/* * __getpwent.c - This file is part of the libc-8086/pwd package for ELKS, * Copyright (C) 1995, 1996 Nat Friedman <ndf@linux.mit.edu>. *  *  This library is free software; you can redistribute it and/or *  modify it under the terms of the GNU Library General Public *  License as published by the Free Software Foundation; either *  version 2 of the License, or (at your option) any later version. * *  This library is distributed in the hope that it will be useful, *  but WITHOUT ANY WARRANTY; without even the implied warranty of *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU *  Library General Public License for more details. * *  You should have received a copy of the GNU Library General Public *  License along with this library; if not, write to the Free *  Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * */#include <stdlib.h>#include <unistd.h>#include <string.h>#include <fcntl.h>#include "pwd.h"#define PWD_BUFFER_SIZE 256/* This isn't as flash as my previous version -- it doesn't dynamically  scale down the gecos on too-long lines, but it also makes fewer syscalls,  so it's probably nicer.  Write me if you want the old version.  Maybe I  should include it as a build-time option... ?  -Nat <ndf@linux.mit.edu> */struct passwd *__getpwent(int pwd_fd){	static char line_buff[PWD_BUFFER_SIZE];	static struct passwd passwd;	char *field_begin;	char *endptr;	char *gid_ptr=NULL;	char *uid_ptr=NULL;	int line_len;	int i;	/* We use the restart label to handle malformatted lines */  restart:	/* Read the passwd line into the static buffer using a minimal of	   syscalls. */	if ((line_len = read(pwd_fd, line_buff, PWD_BUFFER_SIZE)) <= 0)		return NULL;	field_begin = strchr(line_buff, '\n');	if (field_begin != NULL)		lseek(pwd_fd, (long) (1 + field_begin - (line_buff + line_len)),			  SEEK_CUR);	else {						/* The line is too long - skip it. :-\ */		do {			if ((line_len = read(pwd_fd, line_buff, PWD_BUFFER_SIZE)) <= 0)				return NULL;		} while (!(field_begin = strchr(line_buff, '\n')));		lseek(pwd_fd, (long) (field_begin - line_buff) - line_len + 1,			  SEEK_CUR);		goto restart;	}	if (*line_buff == '#' || *line_buff == ' ' || *line_buff == '\n' ||		*line_buff == '\t')		goto restart;	*field_begin = '\0';	/* We've read the line; now parse it. */	field_begin = line_buff;	for (i = 0; i < 7; i++) {		switch (i) {		case 0:			passwd.pw_name = field_begin;			break;		case 1:			passwd.pw_passwd = field_begin;			break;		case 2:			uid_ptr = field_begin;			break;		case 3:			gid_ptr = field_begin;			break;		case 4:			passwd.pw_gecos = field_begin;			break;		case 5:			passwd.pw_dir = field_begin;			break;		case 6:			passwd.pw_shell = field_begin;			break;		}		if (i < 6) {			field_begin = strchr(field_begin, ':');			if (field_begin == NULL)				goto restart;			*field_begin++ = '\0';		}	}	passwd.pw_gid = (gid_t) strtoul(gid_ptr, &endptr, 10);	if (*endptr != '\0')		goto restart;	passwd.pw_uid = (uid_t) strtoul(uid_ptr, &endptr, 10);	if (*endptr != '\0')		goto restart;	return &passwd;}