bslstl_stringviewlikeparam.h

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/// @file bslstl_stringviewlikeparam.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslstl_stringviewlikeparam.h                                      -*-C++-*-
#ifndef INCLUDED_BSLSTL_STRINGVIEWLIKEPARAM
#define INCLUDED_BSLSTL_STRINGVIEWLIKEPARAM
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslstl_stringviewlikeparam bslstl_stringviewlikeparam
/// @brief  Provide macros for SFINAE constraints on string-view-like params.
/// @addtogroup bsl
/// @{
/// @addtogroup bslstl
/// @{
/// @addtogroup bslstl_stringviewlikeparam
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslstl_stringviewlikeparam-purpose"> Purpose</a>
/// * <a href="#bslstl_stringviewlikeparam-macros"> Macros </a>
/// * <a href="#bslstl_stringviewlikeparam-description"> Description </a>
///   * <a href="#bslstl_stringviewlikeparam-macro-summary">  Macro Summary </a>
///   * <a href="#bslstl_stringviewlikeparam-usage"> Usage </a>
///     * <a href="#bslstl_stringviewlikeparam-example-1-declaring-a-string-view-like-constructor"> Example 1: Declaring a String-View-Like Constructor </a>
///
/// # Purpose {#bslstl_stringviewlikeparam-purpose}
/// Provide macros for SFINAE constraints on string-view-like params.
///
/// # Macros {#bslstl_stringviewlikeparam-macros}
///
/// -  BSLSTL_STRINGVIEWLIKEPARAM_TYPE_IF_COMPLETE: completeness check
/// -  BSLSTL_STRINGVIEWLIKEPARAM_ENABLE_IF_T: SV-convertible enable_if
/// -  BSLSTL_STRINGVIEWLIKEPARAM_ONLY_ENABLE_IF_T: SV-conv, not C-string
///
/// @see  bslstl_isconvertibletostringview, bslstl_isconvertibletocstring
///
/// # Description {#bslstl_stringviewlikeparam-description}
/// This component provides a set of macros that simplify the
/// declaration of function template parameters constrained to accept
/// "string-view-like" types.  A type is considered "string-view-like" if it is
/// convertible to `bsl::basic_string_view<CHAR_TYPE, CHAR_TRAITS>`.
///
/// The "ONLY" variants additionally exclude types that are convertible to
/// `const CHAR_TYPE *` (C-strings), which is useful for overload resolution
/// when separate overloads exist for C-string arguments.
///
/// These macros are designed to be used in function declarations and
/// definitions where SFINAE is needed to constrain template parameters.
///
/// ##  Macro Summary {#bslstl_stringviewlikeparam-macro-summary}
///
///
/// This section provides a brief description of each macro:
///
/// - `BSLSTL_STRINGVIEWLIKEPARAM_TYPE_IF_COMPLETE`: Helper macro that
///   provides a completeness check for the `STRING_VIEW_LIKE_TYPE` template
///   parameter, working around SFINAE deficiencies in certain compilers.
///
/// - `BSLSTL_STRINGVIEWLIKEPARAM_ENABLE_IF_T(ResultType)`: SFINAE
///   `enable_if` type alias for types convertible to string_view.  The result
///   is `ResultType` if enabled.  Use as:
///   `BSLSTL_STRINGVIEWLIKEPARAM_ENABLE_IF_T(void) * = 0` for declaration,
///   or `BSLSTL_STRINGVIEWLIKEPARAM_ENABLE_IF_T(const ALLOCATOR&) alloc =`
///                                                              `ALLOCATOR()`
///
/// - `BSLSTL_STRINGVIEWLIKEPARAM_ONLY_ENABLE_IF_T(ResultType)`: SFINAE
///   `enable_if` type alias for types convertible to string_view but NOT
///   convertible to C-string (`const CHAR_TYPE *`).  The result is
///   `ResultType` if enabled.  Use as:
///   `BSLSTL_STRINGVIEWLIKEPARAM_ONLY_ENABLE_IF_T(void) * = 0` for
///   declaration, or
///   `BSLSTL_STRINGVIEWLIKEPARAM_ONLY_ENABLE_IF_T(const ALLOCATOR&) alloc =`
///                                                              `ALLOCATOR()`
///
/// ## Usage {#bslstl_stringviewlikeparam-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Declaring a String-View-Like Constructor {#bslstl_stringviewlikeparam-example-1-declaring-a-string-view-like-constructor}
///
///
/// Suppose we want to declare a constructor that accepts any type convertible
/// to `bsl::string_view` but not `const char *`.
///
/// First, we declare the constructor in the class definition:
/// @code
/// template <class STRING_VIEW_LIKE_TYPE>
/// explicit MyClass(const STRING_VIEW_LIKE_TYPE& value,
///                  BSLSTL_STRINGVIEWLIKEPARAM_ONLY_ENABLE_IF_T(void) *= 0);
/// @endcode
/// Then, we define the constructor outside the class:
/// @code
/// template <class STRING_VIEW_LIKE_TYPE>
/// MyClass::MyClass(const STRING_VIEW_LIKE_TYPE& value,
///                  BSLSTL_STRINGVIEWLIKEPARAM_ONLY_ENABLE_IF_T(void) *)
/// {
///     bsl::string_view sv = value;
///     // use sv...
/// }
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslstl
 * @{
 */
/** @addtogroup bslstl_stringviewlikeparam
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslstl_isconvertibletocstring.h>
#include <bslstl_isconvertibletostringview.h>
 
#include <bslmf_enableif.h>
 
#include <bsls_platform.h>
 
/// We need to use an intermediate completeness test to work around
/// deficiencies with SFINAE in the Sun and AIX compilers.
#define BSLSTL_STRINGVIEWLIKEPARAM_TYPE_IF_COMPLETE                           \
    typename bsl::enable_if<0 != sizeof(STRING_VIEW_LIKE_TYPE),               \
                            const STRING_VIEW_LIKE_TYPE&>::type
 
/// Expand to an `enable_if` type alias for `ResultType` that is defined
/// (i.e., SFINAE-friendly) only when the `STRING_VIEW_LIKE_TYPE` template
/// parameter is convertible to
/// `bsl::basic_string_view<CHAR_TYPE, CHAR_TRAITS>`.  The `CHAR_TYPE` and
/// `CHAR_TRAITS` template parameters must be in scope.  The specified
/// `ResultType` (passed as a variadic argument) is the resulting type when
/// the condition is satisfied.
#define BSLSTL_STRINGVIEWLIKEPARAM_ENABLE_IF_T(...)                           \
    typename bsl::enable_if<                                                  \
        BloombergLP::bslstl::IsConvertibleToStringView<                       \
            CHAR_TYPE,                                                        \
            CHAR_TRAITS,                                                      \
            BSLSTL_STRINGVIEWLIKEPARAM_TYPE_IF_COMPLETE>::value,              \
        __VA_ARGS__>::type
 
/// Expand to an `enable_if` type alias for `ResultType` that is defined
/// (i.e., SFINAE-friendly) only when the `STRING_VIEW_LIKE_TYPE` template
/// parameter is convertible to
/// `bsl::basic_string_view<CHAR_TYPE, CHAR_TRAITS>` but is *not*
/// convertible to `const CHAR_TYPE *`.  The `CHAR_TYPE` and `CHAR_TRAITS`
/// template parameters must be in scope.  The specified `ResultType`
/// (passed as a variadic argument) is the resulting type when both
/// conditions are satisfied.
#define BSLSTL_STRINGVIEWLIKEPARAM_ONLY_ENABLE_IF_T(...)                      \
    typename bsl::enable_if<                                                  \
        BloombergLP::bslstl::IsConvertibleToStringView<                       \
            CHAR_TYPE,                                                        \
            CHAR_TRAITS,                                                      \
            BSLSTL_STRINGVIEWLIKEPARAM_TYPE_IF_COMPLETE>::value               \
     && !BloombergLP::bslstl::IsConvertibleToCString<                         \
            CHAR_TYPE,                                                        \
            BSLSTL_STRINGVIEWLIKEPARAM_TYPE_IF_COMPLETE>::value,              \
        __VA_ARGS__>::type
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2026 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */