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| <!DOCTYPE library PUBLIC "-//Boost//DTD BoostBook XML V1.0//EN" |
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| |
| <!-- Copyright (c) 2005 CrystalClear Software, Inc. |
| Subject to the Boost Software License, Version 1.0. |
| (See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt) |
| --> |
| |
| <section id="date_time.io_tutorial" |
| xmlns:xi="http://www.w3.org/2001/XInclude"> |
| <title>Date Time IO Tutorial</title> |
| <bridgehead renderas="sect2">Date Time IO Tutorial</bridgehead> |
| |
| <link linkend="basic_use">Basic Use</link> | |
| <link linkend="format_strings">Format Strings</link> | |
| <link linkend="content_strings">Content Strings</link> | |
| <link linkend="tut_sv">Special Values</link> | |
| <link linkend="tut_dper">Date/Time Periods</link> | |
| <link linkend="tut_dgen">Date Generators</link> |
| |
| <anchor id="basic_use" /> |
| <bridgehead renderas="sect4">Basic Use</bridgehead> |
| <para>Facets are automatically imbued when operators '>>' and '<<' are called. The list of date_time objects that can be streamed are:</para> |
| <bridgehead renderas="sect5">Gregorian</bridgehead> |
| <para> |
| <code>date</code>, |
| <code>days</code>, |
| <code>date_period</code>, |
| <code>greg_month</code>, |
| <code>greg_weekday</code>, |
| <code>greg_year</code>, |
| <code>partial_date</code>, |
| <code>nth_day_of_the_week_in_month</code>, |
| <code>first_day_of_the_week_in_month</code>, |
| <code>last_day_of_the_week_in_month</code>, |
| <code>first_day_of_the_week_after</code>, |
| <code>first_day_of_the_week_before</code> |
| </para> |
| <bridgehead renderas="sect5">Posix_time</bridgehead> |
| <para> |
| <code>ptime</code>, |
| <code>time_period</code>, |
| <code>time_duration</code> |
| </para> |
| <bridgehead renderas="sect5">Local_time</bridgehead> |
| <para> |
| <code>local_date_time</code> |
| </para> |
| |
| <para> |
| The following example is of the basic use of the new IO code, utilizing all the defaults. (this example can be found in the <code>libs/date_time/examples/tutorial</code> directory) |
| </para> |
| <programlisting> |
| <![CDATA[ |
| date d(2004, Feb, 29); |
| time_duration td(12,34,56,789); |
| stringstream ss; |
| ss << d << ' ' << td; |
| ptime pt(not_a_date_time); |
| cout << pt << endl; // "not-a-date-time" |
| ss >> pt; |
| cout << pt << endl; // "2004-Feb-29 12:34:56.000789" |
| ss.str(""); |
| ss << pt << " EDT-05EDT,M4.1.0,M10.5.0"; |
| local_date_time ldt(not_a_date_time); |
| ss >> ldt; |
| cout << ldt << endl; // "2004-Feb-29 12:34:56.000789 EDT" |
| ]]> |
| </programlisting> |
| |
| <para>This example used the default settings for the input and output facets. The default formats are such that interoperability like that shown in the example is possible. NOTE: Input streaming of local_date_time can only be done with a <link linkend="date_time.local_time.posix_time_zone">posix time zone string</link>. The default output format uses a time zone abbreviation. The format can be changed so out and in match (as we will see later in this tutorial).</para> |
| |
| <anchor id="format_strings" /> |
| <bridgehead renderas="sect4">Format Strings</bridgehead> |
| <para>The format strings control the order, type, and style of the date/time elements used. The facets provide some predefined formats (iso_format_specifier, iso_format_extended_specifier, and default_date_format) but the user can easily create their own.</para> |
| (continued from previous example) |
| <programlisting> |
| <![CDATA[ |
| local_time_facet* output_facet = new local_time_facet(); |
| local_time_input_facet* input_facet = new local_time_input_facet(); |
| ss.imbue(locale(locale::classic(), output_facet)); |
| ss.imbue(locale(ss.getloc(), input_facet)); |
| |
| output_facet->format("%a %b %d, %H:%M %z"); |
| ss.str(""); |
| ss << ldt; |
| cout << ss.str() << endl; // "Sun Feb 29, 12:34 EDT" |
| |
| output_facet->format(local_time_facet::iso_time_format_specifier); |
| ss.str(""); |
| ss << ldt; |
| cout << ss.str() << endl; // "20040229T123456.000789-0500" |
| |
| output_facet->format(local_time_facet::iso_time_format_extended_specifier); |
| ss.str(""); |
| ss << ldt; |
| cout << ss.str() << endl; // "2004-02-29 12:34:56.000789-05:00" |
| ]]> |
| </programlisting> |
| |
| <para>Format strings are not limited to date/time elements. Extra verbiage can be placed in a format string. NOTE: When extra verbiage is present in an input format, the data being input must also contain the exact verbiage.</para> |
| (continued from previous example) |
| <programlisting> |
| <![CDATA[ |
| // extra words in format |
| string my_format("The extended ordinal time %Y-%jT%H:%M can also be \ |
| represented as %A %B %d, %Y"); |
| output_facet->format(my_format.c_str()); |
| input_facet->format(my_format.c_str()); |
| ss.str(""); |
| ss << ldt; |
| cout << ss.str() << endl; |
| |
| // matching extra words in input |
| ss.str("The extended ordinal time 2005-128T12:15 can also be \ |
| represented as Sunday May 08, 2005"); |
| ss >> ldt; |
| cout << ldt << endl; |
| ]]> |
| </programlisting> |
| |
| <anchor id="content_strings" /> |
| <bridgehead renderas="sect4">Content Strings</bridgehead> |
| <para>So far we've shown how a user can achieve a great deal of customization with very little effort by using formats. Further customization can be achieved through user defined elements (ie strings). The elements that can be customized are: Special value names, month names, month abbreviations, weekday names, weekday abbreviations, delimiters of the date/time periods, and the phrase elements of the date_generators.</para> |
| <para>The default values for these are as follows:</para> |
| <bridgehead renderas="sect5">Special values</bridgehead> |
| <para> |
| <code>not-a-date-time</code>, |
| <code>-infinity</code>, |
| <code>+infinity</code>, |
| <code>minimum-date-time</code>, |
| <code>maximum-date-time</code> |
| </para> |
| <bridgehead renderas="sect5">Months</bridgehead> |
| <para> |
| <code>English calendar and three letter abbreviations</code> |
| </para> |
| <bridgehead renderas="sect5">Weekdays</bridgehead> |
| <para> |
| <code>English calendar and three letter abbreviations</code> |
| </para> |
| <bridgehead renderas="sect5">Date generator phrase elements</bridgehead> |
| <para> |
| <code>first</code>, |
| <code>second</code>, |
| <code>third</code>, |
| <code>fourth</code>, |
| <code>fifth</code>, |
| <code>last</code>, |
| <code>before</code>, |
| <code>after</code>, |
| <code>of</code> |
| </para> |
| <para>NOTE: We've shown earlier that the components of a date/time representation can be re-ordered via the format string. This is not the case with date_generators. The elements themselves can be customized but their order cannot be changed.</para> |
| |
| <bridgehead renderas="sect4">Content Strings</bridgehead> |
| <para>To illustrate the customization possibilities we will use custom strings for months and weekdays (we will only use long names, is all lowercase, for this example).</para> |
| (continued from previous example) |
| <programlisting> |
| <![CDATA[ |
| // set up the collections of custom strings. |
| // only the full names are altered for the sake of brevity |
| string month_names[12] = { "january", "february", "march", |
| "april", "may", "june", |
| "july", "august", "september", |
| "october", "november", "december" }; |
| vector<string> long_months(&month_names[0], &month_names[12]); |
| string day_names[7] = { "sunday", "monday", "tuesday", "wednesday", |
| "thursday", "friday", "saturday" }; |
| vector<string> long_days(&day_names[0], &day_names[7]); |
| |
| // create date_facet and date_input_facet using all defaults |
| date_facet* date_output = new date_facet(); |
| date_input_facet* date_input = new date_input_facet(); |
| ss.imbue(locale(ss.getloc(), date_output)); |
| ss.imbue(locale(ss.getloc(), date_input)); |
| |
| // replace names in the output facet |
| date_output->long_month_names(long_months); |
| date_output->long_weekday_names(long_days); |
| |
| // replace names in the input facet |
| date_input->long_month_names(long_months); |
| date_input->long_weekday_names(long_days); |
| |
| // customize month, weekday and date formats |
| date_output->format("%Y-%B-%d"); |
| date_input->format("%Y-%B-%d"); |
| date_output->month_format("%B"); // full name |
| date_input->month_format("%B"); // full name |
| date_output->weekday_format("%A"); // full name |
| date_input->weekday_format("%A"); // full name |
| |
| ss.str(""); |
| ss << greg_month(3); |
| cout << ss.str() << endl; // "march" |
| ss.str(""); |
| ss << greg_weekday(3); |
| cout << ss.str() << endl; // "tuesday" |
| ss.str(""); |
| ss << date(2005,Jul,4); |
| cout << ss.str() << endl; // "2005-july-04" |
| ]]> |
| </programlisting> |
| |
| |
| <anchor id="tut_sv" /> |
| <bridgehead renderas="sect4">Special Values</bridgehead> |
| <para>Customizing the input and output of special values is best done by creating a new special_values_parser and special_values_formatter. The new strings can be set at construction time (as in the example below).</para> |
| (continued from previous example) |
| <programlisting> |
| <![CDATA[ |
| // reset the formats to defaults |
| output_facet->format(local_time_facet::default_time_format); |
| input_facet->format(local_time_input_facet::default_time_input_format); |
| |
| // create custom special_values parser and formatter objects |
| // and add them to the facets |
| string sv[5] = {"nadt","neg_inf", "pos_inf", "min_dt", "max_dt" }; |
| vector<string> sv_names(&sv[0], &sv[5]); |
| special_values_parser sv_parser(sv_names.begin(), sv_names.end()); |
| special_values_formatter sv_formatter(sv_names.begin(), sv_names.end()); |
| output_facet->special_values_formatter(sv_formatter); |
| input_facet->special_values_parser(sv_parser); |
| |
| ss.str(""); |
| ldt = local_date_time(not_a_date_time); |
| ss << ldt; |
| cout << ss.str() << endl; // "nadt" |
| |
| ss.str("min_dt"); |
| ss >> ldt; |
| ss.str(""); |
| ss << ldt; |
| cout << ss.str() << endl; // "1400-Jan-01 00:00:00 UTC" |
| ]]> |
| </programlisting> |
| <para>NOTE: even though we sent in strings for min and max to the formatter, they are ignored because those special values construct to actual dates (as shown above).</para> |
| |
| |
| <anchor id="tut_dper" /> |
| <bridgehead renderas="sect4">Date/Time Periods</bridgehead> |
| <para>Customizing the input and output of periods is best done by creating a new period_parser and period_formatter. The new strings can be set at construction time (as in the example below).</para> |
| (continued from previous example) |
| <programlisting> |
| <![CDATA[ |
| // all formats set back to defaults (not shown for brevity) |
| |
| // create our date_period |
| date_period dp(date(2005,Mar,1), days(31)); // month of march |
| |
| // custom period formatter and parser |
| period_formatter per_formatter(period_formatter::AS_OPEN_RANGE, |
| " to ", "from ", " exclusive", " inclusive" ); |
| period_parser per_parser(period_parser::AS_OPEN_RANGE, |
| " to ", "from ", " exclusive" , "inclusive" ); |
| |
| // default output |
| ss.str(""); |
| ss << dp; |
| cout << ss.str() << endl; // "[2005-Mar-01/2005-Mar-31]" |
| |
| // add out custom parser and formatter to the facets |
| date_output->period_formatter(per_formatter); |
| date_input->period_parser(per_parser); |
| |
| // custom output |
| ss.str(""); |
| ss << dp; |
| cout << ss.str() << endl; // "from 2005-Feb-01 to 2005-Apr-01 exclusive" |
| ]]> |
| </programlisting> |
| |
| <anchor id="tut_dgen" /> |
| <bridgehead renderas="sect4">Date Generators</bridgehead> |
| <para>Customizing the input and output of date_generators is done by replacing the existing strings (in the facet) with new strings.</para> |
| <para>NOTE: We've shown earlier that the components of a date/time representation can be re-ordered via the format string. This is not the case with date_generators. The elements themselves can be customized but their order cannot be changed.</para> |
| (continued from previous example) |
| <programlisting> |
| <![CDATA[ |
| // custom date_generator phrases |
| string dg_phrases[9] = { "1st", "2nd", "3rd", "4th", "5th", |
| "final", "prior to", "following", "in" }; |
| vector<string> phrases(&dg_phrases[0], &dg_phrases[9]); |
| |
| // create our date_generator |
| first_day_of_the_week_before d_gen(Monday); |
| |
| // default output |
| ss.str(""); |
| ss << d_gen; |
| cout << ss.str() << endl; // "Mon before" |
| |
| // add our custom strings to the date facets |
| date_output->date_gen_phrase_strings(phrases); |
| date_input->date_gen_element_strings(phrases); |
| |
| // custom output |
| ss.str(""); |
| ss << d_gen; |
| cout << ss.str() << endl; // "Mon prior to" |
| ]]> |
| </programlisting> |
| |
| </section> |