1 #ifndef SQL_HSET_INCLUDED
2 #define SQL_HSET_INCLUDED
3 /* Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
4 
5    This program is free software; you can redistribute it and/or modify
6    it under the terms of the GNU General Public License, version 2.0,
7    as published by the Free Software Foundation.
8 
9    This program is also distributed with certain software (including
10    but not limited to OpenSSL) that is licensed under separate terms,
11    as designated in a particular file or component or in included license
12    documentation.  The authors of MySQL hereby grant you an additional
13    permission to link the program and your derivative works with the
14    separately licensed software that they have included with MySQL.
15 
16    This program is distributed in the hope that it will be useful,
17    but WITHOUT ANY WARRANTY; without even the implied warranty of
18    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
19    GNU General Public License, version 2.0, for more details.
20 
21    You should have received a copy of the GNU General Public License
22    along with this program; if not, write to the Free Software
23    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */
24 
25 #include "my_global.h"
26 #include "hash.h"
27 
28 
29 /**
30   A type-safe wrapper around mysys HASH.
31 */
32 
33 template <typename T, my_hash_get_key K>
34 class Hash_set
35 {
36 public:
37   typedef T Value_type;
38   enum { START_SIZE= 8 };
39   /**
40     Constructs an empty hash. Does not allocate memory, it is done upon
41     the first insert. Thus does not cause or return errors.
42   */
Hash_set()43   Hash_set()
44   {
45     my_hash_clear(&m_hash);
46   }
47   /**
48     Destroy the hash by freeing the buckets table. Does
49     not call destructors for the elements.
50   */
~Hash_set()51   ~Hash_set()
52   {
53     my_hash_free(&m_hash);
54   }
55   /**
56     Insert a single value into a hash. Does not tell whether
57     the value was inserted -- if an identical value existed,
58     it is not replaced.
59 
60     @retval TRUE  Out of memory.
61     @retval FALSE OK. The value either was inserted or existed
62                   in the hash.
63   */
insert(T * value)64   bool insert(T *value)
65   {
66     my_hash_init_opt(&m_hash, &my_charset_bin, START_SIZE, 0, 0, K, 0, MYF(0));
67     size_t key_len;
68     const uchar *key= K(reinterpret_cast<uchar*>(value), &key_len, FALSE);
69     if (my_hash_search(&m_hash, key, key_len) == NULL)
70       return my_hash_insert(&m_hash, reinterpret_cast<uchar *>(value));
71     return FALSE;
72   }
73   /** Is this hash set empty? */
is_empty()74   bool is_empty() const { return m_hash.records == 0; }
75   /** Returns the number of unique elements. */
size()76   size_t size() const { return static_cast<size_t>(m_hash.records); }
77   /** An iterator over hash elements. Is not insert-stable. */
78   class Iterator
79   {
80   public:
Iterator(Hash_set & hash_set)81     Iterator(Hash_set &hash_set)
82       : m_hash(&hash_set.m_hash),
83         m_idx(0)
84     {}
85     /**
86       Return the current element and reposition the iterator to the next
87       element.
88     */
89     inline T *operator++(int)
90     {
91       if (m_idx < m_hash->records)
92         return reinterpret_cast<T*>(my_hash_element(m_hash, m_idx++));
93       return NULL;
94     }
rewind()95     void rewind() { m_idx= 0; }
96   private:
97     HASH *m_hash;
98     uint m_idx;
99   };
100 private:
101   HASH m_hash;
102 };
103 
104 #endif // SQL_HSET_INCLUDED
105