bslh_hashpair.h

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/// @file bslh_hashpair.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslh_hashpair.h                                                    -*-C++-*-
#ifndef INCLUDED_BSLH_HASHPAIR
#define INCLUDED_BSLH_HASHPAIR
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslh_hashpair bslh_hashpair
/// @brief  Provide `hashAppend` for `std::pair`.
/// @addtogroup bsl
/// @{
/// @addtogroup bslh
/// @{
/// @addtogroup bslh_hashpair
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslh_hashpair-purpose"> Purpose</a>
/// * <a href="#bslh_hashpair-description"> Description </a>
///   * <a href="#bslh_hashpair-usage"> Usage </a>
///     * <a href="#bslh_hashpair-example-1-hashing-a-pair-of-integer-values"> Example 1: Hashing a Pair of Integer Values </a>
///
/// # Purpose {#bslh_hashpair-purpose}
/// Provide `hashAppend` for `std::pair`.
///
/// # Description {#bslh_hashpair-description}
/// This component provides a free function template,
/// `bslh::hashAppend`, overloaded for the `std::pair` class template.
/// Including this function allows for `std::pair` types (and types that contain
/// them) to be used as keys in BDE hashed containers.
///
/// ## Usage {#bslh_hashpair-usage}
///
///
/// This section illustrates intended usage of this component.
///
/// ### Example 1: Hashing a Pair of Integer Values {#bslh_hashpair-example-1-hashing-a-pair-of-integer-values}
///
///
/// Suppose one must compute has that combines the hashes of several integer
/// values, each of a different type:
/// @code
/// char  c = 'a';
/// short s = static_cast<short>(1);
/// @endcode
/// First, we can make that calculation by repeated invocations of a
/// 'bslh::DefaultHashAlogorithm object:
/// @code
/// bslh::DefaultHashAlgorithm hasherS;
/// hasherS(&c, sizeof(char));
/// hasherS(&s, sizeof(short));
///
/// bslh::DefaultHashAlgorithm::result_type hashS = hasherS.computeHash();
/// @endcode
/// Now, the same calculation can also be be made if those same values are
/// contained in a single `std::pair` object.
/// @code
/// std::pair<char, short> t = std::make_pair(c, s);
///
/// bslh::DefaultHashAlgorithm hasherT;
/// bslh::hashAppend(hasherT, t);
///
/// bslh::DefaultHashAlgorithm::result_type hashT = hasherT.computeHash();
/// @endcode
/// Finally, we confirm that we computed the same result.
/// @code
/// assert(hashS == hashT);
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslh
 * @{
 */
/** @addtogroup bslh_hashpair
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslh_hash.h>
 
#include <utility> // 'std::pair'
 
 
namespace bslh {
 
// FREE FUNCTIONS
 
/// Invoke the (appropriate) `hashAppend` function, with the specified
/// `algorithm` on the `first` and `second` members, in that order, of the
/// specified `input` pair.
template <class HASH_ALGORITHM, class TYPE1, class TYPE2>
void
hashAppend(HASH_ALGORITHM& algorithm, const std::pair<TYPE1, TYPE2>& input);
 
// ============================================================================
//                          INLINE DEFINITIONS
// ============================================================================
 
// FREE FUNCTIONS
template <class HASH_ALGORITHM, class TYPE1, class TYPE2>
inline
void
hashAppend(HASH_ALGORITHM& algorithm, const std::pair<TYPE1, TYPE2>& input)
{
    hashAppend(algorithm, input.first);
    hashAppend(algorithm, input.second);
}
 
}  // 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */