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window.go
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window.go
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package ratelimit
import "time"
// Window is a time windows for counting events within a span of time. The
// windows slides forward in time so that it spans from the most recent event
// to size time in the past.
type Window struct {
q *queue
size int64
}
// NewWindow creates a new Window that limits the number of events to maximum
// count of events within a duration of time. The capacity sets the maximum
// number of events, and size sets the span of time over which the events are
// counted.
func NewWindow(capacity int, size time.Duration) *Window {
return &Window{
q: &queue{
buf: make([]int64, capacity),
},
size: int64(size),
}
}
// Add attempts to append a new timestamp into the current window. Previously
// added values that are not not within `size` difference from the value being
// added are first removed. Add fails if adding the value would cause the
// window to exceed capacity.
func (w *Window) Add() error {
now := time.Now().UnixNano()
if w.Len() != 0 {
w.q.truncate(now - w.size)
}
return w.q.push(now)
}
// Cap returns the maximum number of items the window can hold.
func (w *Window) Cap() int {
return w.q.cap()
}
// Len returns the number of elements currently in the window.
func (w *Window) Len() int {
return w.q.len()
}
// Span returns the distance from the first to the last item in the window.
func (w *Window) Span() time.Duration {
if w.q.len() < 2 {
return 0
}
return time.Duration(w.q.back() - w.q.front())
}
// Oldest returns the oldest timestamp in the window.
func (w *Window) Oldest() time.Time {
if w.q.len() == 0 {
return time.Time{}
}
return time.Unix(0, w.q.front())
}
// Newest returns the newest timestamp in the window.
func (w *Window) Newest() time.Time {
if w.q.len() == 0 {
return time.Time{}
}
return time.Unix(0, w.q.back())
}