/* idcache.c -- map user and group IDs, cached for speed   Copyright (C) 1985, 1988, 1989, 1990, 1997, 1998 Free Software   Foundation, Inc.   This program is free software; you can redistribute it and/or modify   it under the terms of the GNU General Public License as published by   the Free Software Foundation; either version 2, or (at your option)   any later version.   This program 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 General Public License for more details.   You should have received a copy of the GNU General Public License   along with this program; if not, write to the Free Software Foundation,   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */#if HAVE_CONFIG_H# include <config.h>#endif#include <stdio.h>#include <sys/types.h>#include <pwd.h>#include <grp.h>#if STDC_HEADERS || HAVE_STRING_H# include <string.h>#else# include <strings.h>#endif#if HAVE_UNISTD_H# include <unistd.h>#endif#ifndef _POSIX_VERSIONstruct passwd *getpwuid ();struct passwd *getpwnam ();struct group *getgrgid ();struct group *getgrnam ();#endifchar *xmalloc ();char *xstrdup ();#ifdef __DJGPP__static char digits[] = "0123456789";#endifstruct userid{  union    {      uid_t u;      gid_t g;    } id;  char *name;  struct userid *next;};static struct userid *user_alist;/* The members of this list have names not in the local passwd file.  */static struct userid *nouser_alist;/* Translate UID to a login name, with cache, or NULL if unresolved.  */char *getuser (uid_t uid){  register struct userid *tail;  struct passwd *pwent;  for (tail = user_alist; tail; tail = tail->next)    if (tail->id.u == uid)      return tail->name;  pwent = getpwuid (uid);  tail = (struct userid *) xmalloc (sizeof (struct userid));  tail->id.u = uid;  tail->name = pwent ? xstrdup (pwent->pw_name) : NULL;  /* Add to the head of the list, so most recently used is first.  */  tail->next = user_alist;  user_alist = tail;  return tail->name;}/* Translate USER to a UID, with cache.   Return NULL if there is no such user.   (We also cache which user names have no passwd entry,   so we don't keep looking them up.)  */uid_t *getuidbyname (const char *user){  register struct userid *tail;  struct passwd *pwent;  for (tail = user_alist; tail; tail = tail->next)    /* Avoid a function call for the most common case.  */    if (*tail->name == *user && !strcmp (tail->name, user))      return &tail->id.u;  for (tail = nouser_alist; tail; tail = tail->next)    /* Avoid a function call for the most common case.  */    if (*tail->name == *user && !strcmp (tail->name, user))      return 0;  pwent = getpwnam (user);#ifdef __DJGPP__  /* We need to pretend to be the user USER, to make     pwd functions know about an arbitrary user name.  */  if (!pwent && strspn (user, digits) < strlen (user))    {      setenv ("USER", user, 1);      pwent = getpwnam (user);	/* now it will succeed */    }#endif  tail = (struct userid *) xmalloc (sizeof (struct userid));  tail->name = xstrdup (user);  /* Add to the head of the list, so most recently used is first.  */  if (pwent)    {      tail->id.u = pwent->pw_uid;      tail->next = user_alist;      user_alist = tail;      return &tail->id.u;    }  tail->next = nouser_alist;  nouser_alist = tail;  return 0;}/* Use the same struct as for userids.  */static struct userid *group_alist;static struct userid *nogroup_alist;/* Translate GID to a group name, with cache, or NULL if unresolved.  */char *getgroup (gid_t gid){  register struct userid *tail;  struct group *grent;  for (tail = group_alist; tail; tail = tail->next)    if (tail->id.g == gid)      return tail->name;  grent = getgrgid (gid);  tail = (struct userid *) xmalloc (sizeof (struct userid));  tail->id.g = gid;  tail->name = grent ? xstrdup (grent->gr_name) : NULL;  /* Add to the head of the list, so most recently used is first.  */  tail->next = group_alist;  group_alist = tail;  return tail->name;}/* Translate GROUP to a GID, with cache.   Return NULL if there is no such group.   (We also cache which group names have no group entry,   so we don't keep looking them up.)  */gid_t *getgidbyname (const char *group){  register struct userid *tail;  struct group *grent;  for (tail = group_alist; tail; tail = tail->next)    /* Avoid a function call for the most common case.  */    if (*tail->name == *group && !strcmp (tail->name, group))      return &tail->id.g;  for (tail = nogroup_alist; tail; tail = tail->next)    /* Avoid a function call for the most common case.  */    if (*tail->name == *group && !strcmp (tail->name, group))      return 0;  grent = getgrnam (group);#ifdef __DJGPP__  /* We need to pretend to belong to group GROUP, to make     grp functions know about any arbitrary group name.  */  if (!grent && strspn (group, digits) < strlen (group))    {      setenv ("GROUP", group, 1);      grent = getgrnam (group);	/* now it will succeed */    }#endif  tail = (struct userid *) xmalloc (sizeof (struct userid));  tail->name = xstrdup (group);  /* Add to the head of the list, so most recently used is first.  */  if (grent)    {      tail->id.g = grent->gr_gid;      tail->next = group_alist;      group_alist = tail;      return &tail->id.g;    }  tail->next = nogroup_alist;  nogroup_alist = tail;  return 0;}