bdlb_caselessstringviewhash.h

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/// @file bdlb_caselessstringviewhash.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlb_caselessstringviewhash.h                                      -*-C++-*-
#ifndef INCLUDED_BDLB_CASELESSSTRINGVIEWHASH
#define INCLUDED_BDLB_CASELESSSTRINGVIEWHASH
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlb_caselessstringviewhash bdlb_caselessstringviewhash
/// @brief  Provide a case-insensitive hash functor for string views.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlb
/// @{
/// @addtogroup bdlb_caselessstringviewhash
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlb_caselessstringviewhash-purpose"> Purpose</a>
/// * <a href="#bdlb_caselessstringviewhash-classes"> Classes </a>
/// * <a href="#bdlb_caselessstringviewhash-description"> Description </a>
///   * <a href="#bdlb_caselessstringviewhash-usage"> Usage </a>
///     * <a href="#bdlb_caselessstringviewhash-example-1-basic-use-of-bdlb-caselessstringviewhash"> Example 1: Basic Use of bdlb::CaselessStringViewHash </a>
///
/// # Purpose {#bdlb_caselessstringviewhash-purpose}
/// Provide a case-insensitive hash functor for string views.
///
/// # Classes {#bdlb_caselessstringviewhash-classes}
///
/// -  bdlb::CaselessStringViewHash: case-insensive hash functor
///
/// @see  bdlb_caselessstringviewequalto, bdlb_caselessstringviewless
///
/// # Description {#bdlb_caselessstringviewhash-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 @ref 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 {#bdlb_caselessstringviewhash-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Basic Use of bdlb::CaselessStringViewHash {#bdlb_caselessstringviewhash-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:
/// @code
/// typedef bsl::unordered_map<bsl::string, int> SecuritiesOwnedCS;
///                                                     // case sensitive
///
///
/// typedef bsl::unordered_map<bsl::string,
///                            int,
///                            bdlb::CaselessStringViewHash,
///                            bdlb::CaselessStringViewEqualTo>
///                                                          SecuritiesOwnedCI;
///                                                     // case insensitive
/// @endcode
/// 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:
/// @code
/// SecuritiesOwnedCS securitiesOwnedCS;
///
/// securitiesOwnedCS["IBM"]       = 616;
/// securitiesOwnedCS["Microsoft"] = 6160000;
///
/// assert(2 == securitiesOwnedCS.size());
/// @endcode
/// Then, we create a container for securities holdings, case-insensitive, and
/// fill it:
/// @code
/// SecuritiesOwnedCI securitiesOwnedCI;
///
/// securitiesOwnedCI["IBM"]       = 616;
/// securitiesOwnedCI["Microsoft"] = 6160000;
///
/// assert(2 == securitiesOwnedCI.size());
/// @endcode
/// Now, we try accessing the case-sensitive `securitiesc`:
/// @code
/// 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"));
/// @endcode
/// Finally, we access the case-insensitive `securitiesci`:
/// @code
/// 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"));
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlb
 * @{
 */
/** @addtogroup bdlb_caselessstringviewhash
 * @{
 */
 
#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 bdlb {
 
                       // =============================
                       // 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 Note that   this class is an empty POD type.
///
/// See @ref bdlb_caselessstringviewhash 
struct CaselessStringViewHash {
 
    // PUBLIC TYPES
    typedef bsl::string_view  argument_type;
    typedef bsl::size_t       result_type;
 
    /// Type alias indicating this is a transparent hash functor.
    typedef void              is_transparent;
 
    // TRAITS
    BSLMF_NESTED_TRAIT_DECLARATION(CaselessStringViewHash,
                                                   bsl::is_trivially_copyable);
    BSLMF_NESTED_TRAIT_DECLARATION(CaselessStringViewHash,
                                      bsl::is_trivially_default_constructible);
 
    /// Create a `CaselessStringViewHash` object.
     CaselessStringViewHash() = default;
 
    /// Create a `CaselessStringViewHash` object.  
    /// \note Note that  as
    /// `CaselessStringViewHash` is an empty (stateless) type, this
    /// operation will have no observable effect.
     CaselessStringViewHash(const CaselessStringViewHash& original) =
                                                                    default;
 
    /// Destroy this object.
     ~CaselessStringViewHash() = default;
 
    // MANIPULATORS
 
    /// Assign to this object the value of the specified `rhs` object, and a
    /// return a reference providing modifiable access to this object.  
    /// 
    /// \note Note that   as `CaselessStringViewHash` is an empty (stateless) type, this
    /// operation will have no observable effect.
     CaselessStringViewHash& operator=(const CaselessStringViewHash& rhs) =
                                                                    default;
 
    // ACCESSORS
 
    /// Return a hash code generated from the contents of the specified
    /// null-terminated `argument` string, cast to lower case.  
    /// 
    /// \pre The behavior is undefined   unless `argument` points to a null-terminated string.
    bsl::size_t operator()(bsl::string_view argument) const;
};
 
}  // close package 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */