54 lines
2.0 KiB
Go
54 lines
2.0 KiB
Go
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package astits
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import (
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"fmt"
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"time"
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)
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// parseDVBTime parses a DVB time
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// This field is coded as 16 bits giving the 16 LSBs of MJD followed by 24 bits coded as 6 digits in 4 - bit Binary
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// Coded Decimal (BCD). If the start time is undefined (e.g. for an event in a NVOD reference service) all bits of the
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// field are set to "1".
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// I apologize for the computation which is really messy but details are given in the documentation
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// Page: 160 | Annex C | Link: https://www.dvb.org/resources/public/standards/a38_dvb-si_specification.pdf
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func parseDVBTime(i []byte, offset *int) (t time.Time) {
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// Date
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var mjd = uint16(i[*offset])<<8 | uint16(i[*offset+1])
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var yt = int((float64(mjd) - 15078.2) / 365.25)
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var mt = int((float64(mjd) - 14956.1 - float64(int(float64(yt)*365.25))) / 30.6001)
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var d = int(float64(mjd) - 14956 - float64(int(float64(yt)*365.25)) - float64(int(float64(mt)*30.6001)))
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var k int
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if mt == 14 || mt == 15 {
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k = 1
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}
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var y = yt + k
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var m = mt - 1 - k*12
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t, _ = time.Parse("06-01-02", fmt.Sprintf("%d-%d-%d", y, m, d))
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*offset += 2
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// Time
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t = t.Add(parseDVBDurationSeconds(i, offset))
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return
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}
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// parseDVBDurationMinutes parses a minutes duration
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// 16 bit field containing the duration of the event in hours, minutes. format: 4 digits, 4 - bit BCD = 18 bit
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func parseDVBDurationMinutes(i []byte, offset *int) (d time.Duration) {
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d = parseDVBDurationByte(i[*offset])*time.Hour + parseDVBDurationByte(i[*offset+1])*time.Minute
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*offset += 2
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return
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}
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// parseDVBDurationSeconds parses a seconds duration
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// 24 bit field containing the duration of the event in hours, minutes, seconds. format: 6 digits, 4 - bit BCD = 24 bit
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func parseDVBDurationSeconds(i []byte, offset *int) (d time.Duration) {
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d = parseDVBDurationByte(i[*offset])*time.Hour + parseDVBDurationByte(i[*offset+1])*time.Minute + parseDVBDurationByte(i[*offset+2])*time.Second
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*offset += 3
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return
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}
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// parseDVBDurationByte parses a duration byte
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func parseDVBDurationByte(i byte) time.Duration {
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return time.Duration(uint8(i)>>4*10 + uint8(i)&0xf)
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}
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