New module 'parse-duration'.

[gnulib.git] / lib / parse-duration.h

diff --git a/lib/parse-duration.h b/lib/parse-duration.h
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+++ b/lib/parse-duration.h
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+/* Parse a time duration and return a seconds count
+   Copyright (C) 2008 Free Software Foundation, Inc.
+   Written by Bruce Korb <bkorb@gnu.org>, 2008.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/*
+
+  Readers and users of this function are referred to the ISO-8601
+  specification, with particular attention to "Durations".
+
+  At the time of writing, this worked:
+
+  http://en.wikipedia.org/wiki/ISO_8601#Durations
+
+  The string must start with a 'P', 'T' or a digit.
+
+  ==== if it is a digit
+
+  the string may contain:  NNN d NNN h NNN m NNN s
+  This represents NNN days, NNN hours, NNN minutes and NNN seconds.
+  The embeded white space is optional.
+  These terms must appear in this order.
+  The final "s" is optional.
+  All of the terms ("NNN" plus designator) are optional.
+  Minutes and seconds may optionally be represented as NNN:NNN.
+  Also, hours, minute and seconds may be represented as NNN:NNN:NNN.
+  There is no limitation on the value of any of the terms, except
+  that the final result must fit in a time_t value.
+
+  ==== if it is a 'P' or 'T', please see ISO-8601 for a rigorous definition.
+
+  The 'P' term may be followed by any of three formats:
+    yyyymmdd
+    yy-mm-dd
+    yy Y mm M ww W dd D
+
+  or it may be empty and followed by a 'T'.  The "yyyymmdd" must be eight
+  digits long.  Note:  months are always 30 days and years are always 365
+  days long.  5 years is always 1825, not 1826 or 1827 depending on leap
+  year considerations.  3 months is always 90 days.  There is no consideration
+  for how many days are in the current, next or previous months.
+
+  For the final format:
+  *  Embedded white space is allowed, but it is optional.
+  *  All of the terms are optional.  Any or all-but-one may be omitted.
+  *  The meanings are yy years, mm months, ww weeks and dd days.
+  *  The terms must appear in this order.
+
+  ==== The 'T' term may be followed by any of these formats:
+
+    hhmmss
+    hh:mm:ss
+    hh H mm M ss S
+
+  For the final format:
+  *  Embedded white space is allowed, but it is optional.
+  *  All of the terms are optional.  Any or all-but-one may be omitted.
+  *  The terms must appear in this order.
+
+ */
+#ifndef GNULIB_PARSE_DURATION_H
+#define GNULIB_PARSE_DURATION_H
+
+#include <time.h>
+
+#define BAD_TIME        ((time_t)~0)
+
+extern time_t parse_duration(char const * in_pz);
+
+#endif /* GNULIB_PARSE_DURATION_H */