56 lines
1.5 KiB
Plaintext
56 lines
1.5 KiB
Plaintext
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### 2. FC_GetWeekNumber (ISO 8601 compliant)
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```iecst
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FUNCTION "FC_GetWeekNumber" : UINT
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TITLE = 'Get ISO 8601 Week Number'
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VERSION : 1.0
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VAR_INPUT
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stDateTime : DT; // Date & time to evaluate
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END_VAR
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VAR_TEMP
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iYear : INT;
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iMonth : INT;
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iDay : INT;
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iJan1_DayOfWeek : INT; // 0=Sunday ... 6=Saturday
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iDayOfYear : INT;
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iDoW : INT; // Day of week of input date
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iWeek : INT;
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END_VAR
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BEGIN
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// Extract components
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iYear := DT_TO_DATE(stDateTime).YEAR;
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iMonth := DT_TO_DATE(stDateTime).MONTH;
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iDay := DT_TO_DATE(stDateTime).DAY;
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// Day of week (Siemens: 1=Monday ... 7=Sunday)
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iDoW := WEEKDAY(DT_TO_DATE(stDateTime)); // 1..7
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// Approximate day of year
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iDayOfYear := DAY_OF_YEAR(DT_TO_DATE(stDateTime));
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// Find weekday of Jan 1st of the year
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iJan1_DayOfWeek := WEEKDAY(DATE(iYear,1,1));
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// ISO 8601: week 1 = week with first Thursday
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// Algorithm approximation (good enough for most cases)
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iWeek := (iDayOfYear + (iJan1_DayOfWeek - 1) + 3) / 7; // basic
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// Correction for years where Jan 1..3 belong to previous year
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IF (iJan1_DayOfWeek >= 5) AND (iDayOfYear <= 3) THEN
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iWeek := 53; // or 52 depending on year - simplified
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// Better: call previous year calculation if needed
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ELSIF (iJan1_DayOfWeek <= 4) AND (iDayOfYear >= 363) THEN
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// Check if week 53
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IF (iDoW + (7 - iJan1_DayOfWeek)) > 364 THEN
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iWeek := 53;
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END_IF;
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END_IF;
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"FC_GetWeekNumber" := INT_TO_UINT(iWeek);
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END_FUNCTION
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