3 * Copyright (C) 1997 Kaz Kylheku <kaz@ashi.footprints.net>
5 * Free Software License:
7 * All rights are reserved by the author, with the following exceptions:
8 * Permission is granted to freely reproduce and distribute this software,
9 * possibly in exchange for a fee, provided that this copyright notice appears
10 * intact. Permission is also granted to adapt this software to produce
11 * derivative works, as long as the modified versions carry this copyright
12 * notice and additional notices stating that the work has been modified.
13 * This source code may be translated into executable form and incorporated
14 * into proprietary software; there is no requirement for such software to
15 * contain a copyright notice related to this source.
17 * $Id: hash.h,v 1.2 2009-11-19 10:37:44 franklahm Exp $
27 typedef unsigned long hashcount_t;
28 #define HASHCOUNT_T_MAX ULONG_MAX
30 typedef uint32_t hash_val_t;
31 #define HASH_VAL_T_MAX UINT32_MAX
33 extern int hash_val_t_bit;
35 #ifndef HASH_VAL_T_BIT
36 #define HASH_VAL_T_BIT ((int) hash_val_t_bit)
40 * Hash chain node structure.
42 * 1. This preprocessing directive is for debugging purposes. The effect is
43 * that if the preprocessor symbol KAZLIB_OPAQUE_DEBUG is defined prior to the
44 * inclusion of this header, then the structure shall be declared as having
45 * the single member int __OPAQUE__. This way, any attempts by the
46 * client code to violate the principles of information hiding (by accessing
47 * the structure directly) can be diagnosed at translation time. However,
48 * note the resulting compiled unit is not suitable for linking.
49 * 2. This is a pointer to the next node in the chain. In the last node of a
50 * chain, this pointer is null.
51 * 3. The key is a pointer to some user supplied data that contains a unique
52 * identifier for each hash node in a given table. The interpretation of
53 * the data is up to the user. When creating or initializing a hash table,
54 * the user must supply a pointer to a function for comparing two keys,
55 * and a pointer to a function for hashing a key into a numeric value.
56 * 4. The value is a user-supplied pointer to void which may refer to
57 * any data object. It is not interpreted in any way by the hashing
59 * 5. The hashed key is stored in each node so that we don't have to rehash
60 * each key when the table must grow or shrink.
63 typedef struct hnode_t {
64 #if defined(HASH_IMPLEMENTATION) || !defined(KAZLIB_OPAQUE_DEBUG) /* 1 */
65 struct hnode_t *hash_next; /* 2 */
66 const void *hash_key; /* 3 */
67 void *hash_data; /* 4 */
68 hash_val_t hash_hkey; /* 5 */
75 * The comparison function pointer type. A comparison function takes two keys
76 * and produces a value of -1 if the left key is less than the right key, a
77 * value of 0 if the keys are equal, and a value of 1 if the left key is
78 * greater than the right key.
81 typedef int (*hash_comp_t)(const void *, const void *);
84 * The hashing function performs some computation on a key and produces an
85 * integral value of type hash_val_t based on that key. For best results, the
86 * function should have a good randomness properties in *all* significant bits
87 * over the set of keys that are being inserted into a given hash table. In
88 * particular, the most significant bits of hash_val_t are most significant to
89 * the hash module. Only as the hash table expands are less significant bits
90 * examined. Thus a function that has good distribution in its upper bits but
91 * not lower is preferrable to one that has poor distribution in the upper bits
92 * but not the lower ones.
95 typedef hash_val_t (*hash_fun_t)(const void *);
101 typedef hnode_t *(*hnode_alloc_t)(void *);
102 typedef void (*hnode_free_t)(hnode_t *, void *);
105 * This is the hash table control structure. It keeps track of information
106 * about a hash table, as well as the hash table itself.
108 * 1. Pointer to the hash table proper. The table is an array of pointers to
109 * hash nodes (of type hnode_t). If the table is empty, every element of
110 * this table is a null pointer. A non-null entry points to the first
111 * element of a chain of nodes.
112 * 2. This member keeps track of the size of the hash table---that is, the
113 * number of chain pointers.
114 * 3. The count member maintains the number of elements that are presently
116 * 4. The maximum count is the greatest number of nodes that can populate this
117 * table. If the table contains this many nodes, no more can be inserted,
118 * and the hash_isfull() function returns true.
119 * 5. The high mark is a population threshold, measured as a number of nodes,
120 * which, if exceeded, will trigger a table expansion. Only dynamic hash
121 * tables are subject to this expansion.
122 * 6. The low mark is a minimum population threshold, measured as a number of
123 * nodes. If the table population drops below this value, a table shrinkage
124 * will occur. Only dynamic tables are subject to this reduction. No table
125 * will shrink beneath a certain absolute minimum number of nodes.
126 * 7. This is the a pointer to the hash table's comparison function. The
127 * function is set once at initialization or creation time.
128 * 8. Pointer to the table's hashing function, set once at creation or
129 * initialization time.
130 * 9. The current hash table mask. If the size of the hash table is 2^N,
131 * this value has its low N bits set to 1, and the others clear. It is used
132 * to select bits from the result of the hashing function to compute an
133 * index into the table.
134 * 10. A flag which indicates whether the table is to be dynamically resized. It
135 * is set to 1 in dynamically allocated tables, 0 in tables that are
136 * statically allocated.
139 typedef struct hash_t {
140 #if defined(HASH_IMPLEMENTATION) || !defined(KAZLIB_OPAQUE_DEBUG)
141 struct hnode_t **hash_table; /* 1 */
142 hashcount_t hash_nchains; /* 2 */
143 hashcount_t hash_nodecount; /* 3 */
144 hashcount_t hash_maxcount; /* 4 */
145 hashcount_t hash_highmark; /* 5 */
146 hashcount_t hash_lowmark; /* 6 */
147 hash_comp_t hash_compare; /* 7 */
148 hash_fun_t hash_function; /* 8 */
149 hnode_alloc_t hash_allocnode;
150 hnode_free_t hash_freenode;
152 hash_val_t hash_mask; /* 9 */
153 int hash_dynamic; /* 10 */
160 * Hash scanner structure, used for traversals of the data structure.
162 * 1. Pointer to the hash table that is being traversed.
163 * 2. Reference to the current chain in the table being traversed (the chain
164 * that contains the next node that shall be retrieved).
165 * 3. Pointer to the node that will be retrieved by the subsequent call to
169 typedef struct hscan_t {
170 #if defined(HASH_IMPLEMENTATION) || !defined(KAZLIB_OPAQUE_DEBUG)
171 hash_t *hash_table; /* 1 */
172 hash_val_t hash_chain; /* 2 */
173 hnode_t *hash_next; /* 3 */
180 #endif /* ATALK_HASH_H */