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git.ipfire.org Git - thirdparty/squid.git/blob - lib/hash.cc
5 * DEBUG: section 00 Hash Tables
6 * AUTHOR: Harvest Derived
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38 #include "profiler/Profiler.h"
53 #include <gnumalloc.h>
64 static void hash_next_bucket(hash_table
* hid
);
67 hash_string(const void *data
, unsigned int size
)
69 const unsigned char *s
= static_cast<const unsigned char *>(data
);
81 /* the following function(s) were adapted from
82 * usr/src/lib/libc/db/hash_func.c, 4.4 BSD lite */
84 /* Hash function from Chris Torek. */
86 hash4(const void *data
, unsigned int size
)
88 const char *key
= static_cast<const char *>(data
);
93 #define HASH4a h = (h << 5) - h + *key++;
94 #define HASH4b h = (h << 5) + h + *key++;
100 switch (len
& (8 - 1)) {
138 * hash_create - creates a new hash table, uses the cmp_func
139 * to compare keys. Returns the identification for the hash table;
140 * otherwise returns a negative number on error.
143 hash_create(HASHCMP
* cmp_func
, int hash_sz
, HASHHASH
* hash_func
)
145 hash_table
*hid
= (hash_table
*)xcalloc(1, sizeof(hash_table
));
147 hid
->size
= (unsigned int) DEFAULT_HASH_SIZE
;
149 hid
->size
= (unsigned int) hash_sz
;
150 /* allocate and null the buckets */
151 hid
->buckets
= (hash_link
**)xcalloc(hid
->size
, sizeof(hash_link
*));
153 hid
->hash
= hash_func
;
155 hid
->current_slot
= 0;
160 * hash_join - joins a hash_link under its key lnk->key
161 * into the hash table 'hid'.
163 * It does not copy any data into the hash table, only links pointers.
166 hash_join(hash_table
* hid
, hash_link
* lnk
)
169 i
= hid
->hash(lnk
->key
, hid
->size
);
170 lnk
->next
= hid
->buckets
[i
];
171 hid
->buckets
[i
] = lnk
;
176 * hash_lookup - locates the item under the key 'k' in the hash table
177 * 'hid'. Returns a pointer to the hash bucket on success; otherwise
181 hash_lookup(hash_table
* hid
, const void *k
)
184 PROF_start(hash_lookup
);
186 b
= hid
->hash(k
, hid
->size
);
187 for (hash_link
*walker
= hid
->buckets
[b
]; walker
!= NULL
; walker
= walker
->next
) {
188 if ((hid
->cmp
) (k
, walker
->key
) == 0) {
189 PROF_stop(hash_lookup
);
192 assert(walker
!= walker
->next
);
194 PROF_stop(hash_lookup
);
199 hash_next_bucket(hash_table
* hid
)
201 while (hid
->next
== NULL
&& ++hid
->current_slot
< hid
->size
)
202 hid
->next
= hid
->buckets
[hid
->current_slot
];
206 * hash_first - initializes the hash table for the hash_next()
210 hash_first(hash_table
* hid
)
212 assert(NULL
== hid
->next
);
213 hid
->current_slot
= 0;
214 hid
->next
= hid
->buckets
[hid
->current_slot
];
215 if (NULL
== hid
->next
)
216 hash_next_bucket(hid
);
220 * hash_next - returns the next item in the hash table 'hid'.
221 * Otherwise, returns NULL on error or end of list.
223 * MUST call hash_first() before hash_next().
226 hash_next(hash_table
* hid
)
228 hash_link
*p
= hid
->next
;
232 if (NULL
== hid
->next
)
233 hash_next_bucket(hid
);
238 * hash_last - resets hash traversal state to NULL
242 hash_last(hash_table
* hid
)
246 hid
->current_slot
= 0;
250 * hash_remove_link - deletes the given hash_link node from the
251 * hash table 'hid'. Does not free the item, only removes it
254 * An assertion is triggered if the hash_link is not found in the
258 hash_remove_link(hash_table
* hid
, hash_link
* hl
)
261 int i
= hid
->hash(hl
->key
, hid
->size
);
262 for (hash_link
**P
= &hid
->buckets
[i
]; *P
; P
= &(*P
)->next
) {
266 if (hid
->next
== hl
) {
267 hid
->next
= hl
->next
;
268 if (NULL
== hid
->next
)
269 hash_next_bucket(hid
);
278 * hash_get_bucket - returns the head item of the bucket
279 * in the hash table 'hid'. Otherwise, returns NULL on error.
282 hash_get_bucket(hash_table
* hid
, unsigned int bucket
)
284 if (bucket
>= hid
->size
)
286 return (hid
->buckets
[bucket
]);
290 hashFreeItems(hash_table
* hid
, HASHFREE
* free_func
)
294 hash_link
**list
= (hash_link
**)xcalloc(hid
->count
, sizeof(hash_link
*));
296 while ((l
= hash_next(hid
)) && i
< hid
->count
) {
300 for (int j
= 0; j
< i
; j
++)
301 free_func(*(list
+ j
));
306 hashFreeMemory(hash_table
* hid
)
315 static int hash_primes
[] = {
333 int I
= sizeof(hash_primes
) / sizeof(int);
334 int best_prime
= hash_primes
[0];
335 double min
= fabs(log((double) n
) - log((double) hash_primes
[0]));
337 for (int i
= 0; i
< I
; i
++) {
338 d
= fabs(log((double) n
) - log((double) hash_primes
[i
]));
342 best_prime
= hash_primes
[i
];
348 * return the key of a hash_link as a const string
351 hashKeyStr(hash_link
* hl
)
353 return (const char *) hl
->key
;
359 * hash-driver - Run with a big file as stdin to insert each line into the
360 * hash table, then prints the whole hash table, then deletes a random item,
361 * and prints the table again...
367 LOCAL_ARRAY(char, buf
, BUFSIZ
);
368 LOCAL_ARRAY(char, todelete
, BUFSIZ
);
369 hash_link
*walker
= NULL
;
374 printf("creating hash table\n");
375 if ((hid
= hash_create((HASHCMP
*) strcmp
, 229, hash4
)) < 0) {
376 printf("hash_create error.\n");
379 printf("done creating hash table: %d\n", hid
);
381 while (fgets(buf
, BUFSIZ
, stdin
)) {
382 buf
[strlen(buf
) - 1] = '\0';
383 printf("Inserting '%s' for item %p to hash table: %d\n",
385 hash_insert(hid
, xstrdup(buf
), (void *) 0x12345678);
386 if (random() % 17 == 0)
387 strcpy(todelete
, buf
);
390 printf("walking hash table...\n");
391 for (int i
= 0, walker
= hash_first(hid
); walker
; walker
= hash_next(hid
)) {
392 printf("item %5d: key: '%s' item: %p\n", i
++, walker
->key
,
395 printf("done walking hash table...\n");
398 printf("deleting %s from %d\n", todelete
, hid
);
399 if (hash_delete(hid
, todelete
))
400 printf("hash_delete error\n");
402 printf("walking hash table...\n");
403 for (int i
= 0, walker
= hash_first(hid
); walker
; walker
= hash_next(hid
)) {
404 printf("item %5d: key: '%s' item: %p\n", i
++, walker
->key
,
407 printf("done walking hash table...\n");
410 printf("driver finished.\n");