initial string pool

pkg/store/pools/string.go

@@ -0,0 +1,61 @@
+package pools
+
+import "sync"
+
+// String is a pool for strings.
+type String struct {
+	values map[string]*string
+	counter map[string]uint
+	top uint
+
+	sync.Mutex
+}
+
+// NewString creates a new string pool
+func NewString() *String {
+	return &String{
+		values: map[string]*string{},
+	}
+}
+
+// Acquire a pointer to a string value
+func (p *String) Acquire(s string) *string {
+	p.Lock()
+	defer p.Unlock()
+	// Deduplicate value
+	ptr, ok := p.values[s]
+	if !ok {
+		p.values[s] = &s
+		ptr = &s
+	}
+	// Increment counter and top value
+	cnt, ok := p.counter[s]
+	if !ok {
+		cnt = p.top + 1
+	} else {
+		cnt = cnt + 1
+	}
+	p.counter[s] = cnt
+	if p.top < cnt {
+		p.top = cnt
+	}
+	return ptr
+}
+
+
+
+// GarbageCollect releases all values, which have not been seen
+// again. 
+func (p *String) GarbageCollect() uint {
+	p.Lock()
+	defer p.Unlock()
+	var released uint = 0
+	for k, cnt := range p.counter {
+		if cnt < p.top {
+			delete(p.counter, k)
+			delete(p.values, k)
+			released++
+		}
+	}
+	return released
+}