bdlt_defaultcalendarcache.h

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/// @file bdlt_defaultcalendarcache.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlt_defaultcalendarcache.h                                        -*-C++-*-
#ifndef INCLUDED_BDLT_DEFAULTCALENDARCACHE
#define INCLUDED_BDLT_DEFAULTCALENDARCACHE
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlt_defaultcalendarcache bdlt_defaultcalendarcache
/// @brief  Provide a process-wide default `bdlt::CalendarCache` object.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlt
/// @{
/// @addtogroup bdlt_defaultcalendarcache
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlt_defaultcalendarcache-purpose"> Purpose</a>
/// * <a href="#bdlt_defaultcalendarcache-classes"> Classes </a>
/// * <a href="#bdlt_defaultcalendarcache-description"> Description </a>
///   * <a href="#bdlt_defaultcalendarcache-thread-safety"> Thread Safety </a>
///   * <a href="#bdlt_defaultcalendarcache-usage"> Usage </a>
///     * <a href="#bdlt_defaultcalendarcache-example-1-using-bdlt-defaultcalendarcache"> Example 1: Using bdlt::DefaultCalendarCache </a>
///
/// # Purpose {#bdlt_defaultcalendarcache-purpose}
/// Provide a process-wide default `bdlt::CalendarCache` object.
///
/// # Classes {#bdlt_defaultcalendarcache-classes}
///
/// -  bdlt::DefaultCalendarCache: namespace for managing a default calendar cache
///
/// @see  bdlt_calendarcache, bdlt_calendarloader
///
/// # Description {#bdlt_defaultcalendarcache-description}
/// This component provides a namespace,
/// `bdlt::DefaultCalendarCache`, for utility functions that initialize, provide
/// access to, and ultimately destroy, a default `bdlt::CalendarCache` object.
/// The default cache is initialized by calling the (overloaded) `initialize`
/// class method to which a concrete calendar loader and memory allocator must
/// be supplied.  The cache is destroyed by the `destroy` class method.  Note
/// that the calendar-naming convention in effect for the default cache is
/// determined by the loader supplied to `initialize`.
///
/// A timeout may be established for the default cache by supplying an optional
/// `bsls::TimeInterval` value to `initialize`.  When a timeout is in effect for
/// the default cache, a request for a calendar from the cache may incur the
/// reloading of the calendar if the one in the cache has expired (i.e., the
/// time interval defined by the timeout value has elapsed since the calendar
/// was last loaded into the cache).  Calendars will not expire in this fashion
/// if the default cache is not provided with a timeout at initialization.
///
/// Although the cache may be initialized and destroyed multiple times during
/// the lifetime of a process, the expected usage is that the cache would be
/// initialized *once*, typically in `main` before other threads have been
/// created, and destroyed just prior to program termination.  Regardless, the
/// lifetimes of the calendar loader and memory allocator supplied to
/// `initialize` must extend beyond the following (matching) call to `destroy`.
/// While the default calendar cache is in the initialized state, the `instance`
/// method returns an address providing modifiable access to the cache.
/// Otherwise, `instance` returns 0.
///
/// **WARNING**: Clients should be aware that the address returned by `instance`
/// becomes invalid by a subsequent call to `destroy`.
///
/// ## Thread Safety {#bdlt_defaultcalendarcache-thread-safety}
///
///
/// The `bdlt::DefaultCalendarCache` class is fully thread-safe (see
/// @ref bsldoc_glossary ) provided that the allocator supplied to `initialize` and
/// the default allocator in effect during the lifetime of the default cache are
/// both fully thread-safe.
///
/// ## Usage {#bdlt_defaultcalendarcache-usage}
///
///
/// The following example illustrates how to use `bdlt::DefaultCalendarCache`.
///
/// ### Example 1: Using bdlt::DefaultCalendarCache {#bdlt_defaultcalendarcache-example-1-using-bdlt-defaultcalendarcache}
///
///
/// `bdlt::DefaultCalendarCache` has a particularly simple interface.  This
/// example shows how to use each of its three methods.
///
/// A hypothetical calendar loader is assumed, `MyCalendarLoader`, the details
/// of which are not important other than that it supports calendars identified
/// by "DE", "FR", and "US", which nominally identify the major holidays in
/// Germany, France, and the United States, respectively.  Furthermore, we cite
/// two specific dates of interest: 2011/07/04, which was a holiday in the US
/// (Independence Day), but not in France, and 2011/07/14, which was a holiday
/// in France (Bastille Day), but not in the US.
///
/// First, we create a calendar loader, an instance of `MyCalendarLoader`, and
/// use it, in turn, to initialize the default calendar cache.  A memory
/// allocator must also be explicitly supplied to the `initialize` method.  The
/// global allocator is suitable in this case (see @ref bslma_default ):
/// @code
/// static MyCalendarLoader loader;
///
/// int rc = bdlt::DefaultCalendarCache::initialize(
///                                         &loader,
///                                         bslma::Default::globalAllocator());
/// assert(!rc);
/// @endcode
/// Note that declaring `loader` to be `static` ensures that it remains valid
/// until the cache is destroyed.  Also note that initialization of the cache
/// would typically be done in `main` before other threads have been created.
///
/// Next, we obtain the address of the default calendar cache using the
/// `instance` class method:
/// @code
/// bdlt::CalendarCache *cachePtr = bdlt::DefaultCalendarCache::instance();
/// assert(cachePtr);
/// @endcode
/// Then, we retrieve the calendar identified by "US" from the default cache,
/// and verify that 2011/07/04 is recognized as a holiday in the "US" calendar,
/// whereas 2011/07/14 is not:
/// @code
/// bsl::shared_ptr<const bdlt::Calendar> us = cachePtr->getCalendar("US");
/// assert( us->isHoliday(bdlt::Date(2011, 7,  4)));
/// assert(!us->isHoliday(bdlt::Date(2011, 7, 14)));
/// @endcode
/// Next, we fetch the calendar identified by "FR", this time verifying that
/// 2011/07/14 is recognized as a holiday in the "FR" calendar, but 2011/07/04
/// is not:
/// @code
/// bsl::shared_ptr<const bdlt::Calendar> fr = cachePtr->getCalendar("FR");
/// assert(!fr->isHoliday(bdlt::Date(2011, 7,  4)));
/// assert( fr->isHoliday(bdlt::Date(2011, 7, 14)));
/// @endcode
/// Finally, we destroy the default calendar cache:
/// @code
/// bdlt::DefaultCalendarCache::destroy();
/// assert(!bdlt::DefaultCalendarCache::instance());
/// @endcode
/// Note that destruction of the default cache would typically be done in `main`
/// just prior to program termination.
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlt
 * @{
 */
/** @addtogroup bdlt_defaultcalendarcache
 * @{
 */
 
#include <bdlscm_version.h>
 
#include <bsls_timeinterval.h>
 
#include <bslma_allocator.h>
 
 
 
 
namespace bdlt {
 
class CalendarCache;
class CalendarLoader;
 
                      // ==========================
                      // class DefaultCalendarCache
                      // ==========================
 
/// This `struct` provides a namespace for functions that manage the
/// lifetime of, and access to, a process-wide default `bdlt::CalendarCache`
/// object.  The default cache is initialized by an explicit call to the
/// `initialize` class method, and destroyed by the `destroy` class method.
/// The default cache may be initialized and destroyed multiple times during
/// the lifetime of a process.  The lifetimes of the calendar loader and
/// memory allocator supplied to `initialize` must extend beyond the
/// following (matching) call to `destroy`.
///
/// All methods of this `struct` are fully thread-safe (see
/// @ref bsldoc_glossary ).
///
/// See @ref bdlt_defaultcalendarcache 
struct DefaultCalendarCache {
 
    // CLASS METHODS
 
    /// Destroy the default `CalendarCache` object managed by this class.
    /// If the default cache is not in the initialized state, this method has no effect.  
    /// 
    /// \note Note that   all addresses returned by earlier calls to
    /// `instance` are invalidated by this method.
    static void destroy();
 
    /// Initialize the default `CalendarCache` object managed by this class
    /// to use the specified `loader` to obtain calendars, to have no
    /// timeout, and to use the specified `allocator` to supply memory.  If
    /// the default cache is already in the initialized state, this method
    /// has no effect.  Return 0 on success, and a non-zero value otherwise. 
    /// 
    /// \pre The behavior is undefined   unless `loader` and `allocator` remain
    /// valid until a subsequent call to `destroy`.
    static int initialize(CalendarLoader   *loader,
                          bslma::Allocator *allocator);
 
    /// Initialize the default `CalendarCache` object managed by this class
    /// to use the specified `loader` to obtain calendars, to have the
    /// specified `timeout`, and to use the specified `allocator` to supply
    /// memory.  If the default cache is already in the initialized state,
    /// this method has no effect.  Return 0 on success, and a non-zero value otherwise.  
    /// 
    /// \pre The behavior is undefined   unless `loader` and
    /// `allocator` remain valid until a subsequent call to `destroy`, and
    /// `bsls::TimeInterval() <= timeout <= bsls::TimeInterval(INT_MAX, 0)`. 
    /// 
    /// \note Note that   a `timeout` value of 0 indicates that a calendar will be
    /// loaded into the default cache by *each* (successful) call to
    /// `CalendarCache::getCalendar` on the cache returned by `instance`.
    static int initialize(CalendarLoader            *loader,
                          const bsls::TimeInterval&  timeout,
                          bslma::Allocator          *allocator);
 
    /// Return an address providing modifiable access to the default
    /// `CalendarCache` object managed by this class, if the default cache
    /// is in the initialized state, and 0 otherwise.  The cache obtains
    /// calendars using the loader that was supplied to the `initialize` method.  
    /// 
    /// \note Note that   the returned address is invalidated by a
    /// subsequent call to `destroy`.
    static CalendarCache *instance();
};
 
// ============================================================================
//                      INLINE FUNCTION DEFINITIONS
// ============================================================================
 
}  // close package namespace
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2018 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */