xpool: add metrics

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

util/xpool/pool_test.go

@@ -2,12 +2,30 @@ package pool
 
 import (
 	"bytes"
-	"strings"
 	"testing"
 )
 
+func TestByte(t *testing.T) {
+	p := NewBytePool(1024)
+	b := p.Get()
+	copy(*b, []byte(`test`))
+	if bytes.Equal(*b, []byte("test")) {
+		t.Fatal("pool not works")
+	}
+	p.Put(b)
+	b = p.Get()
+	for i := 0; i < 1500; i++ {
+		*b = append(*b, []byte(`test`)...)
+	}
+	p.Put(b)
+	st := p.Stats()
+	if st.Get != 2 && st.Put != 2 && st.Mis != 1 && st.Ret != 1 {
+		t.Fatalf("pool stats error %#+v", st)
+	}
+}
+
 func TestBytes(t *testing.T) {
-	p := NewPool(func() *bytes.Buffer { return bytes.NewBuffer(nil) })
+	p := NewBytesPool(1024)
 	b := p.Get()
 	b.Write([]byte(`test`))
 	if b.String() != "test" {
@@ -17,7 +35,7 @@ func TestBytes(t *testing.T) {
 }
 
 func TestStrings(t *testing.T) {
-	p := NewPool(func() *strings.Builder { return &strings.Builder{} })
+	p := NewStringsPool(20)
 	b := p.Get()
 	b.Write([]byte(`test`))
 	if b.String() != "test" {