1 files changed, 48 insertions, 0 deletions
diff --git a/pkg/com/counter.go b/pkg/com/counter.go
new file mode 100644
index 0000000..52f9f7f
--- /dev/null
+++ b/pkg/com/counter.go
@@ -0,0 +1,48 @@
+package com
+
+import (
+	"sync"
+	"sync/atomic"
+)
+
+// Counter implements an atomic counter.
+type Counter struct {
+	value uint64
+	mu    sync.Mutex // Protects total.
+	total uint64
+}
+
+// Add adds the given delta to the counter.
+func (c *Counter) Add(delta uint64) {
+	atomic.AddUint64(&c.value, delta)
+}
+
+// Inc increments the counter by one.
+func (c *Counter) Inc() {
+	c.Add(1)
+}
+
+// Reset resets the counter to 0 and returns its previous value.
+// Does not reset the total value returned from Total.
+func (c *Counter) Reset() uint64 {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	v := atomic.SwapUint64(&c.value, 0)
+	c.total += v
+
+	return v
+}
+
+// Total returns the total counter value.
+func (c *Counter) Total() uint64 {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	return c.total + c.Val()
+}
+
+// Val returns the current counter value.
+func (c *Counter) Val() uint64 {
+	return atomic.LoadUint64(&c.value)
+}