bdlf_noop.h

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/// @file bdlf_noop.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlf_noop.h                                                        -*-C++-*-
#ifndef INCLUDED_BDLF_NOOP
#define INCLUDED_BDLF_NOOP
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlf_noop bdlf_noop
/// @brief  Provide a functor class that does nothing.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlf
/// @{
/// @addtogroup bdlf_noop
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlf_noop-purpose"> Purpose</a>
/// * <a href="#bdlf_noop-classes"> Classes </a>
/// * <a href="#bdlf_noop-description"> Description </a>
///   * <a href="#bdlf_noop-usage"> Usage </a>
///     * <a href="#bdlf_noop-example-1-an-unwanted-bsl-function-callback"> Example 1: An Unwanted bsl::function Callback </a>
///     * <a href="#bdlf_noop-example-2-an-unwanted-template-type-callback"> Example 2: An Unwanted Template Type Callback </a>
///
/// # Purpose {#bdlf_noop-purpose}
/// Provide a functor class that does nothing.
///
/// # Classes {#bdlf_noop-classes}
///
/// -  bdlf::NoOp: Functor that accepts any parameters and does nothing.
///
/// # Description {#bdlf_noop-description}
/// This component provides a class, `bdlf::NoOp`, that is a
/// functor whose function-call operator accepts any number of arguments, does
/// nothing (leaving all arguments unmodified), and returns `void`. On platforms
/// where `inline` `constexpr` variables are supported, this component also
/// provides `bdlf::noOp`, which is a `constexpr` variable of type `bdlf::NoOp`.
///
/// ## Usage {#bdlf_noop-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: An Unwanted bsl::function Callback {#bdlf_noop-example-1-an-unwanted-bsl-function-callback}
///
///
/// Asynchronous systems often provide callback-based interfaces that invoke
/// supplied callbacks at later points in time, often when an event has
/// occurred, like the receipt of a data packet on an internet socket.
/// Occasionally, we may need to supply these interfaces with a callback even
/// though there's nothing we need the callback to do. In these cases, it's
/// often possible to supply a "no-op" callback that does nothing.
///
/// Consider, for example, the following hypothetical interface to an
/// asynchronous system:
/// @code
/// struct MyAsyncSystemUtil {
///     // TYPES
///     typedef bsl::function<void(int)> StatusReceivedCallback;
///         // 'StatusReceivedCallback' is an alias for a callback functor that
///         // takes as an argument an integer status indicating success (0),
///         // or failures (any non-zero value).
///
///     static void sendPing(const StatusReceivedCallback& callback);
///         // Send a message to the server that this client is still active.
///         // Invoke the specified 'callback' with the value '0' on the worker
///         // thread when this client receives, within the configured time
///         // limit, an acknowledgement from the server that it received the
///         // message.  Otherwise, invoke the 'callback' with a non-zero value
///         // on the worker thread after the configured time limit has expired
///         // or the server or network responds with an error, whichever comes
///         // first.
/// };
/// @endcode
/// Suppose that we are writing a client for this system that does not need to
/// be concerned about the status of `ping` messages sent to the server, then we
/// can use `bdlf::NoOp` to ignore the acknowledgements:
/// @code
/// void example1()
/// {
///     MyAsyncSystemUtil::sendPing(bdlf::NoOp());
/// }
/// @endcode
///
/// ### Example 2: An Unwanted Template Type Callback {#bdlf_noop-example-2-an-unwanted-template-type-callback}
///
///
/// Suppose that we are working with an asynchronous system whose interface
/// requires a template for a callback instead of a `bsl::function`.
///
/// Consider, for example, the following hypothetical interface to an
/// asynchronous system:
/// @code
/// template <class t_CALLBACK>
/// class AsyncSystem
/// {
///     // This class implements an asynchronous system which does important
///     // example work.  While the important example work is being done, a
///     // callback mechanism of type 't_CALLBACK' is used to provide estimates
///     // about the percentage of the work that is complete.  The type
///     // 't_CALLBACK' must be callable with a single 'int' parameter [0,100].
///
///     // DATA
///     t_CALLBACK d_callback;  // callable that gives feedback when 'run' runs
///
///     public:
///     // CREATORS
///     explicit AsyncSystem(const t_CALLBACK& callback = t_CALLBACK());
///         // Create a 'AsyncSystem' object which can be used to do important
///         // example work.  Optionally specify 'callback', a 't_CALLBACK',
///         // object to be used for giving feedback about progress.  If no
///         // 'callback' is specified, a default-constructed object of type
///         // 't_CALLBACK' will be used.
///
///     // MANIPULATORS
///     void run();
///         // Do the very important example work that this class is designed
///         // to do.  While doing said work, periodically invoke the
///         // 'callback' object provided to the constructor with an estimated
///         // percentage of the task complete as an 'int'.
/// };
/// @endcode
/// Suppose that we are writing a client of this system that has no useful way
/// to report the progress from the callback, then we can use `bdlf::NoOp` to
/// ignore the progress reports:
/// @code
/// void example2()
/// {
///     AsyncSystem<bdlf::NoOp> mySystem;
///     mySystem.run();
/// }
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlf
 * @{
 */
/** @addtogroup bdlf_noop
 * @{
 */
 
#include <bdlscm_version.h>
 
#include <bslmf_istriviallycopyable.h>
#include <bslmf_nestedtraitdeclaration.h>
 
#include <bsla_maybeunused.h>
 
#include <bsls_compilerfeatures.h>
#include <bsls_keyword.h>
 
#if BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
// Include version that can be compiled with C++03
// Generated on Wed Apr 12 13:24:41 2023
// Command line: sim_cpp11_features.pl bdlf_noop.h
# define COMPILING_BDLF_NOOP_H
# include <bdlf_noop_cpp03.h>
# undef COMPILING_BDLF_NOOP_H
#else
 
 
namespace bdlf {
 
                                 // ==========
                                 // class NoOp
                                 // ==========
 
/// This functor class provides a function-call operator that accepts any
/// number of arguments of any type, does nothing (leaving the arguments
/// unmodified), and returns `void`.
///
/// See @ref bdlf_noop 
class NoOp {
 
  public:
    // TRAITS
    BSLMF_NESTED_TRAIT_DECLARATION(NoOp, bsl::is_trivially_copyable);
 
    // TYPES
 
    /// `result_type` is an alias to `void`, which is the type returned by
    /// the function-call operator of this class
    typedef void result_type;
 
#if !BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
    // ACCESSORS
 
    /// Do nothing and ignore all specified `ignored` arguments.
    template <class... t_ARGS>
    inline
    BSLS_KEYWORD_CONSTEXPR_CPP14 void operator()(
                         const t_ARGS&... ignored) const BSLS_KEYWORD_NOEXCEPT;
#endif
};
 
// BDE_VERIFY pragma: push
// BDE_VERIFY pragma: -AQb01
// BDE_VERIFY pragma: -TR17
#ifdef BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES
inline
constexpr NoOp noOp = NoOp();
#else
extern const NoOp noOp;
#endif
// BDE_VERIFY pragma: pop
 
// ============================================================================
//                            INLINE DEFINITIONS
// ============================================================================
 
                                 // ----------
                                 // class NoOp
                                 // ----------
 
#if !BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
template <class... t_ARGS>
BSLS_KEYWORD_CONSTEXPR_CPP14 void NoOp::operator()(
         BSLA_MAYBE_UNUSED const t_ARGS&...ignored) const BSLS_KEYWORD_NOEXCEPT
{
}
#endif
 
}  // close package namespace
 
 
#endif // End C++11 code
 
#endif  // INCLUDED_BDLF_NOOP
 
// ----------------------------------------------------------------------------
// Copyright 2023 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */