46 lines
1.3 KiB
Go
46 lines
1.3 KiB
Go
package reads
|
|
|
|
func Modulo(dividend, modulus int64) int64 {
|
|
r := dividend % modulus
|
|
if r < 0 {
|
|
r += modulus
|
|
}
|
|
return r
|
|
}
|
|
|
|
// WindowStart calculates the start time of a window given a timestamp,
|
|
// the window period (every), and the offset starting from the epoch.
|
|
//
|
|
// Note that the normalized offset value can fall on either side of the
|
|
// normalized timestamp. If it lies to the left we know it represents
|
|
// the start time. Otherwise it represents the stop time, in which case
|
|
// we decrement by the window period to get the start time.
|
|
//
|
|
func WindowStart(t, every, offset int64) int64 {
|
|
mod := Modulo(t, every)
|
|
off := Modulo(offset, every)
|
|
beg := t - mod + off
|
|
if mod < off {
|
|
beg -= every
|
|
}
|
|
return beg
|
|
}
|
|
|
|
// WindowStop calculates the stop time of a window given a timestamp,
|
|
// the window period (every), and the offset starting from the epoch.
|
|
//
|
|
// Note that the normalized offset value can fall on either side of the
|
|
// normalized timestamp. If it lies to the right we know it represents
|
|
// the stop time. Otherwise it represents the start time, in which case
|
|
// we increment by the window period to get the stop time.
|
|
//
|
|
func WindowStop(t, every, offset int64) int64 {
|
|
mod := Modulo(t, every)
|
|
off := Modulo(offset, every)
|
|
end := t - mod + off
|
|
if mod >= off {
|
|
end += every
|
|
}
|
|
return end
|
|
}
|