feat: PR mailru#370 (avoid extra alloc)

Author: prostraction

buffer/pool.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"net"
 	"sync"
+	"unsafe"
 )
 
 // PoolConfig contains configuration for the allocation and reuse strategy.
@@ -47,17 +48,19 @@ func putBuf(buf []byte) {
 		return
 	}
 	if c := buffers[size]; c != nil {
-		c.Put(buf[:0])
+		c.Put(unsafe.Pointer(&buf[:1][0]))
 	}
 }
 
+const maxArraySize = uint((uint64(1)<<50 - 1) & uint64(^uint(0)>>1))
+
 // getBuf gets a chunk from reuse pool or creates a new one if reuse failed.
 func getBuf(size int) []byte {
 	if size >= config.PooledSize {
 		if c := buffers[size]; c != nil {
 			v := c.Get()
 			if v != nil {
-				return v.([]byte)
+				return (*[maxArraySize]byte)(v.(unsafe.Pointer))[:0:size]
 			}
 		}
 	}