1 // Protocol Buffers - Google's data interchange format
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3 // http://code.google.com/p/protobuf/
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31 // from google3/util/gtl/map-util.h
32 // Author: Anton Carver
34 #ifndef GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__
35 #define GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__
37 #include <google/protobuf/stubs/common.h>
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.
45 template <class Collection>
46 const typename Collection::value_type::second_type&
47 FindWithDefault(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()) {
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.
60 template <class Collection>
61 const typename Collection::value_type::second_type*
62 FindOrNull(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()) {
71 // Perform a lookup in a map or hash_map, assuming that the key exists.
72 // Crash if it does not.
74 // This is intended as a replacement for operator[] as an rvalue (for reading)
75 // when the key is guaranteed to exist.
77 // operator[] is discouraged for several reasons:
78 // * It has a side-effect of inserting missing keys
79 // * It is not thread-safe (even when it is not inserting, it can still
80 // choose to resize the underlying storage)
81 // * It invalidates iterators (when it chooses to resize)
82 // * It default constructs a value object even if it doesn't need to
84 // This version assumes the key is printable, and includes it in the fatal log
86 template <class Collection>
87 const typename Collection::value_type::second_type&
88 FindOrDie(const Collection& collection,
89 const typename Collection::value_type::first_type& key) {
90 typename Collection::const_iterator it = collection.find(key);
91 GOOGLE_CHECK(it != collection.end()) << "Map key not found: " << key;
95 // Perform a lookup in a map or hash_map whose values are pointers.
96 // If the key is present a const pointer to the associated value is returned,
97 // otherwise a NULL pointer is returned.
98 // This function does not distinguish between a missing key and a key mapped
100 template <class Collection>
101 const typename Collection::value_type::second_type
102 FindPtrOrNull(const Collection& collection,
103 const typename Collection::value_type::first_type& key) {
104 typename Collection::const_iterator it = collection.find(key);
105 if (it == collection.end()) {
111 // Change the value associated with a particular key in a map or hash_map.
112 // If the key is not present in the map the key and value are inserted,
113 // otherwise the value is updated to be a copy of the value provided.
114 // True indicates that an insert took place, false indicates an update.
115 template <class Collection, class Key, class Value>
116 bool InsertOrUpdate(Collection * const collection,
117 const Key& key, const Value& value) {
118 pair<typename Collection::iterator, bool> ret =
119 collection->insert(typename Collection::value_type(key, value));
122 ret.first->second = value;
128 // Insert a new key and value into a map or hash_map.
129 // If the key is not present in the map the key and value are
130 // inserted, otherwise nothing happens. True indicates that an insert
131 // took place, false indicates the key was already present.
132 template <class Collection, class Key, class Value>
133 bool InsertIfNotPresent(Collection * const collection,
134 const Key& key, const Value& value) {
135 pair<typename Collection::iterator, bool> ret =
136 collection->insert(typename Collection::value_type(key, value));
140 } // namespace protobuf
141 } // namespace google
143 #endif // GOOGLE_PROTOBUF_STUBS_MAP_UTIL_H__