// bdlat_nullablevalueutil.h -*-C++-*-
#ifndef INCLUDED_BDLAT_NULLABLEVALUEUTIL
#define INCLUDED_BDLAT_NULLABLEVALUEUTIL
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
//@PURPOSE: Provide utilities for operating on 'bdlat' "nullable value" types.
//
//@CLASSES:
// bdlat::NullableValueUtil: namespace for utility functions on nullables
//
//@SEE_ALSO: bdlat_nullablevaluefunctions, bdlat_typecategory
//
//@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 {'bdlat_nullablevaluefunctions'} for the set of requirements of
// "nullable value" types in the 'bdlat' framework. See {'bdlat_typecategory'}
// for more general information about this framework.
//
///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 {'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
///-----
// In this section we show intended usage of this component.
//
///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
// {'bdlat_typecategory'|'ACCESSOR' Functors} that will be used to detect
// whether the held value is an array:
//..
// 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;
// }
// };
//..
// 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:
//..
// 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;
// }
// };
//..
// Finally, we can use this utility to detect whether nullable values are
// arrays:
//..
// 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);
// }
//..
#include <bdlscm_version.h>
#include <bdlat_nullablevaluefunctions.h>
#include <bdlat_typecategory.h>
#include <bslmf_assert.h>
#include <bsls_assert.h>
#include <bsls_platform.h>
namespace BloombergLP {
namespace bdlat {
// ========================
// struct NullableValueUtil
// ========================
struct NullableValueUtil {
// This 'struct' provides a namespace for a suite of function templates
// providing non-primitive operations on "nullable value" types.
private:
// PRIVATE TYPES
template <class ACCESSOR>
class AccessByCategoryAdapter;
// 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
// {'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 MANIPULATOR>
class ManipulateByCategoryAdapter;
// 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
// {'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.
public:
// CLASS METHODS
template <class TYPE, class ACCESSOR>
static int accessValueByCategory(const TYPE& object, ACCESSOR& accessor);
// 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
// {'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 {'bdlat_typecategory'|'ACCESSOR' Functors} for the
// requirements on 'accessor'. The behavior is undefined if 'object'
// contains a null value.
template <class TYPE, class MANIPULATOR>
static int manipulateValueByCategory(TYPE *object,
MANIPULATOR& manipulator);
// 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
// {'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
// {'bdlat_typecategory'|'MANIPULATOR' Functors}
// for the requirements on 'manipulator'. The behavior is undefined if
// 'object' contains a null value.
};
// ================================================
// class NullableValueUtil::AccessByCategoryAdapter
// ================================================
template <class ACCESSOR>
class NullableValueUtil::AccessByCategoryAdapter {
// See the class-level documentation of 'NullableValueUtil' for the
// description of this component-private class template.
// DATA
ACCESSOR *d_accessor_p;
// The 'accessor' attribute of this object.
public:
// CREATORS
explicit AccessByCategoryAdapter(ACCESSOR *accessor);
// Create an 'AccessByCategoryAdapter' object having the specified
// 'accessor' attribute.
// ACCESSORS
template <class VALUE_TYPE>
int operator()(const VALUE_TYPE& value) const;
// 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'.
};
// ====================================================
// class NullableValueUtil::ManipulateByCategoryAdapter
// ====================================================
template <class MANIPULATOR>
class NullableValueUtil::ManipulateByCategoryAdapter {
// See the class-level documentation of 'NullableValueUtil' for the
// description of this component-private class template.
// DATA
MANIPULATOR *d_manipulator_p;
// The 'manipulator' attribute of this object.
public:
// CREATORS
explicit ManipulateByCategoryAdapter(MANIPULATOR *manipulator);
// Create a 'ManipulateByCategory' object having the specified
// 'manipulator' attribute value.
// ACCESSORS
template <class VALUE_TYPE>
int operator()(VALUE_TYPE *value) const;
// 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'.
};
// ============================================================================
// 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
} // close enterprise 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 ----------------------------------