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|
package models
// Helper time methods since parsing time can easily overflow and we only support a
// specific time range.
import (
"fmt"
"math"
"time"
)
const (
// MinNanoTime is the minumum time that can be represented.
//
// 1677-09-21 00:12:43.145224194 +0000 UTC
//
// The two lowest minimum integers are used as sentinel values. The
// minimum value needs to be used as a value lower than any other value for
// comparisons and another separate value is needed to act as a sentinel
// default value that is unusable by the user, but usable internally.
// Because these two values need to be used for a special purpose, we do
// not allow users to write points at these two times.
MinNanoTime = int64(math.MinInt64) + 2
// MaxNanoTime is the maximum time that can be represented.
//
// 2262-04-11 23:47:16.854775806 +0000 UTC
//
// The highest time represented by a nanosecond needs to be used for an
// exclusive range in the shard group, so the maximum time needs to be one
// less than the possible maximum number of nanoseconds representable by an
// int64 so that we don't lose a point at that one time.
MaxNanoTime = int64(math.MaxInt64) - 1
)
var (
minNanoTime = time.Unix(0, MinNanoTime).UTC()
maxNanoTime = time.Unix(0, MaxNanoTime).UTC()
// ErrTimeOutOfRange gets returned when time is out of the representable range using int64 nanoseconds since the epoch.
ErrTimeOutOfRange = fmt.Errorf("time outside range %d - %d", MinNanoTime, MaxNanoTime)
)
// SafeCalcTime safely calculates the time given. Will return error if the time is outside the
// supported range.
func SafeCalcTime(timestamp int64, precision string) (time.Time, error) {
mult := GetPrecisionMultiplier(precision)
if t, ok := safeSignedMult(timestamp, mult); ok {
tme := time.Unix(0, t).UTC()
return tme, CheckTime(tme)
}
return time.Time{}, ErrTimeOutOfRange
}
// CheckTime checks that a time is within the safe range.
func CheckTime(t time.Time) error {
if t.Before(minNanoTime) || t.After(maxNanoTime) {
return ErrTimeOutOfRange
}
return nil
}
// Perform the multiplication and check to make sure it didn't overflow.
func safeSignedMult(a, b int64) (int64, bool) {
if a == 0 || b == 0 || a == 1 || b == 1 {
return a * b, true
}
if a == MinNanoTime || b == MaxNanoTime {
return 0, false
}
c := a * b
return c, c/b == a
}
|
