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* time.c (find_time_t): time guess strategy refined again.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@23939 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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2 changed files with 49 additions and 115 deletions
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@ -1,3 +1,7 @@
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Fri Jul 3 02:52:20 2009 Tanaka Akira <akr@fsij.org>
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* time.c (find_time_t): time guess strategy refined again.
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Fri Jul 3 00:36:16 2009 Tanaka Akira <akr@fsij.org>
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* time.c (find_time_t): time guess strategy refined.
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160
time.c
160
time.c
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@ -1860,31 +1860,38 @@ timegm_noleapsecond(struct tm *tm)
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DIV(tm_year+299,400))*86400;
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}
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#ifdef FIND_TIME_NUMGUESS
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#if 0
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#define DEBUG_FIND_TIME_NUMGUESS
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#define DEBUG_REPORT_GUESSRANGE fprintf(stderr, "find time guess range: %ld - %ld : %lu\n", guess_lo, guess_hi, (unsigned_time_t)(guess_hi-guess_lo))
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#endif
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#ifndef DEBUG_REPORT_GUESSRANGE
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#define DEBUG_REPORT_GUESSRANGE
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#endif
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#ifdef DEBUG_FIND_TIME_NUMGUESS
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#define DEBUG_FIND_TIME_NUMGUESS_INC find_time_numguess++,
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static unsigned long long find_time_numguess;
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static VALUE find_time_numguess_getter(void)
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{
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return ULL2NUM(find_time_numguess);
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}
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#else
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#define DEBUG_FIND_TIME_NUMGUESS_INC
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#endif
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static const char *
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find_time_t(struct tm *tptr, int utc_p, time_t *tp)
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{
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time_t guess, guess_lo, guess_hi;
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time_t guess, guess0, guess_lo, guess_hi;
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struct tm *tm, tm_lo, tm_hi;
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int d;
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int find_dst;
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struct tm result;
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int try_interpolation;
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unsigned long range = 0;
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int status;
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#ifdef FIND_TIME_NUMGUESS
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#define GUESS(p) (find_time_numguess++, (utc_p ? gmtime_with_leapsecond(p, &result) : LOCALTIME(p, result)))
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#else
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#define GUESS(p) (utc_p ? gmtime_with_leapsecond(p, &result) : LOCALTIME(p, result))
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#endif
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#define GUESS(p) (DEBUG_FIND_TIME_NUMGUESS_INC (utc_p ? gmtime_with_leapsecond(p, &result) : LOCALTIME(p, result)))
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find_dst = 0 < tptr->tm_isdst;
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@ -1897,7 +1904,8 @@ find_time_t(struct tm *tptr, int utc_p, time_t *tp)
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(time_t)((unsigned_time_t)~(time_t)0 >> 1) :
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~(time_t)0;
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guess = timegm_noleapsecond(tptr);
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DEBUG_REPORT_GUESSRANGE;
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guess0 = guess = timegm_noleapsecond(tptr);
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tm = GUESS(&guess);
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if (tm) {
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d = tmcmp(tptr, tm);
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@ -1910,6 +1918,7 @@ find_time_t(struct tm *tptr, int utc_p, time_t *tp)
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guess_lo = guess;
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guess += 24 * 60 * 60;
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}
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DEBUG_REPORT_GUESSRANGE;
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if (guess_lo < guess && guess < guess_hi && (tm = GUESS(&guess)) != NULL) {
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d = tmcmp(tptr, tm);
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if (d == 0) { goto found; }
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@ -1917,6 +1926,7 @@ find_time_t(struct tm *tptr, int utc_p, time_t *tp)
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guess_hi = guess;
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else
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guess_lo = guess;
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DEBUG_REPORT_GUESSRANGE;
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}
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}
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@ -1934,105 +1944,35 @@ find_time_t(struct tm *tptr, int utc_p, time_t *tp)
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if (d == 0) { guess = guess_hi; goto found; }
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tm_hi = *tm;
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try_interpolation = 1;
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DEBUG_REPORT_GUESSRANGE;
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status = 1;
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while (guess_lo + 1 < guess_hi) {
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if (try_interpolation == 1) {
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int a, b;
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/* there is a gap between guess_lo and guess_hi. */
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range = 0;
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/*
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Try precious guess by a linear interpolation at first.
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`a' and `b' is a coefficient of guess_lo and guess_hi as:
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guess = (guess_lo * a + guess_hi * b) / (a + b)
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However this causes overflow in most cases, following assignment
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is used instead:
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guess = guess_lo / d * a + (guess_lo % d) * a / d
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+ guess_hi / d * b + (guess_hi % d) * b / d
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where d = a + b
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To avoid overflow in this assignment, `d' is restricted to less than
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sqrt(2**31). By this restriction and other reasons, the guess is
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not accurate and some error is expected. `range' approximates
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the maximum error.
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When these parameters are not suitable, i.e. guess is not within
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guess_lo and guess_hi, simple guess by binary search is used.
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*/
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range = 366 * 24 * 60 * 60;
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a = (tm_hi.tm_year - tptr->tm_year);
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b = (tptr->tm_year - tm_lo.tm_year);
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/* 46000 is selected as `some big number less than sqrt(2**31)'. */
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if (a + b <= 46000 / 12) {
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range = 31 * 24 * 60 * 60;
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a *= 12;
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b *= 12;
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a += tm_hi.tm_mon - tptr->tm_mon;
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b += tptr->tm_mon - tm_lo.tm_mon;
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if (a + b <= 46000 / 31) {
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range = 24 * 60 * 60;
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a *= 31;
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b *= 31;
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a += tm_hi.tm_mday - tptr->tm_mday;
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b += tptr->tm_mday - tm_lo.tm_mday;
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if (a + b <= 46000 / 24) {
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range = 60 * 60;
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a *= 24;
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b *= 24;
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a += tm_hi.tm_hour - tptr->tm_hour;
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b += tptr->tm_hour - tm_lo.tm_hour;
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if (a + b <= 46000 / 60) {
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range = 60;
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a *= 60;
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b *= 60;
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a += tm_hi.tm_min - tptr->tm_min;
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b += tptr->tm_min - tm_lo.tm_min;
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if (a + b <= 46000 / 60) {
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range = 1;
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a *= 60;
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b *= 60;
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a += tm_hi.tm_sec - tptr->tm_sec;
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b += tptr->tm_sec - tm_lo.tm_sec;
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}
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}
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}
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}
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}
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if (a <= 0) a = 1;
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if (b <= 0) b = 1;
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d = a + b;
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/*
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Although `/' and `%' may produce unexpected result with negative
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argument, it doesn't cause serious problem because there is a
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fail safe.
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*/
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guess = guess_lo / d * a + (guess_lo % d) * a / d
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+ guess_hi / d * b + (guess_hi % d) * b / d;
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try_interpolation = 2;
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}
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else if (try_interpolation == 2) {
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guess = guess - range;
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range = 0;
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try_interpolation = 1;
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}
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else if (try_interpolation == 3) {
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guess = guess + range;
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range = 0;
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try_interpolation = 1;
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}
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if (try_interpolation == 0 || guess <= guess_lo || guess_hi <= guess) {
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/* Precious guess is invalid. try binary search. */
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if (status == 0) {
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binsearch:
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guess = guess_lo / 2 + guess_hi / 2;
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if (guess <= guess_lo)
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guess = guess_lo + 1;
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else if (guess >= guess_hi)
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guess = guess_hi - 1;
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range = 0;
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try_interpolation = 1;
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status = 1;
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}
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else {
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if (status == 1) {
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time_t guess0_hi = timegm_noleapsecond(&tm_hi);
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guess = guess_hi - (guess0_hi - guess0);
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status = 2;
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}
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else if (status == 2) {
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time_t guess0_lo = timegm_noleapsecond(&tm_lo);
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guess = guess_lo + (guess0 - guess0_lo);
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status = 0;
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}
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if (guess <= guess_lo || guess_hi <= guess) {
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/* Precious guess is invalid. try binary search. */
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goto binsearch;
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}
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}
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tm = GUESS(&guess);
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@ -2041,24 +1981,14 @@ find_time_t(struct tm *tptr, int utc_p, time_t *tp)
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d = tmcmp(tptr, tm);
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if (d < 0) {
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if (range)
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try_interpolation = 2;
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else if ((unsigned_time_t)(guess-guess_lo) > (unsigned_time_t)(guess_hi-guess))
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try_interpolation = 0;
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else
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try_interpolation = 1;
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guess_hi = guess;
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tm_hi = *tm;
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DEBUG_REPORT_GUESSRANGE;
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}
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else if (d > 0) {
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if (range)
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try_interpolation = 3;
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else if ((unsigned_time_t)(guess-guess_lo) < (unsigned_time_t)(guess_hi-guess))
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try_interpolation = 0;
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else
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try_interpolation = 1;
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guess_lo = guess;
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tm_lo = *tm;
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DEBUG_REPORT_GUESSRANGE;
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}
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else {
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found:
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@ -3831,7 +3761,7 @@ Init_Time(void)
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rb_define_method(rb_cTime, "marshal_load", time_mload, 1);
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#endif
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#ifdef FIND_TIME_NUMGUESS
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#ifdef DEBUG_FIND_TIME_NUMGUESS
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rb_define_virtual_variable("$find_time_numguess", find_time_numguess_getter, NULL);
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#endif
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}
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