getttyent.c

它通过提供glibc兼容使得应用程序移植到较小的c 库时相当得容易. 它能够应用到带虚拟存储的Linux和uClinux上.在大多数带MMU部件的平台上为使它更加紧凑,它也能够编译成共享库.uClib

/*
 * Copyright (c) 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#define _GNU_SOURCE
#include <features.h>
#include <ttyent.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <ctype.h>
#include <string.h>

static char zapchar;
static FILE *tf;
static struct ttyent tty;


struct ttyent * getttynam(const char *tty)
{
    register struct ttyent *t;

    setttyent();
    while ((t = getttyent()))
	if (!strcmp(tty, t->ty_name))
	    break;
    endttyent();
    return (t);
}


/* Skip over the current field, removing quotes, and return 
 * a pointer to the next field.
 */
#define	QUOTED	1
static char * skip(register char *p)
{
    register char *t;
    register int c, q;

    for (q = 0, t = p; (c = *p) != '\0'; p++) {
	if (c == '"') {
	    q ^= QUOTED;	/* obscure, but nice */
	    continue;
	}
	if (q == QUOTED && *p == '\\' && *(p+1) == '"')
	    p++;
	*t++ = *p;
	if (q == QUOTED)
	    continue;
	if (c == '#') {
	    zapchar = c;
	    *p = 0;
	    break;
	}
	if (c == '\t' || c == ' ' || c == '\n') {
	    zapchar = c;
	    *p++ = 0;
	    while ((c = *p) == '\t' || c == ' ' || c == '\n')
		p++;
	    break;
	}
    }
    *--t = '\0';
    return (p);
}

static char * value(register char *p)
{

    return ((p = index(p, '=')) ? ++p : NULL);
}

struct ttyent * getttyent(void)
{
    register int c;
    register char *p;
    static char line[BUFSIZ];

    if (!tf && !setttyent())
	return (NULL);
    flockfile (tf);
    for (;;) {
	if (!fgets_unlocked(p = line, sizeof(line), tf)) {
	    funlockfile (tf);
	    return (NULL);
	}
	/* skip lines that are too big */
	if (!index(p, '\n')) {
	    while ((c = getc_unlocked(tf)) != '\n' && c != EOF)
		;
	    continue;
	}
	while (isspace(*p))
	    ++p;
	if (*p && *p != '#')
	    break;
    }

    zapchar = 0;
    tty.ty_name = p;
    p = skip(p);
    if (!*(tty.ty_getty = p))
	tty.ty_getty = tty.ty_type = NULL;
    else {
	p = skip(p);
	if (!*(tty.ty_type = p))
	    tty.ty_type = NULL;
	else
	    p = skip(p);
    }
    tty.ty_status = 0;
    tty.ty_window = NULL;

#define	scmp(e)	!strncmp(p, e, sizeof(e) - 1) && isspace(p[sizeof(e) - 1])
#define	vcmp(e)	!strncmp(p, e, sizeof(e) - 1) && p[sizeof(e) - 1] == '='
    for (; *p; p = skip(p)) {
	if (scmp(_TTYS_OFF))
	    tty.ty_status &= ~TTY_ON;
	else if (scmp(_TTYS_ON))
	    tty.ty_status |= TTY_ON;
	else if (scmp(_TTYS_SECURE))
	    tty.ty_status |= TTY_SECURE;
	else if (vcmp(_TTYS_WINDOW))
	    tty.ty_window = value(p);
	else
	    break;
    }
    /* We can release the lock only here since `zapchar' is global.  */
    funlockfile(tf);

    if (zapchar == '#' || *p == '#')
	while ((c = *++p) == ' ' || c == '\t')
	    ;
    tty.ty_comment = p;
    if (*p == 0)
	tty.ty_comment = 0;
    if ((p = index(p, '\n')))
	*p = '\0';
    return (&tty);
}

int setttyent(void)
{

    if (tf) {
	rewind(tf);
	return (1);
    } else if ((tf = fopen(_PATH_TTYS, "r"))) {
	/* We do the locking ourselves.  */
#ifdef __UCLIBC_HAS_THREADS__
	__fsetlocking (tf, FSETLOCKING_BYCALLER);
#endif
	return (1);
    }
    return (0);
}

int endttyent(void)
{
    int rval;

    if (tf) {
	rval = !(fclose(tf) == EOF);
	tf = NULL;
	return (rval);
    }
    return (1);
}