// bdlb_caselessstringviewhash.h -*-C++-*-
#ifndef INCLUDED_BDLB_CASELESSSTRINGVIEWHASH
#define INCLUDED_BDLB_CASELESSSTRINGVIEWHASH
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
//@PURPOSE: Provide a case-insensitive hash functor for string views.
//
//@CLASSES:
// bdlb::CaselessStringViewHash: case-insensive hash functor
//
//@SEE_ALSO: bdlb_caselessstringviewequalto, bdlb_caselessstringviewless
//
//@DESCRIPTION: This component provides a 'struct',
// 'bdlb::CaselessStringViewHash', that defines a functor to generate a
// case-insensitivee hash code for a string view. This hash functor is
// suitable for supporting 'bsl::string's and 'bsl::string_view's as keys in
// unordered associative containers.
//
// Note that using this component to hash keys into a container and then using
// the 'bdlb_caselessstringviewequalto' component to compare them is less
// efficient than converting all the keys to the same case prior to insertion
// and then just doing straight hashes and string compares.
//
///Usage
///-----
// This section illustrates intended use of this component.
//
///Example 1: Basic Use of 'bdlb::CaselessStringViewHash':
/// - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Suppose we need an associative container to store, for any stock name, the
// number of shares of that stock we own:
//..
// typedef bsl::unordered_map<bsl::string, int> SecuritiesOwnedCS;
// // case sensitive
//
//
// typedef bsl::unordered_map<bsl::string,
// int,
// bdlb::CaselessStringViewHash,
// bdlb::CaselessStringViewEqualTo>
// SecuritiesOwnedCI;
// // case insensitive
//..
// This type of container stores quantities of shares and allows access to them
// by their names, in a case-insensitive manner.
//
// First, we create a container for securities holdings, case-sensitive, and
// fill it:
//..
// SecuritiesOwnedCS securitiesOwnedCS;
//
// securitiesOwnedCS["IBM"] = 616;
// securitiesOwnedCS["Microsoft"] = 6160000;
//
// assert(2 == securitiesOwnedCS.size());
//..
// Then, we create a container for securities holdings, case-insensitive, and
// fill it:
//..
// SecuritiesOwnedCI securitiesOwnedCI;
//
// securitiesOwnedCI["IBM"] = 616;
// securitiesOwnedCI["Microsoft"] = 6160000;
//
// assert(2 == securitiesOwnedCI.size());
//..
// Now, we try accessing the case-sensitive 'securitiesc':
//..
// assert(1 == securitiesOwnedCS.count("IBM"));
// assert(616 == securitiesOwnedCS[ "IBM"]);
//
// assert(0 == securitiesOwnedCS.count("ibm"));
// assert(0 == securitiesOwnedCS.count("Ibm"));
// assert(0 == securitiesOwnedCS.count("iBm"));
//
// assert(1 == securitiesOwnedCS.count("Microsoft"));
// assert(6160000 == securitiesOwnedCS[ "Microsoft"]);
//
// assert(0 == securitiesOwnedCS.count("MICROSOFT"));
// assert(0 == securitiesOwnedCS.count("microsoft"));
// assert(0 == securitiesOwnedCS.count("MICROSOFT"));
//
// assert(0 == securitiesOwnedCS.count("Google"));
//..
// Finally, we access the case-insensitive 'securitiesci':
//..
// assert(1 == securitiesOwnedCI.count("IBM"));
// assert(616 == securitiesOwnedCI[ "IBM"]);
// assert(1 == securitiesOwnedCI.count("ibm"));
// assert(616 == securitiesOwnedCI[ "ibm"]);
// assert(1 == securitiesOwnedCI.count("Ibm"));
// assert(616 == securitiesOwnedCI[ "Ibm"]);
// assert(1 == securitiesOwnedCI.count("iBm"));
// assert(616 == securitiesOwnedCI[ "iBm"]);
//
// assert(1 == securitiesOwnedCI.count("Microsoft"));
// assert(6160000 == securitiesOwnedCI[ "Microsoft"]);
// assert(1 == securitiesOwnedCI.count("MICROSOFT"));
// assert(6160000 == securitiesOwnedCI[ "MICROSOFT"]);
// assert(1 == securitiesOwnedCI.count("microsoft"));
// assert(6160000 == securitiesOwnedCI[ "microsoft"]);
// assert(1 == securitiesOwnedCI.count("MICROSOFT"));
// assert(6160000 == securitiesOwnedCI[ "MICROSOFT"]);
//
// assert(0 == securitiesOwnedCI.count("Google"));
//..
#include <bdlscm_version.h>
#include <bslmf_istriviallycopyable.h>
#include <bslmf_istriviallydefaultconstructible.h>
#include <bslmf_nestedtraitdeclaration.h>
#include <bsl_cstddef.h>
#include <bsl_string_view.h>
namespace BloombergLP {
namespace bdlb {
// =============================
// struct CaselessStringViewHash
// =============================
struct CaselessStringViewHash {
// This 'struct' defines a hash operation for string views enabling
// 'bsl::string's or 'bsl::string_view's to be used as keys in the standard
// unordered associative containers such as 'bsl::unordered_map' and
// 'bsl::unordered_set'. Note that this class is an empty POD type.
// PUBLIC TYPES
typedef bsl::string_view argument_type;
typedef bsl::size_t result_type;
typedef void is_transparent;
// Type alias indicating this is a transparent hash functor.
// TRAITS
BSLMF_NESTED_TRAIT_DECLARATION(CaselessStringViewHash,
bsl::is_trivially_copyable);
BSLMF_NESTED_TRAIT_DECLARATION(CaselessStringViewHash,
bsl::is_trivially_default_constructible);
//! CaselessStringViewHash() = default;
// Create a 'CaselessStringViewHash' object.
//! CaselessStringViewHash(const CaselessStringViewHash& original) =
// default;
// Create a 'CaselessStringViewHash' object. Note that as
// 'CaselessStringViewHash' is an empty (stateless) type, this
// operation will have no observable effect.
//! ~CaselessStringViewHash() = default;
// Destroy this object.
// MANIPULATORS
//! CaselessStringViewHash& operator=(const CaselessStringViewHash& rhs) =
// default;
// Assign to this object the value of the specified 'rhs' object, and a
// return a reference providing modifiable access to this object. Note
// that as 'CaselessStringViewHash' is an empty (stateless) type, this
// operation will have no observable effect.
// ACCESSORS
bsl::size_t operator()(bsl::string_view argument) const;
// Return a hash code generated from the contents of the specified
// null-terminated 'argument' string, cast to lower case. The behavior
// is undefined unless 'argument' points to a null-terminated string.
};
} // close package namespace
} // close enterprise namespace
#endif
// ----------------------------------------------------------------------------
// Copyright 2021 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------