THUAI6/CAPI/cpp/grpc/include/google/protobuf/stubs/hash.h

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// Author: kenton@google.com (Kenton Varda)

#ifndef GOOGLE_PROTOBUF_STUBS_HASH_H__
#define GOOGLE_PROTOBUF_STUBS_HASH_H__

#include <cstring>
#include <string>
#include <unordered_map>
#include <unordered_set>

#define GOOGLE_PROTOBUF_HASH_NAMESPACE_DECLARATION_START \
    namespace google                                     \
    {                                                    \
        namespace protobuf                               \
        {
#define GOOGLE_PROTOBUF_HASH_NAMESPACE_DECLARATION_END \
    }                                                  \
    }

namespace google
{
    namespace protobuf
    {

        template<typename Key>
        struct hash : public std::hash<Key>
        {
        };

        template<typename Key>
        struct hash<const Key*>
        {
            inline size_t operator()(const Key* key) const
            {
                return reinterpret_cast<size_t>(key);
            }
        };

        // Unlike the old SGI version, the TR1 "hash" does not special-case char*.  So,
        // we go ahead and provide our own implementation.
        template<>
        struct hash<const char*>
        {
            inline size_t operator()(const char* str) const
            {
                size_t result = 0;
                for (; *str != '\0'; str++)
                {
                    result = 5 * result + static_cast<size_t>(*str);
                }
                return result;
            }
        };

        template<>
        struct hash<bool>
        {
            size_t operator()(bool x) const
            {
                return static_cast<size_t>(x);
            }
        };

        template<>
        struct hash<std::string>
        {
            inline size_t operator()(const std::string& key) const
            {
                return hash<const char*>()(key.c_str());
            }

            static const size_t bucket_size = 4;
            static const size_t min_buckets = 8;
            inline bool operator()(const std::string& a, const std::string& b) const
            {
                return a < b;
            }
        };

        template<typename First, typename Second>
        struct hash<std::pair<First, Second>>
        {
            inline size_t operator()(const std::pair<First, Second>& key) const
            {
                size_t first_hash = hash<First>()(key.first);
                size_t second_hash = hash<Second>()(key.second);

                // FIXME(kenton):  What is the best way to compute this hash?  I have
                // no idea!  This seems a bit better than an XOR.
                return first_hash * ((1 << 16) - 1) + second_hash;
            }

            static const size_t bucket_size = 4;
            static const size_t min_buckets = 8;
            inline bool operator()(const std::pair<First, Second>& a, const std::pair<First, Second>& b) const
            {
                return a < b;
            }
        };

    }  // namespace protobuf
}  // namespace google

#endif  // GOOGLE_PROTOBUF_STUBS_HASH_H__