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std::time_get::get, std::time_get::do_get

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< cpp‎ | locale‎ | time get
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Defined in header <locale>
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public:

iter_type get(iter_type beg, iter_type end, std::ios_base& str,
              std::ios_base::iostate& err, std::tm* t,

              const char_type* fmtbeg, const char_type* fmtend) const;
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protected:

virtual iter_type do_get(iter_type neg, iter_type end, std::ios_base& str,
                         std::ios_base::iostate& err, std::tm *t,

                         char format, char modifier) const;
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1) Parses the date and time from the input character sequence [beg, end) according to the format provided in the character sequence [fmtbeg, fmtend). The format is expected to follow the format described below, although actual processing of each format specifier can be customized by overriding do_get. The get function performs the following: First, clears the error bits in err by executing err = std::ios_base::goodbit. Then enters a loop, which terminates whenever any of the following conditions becomes true (checked in this order):
a) All characters have been read from the format string (fmtbeg == fmtend)
b) There was a parsing error (err != std::ios_base::goodbit)
c) All characters have been read from the input sequence (beg == end. If this condition terminates the loop, the function sets both eofbit and failbit in err
In the body of the loop, the following steps take place:
a) if the next character in the format string is '%', followed by one or two characters that form a valid std::get_time conversion specifier (see below), these characters are used in the call do_get(beg, end, str, err, t, format, modifier), where format is the primary conversion specifier character, and modifier is the optional modifier (which appears between % and the format character, if present). If there is no modifier, the value '\0' is used. If the format string is ambiguous or ends too early to determine the conversion specifier after '%', eofbit is set in err and the loop is terminated. If, after the call to do_get, no error bits are set in err, the function increments fmtbeg to point right after the conversion specifier and continues the loop.
b) If the next character is whitespace, as indicated by the locale provided in the stream str (i.e. std::isspace(*fmtbeg, str.getloc()) == true, the function keeps incrementing fmtbeg until it either becomes equal to fmtend or points to a non-whitespace character.
c) If the next character in the format string is equivalent to the next character in the input stream according to case-insensitive comparison, the function advances both sequences by one character ++fmtbeg, ++beg; and continues the loop, Otherwise, it sets the failbit in err.
2) Parses one conversion specifier from the input sequence [beg, end) and updates the std::tm structure pointed to by t accordingly.
First, clears the error bits in err by executing err = std::ios_base::goodbit. Then reads characters from the input sequence [beg, end) that are expected by the std::time_get format specifier formed by combining '%', modifier (if not '\0'), and format. If the characters do not combine to form a valid conversion specifier, sets failbit in err. If the end of the input stream is reached after reading a character, sets eofbit in err. If the input string was parsed successfully, updates the corresponding fields of *t.
For complex conversion specifiers, such as '%x' or '%c', or the directives that use the modifiers 'E' and 'O', the function may fail to determine some of the values to store in *t. In such case, it sets eofbit in err and leaves these fields in unspecified state.

Contents

Parameters

beg - iterator designating the start of the sequence to parse
end - one past the end iterator for the sequence to parse
str - a stream object that this function uses to obtain locale facets when needed, e.g. std::ctype to skip whitespace or std::collate to compare strings
err - stream error flags object that is modified by this function to indicate errors
t - pointer to the std::tm object that will hold the result of this function call
fmtbeg - pointer to the first character of a sequence of char_type characters specifying the conversion format

The format string consists of zero or more conversion specifiers, whitespace characters, and ordinary characters (except %). Each ordinary character is expected to match one character in the input stream in case-insensitive comparison. Each whitespace character matches arbitrary whitespace in the input string. Each conversion specification begins with % character, optionally followed by E or O modifier (ignored if unsupported by the locale), followed by the character that determines the behavior of the specifier. The format specifiers match the POSIX function strptime():

Conversion
specifier
Explanation Writes to fields
% matches a literal %. The full conversion specification must be %%. (none)
t matches any whitespace. (none)
n matches any whitespace. (none)
Year
Y parses full year as a 4 digit decimal number, leading zeroes permitted but not required tm_year
EY parses year in the alternative representation, e.g.平成23年 (year Heisei 23) which writes 2011 to tm_year in ja_JP locale tm_year
y parses last 2 digits of year as a decimal number. Range [69,99] results in values 1969 to 1999, range [00,68] results in 2000-2068 tm_year
Oy parses last 2 digits of year using the alternative numeric system, e.g. 十一 is parsed as 11 in ja_JP locale tm_year
Ey parses year as offset from locale's alternative calendar period %EC tm_year
C parses the first 2 digits of year as a decimal number (range [00,99]) tm_year
EC parses the name of the base year (period) in the locale's alternative representation, e.g. 平成 (Heisei era) in ja_JP tm_year
Month
b parses the month name, either full or abbreviated, e.g. Oct tm_mon
h synonym of b tm_mon
B synonym of b tm_mon
m parses the month as a decimal number (range [01,12]), leading zeroes permitted but not required tm_mon
Om parses the month using the alternative numeric system, e.g. 十二 parses as 12 in ja_JP locale tm_mon
Week
U parses the week of the year as a decimal number (Sunday is the first day of the week) (range [00,53]), leading zeroes permitted but not required tm_year, tm_wday, tm_yday
OU parses the week of the year, as by %U, using the alternative numeric system, e.g. 五十二 parses as 52 in ja_JP locale tm_year, tm_wday, tm_yday
W parses the week of the year as a decimal number (Monday is the first day of the week) (range [00,53]), leading zeroes permitted but not required tm_year, tm_wday, tm_yday
OW parses the week of the year, as by %W, using the alternative numeric system, e.g. 五十二 parses as 52 in ja_JP locale tm_year, tm_wday, tm_yday
Day of the year/month
j parses day of the year as a decimal number (range [001,366]), leading zeroes permitted but not required tm_yday
d parses the day of the month as a decimal number (range [01,31]), leading zeroes permitted but not required tm_mday
Od parses the day of the month using the alternative numeric system, e.g 二十七 parses as 23 in ja_JP locale, leading zeroes permitted but not required tm_mday
e synonym of d tm_mday
Oe synonym of Od tm_mday
Day of the week
a parses the name of the day of the week, either full or abbreviated, e.g. Fri tm_wday
A synonym of a tm_wday
w parses weekday as a decimal number, where Sunday is 0 (range [0-6]) tm_wday
Ow parses weekday as a decimal number, where Sunday is 0, using the alternative numeric system, e.g. 二 parses as 2 in ja_JP locale tm_wday
Hour, minute, second
H parses the hour as a decimal number, 24 hour clock (range [00-23]), leading zeroes permitted but not required tm_hour
OH parses hour from 24-hour clock using the alternative numeric system, e.g. 十八 parses as 18 in ja_JP locale tm_hour
I parses hour as a decimal number, 12 hour clock (range [01,12]), leading zeroes permitted but not required tm_hour
OI parses hour from 12-hour clock using the alternative numeric system, e.g. 六 reads as 06 in ja_JP locale tm_hour
M parses minute as a decimal number (range [00,59]), leading zeroes permitted but not required tm_min
OM parses minute using the alternative numeric system, e.g. 二十五 parses as 25 in ja_JP locale tm_min
S parses second as a decimal number (range [00,60]), leading zeroes permitted but not required tm_sec
OS parses second using the alternative numeric system, e.g. 二十四 parses as 24 in ja_JP locale tm_sec
Other
c parses the locale's standard date and time string format, e.g. Sun Oct 17 04:41:13 2010 (locale dependent) all
Ec parses the locale's alternative date and time string format, e.g. expecting 平成23年 (year Heisei 23) instead of 2011年 (year 2011) in ja_JP locale all
x parses the locale's standard date representation all
Ex parses the locale's alternative date representation, e.g. expecting 平成23年 (year Heisei 23) instead of 2011年 (year 2011) in ja_JP locale all
X parses the locale's standard time representation all
EX parses the locale's alternative time representation all
D equivalent to "%m / %d / %y " tm_mon, tm_mday, tm_year
r parses locale's standard 12-hour clock time (in POSIX, "%I : %M : %S %p") tm_hour, tm_min, tm_sec
R equivalent to "%H : %M" tm_hour, tm_min
T equivalent to "%H : %M : %S" tm_hour, tm_min, tm_sec
p parses the locale's equivalent of a.m. or p.m. tm_hour


fmtend - pointer one past the last character of a sequence of char_type characters specifying the conversion format
format - the character that names a conversion specifier
modifier - the optional modifier that may appear between % and the conversion specifier

Return value

Iterator pointing one past the last character in [beg, end) that was parsed successfully.

Notes

The case-insensitive comparison for the non-whitespace non-'%' characters in the format string, the std::collate facet of the locale provided by str is typically, but not necessarily, used.

If a parsing error is encountered, many implementations of this function leave *t completely untouched.

It's unspecified if these functions zero out the fields in *t that they do not set directly: portable programs should initialize every field to zero before calling get().

Example

#include <iostream>
#include <sstream>
#include <locale>
#include <iomanip>
 
int main()
{
    std::istringstream ss("2011-Februar-18 23:12:34");
    ss.imbue(std::locale("de_DE"));
 
    auto& f = std::use_facet<std::time_get<char>>(std::locale("de_DE"));
    std::tm t{};
    std::string s = "%Y-%b-%d %H:%M:%S";
    std::ios_base::iostate err = std::ios_base::goodbit;
    std::istreambuf_iterator<char> ret = f.get(std::istreambuf_iterator<char>(ss),
                                               std::istreambuf_iterator<char>(),
                                               ss, err, &t, &s[0], &s[0] + s.size());
    ss.setstate(err);
 
    if(ss) {
        std::cout << "Successfully parsed as " << std::put_time(&t, "%c");
        if(ret != std::istreambuf_iterator<char>()) {
            std::cout << " Remaining content: ";
            std::copy(ret, std::istreambuf_iterator<char>(),
                           std::ostreambuf_iterator<char>(std::cout));
        } else {
                std::cout << " The input was fully consumed";
        }
    } else {
            std::cout << "Parse failed. Unparsed string: ";
            std::copy(ret, std::istreambuf_iterator<char>(),
                           std::ostreambuf_iterator<char>(std::cout));
    }
    std::cout << '\n';
}

Output:

Successfully parsed, as Sun Feb 18 23:12:34 2011 The input was fully consumed

See also

Template:cpp/io/manip/dcl list get time