// © 2016 and later: Unicode, Inc. and others. // License & terms of use: http://www.unicode.org/copyright.html /* ******************************************************************************* * Copyright (C) 2004 - 2008, International Business Machines Corporation and * others. All Rights Reserved. ******************************************************************************* */ #ifndef UTMSCALE_H #define UTMSCALE_H #include "unicode/utypes.h" #if !UCONFIG_NO_FORMATTING /** * \file * \brief C API: Universal Time Scale * * There are quite a few different conventions for binary datetime, depending on different * platforms and protocols. Some of these have severe drawbacks. For example, people using * Unix time (seconds since Jan 1, 1970) think that they are safe until near the year 2038. * But cases can and do arise where arithmetic manipulations causes serious problems. Consider * the computation of the average of two datetimes, for example: if one calculates them with * <code>averageTime = (time1 + time2)/2</code>, there will be overflow even with dates * around the present. Moreover, even if these problems don't occur, there is the issue of * conversion back and forth between different systems. * * <p> * Binary datetimes differ in a number of ways: the datatype, the unit, * and the epoch (origin). We'll refer to these as time scales. For example: * * <table border="1" cellspacing="0" cellpadding="4"> * <caption>Table 1: Binary Time Scales</caption> * <tr> * <th align="left">Source</th> * <th align="left">Datatype</th> * <th align="left">Unit</th> * <th align="left">Epoch</th> * </tr> * * <tr> * <td>UDTS_JAVA_TIME</td> * <td>int64_t</td> * <td>milliseconds</td> * <td>Jan 1, 1970</td> * </tr> * <tr> * * <td>UDTS_UNIX_TIME</td> * <td>int32_t or int64_t</td> * <td>seconds</td> * <td>Jan 1, 1970</td> * </tr> * <tr> * <td>UDTS_ICU4C_TIME</td> * * <td>double</td> * <td>milliseconds</td> * <td>Jan 1, 1970</td> * </tr> * <tr> * <td>UDTS_WINDOWS_FILE_TIME</td> * <td>int64_t</td> * * <td>ticks (100 nanoseconds)</td> * <td>Jan 1, 1601</td> * </tr> * <tr> * <td>UDTS_DOTNET_DATE_TIME</td> * <td>int64_t</td> * <td>ticks (100 nanoseconds)</td> * * <td>Jan 1, 0001</td> * </tr> * <tr> * <td>UDTS_MAC_OLD_TIME</td> * <td>int32_t or int64_t</td> * <td>seconds</td> * <td>Jan 1, 1904</td> * * </tr> * <tr> * <td>UDTS_MAC_TIME</td> * <td>double</td> * <td>seconds</td> * <td>Jan 1, 2001</td> * </tr> * * <tr> * <td>UDTS_EXCEL_TIME</td> * <td>?</td> * <td>days</td> * <td>Dec 31, 1899</td> * </tr> * <tr> * * <td>UDTS_DB2_TIME</td> * <td>?</td> * <td>days</td> * <td>Dec 31, 1899</td> * </tr> * * <tr> * <td>UDTS_UNIX_MICROSECONDS_TIME</td> * <td>int64_t</td> * <td>microseconds</td> * <td>Jan 1, 1970</td> * </tr> * </table> * * <p> * All of the epochs start at 00:00 am (the earliest possible time on the day in question), * and are assumed to be UTC. * * <p> * The ranges for different datatypes are given in the following table (all values in years). * The range of years includes the entire range expressible with positive and negative * values of the datatype. The range of years for double is the range that would be allowed * without losing precision to the corresponding unit. * * <table border="1" cellspacing="0" cellpadding="4"> * <tr> * <th align="left">Units</th> * <th align="left">int64_t</th> * <th align="left">double</th> * <th align="left">int32_t</th> * </tr> * * <tr> * <td>1 sec</td> * <td align="right">5.84542x10<sup>11</sup></td> * <td align="right">285,420,920.94</td> * <td align="right">136.10</td> * </tr> * <tr> * * <td>1 millisecond</td> * <td align="right">584,542,046.09</td> * <td align="right">285,420.92</td> * <td align="right">0.14</td> * </tr> * <tr> * <td>1 microsecond</td> * * <td align="right">584,542.05</td> * <td align="right">285.42</td> * <td align="right">0.00</td> * </tr> * <tr> * <td>100 nanoseconds (tick)</td> * <td align="right">58,454.20</td> * <td align="right">28.54</td> * <td align="right">0.00</td> * </tr> * <tr> * <td>1 nanosecond</td> * <td align="right">584.5420461</td> * <td align="right">0.2854</td> * <td align="right">0.00</td> * </tr> * </table> * * <p> * These functions implement a universal time scale which can be used as a 'pivot', * and provide conversion functions to and from all other major time scales. * This datetimes to be converted to the pivot time, safely manipulated, * and converted back to any other datetime time scale. * *<p> * So what to use for this pivot? Java time has plenty of range, but cannot represent * .NET <code>System.DateTime</code> values without severe loss of precision. ICU4C time addresses this by using a * <code>double</code> that is otherwise equivalent to the Java time. However, there are disadvantages * with <code>doubles</code>. They provide for much more graceful degradation in arithmetic operations. * But they only have 53 bits of accuracy, which means that they will lose precision when * converting back and forth to ticks. What would really be nice would be a * <code>long double</code> (80 bits -- 64 bit mantissa), but that is not supported on most systems. * *<p> * The Unix extended time uses a structure with two components: time in seconds and a * fractional field (microseconds). However, this is clumsy, slow, and * prone to error (you always have to keep track of overflow and underflow in the * fractional field). <code>BigDecimal</code> would allow for arbitrary precision and arbitrary range, * but we do not want to use this as the normal type, because it is slow and does not * have a fixed size. * *<p> * Because of these issues, we ended up concluding that the .NET framework's * <code>System.DateTime</code> would be the best pivot. However, we use the full range * allowed by the datatype, allowing for datetimes back to 29,000 BC and up to 29,000 AD. * This time scale is very fine grained, does not lose precision, and covers a range that * will meet almost all requirements. It will not handle the range that Java times do, * but frankly, being able to handle dates before 29,000 BC or after 29,000 AD is of very limited interest. * */ /** * <code>UDateTimeScale</code> values are used to specify the time scale used for * conversion into or out if the universal time scale. * * @stable ICU 3.2 */ typedef enum UDateTimeScale { /** * Used in the JDK. Data is a Java <code>long</code> (<code>int64_t</code>). Value * is milliseconds since January 1, 1970. * * @stable ICU 3.2 */ UDTS_JAVA_TIME = 0, /** * Used on Unix systems. Data is <code>int32_t</code> or <code>int64_t</code>. Value * is seconds since January 1, 1970. * * @stable ICU 3.2 */ UDTS_UNIX_TIME, /** * Used in IUC4C. Data is a <code>double</code>. Value * is milliseconds since January 1, 1970. * * @stable ICU 3.2 */ UDTS_ICU4C_TIME, /** * Used in Windows for file times. Data is an <code>int64_t</code>. Value * is ticks (1 tick == 100 nanoseconds) since January 1, 1601. * * @stable ICU 3.2 */ UDTS_WINDOWS_FILE_TIME, /** * Used in the .NET framework's <code>System.DateTime</code> structure. Data is an <code>int64_t</code>. Value * is ticks (1 tick == 100 nanoseconds) since January 1, 0001. * * @stable ICU 3.2 */ UDTS_DOTNET_DATE_TIME, /** * Used in older Macintosh systems. Data is <code>int32_t</code> or <code>int64_t</code>. Value * is seconds since January 1, 1904. * * @stable ICU 3.2 */ UDTS_MAC_OLD_TIME, /** * Used in newer Macintosh systems. Data is a <code>double</code>. Value * is seconds since January 1, 2001. * * @stable ICU 3.2 */ UDTS_MAC_TIME, /** * Used in Excel. Data is an <code>?unknown?</code>. Value * is days since December 31, 1899. * * @stable ICU 3.2 */ UDTS_EXCEL_TIME, /** * Used in DB2. Data is an <code>?unknown?</code>. Value * is days since December 31, 1899. * * @stable ICU 3.2 */ UDTS_DB2_TIME, /** * Data is a <code>long</code>. Value is microseconds since January 1, 1970. * Similar to Unix time (linear value from 1970) and struct timeval * (microseconds resolution). * * @stable ICU 3.8 */ UDTS_UNIX_MICROSECONDS_TIME, #ifndef U_HIDE_DEPRECATED_API /** * The first unused time scale value. The limit of this enum * @deprecated ICU 59 The numeric value may change over time, see ICU ticket #12420. */ UDTS_MAX_SCALE #endif /* U_HIDE_DEPRECATED_API */ } UDateTimeScale; /** * <code>UTimeScaleValue</code> values are used to specify the time scale values * to <code>utmscale_getTimeScaleValue</code>. * * @see utmscale_getTimeScaleValue * * @stable ICU 3.2 */ typedef enum UTimeScaleValue { /** * The constant used to select the units vale * for a time scale. * * @see utmscale_getTimeScaleValue * * @stable ICU 3.2 */ UTSV_UNITS_VALUE = 0, /** * The constant used to select the epoch offset value * for a time scale. * * @see utmscale_getTimeScaleValue * * @stable ICU 3.2 */ UTSV_EPOCH_OFFSET_VALUE=1, /** * The constant used to select the minimum from value * for a time scale. * * @see utmscale_getTimeScaleValue * * @stable ICU 3.2 */ UTSV_FROM_MIN_VALUE=2, /** * The constant used to select the maximum from value * for a time scale. * * @see utmscale_getTimeScaleValue * * @stable ICU 3.2 */ UTSV_FROM_MAX_VALUE=3, /** * The constant used to select the minimum to value * for a time scale. * * @see utmscale_getTimeScaleValue * * @stable ICU 3.2 */ UTSV_TO_MIN_VALUE=4, /** * The constant used to select the maximum to value * for a time scale. * * @see utmscale_getTimeScaleValue * * @stable ICU 3.2 */ UTSV_TO_MAX_VALUE=5, #ifndef U_HIDE_INTERNAL_API /** * The constant used to select the epoch plus one value * for a time scale. * * NOTE: This is an internal value. DO NOT USE IT. May not * actually be equal to the epoch offset value plus one. * * @see utmscale_getTimeScaleValue * * @internal ICU 3.2 */ UTSV_EPOCH_OFFSET_PLUS_1_VALUE=6, /** * The constant used to select the epoch plus one value * for a time scale. * * NOTE: This is an internal value. DO NOT USE IT. May not * actually be equal to the epoch offset value plus one. * * @see utmscale_getTimeScaleValue * * @internal ICU 3.2 */ UTSV_EPOCH_OFFSET_MINUS_1_VALUE=7, /** * The constant used to select the units round value * for a time scale. * * NOTE: This is an internal value. DO NOT USE IT. * * @see utmscale_getTimeScaleValue * * @internal ICU 3.2 */ UTSV_UNITS_ROUND_VALUE=8, /** * The constant used to select the minimum safe rounding value * for a time scale. * * NOTE: This is an internal value. DO NOT USE IT. * * @see utmscale_getTimeScaleValue * * @internal ICU 3.2 */ UTSV_MIN_ROUND_VALUE=9, /** * The constant used to select the maximum safe rounding value * for a time scale. * * NOTE: This is an internal value. DO NOT USE IT. * * @see utmscale_getTimeScaleValue * * @internal ICU 3.2 */ UTSV_MAX_ROUND_VALUE=10, #endif /* U_HIDE_INTERNAL_API */ #ifndef U_HIDE_DEPRECATED_API /** * The number of time scale values, in other words limit of this enum. * * @see utmscale_getTimeScaleValue * @deprecated ICU 59 The numeric value may change over time, see ICU ticket #12420. */ UTSV_MAX_SCALE_VALUE=11 #endif /* U_HIDE_DEPRECATED_API */ } UTimeScaleValue; /** * Get a value associated with a particular time scale. * * @param timeScale The time scale * @param value A constant representing the value to get * @param status The status code. Set to <code>U_ILLEGAL_ARGUMENT_ERROR</code> if arguments are invalid. * @return - the value. * * @stable ICU 3.2 */ U_STABLE int64_t U_EXPORT2 utmscale_getTimeScaleValue(UDateTimeScale timeScale, UTimeScaleValue value, UErrorCode *status); /* Conversion to 'universal time scale' */ /** * Convert a <code>int64_t</code> datetime from the given time scale to the universal time scale. * * @param otherTime The <code>int64_t</code> datetime * @param timeScale The time scale to convert from * @param status The status code. Set to <code>U_ILLEGAL_ARGUMENT_ERROR</code> if the conversion is out of range. * * @return The datetime converted to the universal time scale * * @stable ICU 3.2 */ U_STABLE int64_t U_EXPORT2 utmscale_fromInt64(int64_t otherTime, UDateTimeScale timeScale, UErrorCode *status); /* Conversion from 'universal time scale' */ /** * Convert a datetime from the universal time scale to a <code>int64_t</code> in the given time scale. * * @param universalTime The datetime in the universal time scale * @param timeScale The time scale to convert to * @param status The status code. Set to <code>U_ILLEGAL_ARGUMENT_ERROR</code> if the conversion is out of range. * * @return The datetime converted to the given time scale * * @stable ICU 3.2 */ U_STABLE int64_t U_EXPORT2 utmscale_toInt64(int64_t universalTime, UDateTimeScale timeScale, UErrorCode *status); #endif /* #if !UCONFIG_NO_FORMATTING */ #endif