Add Stats.MaxBytesSize for determining cache capacity

fastcache.go

@@ -53,6 +53,9 @@ type Stats struct {
 	// BytesSize is the current size of the cache in bytes.
 	BytesSize uint64
 
+	// MaxBytesSize is the maximum allowed size of the cache in bytes (aka capacity).
+	MaxBytesSize uint64
+
 	// BigStats contains stats for GetBig/SetBig methods.
 	BigStats
 }
@@ -296,6 +299,7 @@ func (b *bucket) UpdateStats(s *Stats) {
 	for _, chunk := range b.chunks {
 		s.BytesSize += uint64(cap(chunk))
 	}
+	s.MaxBytesSize += uint64(len(b.chunks))*chunkSize
 	b.mu.RUnlock()
 }
 

fastcache_test.go

@@ -112,7 +112,10 @@ func TestCacheWrap(t *testing.T) {
 		t.Fatalf("unexpected number of items; got %d; cannot be smaller than %d", s.EntriesCount, calls/5)
 	}
 	if s.BytesSize < 1024 {
-		t.Fatalf("unexpected number of bytesSize; got %d; cannot be smaller than %d", s.BytesSize, 1024)
+		t.Fatalf("unexpected BytesSize; got %d; cannot be smaller than %d", s.BytesSize, 1024)
+	}
+	if s.MaxBytesSize < 32*1024*1024 {
+		t.Fatalf("unexpected MaxBytesSize; got %d; cannot be smaller than %d", s.MaxBytesSize, 32*1024*1024)
 	}
 }