bdlat_enumutil.h

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/// @file bdlat_enumutil.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlat_enumutil.h                                                   -*-C++-*-
#ifndef INCLUDED_BDLAT_ENUMUTIL
#define INCLUDED_BDLAT_ENUMUTIL
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlat_enumutil bdlat_enumutil
/// @brief  Provide functions for decoding enumerations with fallback values.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlat
/// @{
/// @addtogroup bdlat_enumutil
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlat_enumutil-purpose"> Purpose</a>
/// * <a href="#bdlat_enumutil-classes"> Classes </a>
/// * <a href="#bdlat_enumutil-description"> Description </a>
///   * <a href="#bdlat_enumutil-usage"> Usage </a>
///
/// # Purpose {#bdlat_enumutil-purpose}
/// Provide functions for decoding enumerations with fallback values.
///
/// # Classes {#bdlat_enumutil-classes}
///
/// -  bdlat::EnumUtil: namespace for utility functions for decoding enumerations
///
/// @see  bdlat_enumfunctions
///
/// # Description {#bdlat_enumutil-description}
/// This component provides a `struct`, `bdlat::EnumUtil`, with two
/// utility function templates, `fromIntOrFallbackIfEnabled` and
/// `fromStringOrFallbackIfEnabled`, which respectively attempt to decode a
/// `bdlat` "enumeration" type from the integral or string representation.
/// However, unlike the decoding functions in the `bdlat_EnumFunctions`
/// namespace, when the functions in this component are given values that do not
/// correspond to any enumerator, they attempt to set the result to the
/// "fallback" enumerator value, if possible, instead of failing.
///
/// ## Usage {#bdlat_enumutil-usage}
///
///
/// This section illustrates intended use of this component.
///
/// Suppose you have a C++ `enum` type called `ImageType` whose enumerators
/// represent supported formats for image files, and it exposes "enumeration"
/// behavior as described in @ref bdlat_enumfunctions :
/// @code
/// #include <bdlat_enumfunctions.h>
/// #include <bdlb_string.h>
/// #include <bsl_string.h>
///
/// namespace BloombergLP {
/// namespace mine {
///
/// enum ImageType {
///     JPG     = 0,
///     PNG     = 1,
///     GIF     = 2,
///     UNKNOWN = 100
/// };
///
/// // MANIPULATORS
///
/// int bdlat_enumFromInt(ImageType* result, int number);
///
/// int bdlat_enumFromString(ImageType  *result,
///                          const char *string,
///                          int         stringLength);
///
/// int bdlat_enumMakeFallback(ImageType *result);
///
/// // ACCESSORS
///
/// void bdlat_enumToInt(int *result, const ImageType& value);
///
/// void bdlat_enumToString(bsl::string *result, const ImageType& value);
///
/// bool bdlat_enumHasFallback(const ImageType&);
///
/// bool bdlat_enumIsFallback(const ImageType& value);
///
/// }  // close namespace mine
/// @endcode
/// Next, we provide definitions for the `bdlat_enum*` customization point
/// function overloads:
/// @code
/// // MANIPULATORS
///
/// inline
/// int mine::bdlat_enumFromInt(ImageType *result, int number)
/// {
///     enum { SUCCESS = 0, NOT_FOUND = -1 };
///
///     switch (number) {
///       case JPG: {
///         *result = JPG;
///         return SUCCESS;
///       }
///       case PNG: {
///         *result = PNG;
///         return SUCCESS;
///       }
///       case GIF: {
///         *result = GIF;
///         return SUCCESS;
///       }
///       case UNKNOWN: {
///         *result = UNKNOWN;
///         return SUCCESS;
///       }
///       default: {
///         return NOT_FOUND;
///       }
///     }
/// }
///
/// inline
/// int mine::bdlat_enumFromString(ImageType  *result,
///                                const char *string,
///                                int         stringLength)
/// {
///     enum { SUCCESS = 0, NOT_FOUND = -1 };
///
///     if (bdlb::String::areEqualCaseless("jpg",
///                                        string,
///                                        stringLength)) {
///         *result = JPG;
///         return SUCCESS;
///     }
///
///     if (bdlb::String::areEqualCaseless("png",
///                                        string,
///                                        stringLength)) {
///         *result = PNG;
///         return SUCCESS;
///     }
///
///     if (bdlb::String::areEqualCaseless("gif",
///                                        string,
///                                        stringLength)) {
///         *result = GIF;
///         return SUCCESS;
///     }
///     if (bdlb::String::areEqualCaseless("unknown",
///                                        string,
///                                        stringLength)) {
///         *result = UNKNOWN;
///         return SUCCESS;
///     }
///
///     return NOT_FOUND;
/// }
///
/// inline
/// int mine::bdlat_enumMakeFallback(ImageType *result)
/// {
///     *result = UNKNOWN;
///     return 0;
/// }
///
/// // ACCESSORS
///
/// inline
/// void mine::bdlat_enumToInt(int *result, const ImageType& value)
/// {
///     *result = static_cast<int>(value);
/// }
///
/// inline
/// void mine::bdlat_enumToString(bsl::string *result, const ImageType& value)
/// {
///     switch (value) {
///       case JPG: {
///         *result = "JPG";
///       } break;
///       case PNG: {
///         *result = "PNG";
///       } break;
///       case GIF: {
///         *result = "GIF";
///       } break;
///       case UNKNOWN: {
///         *result = "UNKNOWN";
///       } break;
///       default: {
///         *result = "INVALID";
///       } break;
///     }
/// }
///
/// inline
/// bool mine::bdlat_enumHasFallback(const ImageType&)
/// {
///     return true;
/// }
///
/// inline
/// bool mine::bdlat_enumIsFallback(const ImageType& value)
/// {
///     return value == UNKNOWN;
/// }
/// @endcode
/// To complete the implementation of `mine::ImageType` as an "enumeration" type
/// with fallback enumerator recognized by the `bdlat` framework, we specialize
/// the necessary traits:
/// @code
/// namespace bdlat_EnumFunctions {
/// template <>
/// struct IsEnumeration<mine::ImageType> : bsl::true_type {
/// };
/// template <>
/// struct HasFallbackEnumerator<mine::ImageType> : bsl::true_type {
/// };
/// }  // close namespace bdlat_EnumFunctions
/// }  // close enterprise namespace
/// @endcode
/// We can now use the methods in `EnumUtil` to decode integral and string
/// values into `mine::ImageType` values, falling back to the `mine::UNKNOWN`
/// enumerator value when the integral or string value does not correspond to
/// any enumerator:
/// @code
/// void usageExample()
/// {
///     using namespace BloombergLP;
///
///     mine::ImageType imageType;
///     int rc;
///
///     rc = bdlat::EnumUtil::fromIntOrFallbackIfEnabled(&imageType, 1);
///     assert(0         == rc);
///     assert(mine::PNG == imageType);
///
///     rc = bdlat::EnumUtil::fromIntOrFallbackIfEnabled(&imageType, 4);
///     assert(0             == rc);
///     assert(mine::UNKNOWN == imageType);
///
///     rc = bdlat::EnumUtil::fromStringOrFallbackIfEnabled(&imageType,
///                                                         "GIF",
///                                                         3);
///     assert(0         == rc);
///     assert(mine::GIF == imageType);
///
///     rc = bdlat::EnumUtil::fromStringOrFallbackIfEnabled(&imageType,
///                                                         "WEBP",
///                                                         4);
///     assert(0             == rc);
///     assert(mine::UNKNOWN == imageType);
/// }
/// @endcode
/// Note that the methods in `EnumUtil` may also be used with `bdlat`
/// "enumeration" types that do not support a fallback enumerator.  In such
/// cases, they can fail by returning a non-zero error code.
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlat
 * @{
 */
/** @addtogroup bdlat_enumutil
 * @{
 */
 
#include <bdlat_enumfunctions.h>
 
#include <bslmf_assert.h>
#include <bslmf_integralconstant.h>
 
#include <bsls_platform.h>
 
 
namespace bdlat {
 
                              // ===============
                              // struct EnumUtil
                              // ===============
 
/// This `struct` provides a namespace for functions that decode `bdlat`
/// "enumerations" from integral and string representations, possibly to the
/// "fallback" value (if one exists).
///
/// See @ref bdlat_enumutil 
struct EnumUtil {
 
    // CLASS METHODS
 
    /// Load into the specified `result` the enumerator matching the
    /// specified `number` and return 0 if such an enumerator exists.
    /// Otherwise, if `result` supports a fallback enumerator, load into
    /// `result` the fallback enumerator value and return 0.  Otherwise,
    /// return a non-zero value with no effect on `result`.  
    /// 
    /// \pre The behavior is undefined   unless `TYPE` is a `bdlat` enumeration type.
    template <class TYPE>
    static int fromIntOrFallbackIfEnabled(TYPE *result, int number);
 
    /// Load into the specified `result` the enumerator matching the
    /// specified `string` of the specified `stringLength` and return 0 if
    /// such an enumerator exists.  Otherwise, if `result` supports a
    /// fallback enumerator, load into `result` the fallback enumerator
    /// value and return 0.  Otherwise, return a non-zero value with no effect on `result`.  
    /// 
    /// \pre The behavior is undefined   unless `TYPE` is a
    /// `bdlat` enumeration type.
    template <class TYPE>
    static int fromStringOrFallbackIfEnabled(TYPE       *result,
                                             const char *string,
                                             int         stringLength);
};
 
// ============================================================================
//                            INLINE DEFINITIONS
// ============================================================================
 
                              // ---------------
                              // struct EnumUtil
                              // ---------------
 
// CLASS METHODS
template <class TYPE>
int EnumUtil::fromIntOrFallbackIfEnabled(TYPE *result, int number)
{
#if !defined(BSLS_PLATFORM_CMP_SUN)
    BSLMF_ASSERT((bdlat_EnumFunctions::IsEnumeration<TYPE>::value));
#endif
 
    if (0 == bdlat_EnumFunctions::fromInt(result, number)) {
        return 0;                                                     // RETURN
    }
 
    return bdlat_EnumFunctions::makeFallback(result);
}
 
template <class TYPE>
int EnumUtil::fromStringOrFallbackIfEnabled(TYPE       *result,
                                            const char *string,
                                            int         stringLength)
{
#if !defined(BSLS_PLATFORM_CMP_SUN)
    BSLMF_ASSERT((bdlat_EnumFunctions::IsEnumeration<TYPE>::value));
#endif
 
    if (0 == bdlat_EnumFunctions::fromString(result, string, stringLength)) {
        return 0;                                                     // RETURN
    }
 
    return bdlat_EnumFunctions::makeFallback(result);
}
 
}  // close package namespace
 
 
#endif  // INCLUDED_BDLAT_ENUMUTIL
 
// ----------------------------------------------------------------------------
// 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */