From patchwork Thu Aug 7 09:13:50 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: gary@garygende.com X-Patchwork-Id: 118003 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id C5AFF3858287 for ; Thu, 7 Aug 2025 09:15:33 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C5AFF3858287 Authentication-Results: sourceware.org; dkim=fail reason="signature verification failed" (2048-bit key, secure) header.d=garygende.com header.i=@garygende.com header.a=rsa-sha256 header.s=default header.b=jb80P91X X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from cp07-wa.privatesystems.net (cp07-wa.privatesystems.net [108.160.159.240]) by sourceware.org (Postfix) with ESMTPS id 21748385840C for ; Thu, 7 Aug 2025 09:13:51 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 21748385840C Authentication-Results: sourceware.org; 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if (tp->tm_wday < 0) tp->tm_wday += 7; - y = 1970; -#define DIV(a, b) ((a) / (b) - ((a) % (b) < 0)) -#define LEAPS_THRU_END_OF(y) (DIV (y, 4) - DIV (y, 100) + DIV (y, 400)) + #define MIN_YEAR_GROUP_NUM(a,b) (((a)<(b))?(a):(b)) + /* Start at the begining of a 400 year leapyear cycle */ + y = 1601; + days += DAYS_OFFSET; - while (days < 0 || days >= (__isleap (y) ? 366 : 365)) - { - /* Guess a corrected year, assuming 365 days per year. */ - __time64_t yg = y + days / 365 - (days % 365 < 0); + y += (days / DIVISOR_400) * 400; + days -= (days / DIVISOR_400) * DIVISOR_400; + + /* account for 3x 100 yr cycles being 1 day shorter than a 400 yr cycle */ + y += MIN_YEAR_GROUP_NUM(days / DIVISOR_100, 3) * 100; + days -= MIN_YEAR_GROUP_NUM(days / DIVISOR_100, 3) * DIVISOR_100; + + y += (days / DIVISOR_4) * 4; + days -= (days / DIVISOR_4) * DIVISOR_4; + + y += MIN_YEAR_GROUP_NUM(days / DIVISOR_1, 3); + days -= MIN_YEAR_GROUP_NUM(days / DIVISOR_1, 3) * DIVISOR_1; + + if (days < 0) { + --y; + days += 365; + if (__isleap(y)) ++days; + } - /* Adjust DAYS and Y to match the guessed year. */ - days -= ((yg - y) * 365 - + LEAPS_THRU_END_OF (yg - 1) - - LEAPS_THRU_END_OF (y - 1)); - y = yg; - } tp->tm_year = y - 1900;