// Protocol Buffers - Google's data interchange format

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// https://developers.google.com/protocol-buffers/

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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__