linux网络编程中所用到的读写函数

#UNIX网络编程 卷一

ssize_t readn(int fd, void *buf, size_t count);

/**
*readn - 读取固定字节数
 *@fd: 文件描述符
  *@buf: 接收缓冲区
 *@count: 要读取的字节数
 * 成功返回count，失败返回-1，读到EOF返回<count
 */
ssize_t readn(int fd, void *buf, size_t count)
{
        size_t
	nleft = count;
        ssize_t nread;
       char *bufp = (char*)buf;
       while(nleft > 0) {
              if((nread = read(fd, bufp, nleft)) < 0) {
                     if(errno == EINTR)
                            continue;
                     return -1;
              }
              else if (nread == 0)
                     return  count - nleft;
              bufp+= nread;
              nleft-= nread;
       }
       return  count;
}

###ssize_t writen(int fd, const void *buf, size_t count);

/**
 *writen - 发送固定字节数
 *@fd: 文件描述符
 *@buf: 发送缓冲区
 *@count: 要读取的字节数
 * 成功返回count，失败返回-1
 */
ssize_t writen(int fd, const void *buf,size_t count)
{
       size_t nleft = count;
       ssize_t nwritten;
       char *bufp = (char*)buf;
       while(nleft > 0) {
              if((nwritten = write(fd, bufp, nleft)) < 0) {
                     if(errno == EINTR)
                            continue;
                     return-1;
              }
              else if (nwritten == 0)
                     continue;
              bufp+= nwritten;
              nleft-= nwritten;
       }
       return count;
}

###ssize_t recv_peek(int sockfd, void *buf, size_t len);

/**
 *recv_peek - 仅仅查看套接字缓冲区数据，但不移除数据
 *@sockfd: 套接字
 *@buf: 接收缓冲区
 *@len: 长度
 * 成功返回>=0，失败返回-1
 */
ssize_t recv_peek(int sockfd, void *buf, size_t len)
{
       while(1) {
              int ret = recv(sockfd, buf, len, MSG_PEEK);
              if(ret == -1 && errno == EINTR)
                     continue;
              return ret;
       }
}

###ssize_t readline(int sockfd, void *buf, size_t maxline);

/**
 *readline - 按行读取数据
 *@sockfd: 套接字
 *@buf: 接收缓冲区
 *@maxline: 每行最大长度
 * 成功返回>=0，失败返回-1
 */
ssize_t readline(int sockfd, void *buf,size_t maxline)
{
       int ret;
       int nread;
       char *bufp = buf;
       int nleft = maxline;
       while(1) {
              ret = recv_peek(sockfd, bufp, nleft);
              if(ret < 0)
                     return ret;
              else if (ret == 0)
                     return ret;
               nread = ret;
              int i;
              for(i=0; i<nread; i++) {
                     if(bufp[i] == '\n') {
                            ret= readn(sockfd, bufp, i+1);
                            if(ret != i+1)
                                   exit(EXIT_FAILURE);
                            return ret;
                     }
              }
              if(nread > nleft)
                     exit(EXIT_FAILURE);
              nleft -= nread;
              ret= readn(sockfd, bufp, nread);
              if(ret != nread)
                     exit(EXIT_FAILURE);
              bufp+= nread;
       }
       return -1;
}