summaryrefslogtreecommitdiffstats
path: root/sql/hash_filo.h
blob: 4dba104f71669eef934c1b0b637f494a31045c24 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
/* Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */


/*
** A class for static sized hash tables where old entries are deleted in
** first-in-last-out to usage.
*/

#ifndef  HASH_FILO_H
#define  HASH_FILO_H

#ifdef USE_PRAGMA_INTERFACE
#pragma interface			/* gcc class interface */
#endif

#include "hash.h"        /* my_hash_get_key, my_hash_free_key, HASH */
#include "m_string.h"    /* bzero */
#include "mysqld.h"      /* key_hash_filo_lock */

class hash_filo_element
{
private:
  hash_filo_element *next_used,*prev_used;
 public:
  hash_filo_element() = default;
  hash_filo_element *next()
  { return next_used; }
  hash_filo_element *prev()
  { return prev_used; }

  friend class hash_filo;
};


class hash_filo
{
private:
  PSI_memory_key m_psi_key;
  const uint key_offset, key_length;
  const my_hash_get_key get_key;
  /** Size of this hash table. */
  uint m_size;
  my_hash_free_key free_element;
  bool init;
  CHARSET_INFO *hash_charset;

  hash_filo_element *first_link,*last_link;
public:
  mysql_mutex_t lock;
  HASH cache;

  hash_filo(PSI_memory_key psi_key, uint size_arg, uint key_offset_arg,
            uint key_length_arg, my_hash_get_key get_key_arg,
            my_hash_free_key free_element_arg, CHARSET_INFO *hash_charset_arg)
    : m_psi_key(psi_key), key_offset(key_offset_arg),
    key_length(key_length_arg), get_key(get_key_arg), m_size(size_arg),
    free_element(free_element_arg),init(0), hash_charset(hash_charset_arg),
    first_link(NULL), last_link(NULL)
  {
    bzero((char*) &cache,sizeof(cache));
  }

  ~hash_filo()
  {
    if (init)
    {
      if (cache.array.buffer)	/* Avoid problems with thread library */
	(void) my_hash_free(&cache);
      mysql_mutex_destroy(&lock);
    }
  }
  void clear(bool locked=0)
  {
    if (!init)
    {
      init=1;
      mysql_mutex_init(key_hash_filo_lock, &lock, MY_MUTEX_INIT_FAST);
    }
    if (!locked)
      mysql_mutex_lock(&lock);
    first_link= NULL;
    last_link= NULL;
    (void) my_hash_free(&cache);
    (void) my_hash_init(m_psi_key, &cache,hash_charset,m_size,key_offset,
                        key_length, get_key, free_element, 0);
    if (!locked)
      mysql_mutex_unlock(&lock);
  }

  hash_filo_element *first()
  {
    mysql_mutex_assert_owner(&lock);
    return first_link;
  }

  hash_filo_element *last()
  {
    mysql_mutex_assert_owner(&lock);
    return last_link;
  }

  hash_filo_element *search(uchar* key, size_t length)
  {
    mysql_mutex_assert_owner(&lock);

    hash_filo_element *entry=(hash_filo_element*)
      my_hash_search(&cache,(uchar*) key,length);
    if (entry)
    {						// Found; link it first
      DBUG_ASSERT(first_link != NULL);
      DBUG_ASSERT(last_link != NULL);
      if (entry != first_link)
      {						// Relink used-chain
	if (entry == last_link)
        {
	  last_link= last_link->prev_used;
          /*
            The list must have at least 2 elements,
            otherwise entry would be equal to first_link.
          */
          DBUG_ASSERT(last_link != NULL);
          last_link->next_used= NULL;
        }
	else
	{
          DBUG_ASSERT(entry->next_used != NULL);
          DBUG_ASSERT(entry->prev_used != NULL);
	  entry->next_used->prev_used = entry->prev_used;
	  entry->prev_used->next_used = entry->next_used;
	}
        entry->prev_used= NULL;
        entry->next_used= first_link;

        first_link->prev_used= entry;
        first_link=entry;
      }
    }
    return entry;
  }

  bool add(hash_filo_element *entry)
  {
    if (!m_size) return 1;
    if (cache.records == m_size)
    {
      hash_filo_element *tmp=last_link;
      last_link= last_link->prev_used;
      if (last_link != NULL)
      {
        last_link->next_used= NULL;
      }
      else
      {
        /* Pathological case, m_size == 1 */
        first_link= NULL;
      }
      my_hash_delete(&cache,(uchar*) tmp);
    }
    if (my_hash_insert(&cache,(uchar*) entry))
    {
      if (free_element)
	(*free_element)(entry);		// This should never happen
      return 1;
    }
    entry->prev_used= NULL;
    entry->next_used= first_link;
    if (first_link != NULL)
      first_link->prev_used= entry;
    else
      last_link= entry;
    first_link= entry;

    return 0;
  }

  uint size()
  { return m_size; }

  void resize(uint new_size)
  {
    mysql_mutex_lock(&lock);
    m_size= new_size;
    clear(true);
    mysql_mutex_unlock(&lock);
  }
};

template <class T> class Hash_filo: public hash_filo
{
public:
  Hash_filo(PSI_memory_key psi_key, uint size_arg, uint key_offset_arg, uint
            key_length_arg, my_hash_get_key get_key_arg, my_hash_free_key
            free_element_arg, CHARSET_INFO *hash_charset_arg) :
    hash_filo(psi_key, size_arg, key_offset_arg, key_length_arg,
              get_key_arg, free_element_arg, hash_charset_arg) {}
  T* first() { return (T*)hash_filo::first(); }
  T* last()  { return (T*)hash_filo::last(); }
  T* search(uchar* key, size_t len) { return (T*)hash_filo::search(key, len); }
};

#endif