1  /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
2  
3  /*
4   * Generic non-thread safe hash map implementation.
5   *
6   * Copyright (c) 2019 Facebook
7   */
8  #ifndef __LIBBPF_HASHMAP_H
9  #define __LIBBPF_HASHMAP_H
10  
11  #include <stdbool.h>
12  #include <stddef.h>
13  #include <limits.h>
14  
hash_bits(size_t h,int bits)15  static inline size_t hash_bits(size_t h, int bits)
16  {
17  	/* shuffle bits and return requested number of upper bits */
18  	if (bits == 0)
19  		return 0;
20  
21  #if (__SIZEOF_SIZE_T__ == __SIZEOF_LONG_LONG__)
22  	/* LP64 case */
23  	return (h * 11400714819323198485llu) >> (__SIZEOF_LONG_LONG__ * 8 - bits);
24  #elif (__SIZEOF_SIZE_T__ <= __SIZEOF_LONG__)
25  	return (h * 2654435769lu) >> (__SIZEOF_LONG__ * 8 - bits);
26  #else
27  #	error "Unsupported size_t size"
28  #endif
29  }
30  
31  /* generic C-string hashing function */
str_hash(const char * s)32  static inline size_t str_hash(const char *s)
33  {
34  	size_t h = 0;
35  
36  	while (*s) {
37  		h = h * 31 + *s;
38  		s++;
39  	}
40  	return h;
41  }
42  
43  typedef size_t (*hashmap_hash_fn)(long key, void *ctx);
44  typedef bool (*hashmap_equal_fn)(long key1, long key2, void *ctx);
45  
46  /*
47   * Hashmap interface is polymorphic, keys and values could be either
48   * long-sized integers or pointers, this is achieved as follows:
49   * - interface functions that operate on keys and values are hidden
50   *   behind auxiliary macros, e.g. hashmap_insert <-> hashmap__insert;
51   * - these auxiliary macros cast the key and value parameters as
52   *   long or long *, so the user does not have to specify the casts explicitly;
53   * - for pointer parameters (e.g. old_key) the size of the pointed
54   *   type is verified by hashmap_cast_ptr using _Static_assert;
55   * - when iterating using hashmap__for_each_* forms
56   *   hasmap_entry->key should be used for integer keys and
57   *   hasmap_entry->pkey should be used for pointer keys,
58   *   same goes for values.
59   */
60  struct hashmap_entry {
61  	union {
62  		long key;
63  		const void *pkey;
64  	};
65  	union {
66  		long value;
67  		void *pvalue;
68  	};
69  	struct hashmap_entry *next;
70  };
71  
72  struct hashmap {
73  	hashmap_hash_fn hash_fn;
74  	hashmap_equal_fn equal_fn;
75  	void *ctx;
76  
77  	struct hashmap_entry **buckets;
78  	size_t cap;
79  	size_t cap_bits;
80  	size_t sz;
81  };
82  
83  void hashmap__init(struct hashmap *map, hashmap_hash_fn hash_fn,
84  		   hashmap_equal_fn equal_fn, void *ctx);
85  struct hashmap *hashmap__new(hashmap_hash_fn hash_fn,
86  			     hashmap_equal_fn equal_fn,
87  			     void *ctx);
88  void hashmap__clear(struct hashmap *map);
89  void hashmap__free(struct hashmap *map);
90  
91  size_t hashmap__size(const struct hashmap *map);
92  size_t hashmap__capacity(const struct hashmap *map);
93  
94  /*
95   * Hashmap insertion strategy:
96   * - HASHMAP_ADD - only add key/value if key doesn't exist yet;
97   * - HASHMAP_SET - add key/value pair if key doesn't exist yet; otherwise,
98   *   update value;
99   * - HASHMAP_UPDATE - update value, if key already exists; otherwise, do
100   *   nothing and return -ENOENT;
101   * - HASHMAP_APPEND - always add key/value pair, even if key already exists.
102   *   This turns hashmap into a multimap by allowing multiple values to be
103   *   associated with the same key. Most useful read API for such hashmap is
104   *   hashmap__for_each_key_entry() iteration. If hashmap__find() is still
105   *   used, it will return last inserted key/value entry (first in a bucket
106   *   chain).
107   */
108  enum hashmap_insert_strategy {
109  	HASHMAP_ADD,
110  	HASHMAP_SET,
111  	HASHMAP_UPDATE,
112  	HASHMAP_APPEND,
113  };
114  
115  #define hashmap_cast_ptr(p) ({								\
116  	_Static_assert((__builtin_constant_p((p)) ? (p) == NULL : 0) ||			\
117  				sizeof(*(p)) == sizeof(long),				\
118  		       #p " pointee should be a long-sized integer or a pointer");	\
119  	(long *)(p);									\
120  })
121  
122  /*
123   * hashmap__insert() adds key/value entry w/ various semantics, depending on
124   * provided strategy value. If a given key/value pair replaced already
125   * existing key/value pair, both old key and old value will be returned
126   * through old_key and old_value to allow calling code do proper memory
127   * management.
128   */
129  int hashmap_insert(struct hashmap *map, long key, long value,
130  		   enum hashmap_insert_strategy strategy,
131  		   long *old_key, long *old_value);
132  
133  #define hashmap__insert(map, key, value, strategy, old_key, old_value) \
134  	hashmap_insert((map), (long)(key), (long)(value), (strategy),  \
135  		       hashmap_cast_ptr(old_key),		       \
136  		       hashmap_cast_ptr(old_value))
137  
138  #define hashmap__add(map, key, value) \
139  	hashmap__insert((map), (key), (value), HASHMAP_ADD, NULL, NULL)
140  
141  #define hashmap__set(map, key, value, old_key, old_value) \
142  	hashmap__insert((map), (key), (value), HASHMAP_SET, (old_key), (old_value))
143  
144  #define hashmap__update(map, key, value, old_key, old_value) \
145  	hashmap__insert((map), (key), (value), HASHMAP_UPDATE, (old_key), (old_value))
146  
147  #define hashmap__append(map, key, value) \
148  	hashmap__insert((map), (key), (value), HASHMAP_APPEND, NULL, NULL)
149  
150  bool hashmap_delete(struct hashmap *map, long key, long *old_key, long *old_value);
151  
152  #define hashmap__delete(map, key, old_key, old_value)		       \
153  	hashmap_delete((map), (long)(key),			       \
154  		       hashmap_cast_ptr(old_key),		       \
155  		       hashmap_cast_ptr(old_value))
156  
157  bool hashmap_find(const struct hashmap *map, long key, long *value);
158  
159  #define hashmap__find(map, key, value) \
160  	hashmap_find((map), (long)(key), hashmap_cast_ptr(value))
161  
162  /*
163   * hashmap__for_each_entry - iterate over all entries in hashmap
164   * @map: hashmap to iterate
165   * @cur: struct hashmap_entry * used as a loop cursor
166   * @bkt: integer used as a bucket loop cursor
167   */
168  #define hashmap__for_each_entry(map, cur, bkt)				    \
169  	for (bkt = 0; bkt < map->cap; bkt++)				    \
170  		for (cur = map->buckets[bkt]; cur; cur = cur->next)
171  
172  /*
173   * hashmap__for_each_entry_safe - iterate over all entries in hashmap, safe
174   * against removals
175   * @map: hashmap to iterate
176   * @cur: struct hashmap_entry * used as a loop cursor
177   * @tmp: struct hashmap_entry * used as a temporary next cursor storage
178   * @bkt: integer used as a bucket loop cursor
179   */
180  #define hashmap__for_each_entry_safe(map, cur, tmp, bkt)		    \
181  	for (bkt = 0; bkt < map->cap; bkt++)				    \
182  		for (cur = map->buckets[bkt];				    \
183  		     cur && ({tmp = cur->next; true; });		    \
184  		     cur = tmp)
185  
186  /*
187   * hashmap__for_each_key_entry - iterate over entries associated with given key
188   * @map: hashmap to iterate
189   * @cur: struct hashmap_entry * used as a loop cursor
190   * @key: key to iterate entries for
191   */
192  #define hashmap__for_each_key_entry(map, cur, _key)			    \
193  	for (cur = map->buckets						    \
194  		     ? map->buckets[hash_bits(map->hash_fn((_key), map->ctx), map->cap_bits)] \
195  		     : NULL;						    \
196  	     cur;							    \
197  	     cur = cur->next)						    \
198  		if (map->equal_fn(cur->key, (_key), map->ctx))
199  
200  #define hashmap__for_each_key_entry_safe(map, cur, tmp, _key)		    \
201  	for (cur = map->buckets						    \
202  		     ? map->buckets[hash_bits(map->hash_fn((_key), map->ctx), map->cap_bits)] \
203  		     : NULL;						    \
204  	     cur && ({ tmp = cur->next; true; });			    \
205  	     cur = tmp)							    \
206  		if (map->equal_fn(cur->key, (_key), map->ctx))
207  
208  #endif /* __LIBBPF_HASHMAP_H */
209