CxxUtils::TransparentStringHash Struct Reference

Transparent hash functor for string-like keys. More...

#include <transparent_string_hash.h>

Collaboration diagram for CxxUtils::TransparentStringHash:

Public Types
using	is_transparent = void

Public Member Functions
std::size_t	operator() (std::string_view s) const
	Hash a string view.
std::size_t	operator() (const std::string &s) const
	Hash a string.
std::size_t	operator() (const char *s) const
	Hash a C string.

Detailed Description

Transparent hash functor for string-like keys.

This hash functor allows an associative container with std::string keys to be searched using other string-like types, such as std::string_view or const char*, without first constructing a temporary std::string.

The nested is_transparent type marks this functor as a transparent hash functor, allowing heterogeneous lookup in containers such as std::unordered_map.

Example:

#include "CxxUtils/transparent_string_hash.h"
 
#include <functional>
#include <string>
#include <string_view>
#include <unordered_map>
 
using CLID = unsigned int;
 
using NameMap = std::unordered_map<
  std::string,
  CLID,
  CxxUtils::TransparentStringHash,
  std::equal_to<> >;
 
NameMap nameMap;
nameMap.emplace("MyClass", 123);
 
const std::string key = "MyClass";
const std::string_view view = "MyClass";
const char* cstr = "MyClass";
 
auto fromString = nameMap.find(key);
auto fromStringView = nameMap.find(view);
auto fromCString = nameMap.find(cstr);

Warning

The const char* overload expects a non-null, null-terminated string. For character buffers that are not null-terminated, use std::string_view.

Definition at line 60 of file transparent_string_hash.h.

Member Typedef Documentation

is_transparent

using CxxUtils::TransparentStringHash::is_transparent = void

Definition at line 61 of file transparent_string_hash.h.

Member Function Documentation

operator()() [1/3]

std::size_t CxxUtils::TransparentStringHash::operator() ( const char * s ) const

inline

Hash a C string.

Parameters

s	Null-terminated C string to hash.

Returns

Hash value for s.

Definition at line 89 of file transparent_string_hash.h.

                                   {
      return (*this)(std::string_view{s});
    }

operator()() [2/3]

std::size_t CxxUtils::TransparentStringHash::operator() ( const std::string & s ) const

inline

Hash a string.

Parameters

s	String to hash.

Returns

Hash value for s.

Definition at line 79 of file transparent_string_hash.h.

                                        {
      return (*this)(std::string_view{s});
    }

operator()() [3/3]

std::size_t CxxUtils::TransparentStringHash::operator() ( std::string_view s ) const

inline

Hash a string view.

Parameters

s	String view to hash.

Returns

Hash value for s.

Definition at line 69 of file transparent_string_hash.h.

                                      {
      return std::hash<std::string_view>{}(s);
    }

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The documentation for this struct was generated from the following file:

• transparent_string_hash.h