/** Copyright 2007-2014 Haiku, Inc. All rights reserved.* Distributed under the terms of the MIT License.** Authors:* Axel Dörfler* John Scipione, jscipione@gmail.com** Corresponds to:* headers/os/support/parsedate.h rev 19972*//*!\file parsedate.h\ingroup support\ingroup libroot\brief Date parsing functionsThis is a set a functions for parsing date strings in various formats.It's mostly tailored for parsing user given data, although originally,it was developed to parse the date strings found in usenet messages.The given date will be parsed relative to the specified time, and usinga predefined set of time/date formats.\par Valid Input StringsThe internal formats allow parsedate() to understand a wide range ofinput strings. The format list is ought to be compiled from the Date:line of 80.000 usenet messages.But since this function is also used in end-user applications like theTracker's find panel, it's helpful to know what this function acceptsand what not.Here are some examples of input strings that parsedate() will be ableto convert along with some notes:- "last friday", "this wednesday", "next July""last", "next", and "this" refer to the week or year (dependingon the context). So "last friday" means last week's friday."This wednesday" is referring to this week's wednesday, no matterif it has already passed or not."Next July" refers to next year's July. All of these dates areparsed relative to the specified time (usually "now"), and willbe set to the first moment of that time span: "next monday" ismonday, 0:00:00, midnight.- "now" just returns the time all calculations are relative to.- "next 5 minutes", "5 minutes", "+5 mins" all mean the same thing,that is, current time plus exactly 5 minutes.- "5 weeks" means in 5 weeks from now on.- "8/5/2003", "5.8.2003", "2003-08-05" are all referring to August5th, 2003, again at 0:00 midnight.- "Thursday 3:00" means this week's thursday, at 3 o'clock.\anchor parsedateFormats\par Format SpecifierWhile the get_dateformats() function allow you to retrieve the built-informats, you can also define your own and use set_dateformats() to letparsedate() use them in all subsequent calls.The following is a list valid format specifiers and their meanings:- \b a/A weekday (Sunday, Monday, ...)- \b d day of month (1-31)- \b b/B month name (January, February, ...)- \b month (1-12)- \b y/Y year- \b H/I hours (1-24)- \b M minutes (0-60)- \b S seconds (0-60)- \b p meridian (am/pm)- \b z/Z time zone (i.e. GMT)- \b T time unit, like "last friday", "next 5 minutes", "-15 hours", etc.- \b - dash or slashAny of ",.:" is allowed and will be expected in the input string as is.You can enclose a \b single field with "[]" to mark it as being optional.A blank stands for white space. No other character is allowed.An invalid format string won't do any harm, but of course, no input stringwill ever match that format.For example, "H:M [p]" will match against "21:33", "4:12 am", but not"30:30 pm" (hours out of range), "15:16 GMT" (this time zone is certainlynot a valid meridian specifier), or "4:66" (minutes out of range).\note At the time of this writing, the parsedate() functions are notlocalized and will only recognize English time specificationsfollowing the examples above.*//*!\def PARSEDATE_RELATIVE_TIME\brief relative timeThe time value was computed relative to the specified time.*//*!\def PARSEDATE_DAY_RELATIVE_TIME\brief day relative timeThe time value was computed relative to the specified time, and it would varywith every day passed in the specified time.*//*!\def PARSEDATE_MINUTE_RELATIVE_TIME\brief minute relative timeThe time value was computed relative to the specified time, and it wouldvary with every minute passed in the specified time.*//*!\def PARSEDATE_INVALID_DATE\brief invalid date stringThis flag will be set if the specified date string could not be parsedcorrectly. For example, this may happen if there are some unknown words inthat string.*//*!\fn time_t parsedate(const char *dateString, time_t relativeTo)\brief Parses \a dateString relative to \a relativeToParses the given \a dateString relative to the time specified by\a relativeTo using the internal formats table.\param dateString the date that should be parsed, i.e. "next thursday".\param relativeTo all relative dates will be relative to this time, if -1is passed, the current time will be used.\return The parsed time value or -1 if the \a dateString could not beparsed.*//*!\fn time_t parsedate_etc(const char *dateString, time_t relativeTo,int *_storedFlags)\brief Parses <span class="var">dateString</span> relative to<span class="var">relativeTo</span>This does basically the same as parsedate(), but will set the followingflags in <span class="var">_storedFlags</span>:\htmlonly<table border=1><!-- ToDo: this certainly is a hack --><tr><th bgcolor="#eeeeee">Constant</th><th bgcolor="#eeeeee">Meaning</th></tr><tr><td class="mdname1">PARSEDATE_RELATIVE_TIME</td><td>\endhtmlonly \copydoc PARSEDATE_RELATIVE_TIME \htmlonly</td></tr><tr><td class="mdname1">PARSEDATE_DAY_RELATIVE_TIME</td><td>\endhtmlonly \copydoc PARSEDATE_DAY_RELATIVE_TIME \htmlonly</td></tr><tr><td class="mdname1">PARSEDATE_MINUTE_RELATIVE_TIME</td><td>\endhtmlonly \copydoc PARSEDATE_MINUTE_RELATIVE_TIME \htmlonly</td></tr><tr><td class="mdname1">PARSEDATE_INVALID_DATE</td><td>\endhtmlonly \copydoc PARSEDATE_INVALID_DATE \htmlonlyThis flag will only be set if the function returns -1.</td></tr></table>\endhtmlonly*//*!\fn void set_dateformats(const char* formatTable[])\brief sets the internal format table for parsedate()This function let you set the format table which is used by parsedate().When <span class="var">formatTable</span> is NULL, the standard built-informat table will be set again.\param formatTable the NULL terminated formats list. This list must stayvalid when using parsedate() - it is not copied, but directly used.\see \ref parsedateFormats Format!*//*!\fn const char** get_dateformats(void)\brief returns the internal format table currently used by parsedate()Returns the internal format table currently used by parsedate() - this iseither a pointer to the built-in one, or one that you have previouslyset using set_dateformats().\see \ref set_dateformats()*/