compilers/linux86-0.16.17/libc/getent/__getpwent.c

   1 /*
   2  * __getpwent.c - This file is part of the libc-8086/pwd package for ELKS,
   3  * Copyright (C) 1995, 1996 Nat Friedman <ndf@linux.mit.edu>.
   4  *
   5  *  This library is free software; you can redistribute it and/or
   6  *  modify it under the terms of the GNU Library General Public
   7  *  License as published by the Free Software Foundation; either
   8  *  version 2 of the License, or (at your option) any later version.
   9  *
  10  *  This library is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  *  Library General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU Library General Public
  16  *  License along with this library; if not, write to the Free
  17  *  Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18  *
  19  */
  20
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include <string.h>
  24 #include <fcntl.h>
  25 #include <pwd.h>
  26
  27 #define PWD_BUFFER_SIZE 256
  28
  29 /* This isn't as flash as my previous version -- it doesn't dynamically
  30   scale down the gecos on too-long lines, but it also makes fewer syscalls,
  31   so it's probably nicer.  Write me if you want the old version.  Maybe I
  32   should include it as a build-time option... ?
  33   -Nat <ndf@linux.mit.edu> */
  34
  35 struct passwd *
  36 __getpwent(int pwd_fd)
  37 {
  38   static char line_buff[PWD_BUFFER_SIZE];
  39   static struct passwd passwd;
  40   char * field_begin;
  41   char * endptr;
  42   char * gid_ptr;
  43   char * uid_ptr;
  44   int line_len;
  45   int i;
  46
  47   /* We use the restart label to handle malformatted lines */
  48 restart:
  49   /* Read the passwd line into the static buffer using a minimal of
  50      syscalls. */
  51   if ((line_len=read(pwd_fd, line_buff, PWD_BUFFER_SIZE))<=0)
  52     return NULL;
  53   field_begin=strchr(line_buff, '\n');
  54   if (field_begin!=NULL)
  55     lseek(pwd_fd, (long) (1+field_begin-(line_buff+line_len)), SEEK_CUR);
  56   else /* The line is too long - skip it. :-\ */
  57     {
  58       do { if ((line_len=read(pwd_fd, line_buff, PWD_BUFFER_SIZE))<=0)
  59         return NULL;
  60       } while (!(field_begin=strchr(line_buff, '\n')));
  61       lseek(pwd_fd, (long) (field_begin-line_buff)-line_len+1, SEEK_CUR);
  62       goto restart;
  63     }
  64   if (*line_buff=='#' || *line_buff==' ' || *line_buff=='\n' ||
  65       *line_buff=='\t')
  66       goto restart;
  67   *field_begin='\0';
  68
  69   /* We've read the line; now parse it. */
  70   field_begin=line_buff;
  71   for (i=0;i<7;i++)
  72     {
  73       switch(i)
  74         {
  75         case 0: passwd.pw_name=field_begin; break;
  76         case 1: passwd.pw_passwd=field_begin; break;
  77         case 2: uid_ptr=field_begin; break;
  78         case 3: gid_ptr=field_begin; break;
  79         case 4: passwd.pw_gecos=field_begin; break;
  80         case 5: passwd.pw_dir=field_begin; break;
  81         case 6: passwd.pw_shell=field_begin; break;
  82         }
  83       if (i<6)
  84         {
  85           field_begin=strchr(field_begin, ':');
  86           if (field_begin==NULL) goto restart;
  87           *field_begin++='\0';
  88         }
  89     }
  90   passwd.pw_gid=(gid_t) strtoul(gid_ptr, &endptr, 10);
  91   if (*endptr!='\0') goto restart;
  92
  93   passwd.pw_uid=(uid_t) strtoul(uid_ptr, &endptr, 10);
  94   if (*endptr!='\0') goto restart;
  95
  96   return &passwd;
  97 }
  98
  99