bdlat_nullablevalueutil.h

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/// @file bdlat_nullablevalueutil.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlat_nullablevalueutil.h                                          -*-C++-*-
#ifndef INCLUDED_BDLAT_NULLABLEVALUEUTIL
#define INCLUDED_BDLAT_NULLABLEVALUEUTIL
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlat_nullablevalueutil bdlat_nullablevalueutil
/// @brief  Provide utilities for operating on `bdlat` "nullable value" types.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlat
/// @{
/// @addtogroup bdlat_nullablevalueutil
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlat_nullablevalueutil-purpose"> Purpose</a>
/// * <a href="#bdlat_nullablevalueutil-classes"> Classes </a>
/// * <a href="#bdlat_nullablevalueutil-description"> Description </a>
///   * <a href="#bdlat_nullablevalueutil-primitive-and-derived-functions-of-nullable-values"> Primitive and Derived Functions of Nullable Values </a>
///   * <a href="#bdlat_nullablevalueutil-usage"> Usage </a>
///     * <a href="#bdlat_nullablevalueutil-example-1-accessing-the-held-value-and-its-category"> Example 1: Accessing the Held Value And Its Category </a>
///
/// # Purpose {#bdlat_nullablevalueutil-purpose}
/// Provide utilities for operating on `bdlat` "nullable value" types.
///
/// # Classes {#bdlat_nullablevalueutil-classes}
///
/// -  bdlat::NullableValueUtil: namespace for utility functions on nullables
///
/// @see  bdlat_nullablevaluefunctions, bdlat_typecategory
///
/// # Description {#bdlat_nullablevalueutil-description}
/// This component provides a utility `struct`,
/// `bdlat::NullableValueUtil`, which serves as a namespace for a collection of
/// function templates providing derived operations for "nullable value" types.
/// See @ref bdlat_nullablevaluefunctions  for the set of requirements of
/// "nullable value" types in the `bdlat` framework.  See @ref bdlat_typecategory 
/// for more general information about this framework.
///
/// ## Primitive and Derived Functions of Nullable Values {#bdlat_nullablevalueutil-primitive-and-derived-functions-of-nullable-values}
///
///
/// In order to be "plugged in" to the `bdlat` framework as a "nullable value",
/// a type must meet a set of requirements including providing certain function
/// overloads (customization points) and specifying certain type traits, as
/// specified by the @ref bdlat_nullablevaluefunctions  component.  We call the
/// required function overloads the "primitive" operations of "nullable value"
/// types.  This component provides "derived" operations, which are operations
/// that are exclusively defined in terms of primitive operations, and as such
/// can be used with any "nullable value" type.
///
/// ## Usage {#bdlat_nullablevalueutil-usage}
///
///
/// In this section we show intended usage of this component.
///
/// ### Example 1: Accessing the Held Value And Its Category {#bdlat_nullablevalueutil-example-1-accessing-the-held-value-and-its-category}
///
///
/// Suppose we would like to define a function that detects whether the value
/// held by a nullable value is an array.
///
/// First, we need to define an accessor functor per
/// {@ref bdlat_typecategory |`ACCESSOR` Functors} that will be used to detect
/// whether the held value is an array:
/// @code
/// class MyArrayDetector {
///     // DATA
///     bool d_didVisitArray;
///
///   public:
///     // CREATORS
///     MyArrayDetector()
///     : d_didVisitArray(false)
///     {
///     }
///
///     // MANIPULATORS
///     template <class TYPE>
///     int operator()(const TYPE& object, bdlat_TypeCategory::Array)
///     {
///         d_didVisitArray = true;
///         return 0;
///     }
///
///     template <class TYPE, class OTHER_CATEGORY>
///     int operator()(const TYPE&, OTHER_CATEGORY)
///     {
///         d_didVisitArray = false;
///         return 0;
///     }
///
///     // ACCESSORS
///     bool didVisitArray()
///     {
///         return d_didVisitArray;
///     }
/// };
/// @endcode
/// Then, we can define a utility `struct`, `MyNullableValueUtil`, that provides
/// a function for detecting whether or not the held value of a nullable value
/// is an array:
/// @code
/// struct MyNullableValueUtil {
///
///     // CLASS METHODS
///     template <class TYPE>
///     static int isValueAnArray(bool *isArray, const TYPE& object)
///         // Load the value 'true' to the specified 'isArray' if the value
///         // stored in the specified 'object' has the "array" type category,
///         // and load the value 'false' otherwise.  Return 0 on success,
///         // and a non-zero value otherwise.  If a non-zero value is
///         // returned, the value loaded to 'isArray' is unspecified.  The
///         // behavior is undefined if 'object' contains a null value.
///     {
///         BSLS_ASSERT(bdlat_TypeCategoryFunctions::select(object) ==
///                     bdlat_TypeCategory::e_NULLABLE_VALUE_CATEGORY);
///         BSLS_ASSERT(!bdlat_NullableValueFunctions::isNull(object));
///
///         MyArrayDetector detector;
///         int rc = bdlat::NullableValueUtil::accessValueByCategory(object,
///                                                                  detector);
///         if (0 != rc) {
///             return -1;                                            // RETURN
///         }
///
///         *isArray = detector.didVisitArray();
///         return 0;
///     }
/// };
/// @endcode
/// Finally, we can use this utility to detect whether nullable values are
/// arrays:
/// @code
/// void example()
/// {
///     bdlb::NullableValue<int> valueA(42);
///
///     bool isArray = false;
///     int rc = MyNullableValueUtil::isValueAnArray(&isArray, valueA);
///
///     assert(0 == rc);
///     assert(! isArray);
///
///     bdlb::NullableValue<bsl::vector<int> > valueB;
///     valueB.makeValue(bsl::vector<int>());
///
///     rc = MyNullableValueUtil::isValueAnArray(&isArray, valueB);
///
///     assert(0 == rc);
///     assert(isArray);
/// }
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlat
 * @{
 */
/** @addtogroup bdlat_nullablevalueutil
 * @{
 */
 
#include <bdlscm_version.h>
 
#include <bdlat_nullablevaluefunctions.h>
#include <bdlat_typecategory.h>
 
#include <bslmf_assert.h>
#include <bslmf_integralconstant.h>
 
 
#include <bsls_assert.h>
#include <bsls_platform.h>
 
 
namespace bdlat {
 
                          // ========================
                          // struct NullableValueUtil
                          // ========================
 
/// This `struct` provides a namespace for a suite of function templates
/// providing non-primitive operations on "nullable value" types.
struct NullableValueUtil {
 
  private:
    // PRIVATE TYPES
 
    /// This private class provides a function-object type that adapts a
    /// (categorized) accessor functor to an uncategorized accessor functor.
    /// For the definition of an accessor functor, see
    /// {@ref bdlat_typecategory |`ACCESSOR` Functors}.  An uncategorized
    /// accessor functor is one that does not take a second, `category`,
    /// argument, such as a functor that may be passed to
    /// `bdlat_NullableValueFunctions::accessValue`, for example.
    template <class ACCESSOR>
    class AccessByCategoryAdapter;
 
    /// This private class provides a function-object type that adapts a
    /// (categorized) manipulator functor to an uncategorized manipulator
    /// functor.  For the definition of a manipulator functor, see
    /// {@ref bdlat_typecategory |`MANIPULATOR` Functors}.  An uncategorized
    /// manipulator functor is one that does not take a second, `category`,
    /// argument, such as a functor that may be passed to
    /// `bdlat_NullableValueFunctions::manipulateValue`, for example.
    template <class MANIPULATOR>
    class ManipulateByCategoryAdapter;
 
  public:
    // CLASS METHODS
 
    /// Invoke the specified `accessor` on the non-modifiable value
    /// stored in the specified "nullable" `object` and on a prvalue of
    /// the category tag type for the dynamic category of the value.  See
    /// {@ref bdlat_typecategory |Category Tags and Enumerators} for
    /// documentation about category tags.  Return the value from the
    /// invocation of `accessor`.  The `accessor` must be an accessor
    /// functor.  See {@ref bdlat_typecategory |`ACCESSOR` Functors} for the
    /// requirements on `accessor`.  The behavior is undefined if `object`
    /// contains a null value.
    template <class TYPE, class ACCESSOR>
    static int accessValueByCategory(const TYPE& object, ACCESSOR& accessor);
 
    /// Invoke the specified `manipulator` on the address of the value
    /// stored in the specified "nullable" `object` and on a prvalue of
    /// the category tag type for the dynamic category of the value.  See
    /// {@ref bdlat_typecategory |Category Tags and Enumerators} for
    /// documentation about category tags.  Return the value from the
    /// invocation of `manipulator`.  The `manipulator` must be a
    /// manipulator functor.  See
    /// {@ref bdlat_typecategory |`MANIPULATOR` Functors}
    /// for the requirements on `manipulator`.  The behavior is undefined if
    /// `object` contains a null value.
    template <class TYPE, class MANIPULATOR>
    static int manipulateValueByCategory(TYPE         *object,
                                         MANIPULATOR&  manipulator);
};
 
              // ================================================
              // class NullableValueUtil::AccessByCategoryAdapter
              // ================================================
 
/// See the class-level documentation of `NullableValueUtil` for the
/// description of this component-private class template.
template <class ACCESSOR>
class NullableValueUtil::AccessByCategoryAdapter {
 
    // DATA
 
    // The `accessor` attribute of this object.
    ACCESSOR *d_accessor_p;
 
  public:
    // CREATORS
 
    /// Create an `AccessByCategoryAdapter` object having the specified
    /// `accessor` attribute.
    explicit AccessByCategoryAdapter(ACCESSOR *accessor);
 
    // ACCESSORS
 
    /// Invoke the `accessor` of this object with the specified `value` and
    /// a prvalue of the category tag type for its dynamic category.  Return
    /// the value from the invocation of `accessor`.
    template <class VALUE_TYPE>
    int operator()(const VALUE_TYPE& value) const;
};
 
            // ====================================================
            // class NullableValueUtil::ManipulateByCategoryAdapter
            // ====================================================
 
/// See the class-level documentation of `NullableValueUtil` for the
/// description of this component-private class template.
template <class MANIPULATOR>
class NullableValueUtil::ManipulateByCategoryAdapter {
 
    // DATA
 
    // The `manipulator` attribute of this object.
    MANIPULATOR *d_manipulator_p;
 
  public:
    // CREATORS
 
    /// Create a `ManipulateByCategory` object having the specified
    /// `manipulator` attribute value.
    explicit ManipulateByCategoryAdapter(MANIPULATOR *manipulator);
 
    // ACCESSORS
 
    /// Invoke the `manipulator` of this object with the specified `value`
    /// and a prvalue of the category tag type for its dynamic category.
    /// Return the value from the invocation of the `manipulator`.
    template <class VALUE_TYPE>
    int operator()(VALUE_TYPE *value) const;
};
 
// ============================================================================
//                            INLINE DEFINITIONS
// ============================================================================
 
                          // -----------------------
                          // class NullableValueUtil
                          // -----------------------
 
// CLASS METHODS
template <class TYPE, class ACCESSOR>
inline
int NullableValueUtil::accessValueByCategory(const TYPE& object,
                                             ACCESSOR&   accessor)
{
#if !defined(BSLS_PLATFORM_CMP_SUN)
    BSLMF_ASSERT((bdlat_NullableValueFunctions::IsNullableValue<TYPE>::value));
#endif
    BSLS_ASSERT(bdlat_TypeCategoryFunctions::select(object) ==
                bdlat_TypeCategory::e_NULLABLE_VALUE_CATEGORY);
    BSLS_ASSERT(!bdlat_NullableValueFunctions::isNull(object));
 
    const NullableValueUtil::AccessByCategoryAdapter<ACCESSOR> adapter(
                                                                    &accessor);
    return bdlat_NullableValueFunctions::accessValue(object, adapter);
}
 
template <class TYPE, class MANIPULATOR>
inline
int NullableValueUtil::manipulateValueByCategory(TYPE         *object,
                                                 MANIPULATOR&  manipulator)
{
#if !defined(BSLS_PLATFORM_CMP_SUN)
    BSLMF_ASSERT((bdlat_NullableValueFunctions::IsNullableValue<TYPE>::value));
#endif
    BSLS_ASSERT(object);
    BSLS_ASSERT(bdlat_TypeCategoryFunctions::select(*object) ==
                bdlat_TypeCategory::e_NULLABLE_VALUE_CATEGORY);
    BSLS_ASSERT(!bdlat_NullableValueFunctions::isNull(*object));
 
    const NullableValueUtil::ManipulateByCategoryAdapter<MANIPULATOR> adapter(
                                                                 &manipulator);
    return bdlat_NullableValueFunctions::manipulateValue(object, adapter);
}
 
              // ------------------------------------------------
              // class NullableValueUtil::AccessByCategoryAdapter
              // ------------------------------------------------
 
// CREATORS
template <class ACCESSOR>
inline
NullableValueUtil::AccessByCategoryAdapter<ACCESSOR>::AccessByCategoryAdapter(
                                                            ACCESSOR *accessor)
: d_accessor_p(accessor)
{
}
 
// ACCESSORS
template <class ACCESSOR>
template <class VALUE_TYPE>
inline
int NullableValueUtil::AccessByCategoryAdapter<ACCESSOR>::operator()(
                                                 const VALUE_TYPE& value) const
{
    return bdlat_TypeCategoryUtil::accessByCategory(value, *d_accessor_p);
}
 
            // ----------------------------------------------------
            // class NullableValueUtil::ManipulateByCategoryAdapter
            // ----------------------------------------------------
 
// CREATORS
template <class MANIPULATOR>
inline
NullableValueUtil::ManipulateByCategoryAdapter<
    MANIPULATOR>::ManipulateByCategoryAdapter(MANIPULATOR *manipulator)
: d_manipulator_p(manipulator)
{
}
 
// ACCESSORS
template <class MANIPULATOR>
template <class VALUE_TYPE>
inline
int NullableValueUtil::ManipulateByCategoryAdapter<MANIPULATOR>::operator()(
                                                       VALUE_TYPE *value) const
{
    return bdlat_TypeCategoryUtil::manipulateByCategory(value,
                                                        *d_manipulator_p);
}
 
}  // close package namespace
 
 
#endif  // INCLUDED_BDLAT_NULLABLEVALUEUTIL
 
// ----------------------------------------------------------------------------
// Copyright 2022 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */