Add Drop method to splice pool.

splice/pool.go

@@ -29,10 +29,16 @@ func Used() int {
 	return splicePool.used()
 }
 
+// Return pipe pair to pool
 func Done(p *Pair) {
 	splicePool.done(p)
 }
 
+// Closes and discards pipe pair.
+func Drop(p *Pair) {
+	splicePool.drop(p)
+}
+
 func newSplicePairPool() *pairPool {
 	return &pairPool{}
 }
@@ -61,6 +67,13 @@ func (me *pairPool) total() int {
 	return n
 }
 
+func (me *pairPool) drop(p *Pair) {
+	p.Close()
+	me.Lock()
+	me.usedCount--
+	me.Unlock()
+}
+
 func (me *pairPool) get() (p *Pair, err error) {
 	me.Lock()
 	defer me.Unlock()