From 7fcc87f4673c79e7dbcc7d972e646383b5e47ce3 Mon Sep 17 00:00:00 2001 From: Ulrich Drepper Date: Mon, 6 Sep 1999 17:03:16 +0000 Subject: Update. 1999-09-06 Andreas Schwab * time/tzset.c (compute_change): Replace slow loop to compute T by simple algorithm. --- time/tzset.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) (limited to 'time') diff --git a/time/tzset.c b/time/tzset.c index 24624fa..6af2fba 100644 --- a/time/tzset.c +++ b/time/tzset.c @@ -418,16 +418,23 @@ compute_change (rule, year) int year; { register time_t t; - int y; if (year != -1 && rule->computed_for == year) - /* Operations on times in 1969 will be slower. Oh well. */ + /* Operations on times in 2 BC will be slower. Oh well. */ return 1; /* First set T to January 1st, 0:00:00 GMT in YEAR. */ - t = 0; - for (y = 1970; y < year; ++y) - t += SECSPERDAY * (__isleap (y) ? 366 : 365); + if (year > 1970) + t = ((year - 1970) * 365 + + /* Compute the number of leapdays between 1970 and YEAR + (exclusive). There is a leapday every 4th year ... */ + + ((year - 1) / 4 - 1970 / 4) + /* ... except every 100th year ... */ + - ((year - 1) / 100 - 1970 / 100) + /* ... but still every 400th year. */ + + ((year - 1) / 400 - 1970 / 400)) * SECSPERDAY; + else + t = 0; switch (rule->type) { -- cgit v1.1