1 // Protocol Buffers - Google's data interchange format
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3 // https://developers.google.com/protocol-buffers/
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31 // Author: kenton@google.com (Kenton Varda)
33 // Deals with the fact that hash_map is not defined everywhere.
35 #ifndef GOOGLE_PROTOBUF_STUBS_HASH_H__
36 #define GOOGLE_PROTOBUF_STUBS_HASH_H__
39 #include <google/protobuf/stubs/common.h>
42 #if defined(HAVE_HASH_MAP) && defined(HAVE_HASH_SET)
56 // This system doesn't have hash_map or hash_set. Emulate them using map and
59 // Make hash<T> be the same as less<T>. Note that everywhere where custom
60 // hash functions are defined in the protobuf code, they are also defined such
61 // that they can be used as "less" functions, which is required by MSVC anyway.
62 template <typename Key>
64 // Dummy, just to make derivative hash functions compile.
65 int operator()(const Key& key) {
66 GOOGLE_LOG(FATAL) << "Should never be called.";
70 inline bool operator()(const Key& a, const Key& b) const {
75 // Make sure char* is compared by value.
77 struct hash<const char*> {
78 // Dummy, just to make derivative hash functions compile.
79 int operator()(const char* key) {
80 GOOGLE_LOG(FATAL) << "Should never be called.";
84 inline bool operator()(const char* a, const char* b) const {
85 return strcmp(a, b) < 0;
89 template <typename Key, typename Data,
90 typename HashFcn = hash<Key>,
91 typename EqualKey = int >
92 class hash_map : public std::map<Key, Data, HashFcn> {
97 template <typename Key,
98 typename HashFcn = hash<Key>,
99 typename EqualKey = int >
100 class hash_set : public std::set<Key, HashFcn> {
105 #elif defined(_MSC_VER) && !defined(_STLPORT_VERSION)
107 template <typename Key>
108 struct hash : public HASH_NAMESPACE::hash_compare<Key> {
111 // MSVC's hash_compare<const char*> hashes based on the string contents but
112 // compares based on the string pointer. WTF?
115 inline bool operator()(const char* a, const char* b) const {
116 return strcmp(a, b) < 0;
121 struct hash<const char*>
122 : public HASH_NAMESPACE::hash_compare<const char*, CstringLess> {
125 template <typename Key, typename Data,
126 typename HashFcn = hash<Key>,
127 typename EqualKey = int >
128 class hash_map : public HASH_NAMESPACE::hash_map<
129 Key, Data, HashFcn> {
134 template <typename Key,
135 typename HashFcn = hash<Key>,
136 typename EqualKey = int >
137 class hash_set : public HASH_NAMESPACE::hash_set<
145 template <typename Key>
146 struct hash : public HASH_NAMESPACE::hash<Key> {
149 template <typename Key>
150 struct hash<const Key*> {
151 inline size_t operator()(const Key* key) const {
152 return reinterpret_cast<size_t>(key);
156 // Unlike the old SGI version, the TR1 "hash" does not special-case char*. So,
157 // we go ahead and provide our own implementation.
159 struct hash<const char*> {
160 inline size_t operator()(const char* str) const {
162 for (; *str != '\0'; str++) {
163 result = 5 * result + *str;
169 template <typename Key, typename Data,
170 typename HashFcn = hash<Key>,
171 typename EqualKey = std::equal_to<Key> >
172 class hash_map : public HASH_NAMESPACE::HASH_MAP_CLASS<
173 Key, Data, HashFcn, EqualKey> {
178 template <typename Key,
179 typename HashFcn = hash<Key>,
180 typename EqualKey = std::equal_to<Key> >
181 class hash_set : public HASH_NAMESPACE::HASH_SET_CLASS<
182 Key, HashFcn, EqualKey> {
190 struct hash<string> {
191 inline size_t operator()(const string& key) const {
192 return hash<const char*>()(key.c_str());
195 static const size_t bucket_size = 4;
196 static const size_t min_buckets = 8;
197 inline size_t operator()(const string& a, const string& b) const {
202 template <typename First, typename Second>
203 struct hash<pair<First, Second> > {
204 inline size_t operator()(const pair<First, Second>& key) const {
205 size_t first_hash = hash<First>()(key.first);
206 size_t second_hash = hash<Second>()(key.second);
208 // FIXME(kenton): What is the best way to compute this hash? I have
209 // no idea! This seems a bit better than an XOR.
210 return first_hash * ((1 << 16) - 1) + second_hash;
213 static const size_t bucket_size = 4;
214 static const size_t min_buckets = 8;
215 inline size_t operator()(const pair<First, Second>& a,
216 const pair<First, Second>& b) const {
221 // Used by GCC/SGI STL only. (Why isn't this provided by the standard
224 inline bool operator()(const char* a, const char* b) const {
225 return strcmp(a, b) == 0;
229 } // namespace protobuf
230 } // namespace google
232 #endif // GOOGLE_PROTOBUF_STUBS_HASH_H__