bdlt_posixdateimputil.h

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/// @file bdlt_posixdateimputil.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlt_posixdateimputil.h                                            -*-C++-*-
#ifndef INCLUDED_BDLT_POSIXDATEIMPUTIL
#define INCLUDED_BDLT_POSIXDATEIMPUTIL
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlt_posixdateimputil bdlt_posixdateimputil
/// @brief  Provide low-level support functions for date-value manipulation.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlt
/// @{
/// @addtogroup bdlt_posixdateimputil
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlt_posixdateimputil-purpose"> Purpose</a>
/// * <a href="#bdlt_posixdateimputil-classes"> Classes </a>
/// * <a href="#bdlt_posixdateimputil-description"> Description </a>
///   * <a href="#bdlt_posixdateimputil-representations-valid-dates-and-leap-years"> Representations, Valid Dates, and Leap Years </a>
///   * <a href="#bdlt_posixdateimputil-caching"> Caching </a>
///   * <a href="#bdlt_posixdateimputil-usage"> Usage </a>
///     * <a href="#bdlt_posixdateimputil-creating-a-general-purpose-utility"> Creating a General Purpose Utility </a>
///     * <a href="#bdlt_posixdateimputil-implementing-a-value-semantic-date-type"> Implementing a Value-Semantic Date Type </a>
///
/// # Purpose {#bdlt_posixdateimputil-purpose}
/// Provide low-level support functions for date-value manipulation.
///
/// # Classes {#bdlt_posixdateimputil-classes}
///
/// - bdlt::PosixDateImpUtil: suite of low-level date-related stateless functions
///
/// # Description {#bdlt_posixdateimputil-description}
/// This component implements a utility class,
/// `bdlt::PosixDateImpUtil`, that provides a suite of low-level, date-related
/// functions that can be used to validate, manipulate, and convert among values
/// in three different formats:
/// @code
/// YMD: year/month/day
///  YD: year/dayOfYear
///   S: serialDate
/// @endcode
/// The supplied functionality can also be used for determining leap years,
/// finding the last day in a month, and for determining the day of the week for
/// a given date.  Note that in this component, a "date" is understood to
/// represent a valid day in the range `0001JAN01` to `9999DEC31`, according to
/// the standard UNIX date implementation.
///
/// ## Representations, Valid Dates, and Leap Years {#bdlt_posixdateimputil-representations-valid-dates-and-leap-years}
///
///
/// The "Calendar Date", or "year-month-day (ymd)", is the primary
/// representation and is denoted as "yyyy/mm/dd", with valid years being in the
/// range `[ 1 .. 9999 ]`.  Within a valid year, valid months and valid days are
/// confined to the respective ranges `[ 1 .. 12 ]` and `[ 1 .. 31 ]`.  Valid
/// dates in this representation will range from `0001/01/01` to `9999/12/31`,
/// but are also governed by the standard UNIX (Gregorian) calendar convention.
///
/// The "Day-Of-Year Date", or "year-day (yd)" representation, denoted by
/// "yyyy/ddd", represents dates by their year, again in the range
/// `[ 1 .. 9999 ]`, and the day of year, in the range `[ 1 .. 366 ]`.  Note
/// that valid date values in this representation range from `0001/01` to
/// `9999/365`, with a day-of-year value of 366 permitted for leap years only.
///
/// The "Serial Date" representation depicts dates as consecutive integers,
/// beginning with 1 (representing `0001JAN01`).  In this representation, valid
/// date value are in the range `[ 1 .. 3652061 ]`.
///
/// In a leap year, February has 29 days instead of the usual 28.  For years
/// subsequent to 1752, a year is a leap year if it is divisible by 4, but not
/// divisible by 100, unless it is also divisible by 400.  Prior to 1752, all
/// years divisible by 4 were leap years.  Note that the year 1752 had only
/// `366 - 11 = 355` days, as September 3rd through the 13th were omitted (in a
/// one-time correction to the previous, less accurate, leap-year convention).
///
/// ## Caching {#bdlt_posixdateimputil-caching}
///
///
/// To achieve maximal runtime performance, several of the functions in this
/// component reserve the right to be implemented using statically cached (i.e.,
/// tabulated) values (which is inherently thread-safe).  In all cases where a
/// cache may be used, `bdlt::PosixDateImpUtil` explicitly provides a `NoCache`
/// version (e.g., `ymdToSerialNoCache`) that is guaranteed NOT to use a cache.
/// Although the "normal" (potentially cached) functions typically gain huge
/// performance advantages, the `NoCache` versions may conceivably be preferred
/// by the performance-minded user who is *reasonably* *certain* that the vast
/// majority of date values of interest will miss the cache (thus incurring a
/// small, but unnecessary overhead for the cache-hit tests).  Note, however,
/// that the `NoCache` function variants are provided primarily for testing and
/// for generating that cache in the first place (see
/// `bdlt_posixdateimputil.t.cpp`).
///
/// ## Usage {#bdlt_posixdateimputil-usage}
///
///
/// This component was created primarily to support the implementation of a
/// general-purpose, value-semantic (vocabulary) "Date" type, but also provides
/// many low-level utility functions suitable for direct use by other clients.
///
/// ### Creating a General Purpose Utility {#bdlt_posixdateimputil-creating-a-general-purpose-utility}
///
///
/// Many of the functions provided by this component can be used directly by
/// clients that want to ask questions about a particular date in one of the
/// three supported formats.
///
/// What day of the week was January 3, 2010?
/// @code
/// assert(2 == bdlt::PosixDateImpUtil::ymdToDayOfWeek(2010, 3, 1));
///                                                          // 2 means Monday.
/// @endcode
/// Was the year 2000 a leap year?
/// @code
/// assert(true == bdlt::PosixDateImpUtil::isLeapYear(2000));
///                                                          // Yes, it was.
/// @endcode
/// Was February 29, 1900, a valid date in history?
/// @code
/// assert(false == bdlt::PosixDateImpUtil::isValidYearMonthDay(1900, 2, 29));
///                                                          // No, it was not.
/// @endcode
/// What was the last day of February in 1600?
/// @code
/// assert(29 == bdlt::PosixDateImpUtil::lastDayOfMonth(1600, 2));
///                                                          // The 29th.
/// @endcode
/// How many leap years occur from 1959 to 2012 inclusive?
/// @code
/// assert(14 == bdlt::PosixDateImpUtil::numLeapYears(1959, 2012));
///                                                          // There are 14.
/// @endcode
/// On what day of the year does February 29, 2020 fall?
/// @code
/// assert(60 == bdlt::PosixDateImpUtil::ymdToDayOfYear(2020, 2, 29));
///                                                          // The 60th one.
/// @endcode
/// In what month does the 120th day of 2011 fall?
/// @code
/// assert(4 == bdlt::PosixDateImpUtil::ydToMonth(2011, 120));
///                                                          // 4 means April.
/// @endcode
///
/// ### Implementing a Value-Semantic Date Type {#bdlt_posixdateimputil-implementing-a-value-semantic-date-type}
///
///
/// Using the functions supplied in this component, we can easily implement a
/// C++ class that represents abstract (*mathematical*) date values and performs
/// a few common operations on them.  The internal representation could be any
/// of the three supported by this component; in this example, we will choose to
/// represent the date value internally as a "serial date":
/// @code
/// /// This class represents a valid date in the range
/// /// `[ 0001/01/01 .. 9999/12/31 ]`.
/// class MyDate {
///
///     // DATA
///     int d_serialDate;  // 1 = 0001JAN01, 2 = 0001JAN02, ...
///
///     // FRIENDS
///     friend MyDate operator+(const MyDate&, int);
///     friend MyDate operator+(int, const MyDate&);
///     friend int  operator- (const MyDate&, const MyDate&);
///     friend bool operator==(const MyDate&, const MyDate&);
///
///   private:
///     // PRIVATE CREATORS
///     explicit MyDate(int serialDate);
/// @endcode
/// Next we define the public interface of the class, with function-level
/// documentation conspicuously omitted (note, however, that reference
/// implementations with preconditions asserted will follow):
/// @code
///   public:
///     // TYPES
///     enum Day {
///         SUN = 1,
///         MON = 2,
///         TUE = 3,
///         WED = 4,
///         THU = 5,
///         FRI = 6,
///         SAT = 7
///     };
///
///     // CLASS METHODS
///     static bool isValid(int year, int month, int day);
///
///     // CREATORS
///     MyDate();
///     MyDate(const MyDate& original);
///     ~MyDate();
///
///     // MANIPULATORS
///     MyDate& operator=(const MyDate& rhs);
///     MyDate& operator++();
///     MyDate& operator--();
///     MyDate& operator+=(int numDays);
///     MyDate& operator-=(int numDays);
///     void setYearMonthDay(int year, int month, int day);
///     bool setYearMonthDayIfValid(int year, int month, int day);
///
///     // ACCESSORS
///     void getYearMonthDay(int *year, int *month, int *day) const;
///     int year() const;
///     int month() const;
///     int day() const;
///     Day dayOfWeek() const;
///     bool isLeapYear() const;
///     bsl::ostream& print(bsl::ostream& stream) const;
/// };
///
/// // FREE OPERATORS
/// bool operator==(const MyDate& lhs, const MyDate& rhs);
/// bool operator!=(const MyDate& lhs, const MyDate& rhs);
///
/// bsl::ostream& operator<<(bsl::ostream& stream, const MyDate& rhs);
///
/// MyDate operator+(const MyDate& lhs, int           rhs);
/// MyDate operator+(int           lhs, const MyDate& rhs);
///
/// int operator-(const MyDate& lhs, const MyDate& rhs);
///
/// MyDate operator++(MyDate& object, int);
/// MyDate operator--(MyDate& object, int);
/// @endcode
/// We now provide a reference implementation of each of the methods and free
/// (operator) functions associated with the `MyDate` class defined above (using
/// @ref bsls_assert  to identify preconditions and invariants where appropriate):
/// @code
/// // PRIVATE CREATORS
/// inline
/// MyDate::MyDate(int serialDate)
/// : d_serialDate(serialDate)
/// {
/// }
///
/// // CLASS METHODS
/// inline
/// bool MyDate::isValid(int year, int month, int day)
/// {
///     return bdlt::PosixDateImpUtil::isValidYearMonthDay(year, month, day);
/// }
///
/// // CREATORS
/// inline
/// MyDate::MyDate()
/// : d_serialDate(1)
/// {
/// }
///
/// inline
/// MyDate::MyDate(const MyDate& original)
/// : d_serialDate(original.d_serialDate)
/// {
/// }
///
/// inline
/// MyDate::~MyDate()
/// {
/// }
///
/// // MANIPULATORS
/// inline
/// MyDate& MyDate::operator=(const MyDate& rhs)
/// {
///     d_serialDate = rhs.d_serialDate;
///     return *this;
/// }
///
/// inline
/// MyDate& MyDate::operator++()
/// {
///     ++d_serialDate;
///     BSLS_ASSERT_SAFE(bdlt::PosixDateImpUtil::isValidSerial(d_serialDate));
///     return *this;
/// }
///
/// inline
/// MyDate& MyDate::operator--()
/// {
///     --d_serialDate;
///     BSLS_ASSERT_SAFE(bdlt::PosixDateImpUtil::isValidSerial(d_serialDate));
///     return *this;
/// }
///
/// inline
/// MyDate& MyDate::operator+=(int numDays)
/// {
///     d_serialDate += numDays;
///     BSLS_ASSERT_SAFE(bdlt::PosixDateImpUtil::isValidSerial(d_serialDate));
///     return *this;
/// }
///
/// inline
/// MyDate& MyDate::operator-=(int numDays)
/// {
///     d_serialDate -= numDays;
///     BSLS_ASSERT_SAFE(bdlt::PosixDateImpUtil::isValidSerial(d_serialDate));
///     return *this;
/// }
///
/// inline
/// void MyDate::setYearMonthDay(int year, int month, int day)
/// {
///     d_serialDate = bdlt::PosixDateImpUtil::ymdToSerial(year, month, day);
///     BSLS_ASSERT_SAFE(bdlt::PosixDateImpUtil::isValidSerial(d_serialDate));
/// }
///
/// inline
/// bool MyDate::setYearMonthDayIfValid(int year, int month, int day)
/// {
///     const int newDate = bdlt::PosixDateImpUtil::ymdToSerial(year,
///                                                             month,
///                                                             day);
///     if (bdlt::PosixDateImpUtil::isValidSerial(newDate)) {
///         d_serialDate = newDate;
///         return true;                                              // RETURN
///     }
///     return false;
/// }
///
/// // ACCESSORS
/// inline
/// void MyDate::getYearMonthDay(int *year, int *month, int *day) const
/// {
///     bdlt::PosixDateImpUtil::serialToYmd(year, month, day, d_serialDate);
/// }
///
/// inline
/// int MyDate::year() const
/// {
///     return bdlt::PosixDateImpUtil::serialToYear(d_serialDate);
/// }
///
/// inline
/// int MyDate::month() const
/// {
///     return bdlt::PosixDateImpUtil::serialToMonth(d_serialDate);
/// }
///
/// inline
/// int MyDate::day() const
/// {
///     return bdlt::PosixDateImpUtil::serialToDay(d_serialDate);
/// }
///
/// inline
/// MyDate::Day MyDate::dayOfWeek() const
/// {
///     return MyDate::Day(bdlt::PosixDateImpUtil::serialToDayOfWeek(
///                                                             d_serialDate));
/// }
///
/// inline
/// bool MyDate::isLeapYear() const
/// {
///     return bdlt::PosixDateImpUtil::isLeapYear(year());
/// }
///
/// // FREE OPERATORS
/// inline
/// bool operator==(const MyDate& lhs, const MyDate& rhs)
/// {
///     return lhs.d_serialDate == rhs.d_serialDate;
/// }
///
/// inline
/// bool operator!=(const MyDate& lhs, const MyDate& rhs)
/// {
///     return !(lhs == rhs);
/// }
///
/// inline
/// bsl::ostream& operator<<(bsl::ostream& stream, const MyDate& rhs)
/// {
///     return rhs.print(stream);
/// }
///
/// inline
/// MyDate operator+(const MyDate& lhs, int rhs)
/// {
///     return MyDate(lhs.d_serialDate + rhs);
/// }
///
/// inline
/// MyDate operator+(int lhs, const MyDate& rhs)
/// {
///     return MyDate(lhs + rhs.d_serialDate);
/// }
///
/// inline
/// int operator-(const MyDate& lhs, const MyDate& rhs)
/// {
///     return lhs.d_serialDate - rhs.d_serialDate;
/// }
///
/// inline
/// MyDate operator++(MyDate& object, int)
/// {
///     MyDate tmp(object);
///     ++object;
///     return tmp;
/// }
///
/// inline
/// MyDate operator--(MyDate& object, int)
/// {
///     MyDate tmp(object);
///     --object;
///     return tmp;
/// }
/// @endcode
/// The following definitions would appropriately appear in the implementation
/// (`.cpp`) file:
/// @code
/// const char *const monthNames[] = {
///     0, "JAN", "FEB", "MAR", "APR",
///        "MAY", "JUN", "JUL", "AUG",
///        "SEP", "OCT", "NOV", "DEC"
/// };
///
/// // MANIPULATORS
/// bsl::ostream& MyDate::print(bsl::ostream& stream) const
/// {
///     if (!stream) {
///         return stream;                                            // RETURN
///     }
///
///     // space usage: ddMMMyyyy null
///     const int SIZE = 2 + 3 + 4 + 1;
///     char buf[SIZE];
///
///     int y, m, d;
///     bdlt::PosixDateImpUtil::serialToYmd(&y, &m, &d, d_serialDate);
///
///     buf[0] = d / 10 + '0';
///     buf[1] = d % 10 + '0';
///
///     bsl::memcpy(&buf[2], monthNames[m], 3);
///
///     buf[5] = y / 1000 + '0';
///     buf[6] = ((y % 1000) / 100) + '0';
///     buf[7] = ((y % 100) / 10) + '0';
///     buf[8] = y % 10 + '0';
///     buf[9] = 0;
///
///     stream << buf;
///
///     return stream;
/// }
/// @endcode
/// The following snippets of code illustrate how to create and use a `Mydate`
/// object.  First create a default object, `d1`:
/// @code
/// MyDate d1;                        assert(   1 == d1.year());
///                                   assert(   1 == d1.month());
///                                   assert(   1 == d1.day());
/// @endcode
/// Next, set `d1` to July 4, 1776:
/// @code
/// d1.setYearMonthDay(1776, 7, 4);   assert(1776 == d1.year());
///                                   assert(   7 == d1.month());
///                                   assert(   4 == d1.day());
/// @endcode
/// Then create `d2` as a copy of `d1`:
/// @code
/// MyDate d2(d1);                    assert(1776 == d2.year());
///                                   assert(   7 == d2.month());
///                                   assert(   4 == d2.day());
/// @endcode
/// Now, add six days to the value of `d2`:
/// @code
/// d2 += 6;                          assert(1776 == d2.year());
///                                   assert(   7 == d2.month());
///                                   assert(  10 == d2.day());
/// @endcode
/// Next subtract `d1` from `d2`, storing the difference (in days) in `dDays`:
/// @code
/// int dDays = d2 - d1;              assert(6 == dDays);
/// @endcode
/// Finally, stream the value of `d2` to `stdout`:
/// @code
/// bsl::cout << d2 << bsl::endl;
/// @endcode
/// The streaming operator produces the following output on `stdout`:
/// @code
/// 10JUL1776
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlt
 * @{
 */
/** @addtogroup bdlt_posixdateimputil
 * @{
 */
 
#include <bdlscm_version.h>
 
#include <bsls_assert.h>
 
 
namespace bdlt {
 
                           // =======================
                           // struct PosixDateImpUtil
                           // =======================
 
/// This `struct` provides a namespace for a suite of pure functions that
/// perform low-level operations on date values in a variety of formats.
/// Note that all of these functions, whether or not implemented in terms of
/// a static cache, are stateless, and, as such, are inherently thread-safe.
struct PosixDateImpUtil {
 
  private:
    // PRIVATE TYPES
    struct YearMonthDay{
        short d_year;
        char  d_month;
        char  d_day;
    };
 
    // PRIVATE CLASS DATA
    static const int          s_firstCachedYear;
    static const int          s_lastCachedYear;
    static const int          s_firstCachedSerialDate;
    static const int          s_lastCachedSerialDate;
    static const int          s_cachedSerialDate[][13];
    static const YearMonthDay s_cachedYearMonthDay[];
    static const char         s_cachedDaysInMonth[][13];
 
  public:
    // CLASS METHODS
 
    /// Return `true` if the specified `year` is a leap year, and `false`
    /// otherwise.  The behavior is undefined unless `1 <= year <= 9999`.
    static bool isLeapYear(int year);
 
    /// Return the last day of the specified `month` in the specified
    /// `year`.  The behavior is undefined unless `1 <= year <= 9999` and
    /// `1 <= month <= 12`.  Note that the value returned will be in the
    /// range `[ 28 .. 31 ]`.
    static int lastDayOfMonth(int year, int month);
 
    /// Return the number of leap years occurring between the specified
    /// `year1` and `year2` (inclusive).  The behavior is undefined unless
    /// `1 <= year1 <= 9999`, `1 <= year2 <= 9999`, and `year1 <= year2`.
    static int numLeapYears(int year1, int year2);
 
                        // Is Valid Date
 
    /// Return `true` if the specified `year`, `month`, and `day` represents
    /// a valid date value, and `false` otherwise.  Note that valid date
    /// values are (as fully defined in the component-level documentation)
    /// in the range `[ 0001/01/01 .. 9999/12/31 ]` (except that
    /// `[ 1752/09/03 .. 1752/09/13 ]` are not valid for historical
    /// reasons).
    static bool isValidYearMonthDay(int year, int month, int day);
 
    /// Return `true` if the specified `year`, `month`, and `day` represents
    /// a valid date value, and `false` otherwise.  Note that valid date
    /// values are (as fully defined in the component-level documentation)
    /// in the range `[ 0001/01/01 .. 9999/12/31 ]` (except that
    /// `[ 1752/09/03 .. 1752/09/13 ]` are not valid for historical
    /// reasons).  Also note that this function is guaranteed not to use any
    /// date-cache optimizations.
    static bool isValidYearMonthDayNoCache(int year, int month, int day);
 
    /// Return `true` if the specified `serialDay` represents a valid date
    /// value, and `false` otherwise.  Note that valid date values are (as
    /// fully defined in the component-level documentation) in the range
    /// `[ 1 .. 3652061 ]`.
    static bool isValidSerial(int serialDay);
 
    /// Return `true` if the specified `year` and `dayOfYear` represents a
    /// valid date value, and `false` otherwise.  Note that valid date
    /// values are (as fully defined in the component-level documentation)
    /// in the range `[ 0001/01 .. 9999/365 ]` (except that
    /// `[ 1752/356 .. 1752/366 ]` are not valid for historical reasons).
    static bool isValidYearDay(int year, int dayOfYear);
 
                        // To Serial Date (s)
 
    /// Return the serial date representation of the date value indicated by
    /// the specified `year` and `dayOfYear`.  The behavior is undefined
    /// unless `true == isValidYearDay(year, dayOfYear)`.
    static int ydToSerial(int year, int dayOfYear);
 
    /// Return the serial date representation of the date value indicated by
    /// the specified `year`, `month`, and `day`.  The behavior is undefined
    /// unless `true == isValidYearMonthDay(year, month, day)`.
    static int ymdToSerial(int year, int month, int day);
 
    /// Return the serial date representation of the date value indicated by
    /// the specified `year`, `month`, and `day`.  The behavior is undefined
    /// unless `true == isValidYearMonthDay(year, month, day)`.  Note that
    /// this function is guaranteed not to use any date-cache optimizations.
    static int ymdToSerialNoCache(int year, int month, int day);
 
                        // To Day-Of-Year Date (yd)
 
    /// Return the day of the year of the date value indicated by the
    /// specified `serialDay`.  The behavior is undefined unless
    /// `true == isValidSerial(serialDay)`.
    static int serialToDayOfYear(int serialDay);
 
    /// Load, into the specified `year` and `dayOfYear`, the year-day
    /// representation of the date value indicated by the specified
    /// `serialDay`.  The behavior is undefined unless
    /// `true == isValidSerial(serialDay)`.
    static void serialToYd(int *year, int *dayOfYear, int serialDay);
 
    /// Return the day of the year of the date value indicated by the
    /// specified `year`, `month`, and `day`.  The behavior is undefined
    /// unless `true == isValidYearMonthDay(year, month, day)`.
    static int ymdToDayOfYear(int year, int month, int day);
 
                        // To Calendar Date (ymd)
 
    /// Return the day (of the month) of the date value indicated by the
    /// specified `serialDay`.  The behavior is undefined unless
    /// `true == isValidSerial(serialDay)`.
    static int serialToDay(int serialDay);
 
    /// Return the day (of the month) of the date value indicated by the
    /// specified `serialDay`.  The behavior is undefined unless
    /// `true == isValidSerial(serialDay)`.  Note that this function is
    /// guaranteed not to use any date-cache optimizations.
    static int serialToDayNoCache(int serialDay);
 
    /// Return the month of the date value indicated by the specified
    /// `serialDay`.  The behavior is undefined unless
    /// `true == isValidSerial(serialDay)`.
    static int serialToMonth(int serialDay);
 
    /// Return the month of the date value indicated by the specified
    /// `serialDay`.  The behavior is undefined unless
    /// `true == isValidSerial(serialDay)`.  Note that this function is
    /// guaranteed not to use any date-cache optimizations.
    static int serialToMonthNoCache(int serialDay);
 
    /// Return the year of the date value indicated by the specified
    /// `serialDay`.  The behavior is undefined unless
    /// `true == isValidSerial(serialDay)`.
    static int serialToYear(int serialDay);
 
    /// Return the year of the date value indicated by the specified
    /// `serialDay`.  The behavior is undefined unless
    /// `true == isValidSerial(serialDay)`.  Note that this function is
    /// guaranteed not to use any date-cache optimizations.
    static int serialToYearNoCache(int serialDay);
 
    /// Load, into the specified `year`, `month`, and `day`, the date value
    /// indicated by the specified `serialDay`.  The behavior is undefined
    /// unless `true == isValidSerial(serialDay)`.
    static void serialToYmd(int *year, int *month, int *day, int serialDay);
 
    /// Load, into the specified `year`, `month`, and `day`, the date value
    /// indicated by the specified `serialDay`.  The behavior is undefined
    /// unless `true == isValidSerial(serialDay)`.  Note that this function
    /// is guaranteed not to use any date-cache-optimizations.
    static void serialToYmdNoCache(int *year,
                                   int *month,
                                   int *day,
                                   int  serialDay);
 
    /// Return the day (of the month) of the date value indicated by the
    /// specified `year` and `dayOfYear`.  The behavior is undefined unless
    /// `true == isValidYearDay(year, dayOfYear)`.
    static int ydToDay(int year, int dayOfYear);
 
    /// Load, into the specified `month` and `day`, the (partial) calendar
    /// date representation of the date value indicated by the specified
    /// `year` and `dayOfYear`.  The behavior is undefined unless
    /// `true == isValidYearDay(year, dayOfYear)`.
    static void ydToMd(int *month, int *day, int year, int dayOfYear);
 
    /// Return the month of the date value indicated by the specified `year`
    /// and `dayOfYear`.  The behavior is undefined unless
    /// `true == isValidYearDay(year, dayOfYear)`.
    static int ydToMonth(int year, int dayOfYear);
 
                        // To Day of Week '[ SUN = 1, MON .. SAT ]'
 
    /// Return, as an integer (with `1 = SUN`, `2 = MON`, ..., and
    /// `7 = SAT`), the day (of the week) of the date value indicated by the
    /// specified `serialDay`.  The behavior is undefined unless
    /// `true == isValidSerial(serialDay)`.
    static int serialToDayOfWeek(int serialDay);
 
    /// Return, as an integer (with `1 = SUN`, `2 = MON`, ..., and
    /// `7 = SAT`), the day (of the week) of the date value indicated by the
    /// specified `year` and `dayOfYear`.  The behavior is undefined unless
    /// `true == isValidYearDay(year, dayOfYear)`.
    static int ydToDayOfWeek(int year, int dayOfYear);
 
    /// Return, as an integer (with `1 = SUN`, `2 = MON`, ..., and
    /// `7 = SAT`), the day (of the week) of the date value indicated by the
    /// specified `year`, `month`, and `day`.  The behavior is undefined
    /// unless `true == isValidYearMonthDay(year, month, day)`.
    static int ymdToDayOfWeek(int year, int month, int day);
};
 
// ============================================================================
//                              INLINE DEFINITIONS
// ============================================================================
 
                           // -----------------------
                           // struct PosixDateImpUtil
                           // -----------------------
 
// CLASS METHODS
inline
bool PosixDateImpUtil::isLeapYear(int year)
{
    BSLS_ASSERT_SAFE(1 <= year);  BSLS_ASSERT_SAFE(year <= 9999);
 
    // Note relative probabilities: (1) not a modern leap year (most likely),
    // (2) not turn of any century (e.g., was not 2000), (3) year was a
    // multiple of 400 (e.g., was 2000), and (4) year was not after 1752 (most
    // unlikely).
 
    return 0 == year % 4
        && (0 != year % 100 || 0 == year % 400 || year <= 1752);
}
 
                        // Is Valid Date
 
inline
bool PosixDateImpUtil::isValidYearMonthDay(int year, int month, int day)
{
    // Check month and day; the cache cannot catch out-of-range issues.
 
    if (month < 1 || month > 12 || day < 1) {
        return false;                                                 // RETURN
    }
 
    if (s_firstCachedYear <= year && year <= s_lastCachedYear) {
        return day <= s_cachedDaysInMonth[year - s_firstCachedYear][month];
                                                                      // RETURN
    }
    else {
        return isValidYearMonthDayNoCache(year, month, day);          // RETURN
    }
}
 
inline
bool PosixDateImpUtil::isValidSerial(int serialDay)
{
    return (static_cast<unsigned>(serialDay) - 1) < 3652061; // # == 9999/12/31
}
 
                        // To Day-Of-Year Date (yd)
 
inline
int PosixDateImpUtil::serialToDayOfYear(int serialDay)
{
    BSLS_ASSERT_SAFE(true == isValidSerial(serialDay));
 
    int dayOfYear, year;
    serialToYd(&year, &dayOfYear, serialDay);
    return dayOfYear;
}
 
                        // To Calendar Date (ymd)
 
inline
int PosixDateImpUtil::serialToDayNoCache(int serialDay)
{
    BSLS_ASSERT_SAFE(true == isValidSerial(serialDay));
 
    int year, month, day;
    serialToYmdNoCache(&year, &month, &day, serialDay);
    return day;
}
 
inline
int PosixDateImpUtil::serialToMonthNoCache(int serialDay)
{
    BSLS_ASSERT_SAFE(true == isValidSerial(serialDay));
 
    int year, month, day;
    serialToYmdNoCache(&year, &month, &day, serialDay);
    return month;
}
 
inline
int PosixDateImpUtil::serialToYearNoCache(int serialDay)
{
    BSLS_ASSERT_SAFE(true == isValidSerial(serialDay));
 
    int year, month, day;
    serialToYmdNoCache(&year, &month, &day, serialDay);
    return year;
}
 
inline
void PosixDateImpUtil::serialToYmdNoCache(int *year,
                                          int *month,
                                          int *day,
                                          int  serialDay)
{
    BSLS_ASSERT_SAFE(year);
    BSLS_ASSERT_SAFE(month);
    BSLS_ASSERT_SAFE(day);
    BSLS_ASSERT_SAFE(true == isValidSerial(serialDay));
 
    int dayOfYear;
    serialToYd(year, &dayOfYear, serialDay);
    ydToMd(month, day, *year, dayOfYear);
}
 
inline
int PosixDateImpUtil::ydToDay(int year, int dayOfYear)
{
    BSLS_ASSERT_SAFE(true == isValidYearDay(year, dayOfYear));
 
    int month, day;
    ydToMd(&month, &day, year, dayOfYear);
    return day;
}
 
inline
int PosixDateImpUtil::ydToMonth(int year, int dayOfYear)
{
    BSLS_ASSERT_SAFE(true == isValidYearDay(year, dayOfYear));
 
    int month, day;
    ydToMd(&month, &day, year, dayOfYear);
    return month;
}
 
                        // To Day of Week '[ SUN = 1, MON .. SAT ]'
 
inline
int PosixDateImpUtil::ydToDayOfWeek(int year, int dayOfYear)
{
    BSLS_ASSERT_SAFE(true == isValidYearDay(year, dayOfYear));
 
    return serialToDayOfWeek(ydToSerial(year, dayOfYear));
}
 
inline
int PosixDateImpUtil::ymdToDayOfWeek(int year, int month, int day)
{
    BSLS_ASSERT_SAFE(true == isValidYearMonthDay(year, month, day));
 
    return serialToDayOfWeek(ymdToSerial(year, month, day));
}
 
}  // close package namespace
 
 
#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 ----------------------------------
 
/** @} */
/** @} */
/** @} */