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Document rtptime.

This commit is contained in:
Juliusz Chroboczek 2021-04-30 12:57:03 +02:00
parent 6c752b58bc
commit cd1ac8a8c9

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@ -1,40 +1,51 @@
// Package rtptime manipulates RTP and NTP time
package rtptime package rtptime
import ( import (
"time" "time"
) )
// epoch is the origin of NTP time
var epoch = time.Now() var epoch = time.Now()
// FromDuration converts a time.Duration into units of 1/hz.
func FromDuration(d time.Duration, hz uint32) uint64 { func FromDuration(d time.Duration, hz uint32) uint64 {
return uint64(d) * uint64(hz) / uint64(time.Second) return uint64(d) * uint64(hz) / uint64(time.Second)
} }
// ToDuration converts units of 1/hz into a time.Duration.
func ToDuration(tm uint64, hz uint32) time.Duration { func ToDuration(tm uint64, hz uint32) time.Duration {
return time.Duration(tm * uint64(time.Second) / uint64(hz)) return time.Duration(tm * uint64(time.Second) / uint64(hz))
} }
// Now returns the current time in units of 1/hz from an arbitrary origin.
func Now(hz uint32) uint64 { func Now(hz uint32) uint64 {
return FromDuration(time.Since(epoch), hz) return FromDuration(time.Since(epoch), hz)
} }
// Microseconds is like Now, but uses microseconds.
func Microseconds() uint64 { func Microseconds() uint64 {
return Now(1000000) return Now(1000000)
} }
// JiffiesPerSec is the LCM of 48000, 96000 and 65536 // JiffiesPerSec is the number of jiffies in a second. This is the LCM of
// 48000, 96000 and 65536.
const JiffiesPerSec = 24576000 const JiffiesPerSec = 24576000
// Jiffies returns the current time in jiffies.
func Jiffies() uint64 { func Jiffies() uint64 {
return Now(JiffiesPerSec) return Now(JiffiesPerSec)
} }
// TimeToJiffies converts a time.Time into jiffies.
func TimeToJiffies(tm time.Time) uint64 { func TimeToJiffies(tm time.Time) uint64 {
return FromDuration(tm.Sub(epoch), JiffiesPerSec) return FromDuration(tm.Sub(epoch), JiffiesPerSec)
} }
// The origin of NTP time.
var ntpEpoch = time.Date(1900, 1, 1, 0, 0, 0, 0, time.UTC) var ntpEpoch = time.Date(1900, 1, 1, 0, 0, 0, 0, time.UTC)
// NTPToTime converts an NTP time into a time.Time.
func NTPToTime(ntp uint64) time.Time { func NTPToTime(ntp uint64) time.Time {
sec := uint32(ntp >> 32) sec := uint32(ntp >> 32)
frac := uint32(ntp & 0xFFFFFFFF) frac := uint32(ntp & 0xFFFFFFFF)
@ -44,6 +55,7 @@ func NTPToTime(ntp uint64) time.Time {
) )
} }
// TimeToNTP converts a time.Time into an NTP time.
func TimeToNTP(tm time.Time) uint64 { func TimeToNTP(tm time.Time) uint64 {
d := tm.Sub(ntpEpoch) d := tm.Sub(ntpEpoch)
sec := uint32(d / time.Second) sec := uint32(d / time.Second)