util.c

unix环境高级编程第二版配套源代码 unix环境高级编程第二版配套源代码

#include "apue.h"
#include "print.h"
#include <ctype.h>
#include <sys/select.h>

#define MAXCFGLINE 512
#define MAXKWLEN   16
#define MAXFMTLEN  16

/*
 * Get the address list for the given host and service and
 * return through ailistpp.  Returns 0 on success or an error
 * code on failure.  Note that we do not set errno if we
 * encounter an error.
 *
 * LOCKING: none.
 */
int
getaddrlist(const char *host, const char *service,
  struct addrinfo **ailistpp)
{
	int				err;
	struct addrinfo	hint;

	hint.ai_flags = AI_CANONNAME;
	hint.ai_family = AF_INET;
	hint.ai_socktype = SOCK_STREAM;
	hint.ai_protocol = 0;
	hint.ai_addrlen = 0;
	hint.ai_canonname = NULL;
	hint.ai_addr = NULL;
	hint.ai_next = NULL;
	err = getaddrinfo(host, service, &hint, ailistpp);
	return(err);
}

/*
 * Given a keyword, scan the configuration file for a match
 * and return the string value corresponding to the keyword.
 *
 * LOCKING: none.
 */
static char *
scan_configfile(char *keyword)
{
	int				n, match;
	FILE			*fp;
	char			keybuf[MAXKWLEN], pattern[MAXFMTLEN];
	char			line[MAXCFGLINE];
	static char		valbuf[MAXCFGLINE];

	if ((fp = fopen(CONFIG_FILE, "r")) == NULL)
		log_sys("can't open %s", CONFIG_FILE);
	sprintf(pattern, "%%%ds %%%ds", MAXKWLEN-1, MAXCFGLINE-1);
	match = 0;
	while (fgets(line, MAXCFGLINE, fp) != NULL) {
		n = sscanf(line, pattern, keybuf, valbuf);
		if (n == 2 && strcmp(keyword, keybuf) == 0) {
			match = 1;
			break;
		}
	}
	fclose(fp);
	if (match != 0)
		return(valbuf);
	else
		return(NULL);
}

/*
 * Return the host name running the print server or NULL on error.
 *
 * LOCKING: none.
 */
char *
get_printserver(void)
{
	return(scan_configfile("printserver"));
}

/*
 * Return the address of the network printer or NULL on error.
 *
 * LOCKING: none.
 */
struct addrinfo *
get_printaddr(void)
{
	int				err;
	char			*p;
	struct addrinfo	*ailist;

	if ((p = scan_configfile("printer")) != NULL) {
		if ((err = getaddrlist(p, "ipp", &ailist)) != 0) {
			log_msg("no address information for %s", p);
			return(NULL);
		}
		return(ailist);
	}
	log_msg("no printer address specified");
	return(NULL);
}

/*
 * "Timed" read - timout specifies the # of seconds to wait before
 * giving up (5th argument to select controls how long to wait for
 * data to be readable).  Returns # of bytes read or -1 on error.
 *
 * LOCKING: none.
 */
ssize_t
tread(int fd, void *buf, size_t nbytes, unsigned int timout)
{
	int				nfds;
	fd_set			readfds;
	struct timeval	tv;

	tv.tv_sec = timout;
	tv.tv_usec = 0;
	FD_ZERO(&readfds);
	FD_SET(fd, &readfds);
	nfds = select(fd+1, &readfds, NULL, NULL, &tv);
	if (nfds <= 0) {
		if (nfds == 0)
			errno = ETIME;
		return(-1);
	}
	return(read(fd, buf, nbytes));
}

/*
 * "Timed" read - timout specifies the number of seconds to wait
 * per read call before giving up, but read exactly nbytes bytes.
 * Returns number of bytes read or -1 on error.
 *
 * LOCKING: none.
 */
ssize_t
treadn(int fd, void *buf, size_t nbytes, unsigned int timout)
{
	size_t	nleft;
	ssize_t	nread;

	nleft = nbytes;
	while (nleft > 0) {
		if ((nread = tread(fd, buf, nleft, timout)) < 0) {
			if (nleft == nbytes)
				return(-1); /* error, return -1 */
			else
				break;      /* error, return amount read so far */
		} else if (nread == 0) {
			break;          /* EOF */
		}
		nleft -= nread;
		buf += nread;
	}
	return(nbytes - nleft);      /* return >= 0 */
}