# FBB::Hash(3bobcat)

## Key hashing containers
(libbobcat-dev_6.11.00)

## 2005-2025

## NAME

FBB::Hash - Various mapping template classes using hashing

## SYNOPSIS

#include <bobcat/hash>

## DESCRIPTION

The FBB:Hash group of template classes offer hashing-based mapping. Various variants are available, all based on the facilities offered by the unordered_map.

The hash-map offered in the unordered_map container has a fairly complex construction interface, and Hash is an attempt to simplify this part of its interface. In practice, hashing uses a textual key, which may be std::string or char * based, and the keys may be used either case sensitively or case insensitively. Hash merely requires its users to specify the map's value type, while the key may be a char const * or std::string, used case sensitively or case insensitively.

## NAMESPACE

FBB
All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace FBB.

## INHERITS FROM

std::unordered_map, using various instantiations.

## TYPE

All variants define value_type as the corresponding unordered_map value_type. In practice a value_type defines a std::pair<Key, Value>, where Key represents the hash's key-type and Value represents the hash's value type.

## CONSTRUCTORS

Variants of the FBB::Hash container are available for char const * or std::string keys, used case sensitively or case insensitively.

All variants support default and move construction (as well as move assignment), support construction from initializer lists. and support construction from iterators defining a half-open range of value_type values.

The following variants are available (showing their default constructors). Value refers to the value type stored in the hash table.

- HashCharPtr<Value>():
  this hash table uses case sensitive char const * keys;

- HashCharCasePtr<Value>():
  this hash table uses case insensitive char const * keys;

- HashString<Value>():
  this hash table uses case sensitive std::string keys;

- HashStringCase<Value>():
  this hash table uses case insensitive std::string keys;

## OVERLOADED OPERATOR

In addition to the index operator inherited from unordered_map the overloaded copy and move assignment operators are available for all Hash containers.

## MEMBER FUNCTIONS

All members of the unordered_map container are available, as Hash inherits from this template class.

## EXAMPLE

        #include <iostream>
        #include <bobcat/hash>

        using namespace std;
        using namespace FBB;

        pair<char const *, size_t> ap[] =
        {
            pair<char const *, size_t>("one", 1),
            pair<char const *, size_t>("two", 2),
        };

        int main()
        {
            HashCharPtr<size_t> hcp;
            HashCharPtr<size_t> hcp2(ap, ap + 2);
            HashCharPtr<size_t> hcp3(hcp2);

            hcp = hcp2;

            cout << hcp2["one"] << endl;
        }

## FILES

bobcat/hash - defines the class interface

## SEE ALSO

bobcat(7)

## BUGS

None Reported.

## BOBCAT PROJECT FILES

- https://fbb-git.gitlab.io/bobcat/: gitlab project page;

Debian Bobcat project files:

- libbobcat6: debian package containing the shared library, changelog and copyright note;
- libbobcat-dev: debian package containing the static library, headers, manual pages, and developer info;

## BOBCAT

Bobcat is an acronym of `Brokken's Own Base Classes And Templates'.

## COPYRIGHT

This is free software, distributed under the terms of the GNU General Public License (GPL).

## AUTHOR

Frank B. Brokken (f.b.brokken@rug.nl).