summaryrefslogtreecommitdiffstats
path: root/sql/sql_plist.h
blob: 7f75208ca09e64d83779dedc2a906c707c68a146 (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
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
#ifndef SQL_PLIST_H
#define SQL_PLIST_H
/* Copyright (c) 2008, 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 */


template <typename T, typename L>
class I_P_List_iterator;
class I_P_List_null_counter;
template <typename T> class I_P_List_no_push_back;


/**
   Intrusive parameterized list.

   Unlike I_List does not require its elements to be descendant of ilink
   class and therefore allows them to participate in several such lists
   simultaneously.

   Unlike List is doubly-linked list and thus supports efficient deletion
   of element without iterator.

   @param T  Type of elements which will belong to list.
   @param B  Class which via its methods specifies which members
             of T should be used for participating in this list.
             Here is typical layout of such class:

             struct B
             {
               static inline T **next_ptr(T *el)
               {
                 return &el->next;
               }
               static inline T ***prev_ptr(T *el)
               {
                 return &el->prev;
               }
             };
   @param C  Policy class specifying how counting of elements in the list
             should be done. Instance of this class is also used as a place
             where information about number of list elements is stored.
             @sa I_P_List_null_counter, I_P_List_counter
   @param I  Policy class specifying whether I_P_List should support
             efficient push_back() operation. Instance of this class
             is used as place where we store information to support
             this operation.
             @sa I_P_List_no_push_back, I_P_List_fast_push_back.
*/

template <typename T, typename B,
          typename C = I_P_List_null_counter,
          typename I = I_P_List_no_push_back<T> >
class I_P_List : public C, public I
{
  T *m_first;

  /*
    Do not prohibit copying of I_P_List object to simplify their usage in
    backup/restore scenarios. Note that performing any operations on such
    is a bad idea.
  */
public:
  I_P_List() : I(&m_first), m_first(NULL) {};
  /*
    empty() is used in many places in the code instead of a constructor, to
    initialize a bzero-ed I_P_List instance.
  */

  inline void empty()      { m_first= NULL; C::reset(); I::set_last(&m_first); }
  inline bool is_empty() const { return (m_first == NULL); }
  inline void push_front(T* a)
  {
    *B::next_ptr(a)= m_first;
    if (m_first)
      *B::prev_ptr(m_first)= B::next_ptr(a);
    else
      I::set_last(B::next_ptr(a));
    m_first= a;
    *B::prev_ptr(a)= &m_first;
    C::inc();
  }
  inline void push_back(T *a)
  {
    T **last= I::get_last();
    *B::next_ptr(a)= *last;
    *last= a;
    *B::prev_ptr(a)= last;
    I::set_last(B::next_ptr(a));
    C::inc();
  }
  inline void insert_after(T *pos, T *a)
  {
    if (pos == NULL)
      push_front(a);
    else
    {
      *B::next_ptr(a)= *B::next_ptr(pos);
      *B::prev_ptr(a)= B::next_ptr(pos);
      *B::next_ptr(pos)= a;
      if (*B::next_ptr(a))
      {
        T *old_next= *B::next_ptr(a);
        *B::prev_ptr(old_next)= B::next_ptr(a);
      }
      else
        I::set_last(B::next_ptr(a));
      C::inc();
    }
  }
  inline void remove(T *a)
  {
    T *next= *B::next_ptr(a);
    if (next)
      *B::prev_ptr(next)= *B::prev_ptr(a);
    else
      I::set_last(*B::prev_ptr(a));
    **B::prev_ptr(a)= next;
    C::dec();
  }
  inline T* front() { return m_first; }
  inline const T *front() const { return m_first; }
  inline T* pop_front()
  {
    T *result= front();

    if (result)
      remove(result);

    return result;
  }
  void swap(I_P_List<T, B, C> &rhs)
  {
    swap_variables(T *, m_first, rhs.m_first);
    I::swap(rhs);
    if (m_first)
      *B::prev_ptr(m_first)= &m_first;
    else
      I::set_last(&m_first);
    if (rhs.m_first)
      *B::prev_ptr(rhs.m_first)= &rhs.m_first;
    else
      I::set_last(&rhs.m_first);
    C::swap(rhs);
  }
  typedef B Adapter;
  typedef I_P_List<T, B, C, I> Base;
  typedef I_P_List_iterator<T, Base> Iterator;
  typedef I_P_List_iterator<const T, Base> Const_Iterator;
#ifndef _lint
  friend class I_P_List_iterator<T, Base>;
  friend class I_P_List_iterator<const T, Base>;
#endif
};


/**
   Iterator for I_P_List.
*/

template <typename T, typename L>
class I_P_List_iterator
{
  const L *list;
  T *current;
public:
  I_P_List_iterator(const L &a)
    : list(&a), current(a.m_first) {}
  I_P_List_iterator(const L &a, T* current_arg)
    : list(&a), current(current_arg) {}
  inline void init(const L &a)
  {
    list= &a;
    current= a.m_first;
  }
  /**
    Operator for it++

    @note since we save next element pointer, caller may remove current element.
    Such modification doesn't invalidate iterator.
  */
  inline T* operator++(int)
  {
    T *result= current;
    if (result)
      current= *L::Adapter::next_ptr(current);
    return result;
  }
  /* Operator for ++it */
  inline T* operator++()
  {
    current= *L::Adapter::next_ptr(current);
    return current;
  }
  inline void rewind()
  {
    current= list->m_first;
  }
};


/**
  Hook class which via its methods specifies which members
  of T should be used for participating in a intrusive list.
*/

template <typename T, T* T::*next, T** T::*prev>
struct I_P_List_adapter
{
  static inline T **next_ptr(T *el) { return &(el->*next); }
  static inline const T* const* next_ptr(const T *el) { return &(el->*next); }
  static inline T ***prev_ptr(T *el) { return &(el->*prev); }
};


/**
  Element counting policy class for I_P_List to be used in
  cases when no element counting should be done.
*/

class I_P_List_null_counter
{
protected:
  void reset() {}
  void inc() {}
  void dec() {}
  void swap(I_P_List_null_counter &) {}
};


/**
  Element counting policy class for I_P_List which provides
  basic element counting.
*/

class I_P_List_counter
{
  uint m_counter;
protected:
  I_P_List_counter() : m_counter (0) {}
  void reset() {m_counter= 0;}
  void inc() {m_counter++;}
  void dec() {m_counter--;}
  void swap(I_P_List_counter &rhs)
  { swap_variables(uint, m_counter, rhs.m_counter); }
public:
  uint elements() const { return m_counter; }
};


/**
  A null insertion policy class for I_P_List to be used
  in cases when push_back() operation is not necessary.
*/

template <typename T> class I_P_List_no_push_back
{
protected:
  I_P_List_no_push_back(T **) {}
  void set_last(T **) {}
  /*
    T** get_last() const method is intentionally left unimplemented
    in order to prohibit usage of push_back() method in lists which
    use this policy.
  */
  void swap(I_P_List_no_push_back<T> &) {}
};


/**
  An insertion policy class for I_P_List which can
  be used when fast push_back() operation is required.
*/

template <typename T> class I_P_List_fast_push_back
{
  T **m_last;
protected:
  I_P_List_fast_push_back(T **a) : m_last(a) { };
  void set_last(T **a) { m_last= a; }
  T** get_last() const { return m_last; }
  void swap(I_P_List_fast_push_back<T> &rhs)
  { swap_variables(T**, m_last, rhs.m_last); }
};

#endif