146 lines
4.8 KiB
C
146 lines
4.8 KiB
C
//*****************************************************************************
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//
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//! @file am_util_time.h
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//!
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//! @brief Functions useful for RTC, calendar, time, etc. computations.
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//
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//*****************************************************************************
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//*****************************************************************************
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//
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// Copyright (c) 2020, Ambiq Micro
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// All rights reserved.
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are met:
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//
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// 1. Redistributions of source code must retain the above copyright notice,
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// this list of conditions and the following disclaimer.
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//
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// 2. Redistributions in binary form must reproduce the above copyright
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// notice, this list of conditions and the following disclaimer in the
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// documentation and/or other materials provided with the distribution.
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//
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// 3. Neither the name of the copyright holder nor the names of its
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// contributors may be used to endorse or promote products derived from this
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// software without specific prior written permission.
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//
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// Third party software included in this distribution is subject to the
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// additional license terms as defined in the /docs/licenses directory.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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//
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// This is part of revision 2.4.2 of the AmbiqSuite Development Package.
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//
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//*****************************************************************************
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#include <stdint.h>
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#include <stdbool.h>
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#include "am_util_time.h"
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//*****************************************************************************
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//
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// Macro definitions.
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//
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//*****************************************************************************
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#define AM_UTIL_TIME_IS_LEAP_YEAR(year) \
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(year % 4 == 0 && ((year % 100 != 0) || (year % 400 != 0)))
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//*****************************************************************************
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//
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// Local variables.
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//
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//*****************************************************************************
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//
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// Numer of days in each month in a standard year.
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//
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const static uint32_t g_iDaysPerMonth[] =
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{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
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//
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// Weekday drift numbers for each month.
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//
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const static int g_iMonthOffsets[] =
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{4, 0, 0, 3, 5, 1, 3, 6, 2, 4, 0, 2};
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//*****************************************************************************
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//
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//! @brief Compute the day of the week given the month, day, and year.
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//!
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//! @param iYear - The year of the desired date (e.g. 2016).
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//! @param iMonth - The month of the desired date (1-12).
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//! @param iDay - The day of the month of the desired date (1-31).
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//!
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//! This function is general in nature, but is designed to be used with the RTC.
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//!
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//! @returns An index value indicating the day of the week.
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//! 0-6 indicate Sun, Mon, Tue, Wed, Thu, Fri, Sat, respectively.
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//! 7 indicates that the given date is invalid (e.g. 2/29/2015).
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//
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//*****************************************************************************
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int
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am_util_time_computeDayofWeek(int iYear, int iMonth, int iDay)
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{
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bool bInvalidDay;
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int iYearOffset;
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int iMonthOffset;
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int iWeekday;
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int iLeapYearOffset = 0;
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//
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// Validate inputs. Return 7 if any are out-of-bounds.
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//
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if ( (iMonth < 1) || (iMonth > 12) || (iYear < 0) || (iDay < 1) )
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{
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return 7;
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}
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//
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// Make sure this day actually exists in this month. Make sure to include
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// an exception for leap years.
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//
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if (iDay > g_iDaysPerMonth[iMonth - 1])
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{
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if (iMonth == 2 && AM_UTIL_TIME_IS_LEAP_YEAR(iYear) && iDay == 29)
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{
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bInvalidDay = false;
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}
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else
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{
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bInvalidDay = true;
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}
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}
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else
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{
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bInvalidDay = false;
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}
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if (bInvalidDay)
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{
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return 7;
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}
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iYearOffset = 2 + iYear + iYear / 4 - iYear / 100 + iYear / 400;
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iMonthOffset = g_iMonthOffsets[iMonth - 1];
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if (AM_UTIL_TIME_IS_LEAP_YEAR(iYear) && (iMonth < 3))
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{
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iLeapYearOffset = -1;
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}
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iWeekday = iDay + iYearOffset + iMonthOffset + iLeapYearOffset;
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return iWeekday % 7;
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}
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