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