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/*
* Top users/processes display for Unix
* Version 3
*
* This program may be freely redistributed,
* but this entire comment MUST remain intact.
*
* Copyright (c) 1984, 1989, William LeFebvre, Rice University
* Copyright (c) 1989, 1990, 1992, William LeFebvre, Northwestern University
*/
/*
* Username translation code for top.
*
* These routines handle uid to username mapping.
* They use a hashing table scheme to reduce reading overhead.
* For the time being, these are very straightforward hashing routines.
* Maybe someday I'll put in something better. But with the advent of
* "random access" password files, it might not be worth the effort.
*
* Changes to these have been provided by John Gilmore (gnu@toad.com).
*
* The hash has been simplified in this release, to avoid the
* table overflow problems of previous releases. If the value
* at the initial hash location is not right, it is replaced
* by the right value. Collisions will cause us to call getpw*
* but hey, this is a cache, not the Library of Congress.
* This makes the table size independent of the passwd file size.
*/
#include "os.h"
#include <pwd.h>
#include "pg_top.h"
#include "utils.h"
struct hash_el
{
int uid;
char name[9];
};
#define is_empty_hash(x) (hash_table[x].name[0] == 0)
/* simple minded hashing function */
/* Uid "nobody" is -2 results in hashit(-2) = -2 which is out of bounds for
the hash_table. Applied abs() function to fix. 2/16/96 tpugh
*/
#define hashit(i) (abs(i) % Table_size)
/* K&R requires that statically declared tables be initialized to zero. */
/* We depend on that for hash_table and YOUR compiler had BETTER do it! */
struct hash_el hash_table[Table_size];
void
init_hash()
{
/*
* There used to be some steps we had to take to initialize things. We
* don't need to do that anymore, but we will leave this stub in just in
* case future changes require initialization steps.
*/
}
int
enter_user(int uid, char *name, int wecare)
{
register int hashindex;
#ifdef DEBUG
dprintf("enter_hash(%d, %s, %d)\n", uid, name, wecare);
#endif
hashindex = hashit(uid);
if (!is_empty_hash(hashindex))
{
if (!wecare)
return 0; /* Don't clobber a slot for trash */
if (hash_table[hashindex].uid == uid)
return (hashindex); /* Fortuitous find */
}
/* empty or wrong slot -- fill it with new value */
hash_table[hashindex].uid = uid;
(void) strncpy(hash_table[hashindex].name, name, 8);
return (hashindex);
}
/*
* Get a userid->name mapping from the system.
* If the passwd database is hashed (#define RANDOM_PW), we
* just handle this uid. Otherwise we scan the passwd file
* and cache any entries we pass over while looking.
*/
int
get_user(int uid)
{
struct passwd *pwd;
#ifdef RANDOM_PW
/* no performance penalty for using getpwuid makes it easy */
if ((pwd = getpwuid(uid)) != NULL)
{
return (enter_user(pwd->pw_uid, pwd->pw_name, 1));
}
#else
int from_start = 0;
/*
* If we just called getpwuid each time, things would be very slow since
* that just iterates through the passwd file each time. So, we walk
* through the file instead (using getpwent) and cache each entry as we
* go. Once the right record is found, we cache it and return
* immediately. The next time we come in, getpwent will get the next
* record. In theory, we never have to read the passwd file a second time
* (because we cache everything we read). But in practice, the cache may
* not be large enough, so if we don't find it the first time we have to
* scan the file a second time. This is not very efficient, but it will
* do for now.
*/
while (from_start++ < 2)
{
while ((pwd = getpwent()) != NULL)
{
if (pwd->pw_uid == uid)
{
return (enter_user(pwd->pw_uid, pwd->pw_name, 1));
}
(void) enter_user(pwd->pw_uid, pwd->pw_name, 0);
}
/* try again */
setpwent();
}
#endif
/* if we can't find the name at all, then use the uid as the name */
return (enter_user(uid, itoa7(uid), 1));
}
char *
username(uid_t uid)
{
register int hashindex;
hashindex = hashit(uid);
if (is_empty_hash(hashindex) || (hash_table[hashindex].uid != uid))
{
/* not here or not right -- get it out of passwd */
hashindex = get_user(uid);
}
return (hash_table[hashindex].name);
}
int
userid(char *username)
{
struct passwd *pwd;
/*
* Eventually we want this to enter everything in the hash table, but for
* now we just do it simply and remember just the result.
*/
if ((pwd = getpwnam(username)) == NULL)
{
return (-1);
}
/* enter the result in the hash table */
enter_user(pwd->pw_uid, username, 1);
/* return our result */
return (pwd->pw_uid);
}
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