MongoDB C++ Driver  legacy-1.1.2
ordering.h
1 // ordering.h
2 
3 /* Copyright 2009 10gen Inc.
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  * http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17 
18 #pragma once
19 
20 #include "mongo/bson/bsonobj.h"
21 #include "mongo/bson/bsonobjiterator.h"
22 
23 namespace mongo {
24 
25 // todo: ideally move to db/ instead of bson/, but elim any dependencies first
26 
32 class Ordering {
33  unsigned bits;
34  Ordering(unsigned b) : bits(b) {}
35 
36 public:
37  Ordering(const Ordering& r) : bits(r.bits) {}
38  void operator=(const Ordering& r) {
39  bits = r.bits;
40  }
41 
46  int get(int i) const {
47  return ((1 << i) & bits) ? -1 : 1;
48  }
49 
50  // for woCompare...
51  unsigned descending(unsigned mask) const {
52  return bits & mask;
53  }
54 
55  /*operator std::string() const {
56  StringBuilder buf;
57  for ( unsigned i=0; i<nkeys; i++)
58  buf.append( get(i) > 0 ? "+" : "-" );
59  return buf.str();
60  }*/
61 
62  static Ordering make(const BSONObj& obj) {
63  unsigned b = 0;
64  BSONObjIterator k(obj);
65  unsigned n = 0;
66  while (1) {
67  BSONElement e = k.next();
68  if (e.eoo())
69  break;
70  uassert(13103, "too many compound keys", n <= 31);
71  if (e.number() < 0)
72  b |= (1 << n);
73  n++;
74  }
75  return Ordering(b);
76  }
77 };
78 }
Utility functions for parsing numbers from strings.
Definition: compare_numbers.h:20
A precomputation of a BSON index or sort key pattern.
Definition: ordering.h:32