bdlt_timetz.h

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/// @file bdlt_timetz.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlt_timetz.h                                                      -*-C++-*-
#ifndef INCLUDED_BDLT_TIMETZ
#define INCLUDED_BDLT_TIMETZ
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlt_timetz bdlt_timetz
/// @brief  Provide a representation of a time with time zone offset.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlt
/// @{
/// @addtogroup bdlt_timetz
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlt_timetz-purpose"> Purpose</a>
/// * <a href="#bdlt_timetz-classes"> Classes </a>
/// * <a href="#bdlt_timetz-description"> Description </a>
///   * <a href="#bdlt_timetz-attributes"> Attributes </a>
///   * <a href="#bdlt_timetz-caveats-on-time-zone-support"> Caveats on Time Zone Support </a>
///   * <a href="#bdlt_timetz-iso-standard-text-representation"> ISO Standard Text Representation </a>
///   * <a href="#bdlt_timetz-usage"> Usage </a>
///     * <a href="#bdlt_timetz-example-1-comparing-times-from-multiple-time-zones"> Example 1: Comparing Times from Multiple Time Zones </a>
///
/// # Purpose {#bdlt_timetz-purpose}
/// Provide a representation of a time with time zone offset.
///
/// # Classes {#bdlt_timetz-classes}
///
/// -  bdlt::TimeTz: local-time value with time zone offset from UTC
///
/// @see  bdlt_time, bdlt_datetimetz
///
/// # Description {#bdlt_timetz-description}
/// This component provides a single, simply constrained
/// value-semantic class, `bdlt::TimeTz`, that represents a time value in a
/// particular time zone.  Each `bdlt::TimeTz` object contains a time zone
/// offset from UTC (in minutes) and a `bdlt::Time` value in that time zone.
/// For logical consistency, the time value and offset should correspond to a
/// geographically valid time zone, but such consistency is the user's
/// responsibility.  This component does not enforce logical constraints on any
/// values.
///
/// The `localTime` and `utcTime` methods return `bdlt::Time` values
/// corresponding to the local time and UTC time represented by the object,
/// respectively.  In addition, the `offset` method returns the time zone offset
/// in minutes from UTC (i.e., `UTC + offset` equals local time).
///
/// ## Attributes {#bdlt_timetz-attributes}
///
///
/// @code
/// Name                Type         Default         Simple Constraints
/// ------------------  -----------  --------------  ------------------
/// localTime           bdlt::Time   '24:00:00.000'  none
/// offset              int          0               ( -1440 .. 1440 )
/// @endcode
/// * `localTime`: local time in the timezone described by `offset`.
/// * `offset`: offset from UTC (in minutes) of the time zone in which
///   `localTime` occurs.
///
/// ## Caveats on Time Zone Support {#bdlt_timetz-caveats-on-time-zone-support}
///
///
/// A `bdlt::TimeTz` value is intended to be interpreted as a value in a local
/// time zone, along with the offset of that value from UTC.  However, there are
/// some problems with this simple interpretation.  First of all, the offset
/// value may not correspond to any time zone that has ever existed.  For
/// example, the offset value could be set to one minute, or to 1,234 minutes.
/// The meaning of the resulting "local time" value is always clear, but the
/// local time might not correspond to any geographical or historical time zone.
///
/// For these reasons (and others), this component cannot and does not perform
/// any validation relating to time zones or offsets.  The user must take care
/// to honor the "local time" contract of this component.
///
/// ## ISO Standard Text Representation {#bdlt_timetz-iso-standard-text-representation}
///
///
/// A common standard text representation of a date and time value is described
/// by ISO 8601.  BDE provides the @ref bdlt_iso8601util  component for conversion
/// to and from the standard ISO8601 format.
///
/// ## Usage {#bdlt_timetz-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Comparing Times from Multiple Time Zones {#bdlt_timetz-example-1-comparing-times-from-multiple-time-zones}
///
///
/// Some legacy systems may represent points in time as a combination of a local
/// time-of-day plus an offset from UTC, with an underlying assumption that the
/// dates on which points in time occur can be inferred from context.  Assuming
/// that we know that two such times fall on the same (local) calendar date, we
/// can determine whether or not the two times coincide by comparing their
/// `bdlt::TimeTz` representations.
///
/// First, we define three `bdlt::TimeTz` objects representing the time in three
/// different time zones on the same (local) date:
/// @code
/// bdlt::TimeTz newYorkTime(bdlt::Time(9, 30, 0, 0.0),
///                          -5 * bdlt::TimeUnitRatio::k_MINUTES_PER_HOUR);
/// bdlt::TimeTz chicagoTime(bdlt::Time(8, 30, 0, 0.0),
///                          -6 * bdlt::TimeUnitRatio::k_MINUTES_PER_HOUR);
/// bdlt::TimeTz phoenixTime(bdlt::Time(6, 30, 0, 0.0),
///                          -7 * bdlt::TimeUnitRatio::k_MINUTES_PER_HOUR);
/// @endcode
/// Then, we observe that the local times are distinct:
/// @code
/// assert(newYorkTime.localTime() != chicagoTime.localTime());
/// assert(chicagoTime.localTime() != phoenixTime.localTime());
/// assert(phoenixTime.localTime() != newYorkTime.localTime());
/// @endcode
/// Next, we observe that `newYorkTime` and `chicagoTime` actually represent the
/// same point in time:
/// @code
/// assert(newYorkTime.utcTime() == chicagoTime.utcTime());
/// @endcode
/// Finally, we observe that `phoenixTime` is one hour earlier than
/// `newYorkTime`:
/// @code
/// bdlt::DatetimeInterval delta =
///                              newYorkTime.utcTime() - phoenixTime.utcTime();
///
/// assert(0 == delta.days());
/// assert(1 == delta.hours());
/// assert(0 == delta.minutes());
/// assert(0 == delta.seconds());
/// assert(0 == delta.milliseconds());
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlt
 * @{
 */
/** @addtogroup bdlt_timetz
 * @{
 */
 
#include <bdlscm_version.h>
 
#include <bdlt_time.h>
 
#include <bslh_hash.h>
 
#include <bslmf_integralconstant.h>
#include <bslmf_isbitwisecopyable.h>
 
#include <bsls_annotation.h>
#include <bsls_assert.h>
#include <bsls_review.h>
 
#include <bsl_iosfwd.h>
 
 
 
namespace bdlt {
 
                                // ============
                                // class TimeTz
                                // ============
 
/// This value-semantic class describes a time value in a particular time
/// zone, which is indicated using an offset from UTC (in minutes).  The
/// offset is available via the `offset` method, and is defined by the
/// relationship: `localTime() - offset() == utcTime`.  The time and offset
/// values are logically assumed to correspond to geographically valid
/// values, however, this constraint is not enforced.
///
/// This class:
/// * supports a complete set of *value-semantic* operations
/// * supports BDEX streaming
/// For terminology see @ref bsldoc_glossary .
///
/// See @ref bdlt_timetz 
class TimeTz {
 
    // PRIVATE TYPES
 
    /// This enumeration specifies the minimum and maximum time zone offset
    /// values.
    enum ValidOffsetRange {
 
        k_MAX_OFFSET =  1440,
        k_MIN_OFFSET = -1440
    };
 
    // DATA
    Time d_localTime;    // time value in timezone specified by 'd_offset'
    int  d_offset;       // offset from UTC (in minutes)
 
  public:
    // CLASS METHODS
 
    /// Return `true` if the specified `localTime` and the specified time
    /// zone `offset` represent a valid `TimeTz` value, and `false`
    /// otherwise.  A `localTime` and `offset` represent a valid `TimeTz`
    /// value if `offset` is in the range `( -1440 .. 1440 )`, and `offset`
    /// is 0 if `localTime` has the value `24:00:00.000`.  Note that a
    /// `true` result from this function does not guarantee that `offset`
    /// corresponds to any geographical or historical time zone.  Also note
    /// that a `true` result from this function does not guarantee that
    /// `localTime` itself is a valid `Time` object.
    static bool isValid(const Time& localTime, int offset);
 
                               // BDEX Streaming
 
    /// Return the maximum valid BDEX format version, as indicated by the
    /// specified `versionSelector`, to be passed to the `bdexStreamOut`
    /// method.  Note that it is highly recommended that `versionSelector`
    /// be formatted as "YYYYMMDD", a date representation.  Also note that
    /// `versionSelector` should be a *compile*-time-chosen value that
    /// selects a format version supported by both externalizer and
    /// unexternalizer.  See the `bslx` package-level documentation for more
    /// information on BDEX streaming of value-semantic types and
    /// containers.
    static int maxSupportedBdexVersion(int versionSelector);
 
    // CREATORS
 
    /// Create a `TimeTz` object having the (default) attribute values.
    TimeTz();
 
    /// Create a `TimeTz` object whose local time and offset attributes have
    /// the specified `localTime` and `offset` values respectively.  The
    /// behavior is undefined unless `offset` is in the range
    /// `( -1440 .. 1440 )`, and `offset` is 0 if `localTime` has the value
    /// `24:00:00.000`.  Note that this method provides no validation, and
    /// it is the user's responsibility to ensure that `offset` represents a
    /// valid time zone and that `localTime` represents a valid time in that
    /// time zone.
    TimeTz(const Time& localTime, int offset);
 
    /// Construct a `TimeTz` object having the same value as the specified
    /// `original` `TimeTz` object.
    TimeTz(const TimeTz& original);
 
    /// Destroy this object.
    ~TimeTz();
 
    // MANIPULATORS
 
    /// Assign to this object the value of the specified `rhs` object, and
    /// return a reference providing modifiable access to this object.
    TimeTz& operator=(const TimeTz& rhs);
 
    /// Set the local time and time zone offset attributes of this object to
    /// the specified `localTime` and `offset` values respectively.  The
    /// behavior is undefined unless `offset` is in the range
    /// `( -1440 .. 1440 )`.  Note that this method provides no validation,
    /// and it is the user's responsibility to assure the consistency of the
    /// resulting value.
    void setTimeTz(const Time& localTime, int offset);
 
    /// Set the local time and the time zone offset of this object to the
    /// specified `localTime` and `offset` values respectively if
    /// `localTime` and `offset` represent a valid `TimeTz` value, and leave
    /// the object unmodified otherwise.  Return 0 on success, and a
    /// non-zero value otherwise.
    int setTimeTzIfValid(const Time& localTime, int offset);
 
                                  // Aspects
 
    /// Assign to this object the value read from the specified input
    /// `stream` using the specified `version` format, and return a
    /// reference to `stream`.  If `stream` is initially invalid, this
    /// operation has no effect.  If `version` is not supported, this object
    /// is unaltered and `stream` is invalidated, but otherwise unmodified.
    /// If `version` is supported but `stream` becomes invalid during this
    /// operation, this object has an undefined, but valid, state.  Note
    /// that no version is read from `stream`.  See the `bslx` package-level
    /// documentation for more information on BDEX streaming of
    /// value-semantic types and containers.
    template <class STREAM>
    STREAM& bdexStreamIn(STREAM& stream, int version);
 
    // ACCESSORS
 
    /// Return a `Time` object having the value of the local time attribute
    /// of this object.  Note that the `Time` value returned is the value
    /// stored in this object, and may be different from the local time of
    /// the system.
    Time localTime() const;
 
    /// Return the time zone offset of this object in minutes from UTC.
    int offset() const;
 
    /// Return a `Time` object having the value of the UTC time represented
    /// by this object.  Note that the returned value is equal to
    /// `localTime() - offset()` minutes.
    Time utcTime() const;
 
                                  // Aspects
 
    /// Write the value of this object, using the specified `version`
    /// format, to the specified output `stream`, and return a reference to
    /// `stream`.  If `stream` is initially invalid, this operation has no
    /// effect.  If `version` is not supported, `stream` is invalidated, but
    /// otherwise unmodified.  Note that `version` is not written to
    /// `stream`.  See the `bslx` package-level documentation for more
    /// information on BDEX streaming of value-semantic types and
    /// containers.
    template <class STREAM>
    STREAM& bdexStreamOut(STREAM& stream, int version) const;
 
    /// Write the value of this object to the specified output `stream` in a
    /// human-readable format, and return a reference to `stream`.
    /// Optionally specify an initial indentation `level`, whose absolute
    /// value is incremented recursively for nested objects.  If `level` is
    /// specified, optionally specify `spacesPerLevel`, whose absolute value
    /// indicates the number of spaces per indentation level for this and
    /// all of its nested objects.  If `level` is negative, suppress
    /// indentation of the first line.  If `spacesPerLevel` is negative,
    /// format the entire output on one line, suppressing all but the
    /// initial indentation (as governed by `level`).  If `stream` is not
    /// valid on entry, this operation has no effect.  Note that the format
    /// is not fully specified, and can change without notice.
    bsl::ostream& print(bsl::ostream& stream,
                        int           level = 0,
                        int           spacesPerLevel = 4) const;
 
#ifndef BDE_OPENSOURCE_PUBLICATION  // pending deprecation
 
    // DEPRECATED
 
    /// @deprecated  replaced by `utcTime`.
    ///
    /// Return a `Time` object having the value of the UTC time represented
    /// by this object.  Note that the returned value is equal to
    /// `localTime() - offset()` minutes.
    Time gmtTime() const;
 
    /// @deprecated  Use @ref maxSupportedBdexVersion(int) instead.
    ///
    /// Return the most current BDEX streaming version number supported by
    /// this class.
    static int maxSupportedBdexVersion();
 
    /// @deprecated  replaced by `setTimeTzIfValid`.
    ///
    /// Set the local time and the time zone offset of this object to the
    /// specified `localTime` and `offset` values respectively if
    /// `localTime` and `offset` represent a valid `TimeTz` value.  Return 0
    /// on success, and a non-zero value with no effect on this object
    /// otherwise.
    int validateAndSetTimeTz(const Time& localTime, int offset);
 
#endif // BDE_OPENSOURCE_PUBLICATION -- pending deprecation
};
 
// FREE OPERATORS
 
/// Return `true` if the specified `lhs` and `rhs` objects have the same
/// value, and `false` otherwise.  Two `TimeTz` objects have the same value
/// if their corresponding `localTime` and `offset` attributes have the same
/// values.
bool operator==(const TimeTz& lhs, const TimeTz& rhs);
 
/// Return `true` if the specified `lhs` and `rhs` objects do not have the
/// same value, and `false` otherwise.  Two `TimeTz` objects do not have the
/// same value if any of their corresponding `localTime` and `offset`
/// attributes have different values.
bool operator!=(const TimeTz& lhs, const TimeTz& rhs);
 
/// Write the value of the specified `object` to the specified output
/// `stream` in a single-line format, and return a reference providing
/// modifiable access to `stream`.  If `stream` is not valid on entry, this
/// operation has no effect.  Note that this human-readable format is not
/// fully specified and can change without notice.  Also note that this
/// method has the same behavior as `object.print(stream, 0, -1)`, but with
/// the attribute names elided.
bsl::ostream& operator<<(bsl::ostream& stream, const TimeTz& object);
 
// FREE FUNCTIONS
 
/// Pass the specified `object` to the specified `hashAlg`.  This function
/// integrates with the `bslh` modular hashing system and effectively
/// provides a `bsl::hash` specialization for `TimeTz`.  Note that two
/// objects which represent the same UTC time but have different offsets
/// will not (necessarily) hash to the same value.
template <class HASHALG>
void hashAppend(HASHALG& hashAlg, const TimeTz& object);
 
// ============================================================================
//                            INLINE DEFINITIONS
// ============================================================================
 
                             // ------------
                             // class TimeTz
                             // ------------
 
// CLASS METHODS
inline
bool TimeTz::isValid(const Time& localTime, int offset)
{
    return offset > k_MIN_OFFSET
        && offset < k_MAX_OFFSET
        && (bdlt::Time() != localTime || 0 == offset);
}
 
                                  // Aspects
 
inline
int TimeTz::maxSupportedBdexVersion(int versionSelector)
{
    if (versionSelector >= 20170401) {
        return 2;                                                     // RETURN
    }
    return 1;
}
 
// CREATORS
inline
TimeTz::TimeTz()
: d_localTime()
, d_offset(0)
{
}
 
inline
TimeTz::TimeTz(const Time& localTime, int offset)
: d_localTime(localTime)
, d_offset(offset)
{
    BSLS_REVIEW(isValid(localTime, offset));
}
 
inline
TimeTz::TimeTz(const TimeTz& original)
: d_localTime(original.d_localTime)
, d_offset(original.d_offset)
{
}
 
inline
TimeTz::~TimeTz()
{
    BSLS_REVIEW(isValid(d_localTime, d_offset));
}
 
// MANIPULATORS
inline
TimeTz& TimeTz::operator=(const TimeTz& rhs)
{
    d_localTime = rhs.d_localTime;
    d_offset    = rhs.d_offset;
 
    return *this;
}
 
inline
void TimeTz::setTimeTz(const Time& localTime, int offset)
{
    BSLS_REVIEW(isValid(localTime, offset));
 
    d_localTime = localTime;
    d_offset    = offset;
}
 
inline
int TimeTz::setTimeTzIfValid(const Time& localTime, int offset)
{
    if (isValid(localTime, offset)) {
        setTimeTz(localTime, offset);
 
        return 0;                                                     // RETURN
    }
    return -1;
}
 
                                  // Aspects
 
template <class STREAM>
STREAM& TimeTz::bdexStreamIn(STREAM& stream, int version)
{
    if (stream) {
        switch (version) { // switch on the schema version
          case 2:
            BSLS_ANNOTATION_FALLTHROUGH;
          case 1: {
            Time time;
            time.bdexStreamIn(stream, version);
 
            int offset;
            stream.getInt32(offset);
 
            if (stream && isValid(time, offset)) {
                setTimeTz(time, offset);
            }
            else {
                stream.invalidate();
            }
          } break;
          default: {
            stream.invalidate();  // unrecognized version number
          }
        }
    }
    return stream;
}
 
// ACCESSORS
inline
Time TimeTz::localTime() const
{
    return d_localTime;
}
 
inline
int TimeTz::offset() const
{
    return d_offset;
}
 
inline
Time TimeTz::utcTime() const
{
    Time utc(d_localTime);
 
    if (d_offset) {
        // N.B. adding -0 minutes to a default-constructed 'Time' object (with
        // value '24:00:00.000') would convert it to a 'Time' object with value
        // '00:00:00.000'.  The branch here preserves the 'localTime' attribute
        // for a default-constructed 'TimeTz' object.
 
        utc.addMinutes(-d_offset);
    }
 
    return utc;
}
 
                                  // Aspects
 
template <class STREAM>
STREAM& TimeTz::bdexStreamOut(STREAM& stream, int version) const
{
    if (stream) {
        switch (version) { // switch on the schema version
          case 2:
            BSLS_ANNOTATION_FALLTHROUGH;
          case 1: {
            d_localTime.bdexStreamOut(stream, version);
            stream.putInt32(d_offset);
          } break;
          default: {
            stream.invalidate();  // unrecognized version number
          }
        }
    }
    return stream;
}
 
#ifndef BDE_OPENSOURCE_PUBLICATION  // pending deprecation
// DEPRECATED
inline
Time TimeTz::gmtTime() const
{
    return utcTime();
}
 
inline
int TimeTz::maxSupportedBdexVersion()
{
    return maxSupportedBdexVersion(0);
}
 
inline
int TimeTz::validateAndSetTimeTz(const Time& localTime, int offset)
{
    return setTimeTzIfValid(localTime, offset);
}
#endif // BDE_OPENSOURCE_PUBLICATION -- pending deprecation
 
}  // close package namespace
 
// FREE OPERATORS
inline
bool bdlt::operator==(const TimeTz& lhs, const TimeTz& rhs)
{
    return lhs.localTime() == rhs.localTime()
        && lhs.offset()    == rhs.offset();
}
 
inline
bool bdlt::operator!=(const TimeTz& lhs, const TimeTz& rhs)
{
    return lhs.localTime() != rhs.localTime()
        || lhs.offset()    != rhs.offset();
}
 
inline
bsl::ostream& bdlt::operator<<(bsl::ostream& stream, const TimeTz& object)
{
    return object.print(stream, 0, -1);
}
 
// FREE FUNCTIONS
template <class HASHALG>
inline
void bdlt::hashAppend(HASHALG& hashAlg, const TimeTz& object)
{
    using ::BloombergLP::bslh::hashAppend;
    hashAppend(hashAlg, object.localTime());
    hashAppend(hashAlg, object.offset());
}
 
namespace bslmf {
 
// TRAITS
 
/// This template specialization for `IsBitwiseCopyable` indicates that
/// `bdlt::TimeTz` is a bitwise copyable type.
template <>
struct IsBitwiseCopyable<BloombergLP::bdlt::TimeTz> : bsl::true_type {
};
 
}  // close namespace bslmf
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2014 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */