src/google/protobuf/stubs/map-util.h

   1 // Protocol Buffers - Google's data interchange format
   2 // Copyright 2008 Google Inc.
   3 // http://code.google.com/p/protobuf/
   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 // from google3/util/gtl/map-util.h
  18 // Author: Anton Carver
  19
  20 #ifndef GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__
  21 #define GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__
  22
  23 #include <google/protobuf/stubs/common.h>
  24
  25 namespace google {
  26 namespace protobuf {
  27
  28 // Perform a lookup in a map or hash_map.
  29 // If the key is present a const pointer to the associated value is returned,
  30 // otherwise a NULL pointer is returned.
  31 template <class Collection>
  32 const typename Collection::value_type::second_type*
  33 FindOrNull(const Collection& collection,
  34            const typename Collection::value_type::first_type& key) {
  35   typename Collection::const_iterator it = collection.find(key);
  36   if (it == collection.end()) {
  37     return 0;
  38   }
  39   return &it->second;
  40 }
  41
  42 // Perform a lookup in a map or hash_map whose values are pointers.
  43 // If the key is present a const pointer to the associated value is returned,
  44 // otherwise a NULL pointer is returned.
  45 // This function does not distinguish between a missing key and a key mapped
  46 // to a NULL value.
  47 template <class Collection>
  48 const typename Collection::value_type::second_type
  49 FindPtrOrNull(const Collection& collection,
  50               const typename Collection::value_type::first_type& key) {
  51   typename Collection::const_iterator it = collection.find(key);
  52   if (it == collection.end()) {
  53     return 0;
  54   }
  55   return it->second;
  56 }
  57
  58 // Change the value associated with a particular key in a map or hash_map.
  59 // If the key is not present in the map the key and value are inserted,
  60 // otherwise the value is updated to be a copy of the value provided.
  61 // True indicates that an insert took place, false indicates an update.
  62 template <class Collection, class Key, class Value>
  63 bool InsertOrUpdate(Collection * const collection,
  64                    const Key& key, const Value& value) {
  65   pair<typename Collection::iterator, bool> ret =
  66     collection->insert(typename Collection::value_type(key, value));
  67   if (!ret.second) {
  68     // update
  69     ret.first->second = value;
  70     return false;
  71   }
  72   return true;
  73 }
  74
  75 // Insert a new key and value into a map or hash_map.
  76 // If the key is not present in the map the key and value are
  77 // inserted, otherwise nothing happens. True indicates that an insert
  78 // took place, false indicates the key was already present.
  79 template <class Collection, class Key, class Value>
  80 bool InsertIfNotPresent(Collection * const collection,
  81                         const Key& key, const Value& value) {
  82   pair<typename Collection::iterator, bool> ret =
  83     collection->insert(typename Collection::value_type(key, value));
  84   return ret.second;
  85 }
  86
  87 }  // namespace protobuf
  88 }  // namespace google
  89
  90 #endif  // GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__