move multibuffer into dedicated folder

multiframe.go

@@ -0,0 +1,37 @@
+package gortsplib
+
+import (
+	"github.com/aler9/gortsplib/base"
+)
+
+type multiFrame struct {
+	count  int
+	frames []*base.InterleavedFrame
+	cur    int
+}
+
+func newMultiFrame(count int, bufsize int) *multiFrame {
+	frames := make([]*base.InterleavedFrame, count)
+	for i := 0; i < count; i++ {
+		frames[i] = &base.InterleavedFrame{
+			Content: make([]byte, 0, bufsize),
+		}
+	}
+
+	return &multiFrame{
+		count:  count,
+		frames: frames,
+	}
+}
+
+func (mf *multiFrame) next() *base.InterleavedFrame {
+	ret := mf.frames[mf.cur]
+	mf.cur += 1
+	if mf.cur >= mf.count {
+		mf.cur = 0
+	}
+
+	ret.Content = ret.Content[:cap(ret.Content)]
+
+	return ret
+}