map-util.h revision fbaaef999ba563838ebd00874ed8a1c01fbf286d 
1// Protocol Buffers - Google's data interchange format
2// Copyright 2008 Google Inc.  All rights reserved.
3// http://code.google.com/p/protobuf/
4//
5// Redistribution and use in source and binary forms, with or without
6// modification, are permitted provided that the following conditions are
7// met:
8//
9//     * Redistributions of source code must retain the above copyright
10// notice, this list of conditions and the following disclaimer.
11//     * Redistributions in binary form must reproduce the above
12// copyright notice, this list of conditions and the following disclaimer
13// in the documentation and/or other materials provided with the
14// distribution.
15//     * Neither the name of Google Inc. nor the names of its
16// contributors may be used to endorse or promote products derived from
17// this software without specific prior written permission.
18//
19// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30
31// from google3/util/gtl/map-util.h
32// Author: Anton Carver
33
34#ifndef GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__
35#define GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__
36
37#include <google/protobuf/stubs/common.h>
38
39namespace google {
40namespace protobuf {
41
42// Perform a lookup in a map or hash_map.
43// If the key is present in the map then the value associated with that
44// key is returned, otherwise the value passed as a default is returned.
45template <class Collection>
46const typename Collection::value_type::second_type&
47FindWithDefault(const Collection& collection,
48                const typename Collection::value_type::first_type& key,
49                const typename Collection::value_type::second_type& value) {
50  typename Collection::const_iterator it = collection.find(key);
51  if (it == collection.end()) {
52    return value;
53  }
54  return it->second;
55}
56
57// Perform a lookup in a map or hash_map.
58// If the key is present a const pointer to the associated value is returned,
59// otherwise a NULL pointer is returned.
60template <class Collection>
61const typename Collection::value_type::second_type*
62FindOrNull(const Collection& collection,
63           const typename Collection::value_type::first_type& key) {
64  typename Collection::const_iterator it = collection.find(key);
65  if (it == collection.end()) {
66    return 0;
67  }
68  return &it->second;
69}
70
71// Perform a lookup in a map or hash_map whose values are pointers.
72// If the key is present a const pointer to the associated value is returned,
73// otherwise a NULL pointer is returned.
74// This function does not distinguish between a missing key and a key mapped
75// to a NULL value.
76template <class Collection>
77const typename Collection::value_type::second_type
78FindPtrOrNull(const Collection& collection,
79              const typename Collection::value_type::first_type& key) {
80  typename Collection::const_iterator it = collection.find(key);
81  if (it == collection.end()) {
82    return 0;
83  }
84  return it->second;
85}
86
87// Change the value associated with a particular key in a map or hash_map.
88// If the key is not present in the map the key and value are inserted,
89// otherwise the value is updated to be a copy of the value provided.
90// True indicates that an insert took place, false indicates an update.
91template <class Collection, class Key, class Value>
92bool InsertOrUpdate(Collection * const collection,
93                   const Key& key, const Value& value) {
94  pair<typename Collection::iterator, bool> ret =
95    collection->insert(typename Collection::value_type(key, value));
96  if (!ret.second) {
97    // update
98    ret.first->second = value;
99    return false;
100  }
101  return true;
102}
103
104// Insert a new key and value into a map or hash_map.
105// If the key is not present in the map the key and value are
106// inserted, otherwise nothing happens. True indicates that an insert
107// took place, false indicates the key was already present.
108template <class Collection, class Key, class Value>
109bool InsertIfNotPresent(Collection * const collection,
110                        const Key& key, const Value& value) {
111  pair<typename Collection::iterator, bool> ret =
112    collection->insert(typename Collection::value_type(key, value));
113  return ret.second;
114}
115
116}  // namespace protobuf
117}  // namespace google
118
119#endif  // GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__
120