1 files changed, 99 insertions, 0 deletions
diff --git a/vendor/github.com/puzpuzpuz/xsync/v3/counter.go b/vendor/github.com/puzpuzpuz/xsync/v3/counter.go
new file mode 100644
index 000000000..4d4dc87d2
--- /dev/null
+++ b/vendor/github.com/puzpuzpuz/xsync/v3/counter.go
@@ -0,0 +1,99 @@
+package xsync
+
+import (
+	"sync"
+	"sync/atomic"
+)
+
+// pool for P tokens
+var ptokenPool sync.Pool
+
+// a P token is used to point at the current OS thread (P)
+// on which the goroutine is run; exact identity of the thread,
+// as well as P migration tolerance, is not important since
+// it's used to as a best effort mechanism for assigning
+// concurrent operations (goroutines) to different stripes of
+// the counter
+type ptoken struct {
+	idx uint32
+	//lint:ignore U1000 prevents false sharing
+	pad [cacheLineSize - 4]byte
+}
+
+// A Counter is a striped int64 counter.
+//
+// Should be preferred over a single atomically updated int64
+// counter in high contention scenarios.
+//
+// A Counter must not be copied after first use.
+type Counter struct {
+	stripes []cstripe
+	mask    uint32
+}
+
+type cstripe struct {
+	c int64
+	//lint:ignore U1000 prevents false sharing
+	pad [cacheLineSize - 8]byte
+}
+
+// NewCounter creates a new Counter instance.
+func NewCounter() *Counter {
+	nstripes := nextPowOf2(parallelism())
+	c := Counter{
+		stripes: make([]cstripe, nstripes),
+		mask:    nstripes - 1,
+	}
+	return &c
+}
+
+// Inc increments the counter by 1.
+func (c *Counter) Inc() {
+	c.Add(1)
+}
+
+// Dec decrements the counter by 1.
+func (c *Counter) Dec() {
+	c.Add(-1)
+}
+
+// Add adds the delta to the counter.
+func (c *Counter) Add(delta int64) {
+	t, ok := ptokenPool.Get().(*ptoken)
+	if !ok {
+		t = new(ptoken)
+		t.idx = runtime_fastrand()
+	}
+	for {
+		stripe := &c.stripes[t.idx&c.mask]
+		cnt := atomic.LoadInt64(&stripe.c)
+		if atomic.CompareAndSwapInt64(&stripe.c, cnt, cnt+delta) {
+			break
+		}
+		// Give a try with another randomly selected stripe.
+		t.idx = runtime_fastrand()
+	}
+	ptokenPool.Put(t)
+}
+
+// Value returns the current counter value.
+// The returned value may not include all of the latest operations in
+// presence of concurrent modifications of the counter.
+func (c *Counter) Value() int64 {
+	v := int64(0)
+	for i := 0; i < len(c.stripes); i++ {
+		stripe := &c.stripes[i]
+		v += atomic.LoadInt64(&stripe.c)
+	}
+	return v
+}
+
+// Reset resets the counter to zero.
+// This method should only be used when it is known that there are
+// no concurrent modifications of the counter.
+func (c *Counter) Reset() {
+	for i := 0; i < len(c.stripes); i++ {
+		stripe := &c.stripes[i]
+		atomic.StoreInt64(&stripe.c, 0)
+	}
+}