_seconds;
timeout.tv_usec = 0;
do
{
/* 一量连接建立，套接字就可写 */
ret = select(fd + 1, NULL, &connect_fdset, NULL, &timeout);
} while (ret < 0 && errno == EINTR);
if (ret == 0)
{
ret = -1;
errno = ETIMEDOUT;
}
else if (ret < 0)
return -1;
else if (ret == 1)
{
//printf("BBBBB\n");
/* ret返回为1，可能有两种情况，一种是连接建立成功，一种是套接字产生错误，*/
/* 此时错误信息不会保存至errno变量中，因此，需要调用getsockopt来获取。 */
int err;
socklen_t socklen = sizeof(err);
int sockoptret = getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &socklen);
if (sockoptret == -1)
{
return -1;
}
if (err == 0)
{
//printf("DDDDDDD\n");
ret = 0;
}
else
{
//printf("CCCCCC\n");
errno = err;
ret = -1;
}
}
}
if (wait_seconds > 0)
{
deactivate_nonblock(fd);
}
return ret;
}