2 * Copyright (c) 1998-2010 Luigi Rizzo, Universita` di Pisa
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28 * Binary heap and hash tables, header file
36 #define DN_KEY_LT(a,b) ((int64_t)((a)-(b)) < 0)
37 #define DN_KEY_LEQ(a,b) ((int64_t)((a)-(b)) <= 0)
40 * This module implements a binary heap supporting random extraction.
42 * A heap entry contains an uint64_t key and a pointer to object.
43 * DN_KEY_LT(a,b) returns true if key 'a' is smaller than 'b'
45 * The heap is a struct dn_heap plus a dynamically allocated
46 * array of dn_heap_entry entries. 'size' represents the size of
47 * the array, 'elements' count entries in use. The topmost
48 * element has the smallest key.
49 * The heap supports ordered insert, and extract from the top.
50 * To extract an object from the middle of the heap, we the object
51 * must reserve an 'int32_t' to store the position of the object
52 * in the heap itself, and the location of this field must be
53 * passed as an argument to heap_init() -- use -1 if the feature
56 struct dn_heap_entry {
57 uint64_t key; /* sorting key, smallest comes first */
58 void *object; /* object pointer */
62 int size; /* the size of the array */
63 int elements; /* elements in use */
64 int ofs; /* offset in the object of heap index */
65 struct dn_heap_entry *p; /* array of "size" entries */
74 * heap_init() reinitializes the heap setting the size and the offset
75 * of the index for random extraction (use -1 if not used).
76 * The 'elements' counter is set to 0.
78 * SET_HEAP_OFS() indicates where, in the object, is stored the index
79 * for random extractions from the heap.
81 * heap_free() frees the memory associated to a heap.
83 * heap_insert() adds a key-pointer pair to the heap
85 * HEAP_TOP() returns a pointer to the top element of the heap,
86 * but makes no checks on its existence (XXX should we change ?)
88 * heap_extract() removes the entry at the top, returing the pointer.
89 * (the key should have been read before).
91 * heap_scan() invokes a callback on each entry of the heap.
92 * The callback can return a combination of HEAP_SCAN_DEL and
93 * HEAP_SCAN_END. HEAP_SCAN_DEL means the current element must
94 * be removed, and HEAP_SCAN_END means to terminate the scan.
95 * heap_scan() returns the number of elements removed.
96 * Because the order is not guaranteed, we should use heap_scan()
97 * only as a last resort mechanism.
99 #define HEAP_TOP(h) ((h)->p)
100 #define SET_HEAP_OFS(h, n) do { (h)->ofs = n; } while (0)
101 int heap_init(struct dn_heap *h, int size, int ofs);
102 int heap_insert(struct dn_heap *h, uint64_t key1, void *p);
103 void heap_extract(struct dn_heap *h, void *obj);
104 void heap_free(struct dn_heap *h);
105 int heap_scan(struct dn_heap *, int (*)(void *, uintptr_t), uintptr_t);
107 /*------------------------------------------------------
108 * This module implements a generic hash table with support for
109 * running callbacks on the entire table. To avoid allocating
110 * memory during hash table operations, objects must reserve
111 * space for a link field. XXX if the heap is moderately full,
112 * an SLIST suffices, and we can tolerate the cost of a hash
113 * computation on each removal.
115 * dn_ht_init() initializes the table, setting the number of
116 * buckets, the offset of the link field, the main callbacks.
119 * hash(key, flags, arg) called to return a bucket index.
120 * match(obj, key, flags, arg) called to determine if key
121 * matches the current 'obj' in the heap
122 * newh(key, flags, arg) optional, used to allocate a new
123 * object during insertions.
125 * dn_ht_free() frees the heap or unlink elements.
126 * DNHT_REMOVE unlink elements, 0 frees the heap.
127 * You need two calls to do both.
129 * dn_ht_find() is the main lookup function, which can also be
130 * used to insert or delete elements in the hash table.
131 * The final 'arg' is passed to all callbacks.
133 * dn_ht_scan() is used to invoke a callback on all entries of
134 * the heap, or possibly on just one bucket. The callback
135 * is invoked with a pointer to the object, and must return
136 * one of DNHT_SCAN_DEL or DNHT_SCAN_END to request the
137 * removal of the object from the heap and the end of the
138 * scan, respectively.
140 * dn_ht_scan_bucket() is similar to dn_ht_scan(), except that it scans
141 * only the specific bucket of the table. The bucket is a in-out
142 * parameter and return a valid bucket number if the original
145 * A combination of flags can be used to modify the operation
146 * of the dn_ht_find(), and of the callbacks:
148 * DNHT_KEY_IS_OBJ means the key is the object pointer.
149 * It is usually of interest for the hash and match functions.
151 * DNHT_MATCH_PTR during a lookup, match pointers instead
152 * of calling match(). Normally used when removing specific
153 * entries. Does not imply KEY_IS_OBJ as the latter _is_ used
154 * by the match function.
156 * DNHT_INSERT insert the element if not found.
157 * Calls new() to allocates a new object unless
158 * DNHT_KEY_IS_OBJ is set.
160 * DNHT_UNIQUE only insert if object not found.
161 * XXX should it imply DNHT_INSERT ?
163 * DNHT_REMOVE remove objects if we find them.
165 struct dn_ht; /* should be opaque */
167 struct dn_ht *dn_ht_init(struct dn_ht *, int buckets, int ofs,
168 uint32_t (*hash)(uintptr_t, int, void *),
169 int (*match)(void *, uintptr_t, int, void *),
170 void *(*newh)(uintptr_t, int, void *));
171 void dn_ht_free(struct dn_ht *, int flags);
173 void *dn_ht_find(struct dn_ht *, uintptr_t, int, void *);
174 int dn_ht_scan(struct dn_ht *, int (*)(void *, void *), void *);
175 int dn_ht_scan_bucket(struct dn_ht *, int * , int (*)(void *, void *), void *);
176 int dn_ht_entries(struct dn_ht *);
178 enum { /* flags values.
179 * first two are returned by the scan callback to indicate
180 * to delete the matching element or to end the scan
182 DNHT_SCAN_DEL = 0x0001,
183 DNHT_SCAN_END = 0x0002,
184 DNHT_KEY_IS_OBJ = 0x0004, /* key is the obj pointer */
185 DNHT_MATCH_PTR = 0x0008, /* match by pointer, not match() */
186 DNHT_INSERT = 0x0010, /* insert if not found */
187 DNHT_UNIQUE = 0x0020, /* report error if already there */
188 DNHT_REMOVE = 0x0040, /* remove on find or dn_ht_free */
191 #endif /* _IP_DN_HEAP_H */