}
\f
/* Converts struct tm to time_t, assuming the data in tm is UTC rather
- than local timezone (mktime assumes the latter).
+ than local timezone.
+
+ mktime is similar but assumes struct tm, also known as the
+ "broken-down" form of time, is in local time zone. mktime_from_utc
+ uses mktime to make the conversion understanding that an offset
+ will be introduced by the local time assumption.
+
+ mktime_from_utc then measures the introduced offset by applying
+ gmtime to the initial result and applying mktime to the resulting
+ "broken-down" form. The difference between the two mktime results
+ is the measured offset which is then subtracted from the initial
+ mktime result to yield a calendar time which is the value returned.
+
+ tm_isdst in struct tm is set to 0 to force mktime to introduce a
+ consistent offset (the non DST offset) since tm and tm+o might be
+ on opposite sides of a DST change.
+
+ Some implementations of mktime return -1 for the nonexistent
+ localtime hour at the beginning of DST. In this event, use
+ mktime(tm - 1hr) + 3600.
+
+ Schematically
+ mktime(tm) --> t+o
+ gmtime(t+o) --> tm+o
+ mktime(tm+o) --> t+2o
+ t+o - (t+2o - t+o) = t
+
+ Note that glibc contains a function of the same purpose named
+ `timegm' (reverse of gmtime). But obviously, it is not universally
+ available, and unfortunately it is not straightforwardly
+ extractable for use here. Perhaps configure should detect timegm
+ and use it where available.
Contributed by Roger Beeman <beeman@cisco.com>, with the help of
Mark Baushke <mdb@cisco.com> and the rest of the Gurus at CISCO.
`+X', or at the end of the string.
In extended regexp parlance, the function returns 1 if P matches
- "^ *(GMT|[+-][0-9]|$)", 0 otherwise. P being NULL (a valid result of
- strptime()) is considered a failure and 0 is returned. */
+ "^ *(GMT|[+-][0-9]|$)", 0 otherwise. P being NULL (which strptime
+ can return) is considered a failure and 0 is returned. */
static int
check_end (const char *p)
{
return 0;
}
-/* Convert TIME_STRING time to time_t. TIME_STRING can be in any of
- the three formats RFC2068 allows the HTTP servers to emit --
- RFC1123-date, RFC850-date or asctime-date. Timezones are ignored,
- and should be GMT.
-
- We use strptime() to recognize various dates, which makes it a
- little bit slacker than the RFC1123/RFC850/asctime (e.g. it always
- allows shortened dates and months, one-digit days, etc.). It also
- allows more than one space anywhere where the specs require one SP.
- The routine should probably be even more forgiving (as recommended
- by RFC2068), but I do not have the time to write one.
-
- Return the computed time_t representation, or -1 if all the
- schemes fail.
-
- Needless to say, what we *really* need here is something like
- Marcus Hennecke's atotm(), which is forgiving, fast, to-the-point,
- and does not use strptime(). atotm() is to be found in the sources
- of `phttpd', a little-known HTTP server written by Peter Erikson. */
+/* Convert the textual specification of time in TIME_STRING to the
+ number of seconds since the Epoch.
+
+ TIME_STRING can be in any of the three formats RFC2068 allows the
+ HTTP servers to emit -- RFC1123-date, RFC850-date or asctime-date.
+ Timezones are ignored, and should be GMT.
+
+ Return the computed time_t representation, or -1 if the conversion
+ fails.
+
+ This function uses strptime with various string formats for parsing
+ TIME_STRING. This results in a parser that is not as lenient in
+ interpreting TIME_STRING as I would like it to be. Being based on
+ strptime, it always allows shortened months, one-digit days, etc.,
+ but due to the multitude of formats in which time can be
+ represented, an ideal HTTP time parser would be even more
+ forgiving. It should completely ignore things like week days and
+ concentrate only on the various forms of representing years,
+ months, days, hours, minutes, and seconds. For example, it would
+ be nice if it accepted ISO 8601 out of the box.
+
+ I've investigated free and PD code for this purpose, but none was
+ usable. getdate was big and unwieldy, and had potential copyright
+ issues, or so I was informed. Dr. Marcus Hennecke's atotm(),
+ distributed with phttpd, is excellent, but we cannot use it because
+ it is not assigned to the FSF. So I stuck it with strptime. */
+
time_t
http_atotm (char *time_string)
{
+ /* NOTE: Solaris strptime man page claims that %n and %t match white
+ space, but that's not universally available. Instead, we simply
+ use ` ' to mean "skip all WS", which works under all strptime
+ implementations I've tested. */
+
+ static const char *time_formats[] = {
+ "%a, %d %b %Y %T", /* RFC1123: Thu, 29 Jan 1998 22:12:57 */
+ "%A, %d-%b-%y %T", /* RFC850: Thursday, 29-Jan-98 22:12:57 */
+ "%a, %d-%b-%Y %T", /* pseudo-RFC850: Thu, 29-Jan-1998 22:12:57
+ (google.com uses this for their cookies.) */
+ "%a %b %d %T %Y" /* asctime: Thu Jan 29 22:12:57 1998 */
+ };
+
+ int i;
struct tm t;
/* According to Roger Beeman, we need to initialize tm_isdst, since
t.tm_isdst = 0;
/* Note that under foreign locales Solaris strptime() fails to
- recognize English dates, which renders this function useless. I
- assume that other non-GNU strptime's are plagued by the same
- disease. We solve this by setting only LC_MESSAGES in
- i18n_initialize(), instead of LC_ALL.
+ recognize English dates, which renders this function useless. We
+ solve this by being careful not to affect LC_TIME when
+ initializing locale.
- Another solution could be to temporarily set locale to C, invoke
+ Another solution would be to temporarily set locale to C, invoke
strptime(), and restore it back. This is slow and dirty,
however, and locale support other than LC_MESSAGES can mess other
things, so I rather chose to stick with just setting LC_MESSAGES.
- Also note that none of this is necessary under GNU strptime(),
- because it recognizes both international and local dates. */
-
- /* NOTE: We don't use `%n' for white space, as OSF's strptime uses
- it to eat all white space up to (and including) a newline, and
- the function fails if there is no newline (!).
-
- Let's hope all strptime() implementations use ` ' to skip *all*
- whitespace instead of just one (it works that way on all the
- systems I've tested it on). */
-
- /* RFC1123: Thu, 29 Jan 1998 22:12:57 */
- if (check_end (strptime (time_string, "%a, %d %b %Y %T", &t)))
- return mktime_from_utc (&t);
- /* RFC850: Thursday, 29-Jan-98 22:12:57 */
- if (check_end (strptime (time_string, "%A, %d-%b-%y %T", &t)))
- return mktime_from_utc (&t);
- /* pseudo-RFC850: Thu, 29-Jan-1998 22:12:57
- (google.com uses this for their cookies.)*/
- if (check_end (strptime (time_string, "%a, %d-%b-%Y %T", &t)))
- return mktime_from_utc (&t);
- /* asctime: Thu Jan 29 22:12:57 1998 */
- if (check_end (strptime (time_string, "%a %b %d %T %Y", &t)))
- return mktime_from_utc (&t);
- /* Failure. */
+ GNU strptime does not have this problem because it recognizes
+ both international and local dates. */
+
+ for (i = 0; i < ARRAY_SIZE (time_formats); i++)
+ if (check_end (strptime (time_string, time_formats[i], &t)))
+ return mktime_from_utc (&t);
+
+ /* All formats have failed. */
return -1;
}
\f
projects / wget / commitdiff