Adding upstream version 3.0.0.

Signed-off-by: Daniel Baumann <daniel@debian.org>

ratelimiter.go

@@ -0,0 +1,42 @@
+package g8
+
+import (
+	"sync"
+	"time"
+)
+
+// RateLimiter is a fixed rate limiter
+type RateLimiter struct {
+	maximumExecutionsPerSecond int
+	executionsLeftInWindow     int
+	windowStartTime            time.Time
+	mutex                      sync.Mutex
+}
+
+// NewRateLimiter creates a RateLimiter
+func NewRateLimiter(maximumExecutionsPerSecond int) *RateLimiter {
+	return &RateLimiter{
+		windowStartTime:            time.Now(),
+		executionsLeftInWindow:     maximumExecutionsPerSecond,
+		maximumExecutionsPerSecond: maximumExecutionsPerSecond,
+	}
+}
+
+// Try updates the number of executions if the rate limit quota hasn't been reached and returns whether the
+// attempt was successful or not.
+//
+// Returns false if the execution was not successful (rate limit quota has been reached)
+// Returns true if the execution was successful (rate limit quota has not been reached)
+func (r *RateLimiter) Try() bool {
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+	if time.Now().Add(-time.Second).After(r.windowStartTime) {
+		r.windowStartTime = time.Now()
+		r.executionsLeftInWindow = r.maximumExecutionsPerSecond
+	}
+	if r.executionsLeftInWindow == 0 {
+		return false
+	}
+	r.executionsLeftInWindow--
+	return true
+}