1 /*
2  * SHL - Dynamic hash-table
3  *
4  * Written-by: Rusty Russell <rusty@rustcorp.com.au>
5  * Adjusted-by: David Herrmann <dh.herrmann@gmail.com>
6  * Licensed under LGPLv2+ - see LICENSE_htable file for details
7  */
8 
9 /*
10  * Please see ccan/htable/_info at:
11  *   https://github.com/rustyrussell/ccan/tree/master/ccan/htable
12  * for information on the hashtable algorithm. This file copies the code inline
13  * and is released under the same conditions.
14  *
15  * At the end of the file you can find some helpers to use this htable to store
16  * objects with "unsigned long" or "char*" keys.
17  */
18 
19 #include <assert.h>
20 #include <errno.h>
21 #include <limits.h>
22 #include <stdbool.h>
23 #include <stdint.h>
24 #include <stdlib.h>
25 #include <string.h>
26 #include "shl_htable.h"
27 
28 #define COLD __attribute__((cold))
29 
30 struct htable {
31 	/* KEEP IN SYNC WITH "struct shl_htable_int" */
32 	size_t (*rehash)(const void *elem, void *priv);
33 	void *priv;
34 	unsigned int bits;
35 	size_t elems, deleted, max, max_with_deleted;
36 	/* These are the bits which are the same in all pointers. */
37 	uintptr_t common_mask, common_bits;
38 	uintptr_t perfect_bit;
39 	uintptr_t *table;
40 };
41 
42 #define HTABLE_INITIALIZER(name, rehash, priv)				\
43 	{ rehash, priv, 0, 0, 0, 0, 0, -1, 0, 0, &name.perfect_bit }
44 
45 struct htable_iter {
46 	size_t off;
47 };
48 
49 /*
50  * INLINE COPY OF ccan/htable.c
51  */
52 
53 /* We use 0x1 as deleted marker. */
54 #define HTABLE_DELETED (0x1)
55 
56 /* We clear out the bits which are always the same, and put metadata there. */
get_extra_ptr_bits(const struct htable * ht,uintptr_t e)57 static inline uintptr_t get_extra_ptr_bits(const struct htable *ht,
58 					   uintptr_t e)
59 {
60 	return e & ht->common_mask;
61 }
62 
get_raw_ptr(const struct htable * ht,uintptr_t e)63 static inline void *get_raw_ptr(const struct htable *ht, uintptr_t e)
64 {
65 	return (void *)((e & ~ht->common_mask) | ht->common_bits);
66 }
67 
make_hval(const struct htable * ht,const void * p,uintptr_t bits)68 static inline uintptr_t make_hval(const struct htable *ht,
69 				  const void *p, uintptr_t bits)
70 {
71 	return ((uintptr_t)p & ~ht->common_mask) | bits;
72 }
73 
entry_is_valid(uintptr_t e)74 static inline bool entry_is_valid(uintptr_t e)
75 {
76 	return e > HTABLE_DELETED;
77 }
78 
get_hash_ptr_bits(const struct htable * ht,size_t hash)79 static inline uintptr_t get_hash_ptr_bits(const struct htable *ht,
80 					  size_t hash)
81 {
82 	/* Shuffling the extra bits (as specified in mask) down the
83 	 * end is quite expensive.  But the lower bits are redundant, so
84 	 * we fold the value first. */
85 	return (hash ^ (hash >> ht->bits))
86 		& ht->common_mask & ~ht->perfect_bit;
87 }
88 
htable_init(struct htable * ht,size_t (* rehash)(const void * elem,void * priv),void * priv)89 static void htable_init(struct htable *ht,
90 			size_t (*rehash)(const void *elem, void *priv),
91 			void *priv)
92 {
93 	struct htable empty = HTABLE_INITIALIZER(empty, NULL, NULL);
94 	*ht = empty;
95 	ht->rehash = rehash;
96 	ht->priv = priv;
97 	ht->table = &ht->perfect_bit;
98 }
99 
htable_clear(struct htable * ht,void (* free_cb)(void * entry,void * ctx),void * ctx)100 static void htable_clear(struct htable *ht,
101 			 void (*free_cb) (void *entry, void *ctx),
102 			 void *ctx)
103 {
104 	size_t i;
105 
106 	if (ht->table != &ht->perfect_bit) {
107 		if (free_cb) {
108 			for (i = 0; i < (size_t)1 << ht->bits; ++i) {
109 				if (entry_is_valid(ht->table[i]))
110 					free_cb(get_raw_ptr(ht, ht->table[i]),
111 						ctx);
112 			}
113 		}
114 
115 		free((void *)ht->table);
116 	}
117 
118 	htable_init(ht, ht->rehash, ht->priv);
119 }
120 
htable_visit(struct htable * ht,void (* visit_cb)(void * elem,void * ctx),void * ctx)121 static void htable_visit(struct htable *ht,
122 			 void (*visit_cb) (void *elem, void *ctx),
123 			 void *ctx)
124 {
125 	size_t i;
126 
127 	if (visit_cb && ht->table != &ht->perfect_bit) {
128 		for (i = 0; i < (size_t)1 << ht->bits; ++i) {
129 			if (entry_is_valid(ht->table[i]))
130 				visit_cb(get_raw_ptr(ht, ht->table[i]), ctx);
131 		}
132 	}
133 }
134 
hash_bucket(const struct htable * ht,size_t h)135 static size_t hash_bucket(const struct htable *ht, size_t h)
136 {
137 	return h & ((1 << ht->bits)-1);
138 }
139 
htable_val(const struct htable * ht,struct htable_iter * i,size_t hash,uintptr_t perfect)140 static void *htable_val(const struct htable *ht,
141 			struct htable_iter *i, size_t hash, uintptr_t perfect)
142 {
143 	uintptr_t h2 = get_hash_ptr_bits(ht, hash) | perfect;
144 
145 	while (ht->table[i->off]) {
146 		if (ht->table[i->off] != HTABLE_DELETED) {
147 			if (get_extra_ptr_bits(ht, ht->table[i->off]) == h2)
148 				return get_raw_ptr(ht, ht->table[i->off]);
149 		}
150 		i->off = (i->off + 1) & ((1 << ht->bits)-1);
151 		h2 &= ~perfect;
152 	}
153 	return NULL;
154 }
155 
htable_firstval(const struct htable * ht,struct htable_iter * i,size_t hash)156 static void *htable_firstval(const struct htable *ht,
157 			     struct htable_iter *i, size_t hash)
158 {
159 	i->off = hash_bucket(ht, hash);
160 	return htable_val(ht, i, hash, ht->perfect_bit);
161 }
162 
htable_nextval(const struct htable * ht,struct htable_iter * i,size_t hash)163 static void *htable_nextval(const struct htable *ht,
164 			    struct htable_iter *i, size_t hash)
165 {
166 	i->off = (i->off + 1) & ((1 << ht->bits)-1);
167 	return htable_val(ht, i, hash, 0);
168 }
169 
170 /* This does not expand the hash table, that's up to caller. */
ht_add(struct htable * ht,const void * new,size_t h)171 static void ht_add(struct htable *ht, const void *new, size_t h)
172 {
173 	size_t i;
174 	uintptr_t perfect = ht->perfect_bit;
175 
176 	i = hash_bucket(ht, h);
177 
178 	while (entry_is_valid(ht->table[i])) {
179 		perfect = 0;
180 		i = (i + 1) & ((1 << ht->bits)-1);
181 	}
182 	ht->table[i] = make_hval(ht, new, get_hash_ptr_bits(ht, h)|perfect);
183 }
184 
double_table(struct htable * ht)185 static COLD bool double_table(struct htable *ht)
186 {
187 	unsigned int i;
188 	size_t oldnum = (size_t)1 << ht->bits;
189 	uintptr_t *oldtable, e;
190 
191 	oldtable = ht->table;
192 	ht->table = calloc(1 << (ht->bits+1), sizeof(size_t));
193 	if (!ht->table) {
194 		ht->table = oldtable;
195 		return false;
196 	}
197 	ht->bits++;
198 	ht->max = ((size_t)3 << ht->bits) / 4;
199 	ht->max_with_deleted = ((size_t)9 << ht->bits) / 10;
200 
201 	/* If we lost our "perfect bit", get it back now. */
202 	if (!ht->perfect_bit && ht->common_mask) {
203 		for (i = 0; i < sizeof(ht->common_mask) * CHAR_BIT; i++) {
204 			if (ht->common_mask & ((size_t)1 << i)) {
205 				ht->perfect_bit = (size_t)1 << i;
206 				break;
207 			}
208 		}
209 	}
210 
211 	if (oldtable != &ht->perfect_bit) {
212 		for (i = 0; i < oldnum; i++) {
213 			if (entry_is_valid(e = oldtable[i])) {
214 				void *p = get_raw_ptr(ht, e);
215 				ht_add(ht, p, ht->rehash(p, ht->priv));
216 			}
217 		}
218 		free(oldtable);
219 	}
220 	ht->deleted = 0;
221 	return true;
222 }
223 
rehash_table(struct htable * ht)224 static COLD void rehash_table(struct htable *ht)
225 {
226 	size_t start, i;
227 	uintptr_t e;
228 
229 	/* Beware wrap cases: we need to start from first empty bucket. */
230 	for (start = 0; ht->table[start]; start++);
231 
232 	for (i = 0; i < (size_t)1 << ht->bits; i++) {
233 		size_t h = (i + start) & ((1 << ht->bits)-1);
234 		e = ht->table[h];
235 		if (!e)
236 			continue;
237 		if (e == HTABLE_DELETED)
238 			ht->table[h] = 0;
239 		else if (!(e & ht->perfect_bit)) {
240 			void *p = get_raw_ptr(ht, e);
241 			ht->table[h] = 0;
242 			ht_add(ht, p, ht->rehash(p, ht->priv));
243 		}
244 	}
245 	ht->deleted = 0;
246 }
247 
248 /* We stole some bits, now we need to put them back... */
update_common(struct htable * ht,const void * p)249 static COLD void update_common(struct htable *ht, const void *p)
250 {
251 	unsigned int i;
252 	uintptr_t maskdiff, bitsdiff;
253 
254 	if (ht->elems == 0) {
255 		/* Always reveal one bit of the pointer in the bucket,
256 		 * so it's not zero or HTABLE_DELETED (1), even if
257 		 * hash happens to be 0.  Assumes (void *)1 is not a
258 		 * valid pointer. */
259 		for (i = sizeof(uintptr_t)*CHAR_BIT - 1; i > 0; i--) {
260 			if ((uintptr_t)p & ((uintptr_t)1 << i))
261 				break;
262 		}
263 
264 		ht->common_mask = ~((uintptr_t)1 << i);
265 		ht->common_bits = ((uintptr_t)p & ht->common_mask);
266 		ht->perfect_bit = 1;
267 		return;
268 	}
269 
270 	/* Find bits which are unequal to old common set. */
271 	maskdiff = ht->common_bits ^ ((uintptr_t)p & ht->common_mask);
272 
273 	/* These are the bits which go there in existing entries. */
274 	bitsdiff = ht->common_bits & maskdiff;
275 
276 	for (i = 0; i < (size_t)1 << ht->bits; i++) {
277 		if (!entry_is_valid(ht->table[i]))
278 			continue;
279 		/* Clear the bits no longer in the mask, set them as
280 		 * expected. */
281 		ht->table[i] &= ~maskdiff;
282 		ht->table[i] |= bitsdiff;
283 	}
284 
285 	/* Take away those bits from our mask, bits and perfect bit. */
286 	ht->common_mask &= ~maskdiff;
287 	ht->common_bits &= ~maskdiff;
288 	ht->perfect_bit &= ~maskdiff;
289 }
290 
htable_add(struct htable * ht,size_t hash,const void * p)291 static bool htable_add(struct htable *ht, size_t hash, const void *p)
292 {
293 	if (ht->elems+1 > ht->max && !double_table(ht))
294 		return false;
295 	if (ht->elems+1 + ht->deleted > ht->max_with_deleted)
296 		rehash_table(ht);
297 	assert(p);
298 	if (((uintptr_t)p & ht->common_mask) != ht->common_bits)
299 		update_common(ht, p);
300 
301 	ht_add(ht, p, hash);
302 	ht->elems++;
303 	return true;
304 }
305 
htable_delval(struct htable * ht,struct htable_iter * i)306 static void htable_delval(struct htable *ht, struct htable_iter *i)
307 {
308 	assert(i->off < (size_t)1 << ht->bits);
309 	assert(entry_is_valid(ht->table[i->off]));
310 
311 	ht->elems--;
312 	ht->table[i->off] = HTABLE_DELETED;
313 	ht->deleted++;
314 }
315 
316 /*
317  * Wrapper code to make it easier to use this hash-table as map.
318  */
319 
shl_htable_init(struct shl_htable * htable,bool (* compare)(const void * a,const void * b),size_t (* rehash)(const void * elem,void * priv),void * priv)320 void shl_htable_init(struct shl_htable *htable,
321 		     bool (*compare) (const void *a, const void *b),
322 		     size_t (*rehash)(const void *elem, void *priv),
323 		     void *priv)
324 {
325 	struct htable *ht = (void*)&htable->htable;
326 
327 	htable->compare = compare;
328 	htable_init(ht, rehash, priv);
329 }
330 
shl_htable_clear(struct shl_htable * htable,void (* free_cb)(void * elem,void * ctx),void * ctx)331 void shl_htable_clear(struct shl_htable *htable,
332 		      void (*free_cb) (void *elem, void *ctx),
333 		      void *ctx)
334 {
335 	struct htable *ht = (void*)&htable->htable;
336 
337 	htable_clear(ht, free_cb, ctx);
338 }
339 
shl_htable_visit(struct shl_htable * htable,void (* visit_cb)(void * elem,void * ctx),void * ctx)340 void shl_htable_visit(struct shl_htable *htable,
341 		      void (*visit_cb) (void *elem, void *ctx),
342 		      void *ctx)
343 {
344 	struct htable *ht = (void*)&htable->htable;
345 
346 	htable_visit(ht, visit_cb, ctx);
347 }
348 
shl_htable_lookup(struct shl_htable * htable,const void * obj,size_t hash,void ** out)349 bool shl_htable_lookup(struct shl_htable *htable, const void *obj, size_t hash,
350 		       void **out)
351 {
352 	struct htable *ht = (void*)&htable->htable;
353 	struct htable_iter i;
354 	void *c;
355 
356 	for (c = htable_firstval(ht, &i, hash);
357 	     c;
358 	     c = htable_nextval(ht, &i, hash)) {
359 		if (htable->compare(obj, c)) {
360 			if (out)
361 				*out = c;
362 			return true;
363 		}
364 	}
365 
366 	return false;
367 }
368 
shl_htable_insert(struct shl_htable * htable,const void * obj,size_t hash)369 int shl_htable_insert(struct shl_htable *htable, const void *obj, size_t hash)
370 {
371 	struct htable *ht = (void*)&htable->htable;
372 	bool b;
373 
374 	b = htable_add(ht, hash, (void*)obj);
375 	return b ? 0 : -ENOMEM;
376 }
377 
shl_htable_remove(struct shl_htable * htable,const void * obj,size_t hash,void ** out)378 bool shl_htable_remove(struct shl_htable *htable, const void *obj, size_t hash,
379 		       void **out)
380 {
381 	struct htable *ht = (void*)&htable->htable;
382 	struct htable_iter i;
383 	void *c;
384 
385 	for (c = htable_firstval(ht, &i, hash);
386 	     c;
387 	     c = htable_nextval(ht, &i, hash)) {
388 		if (htable->compare(obj, c)) {
389 			if (out)
390 				*out = c;
391 			htable_delval(ht, &i);
392 			return true;
393 		}
394 	}
395 
396 	return false;
397 }
398 
399 /*
400  * Helpers
401  */
402 
shl_htable_compare_ulong(const void * a,const void * b)403 bool shl_htable_compare_ulong(const void *a, const void *b)
404 {
405 	return *(const unsigned long*)a == *(const unsigned long*)b;
406 }
407 
shl_htable_rehash_ulong(const void * elem,void * priv)408 size_t shl_htable_rehash_ulong(const void *elem, void *priv)
409 {
410 	return (size_t)*(const unsigned long*)elem;
411 }
412 
shl_htable_compare_str(const void * a,const void * b)413 bool shl_htable_compare_str(const void *a, const void *b)
414 {
415 	return !strcmp(*(char**)a, *(char**)b);
416 }
417 
418 /* DJB's hash function */
shl_htable_rehash_str(const void * elem,void * priv)419 size_t shl_htable_rehash_str(const void *elem, void *priv)
420 {
421 	const char *str = *(char**)elem;
422 	size_t hash = 5381;
423 
424 	for ( ; *str; ++str)
425 		hash = (hash << 5) + hash + (size_t)*str;
426 
427 	return hash;
428 }
429