1 /* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2 // vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
3 #ident "$Id$"
4 /*======
5 This file is part of PerconaFT.
6 
7 
8 Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved.
9 
10     PerconaFT is free software: you can redistribute it and/or modify
11     it under the terms of the GNU General Public License, version 2,
12     as published by the Free Software Foundation.
13 
14     PerconaFT is distributed in the hope that it will be useful,
15     but WITHOUT ANY WARRANTY; without even the implied warranty of
16     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
17     GNU General Public License for more details.
18 
19     You should have received a copy of the GNU General Public License
20     along with PerconaFT.  If not, see <http://www.gnu.org/licenses/>.
21 
22 ----------------------------------------
23 
24     PerconaFT is free software: you can redistribute it and/or modify
25     it under the terms of the GNU Affero General Public License, version 3,
26     as published by the Free Software Foundation.
27 
28     PerconaFT is distributed in the hope that it will be useful,
29     but WITHOUT ANY WARRANTY; without even the implied warranty of
30     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
31     GNU Affero General Public License for more details.
32 
33     You should have received a copy of the GNU Affero General Public License
34     along with PerconaFT.  If not, see <http://www.gnu.org/licenses/>.
35 
36 ----------------------------------------
37 
38    Licensed under the Apache License, Version 2.0 (the "License");
39    you may not use this file except in compliance with the License.
40    You may obtain a copy of the License at
41 
42        http://www.apache.org/licenses/LICENSE-2.0
43 
44    Unless required by applicable law or agreed to in writing, software
45    distributed under the License is distributed on an "AS IS" BASIS,
46    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
47    See the License for the specific language governing permissions and
48    limitations under the License.
49 ======= */
50 
51 #ident "Copyright (c) 2006, 2015, Percona and/or its affiliates. All rights reserved."
52 
53 #pragma once
54 
55 #include <ft/comparator.h>
56 
57 namespace toku {
58 
59 // A keyrange has a left and right key as endpoints.
60 //
61 // When a keyrange is created it owns no memory, but when it copies
62 // or extends another keyrange, it copies memory as necessary. This
63 // means it is cheap in the common case.
64 
65 class keyrange {
66 public:
67 
68     // effect: constructor that borrows left and right key pointers.
69     //         no memory is allocated or copied.
70     void create(const DBT *left_key, const DBT *right_key);
71 
72     // effect: constructor that allocates and copies another keyrange's points.
73     void create_copy(const keyrange &range);
74 
75     // effect: destroys the keyrange, freeing any allocated memory
76     void destroy(void);
77 
78     // effect: extends the keyrange by choosing the leftmost and rightmost
79     //         endpoints from this range and the given range.
80     //         replaced keys in this range are freed, new keys are copied.
81     void extend(const comparator &cmp, const keyrange &range);
82 
83     // returns: the amount of memory this keyrange takes. does not account
84     //          for point optimizations or malloc overhead.
85     uint64_t get_memory_size(void) const;
86 
87     // returns: pointer to the left key of this range
88     const DBT *get_left_key(void) const;
89 
90     // returns: pointer to the right key of this range
91     const DBT *get_right_key(void) const;
92 
93     // two ranges are either equal, lt, gt, or overlapping
94     enum comparison {
95         EQUALS,
96         LESS_THAN,
97         GREATER_THAN,
98         OVERLAPS
99     };
100 
101     // effect: compares this range to the given range
102     // returns: LESS_THAN    if given range is strictly to the left
103     //          GREATER_THAN if given range is strictly to the right
104     //          EQUALS       if given range has the same left and right endpoints
105     //          OVERLAPS     if at least one of the given range's endpoints falls
106     //                       between this range's endpoints
107     comparison compare(const comparator &cmp, const keyrange &range) const;
108 
109     // returns: true if the range and the given range are equal or overlapping
110     bool overlaps(const comparator &cmp, const keyrange &range) const;
111 
112     // returns: a keyrange representing -inf, +inf
113     static keyrange get_infinite_range(void);
114 
115 private:
116     // some keys should be copied, some keys should not be.
117     //
118     // to support both, we use two DBTs for copies and two pointers
119     // for temporaries. the access rule is:
120     // - if a pointer is non-null, then it reprsents the key.
121     // - otherwise the pointer is null, and the key is in the copy.
122     DBT m_left_key_copy;
123     DBT m_right_key_copy;
124     const DBT *m_left_key;
125     const DBT *m_right_key;
126 
127     // if this range is a point range, then m_left_key == m_right_key
128     // and the actual data is stored exactly once in m_left_key_copy.
129     bool m_point_range;
130 
131     // effect: initializes a keyrange to be empty
132     void init_empty(void);
133 
134     // effect: copies the given key once into the left key copy
135     //         and sets the right key copy to share the left.
136     // rationale: optimization for point ranges to only do one malloc
137     void set_both_keys(const DBT *key);
138 
139     // effect: destroys the current left key. sets and copies the new one.
140     void replace_left_key(const DBT *key);
141 
142     // effect: destroys the current right key. sets and copies the new one.
143     void replace_right_key(const DBT *key);
144 };
145 
146 } /* namespace toku */
147