1 files changed, 72 insertions, 0 deletions
diff --git a/vendor/github.com/xtaci/smux/alloc.go b/vendor/github.com/xtaci/smux/alloc.go
new file mode 100644
index 0000000..9e3acf3
--- /dev/null
+++ b/vendor/github.com/xtaci/smux/alloc.go
@@ -0,0 +1,72 @@
+package smux
+
+import (
+	"errors"
+	"sync"
+)
+
+var (
+	defaultAllocator *Allocator
+	debruijinPos     = [...]byte{0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31}
+)
+
+func init() {
+	defaultAllocator = NewAllocator()
+}
+
+// Allocator for incoming frames, optimized to prevent overwriting after zeroing
+type Allocator struct {
+	buffers []sync.Pool
+}
+
+// NewAllocator initiates a []byte allocator for frames less than 65536 bytes,
+// the waste(memory fragmentation) of space allocation is guaranteed to be
+// no more than 50%.
+func NewAllocator() *Allocator {
+	alloc := new(Allocator)
+	alloc.buffers = make([]sync.Pool, 17) // 1B -> 64K
+	for k := range alloc.buffers {
+		i := k
+		alloc.buffers[k].New = func() interface{} {
+			return make([]byte, 1<<uint32(i))
+		}
+	}
+	return alloc
+}
+
+// Get a []byte from pool with most appropriate cap
+func (alloc *Allocator) Get(size int) []byte {
+	if size <= 0 || size > 65536 {
+		return nil
+	}
+
+	bits := msb(size)
+	if size == 1<<bits {
+		return alloc.buffers[bits].Get().([]byte)[:size]
+	} else {
+		return alloc.buffers[bits+1].Get().([]byte)[:size]
+	}
+}
+
+// Put returns a []byte to pool for future use,
+// which the cap must be exactly 2^n
+func (alloc *Allocator) Put(buf []byte) error {
+	bits := msb(cap(buf))
+	if cap(buf) == 0 || cap(buf) > 65536 || cap(buf) != 1<<bits {
+		return errors.New("allocator Put() incorrect buffer size")
+	}
+	alloc.buffers[bits].Put(buf)
+	return nil
+}
+
+// msb return the pos of most significiant bit
+// http://supertech.csail.mit.edu/papers/debruijn.pdf
+func msb(size int) byte {
+	v := uint32(size)
+	v |= v >> 1
+	v |= v >> 2
+	v |= v >> 4
+	v |= v >> 8
+	v |= v >> 16
+	return debruijinPos[(v*0x07C4ACDD)>>27]
+}