错误处理函数（补充：Socket编程）

错误函数处理     （理解不到位）

        Socket编程的例子不仅功能简单，而且简单到几乎没有什么错误处理，我们知道，系统调用不能保证每次都成功，必须进行出错处理，这样一方面可以保证程序逻辑正常，另一方面可以迅速得到故障信息。

        为使错误处理的代码不影响主程序的可读性，我们把与socket相关的一些系统函数加上错误处理代码包装成新的函数，做成一个模块wrap.c：

 跳转到 man ：光标放在函数名称处，vim命令模式下输入2K

wrap.c / wrap.h  封装好，后面有关于socket函数的，可直接用

/* wrap.h */
#ifndef __WRAP_H_
#define __WRAP_H_

void perr_exit(const char *s);
int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr);
int Bind(int fd, const struct sockaddr *sa, socklen_t salen);
int Connect(int fd, const struct sockaddr *sa, socklen_t salen);
int Listen(int fd, int backlog);
int Socket(int family, int type, int protocol);
ssize_t Read(int fd, void *ptr, size_t nbytes);
ssize_t Write(int fd, const void *ptr, size_t nbytes);
int Close(int fd);
ssize_t Readn(int fd, void *vptr, size_t n);
ssize_t Writen(int fd, const void *vptr, size_t n);
ssize_t my_read(int fd, char *ptr);
ssize_t Readline(int fd, void *vptr, size_t maxlen);

#endif

/* wrap.c */
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>

void perr_exit(const char *s)
{
	perror(s);
	exit(-1);
}

int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr)
{
	int n;

again:
	if ((n = accept(fd, sa, salenptr)) < 0) {
		if ((errno == ECONNABORTED) || (errno == EINTR))
			goto again;
		else
			perr_exit("accept error");
	}
	return n;
}

int Bind(int fd, const struct sockaddr *sa, socklen_t salen)
{
    int n;

	if ((n = bind(fd, sa, salen)) < 0)
		perr_exit("bind error");

    return n;
}

int Connect(int fd, const struct sockaddr *sa, socklen_t salen)
{
    int n;
    n = connect(fd, sa, salen);
	if (n < 0) {
		perr_exit("connect error");
    }

    return n;
}

int Listen(int fd, int backlog)
{
    int n;

	if ((n = listen(fd, backlog)) < 0)
		perr_exit("listen error");

    return n;
}

int Socket(int family, int type, int protocol)
{
	int n;

	if ((n = socket(family, type, protocol)) < 0)
		perr_exit("socket error");

	return n;
}

ssize_t Read(int fd, void *ptr, size_t nbytes)
{
	ssize_t n;

again:
	if ( (n = read(fd, ptr, nbytes)) == -1) {
		if (errno == EINTR)
			goto again;
		else
			return -1;
	}

	return n;
}

ssize_t Write(int fd, const void *ptr, size_t nbytes)
{
	ssize_t n;

again:
	if ((n = write(fd, ptr, nbytes)) == -1) {
		if (errno == EINTR)
			goto again;
		else
			return -1;
	}
	return n;
}

int Close(int fd)
{
    int n;
	if ((n = close(fd)) == -1)
		perr_exit("close error");

    return n;
}

/*参三: 应该读取的字节数*/                          //socket 4096  readn(cfd, buf, 4096)   nleft = 4096-1500
ssize_t Readn(int fd, void *vptr, size_t n)
{
	size_t  nleft;              //usigned int 剩余未读取的字节数
	ssize_t nread;              //int 实际读到的字节数
	char   *ptr;

	ptr = vptr;
	nleft = n;                  //n 未读取字节数

	while (nleft > 0) {
		if ((nread = read(fd, ptr, nleft)) < 0) {
			if (errno == EINTR)
				nread = 0;
			else
				return -1;
		} else if (nread == 0)
			break;

		nleft -= nread;   //nleft = nleft - nread 
		ptr += nread;
	}
	return n - nleft;
}

ssize_t Writen(int fd, const void *vptr, size_t n)
{
	size_t nleft;
	ssize_t nwritten;
	const char *ptr;

	ptr = vptr;
	nleft = n;
	while (nleft > 0) {
		if ( (nwritten = write(fd, ptr, nleft)) <= 0) {
			if (nwritten < 0 && errno == EINTR)
				nwritten = 0;
			else
				return -1;
		}
		nleft -= nwritten;
		ptr += nwritten;
	}
	return n;
}

static ssize_t my_read(int fd, char *ptr)
{
	static int read_cnt;
	static char *read_ptr;
	static char read_buf[100];

	if (read_cnt <= 0) {
again:
		if ( (read_cnt = read(fd, read_buf, sizeof(read_buf))) < 0) {   //"hello\n"
			if (errno == EINTR)
				goto again;
			return -1;
		} else if (read_cnt == 0)
			return 0;

		read_ptr = read_buf;
	}
	read_cnt--;
	*ptr = *read_ptr++;

	return 1;
}

/*readline --- fgets*/    
//传出参数 vptr
ssize_t Readline(int fd, void *vptr, size_t maxlen)
{
	ssize_t n, rc;
	char    c, *ptr;
	ptr = vptr;

	for (n = 1; n < maxlen; n++) {
		if ((rc = my_read(fd, &c)) == 1) {   //ptr[] = hello\n
			*ptr++ = c;
			if (c == '\n')
				break;
		} else if (rc == 0) {
			*ptr = 0;
			return n-1;
		} else
			return -1;
	}
	*ptr = 0;

	return n;
}

/* server.c */
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <strings.h>
#include <string.h>
#include <ctype.h>
#include <arpa/inet.h>

#include "wrap.h"

#define SERV_PORT 6666

int main(void)
{
    int sfd, cfd;
    int len, i;
    char buf[BUFSIZ], clie_IP[BUFSIZ];

    struct sockaddr_in serv_addr, clie_addr;
    socklen_t clie_addr_len;

    sfd = Socket(AF_INET, SOCK_STREAM, 0);

    int opt = 1;
    setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

    bzero(&serv_addr, sizeof(serv_addr));           
    serv_addr.sin_family = AF_INET;                 
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);  
    serv_addr.sin_port = htons(SERV_PORT);          

    Bind(sfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr));

    Listen(sfd, 2);                                

    printf("wait for client connect ...\n");

    clie_addr_len = sizeof(clie_addr_len);
    cfd = Accept(sfd, (struct sockaddr *)&clie_addr, &clie_addr_len);
    printf("cfd = ----%d\n", cfd);

    printf("client IP: %s  port:%d\n", 
            inet_ntop(AF_INET, &clie_addr.sin_addr.s_addr, clie_IP, sizeof(clie_IP)), 
            ntohs(clie_addr.sin_port));

    while (1) {
        len = Read(cfd, buf, sizeof(buf));
        Write(STDOUT_FILENO, buf, len);

        for (i = 0; i < len; i++)
            buf[i] = toupper(buf[i]);
        Write(cfd, buf, len); 
    }

    Close(sfd);
    Close(cfd);

    return 0;
}

/* client.c */
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>

#include "wrap.h"

#define SERV_IP "127.0.0.1"
#define SERV_PORT 6666

int main(void)
{
    int sfd, len;
    struct sockaddr_in serv_addr;
    char buf[BUFSIZ]; 

    sfd = Socket(AF_INET, SOCK_STREAM, 0);

    bzero(&serv_addr, sizeof(serv_addr));                       
    serv_addr.sin_family = AF_INET;                             
    inet_pton(AF_INET, SERV_IP, &serv_addr.sin_addr.s_addr);    
    serv_addr.sin_port = htons(SERV_PORT);                      

    Connect(sfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr));

    while (1) {
        fgets(buf, sizeof(buf), stdin);
        int r = Write(sfd, buf, strlen(buf));       
        printf("Write r ======== %d\n", r);
        len = Read(sfd, buf, sizeof(buf));
        printf("Read len ========= %d\n", len);
        Write(STDOUT_FILENO, buf, len);
    }

    Close(sfd);

    return 0;
}