1 files changed, 181 insertions, 0 deletions
diff --git a/pkg/tcpip/buffer/view.go b/pkg/tcpip/buffer/view.go
new file mode 100644
index 000000000..241ccc7a8
--- /dev/null
+++ b/pkg/tcpip/buffer/view.go
@@ -0,0 +1,181 @@
+// Copyright 2016 The Netstack Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package buffer provides the implementation of a buffer view.
+package buffer
+
+// View is a slice of a buffer, with convenience methods.
+type View []byte
+
+// NewView allocates a new buffer and returns an initialized view that covers
+// the whole buffer.
+func NewView(size int) View {
+	return make(View, size)
+}
+
+// NewViewFromBytes allocates a new buffer and copies in the given bytes.
+func NewViewFromBytes(b []byte) View {
+	return append(View(nil), b...)
+}
+
+// TrimFront removes the first "count" bytes from the visible section of the
+// buffer.
+func (v *View) TrimFront(count int) {
+	*v = (*v)[count:]
+}
+
+// CapLength irreversibly reduces the length of the visible section of the
+// buffer to the value specified.
+func (v *View) CapLength(length int) {
+	// We also set the slice cap because if we don't, one would be able to
+	// expand the view back to include the region just excluded. We want to
+	// prevent that to avoid potential data leak if we have uninitialized
+	// data in excluded region.
+	*v = (*v)[:length:length]
+}
+
+// ToVectorisedView transforms a View in a VectorisedView from an
+// already-allocated slice of View.
+func (v *View) ToVectorisedView(views [1]View) VectorisedView {
+	views[0] = *v
+	return NewVectorisedView(len(*v), views[:])
+}
+
+// VectorisedView is a vectorised version of View using non contigous memory.
+// It supports all the convenience methods supported by View.
+type VectorisedView struct {
+	views []View
+	size  int
+}
+
+// NewVectorisedView creates a new vectorised view from an already-allocated slice
+// of View and sets its size.
+func NewVectorisedView(size int, views []View) VectorisedView {
+	return VectorisedView{views: views, size: size}
+}
+
+// TrimFront removes the first "count" bytes of the vectorised view.
+func (vv *VectorisedView) TrimFront(count int) {
+	for count > 0 && len(vv.views) > 0 {
+		if count < len(vv.views[0]) {
+			vv.size -= count
+			vv.views[0].TrimFront(count)
+			return
+		}
+		count -= len(vv.views[0])
+		vv.RemoveFirst()
+	}
+}
+
+// CapLength irreversibly reduces the length of the vectorised view.
+func (vv *VectorisedView) CapLength(length int) {
+	if length < 0 {
+		length = 0
+	}
+	if vv.size < length {
+		return
+	}
+	vv.size = length
+	for i := range vv.views {
+		v := &vv.views[i]
+		if len(*v) >= length {
+			if length == 0 {
+				vv.views = vv.views[:i]
+			} else {
+				v.CapLength(length)
+				vv.views = vv.views[:i+1]
+			}
+			return
+		}
+		length -= len(*v)
+	}
+}
+
+// Clone returns a clone of this VectorisedView.
+// If the buffer argument is large enough to contain all the Views of this VectorisedView,
+// the method will avoid allocations and use the buffer to store the Views of the clone.
+func (vv *VectorisedView) Clone(buffer []View) VectorisedView {
+	var views []View
+	if len(buffer) >= len(vv.views) {
+		views = buffer[:len(vv.views)]
+	} else {
+		views = make([]View, len(vv.views))
+	}
+	for i, v := range vv.views {
+		views[i] = v
+	}
+	return VectorisedView{views: views, size: vv.size}
+}
+
+// First returns the first view of the vectorised view.
+// It panics if the vectorised view is empty.
+func (vv *VectorisedView) First() View {
+	if len(vv.views) == 0 {
+		return nil
+	}
+	return vv.views[0]
+}
+
+// RemoveFirst removes the first view of the vectorised view.
+func (vv *VectorisedView) RemoveFirst() {
+	if len(vv.views) == 0 {
+		return
+	}
+	vv.size -= len(vv.views[0])
+	vv.views = vv.views[1:]
+}
+
+// SetSize unsafely sets the size of the VectorisedView.
+func (vv *VectorisedView) SetSize(size int) {
+	vv.size = size
+}
+
+// SetViews unsafely sets the views of the VectorisedView.
+func (vv *VectorisedView) SetViews(views []View) {
+	vv.views = views
+}
+
+// Size returns the size in bytes of the entire content stored in the vectorised view.
+func (vv *VectorisedView) Size() int {
+	return vv.size
+}
+
+// ToView returns the a single view containing the content of the vectorised view.
+func (vv *VectorisedView) ToView() View {
+	v := make([]byte, vv.size)
+	u := v
+	for i := range vv.views {
+		n := copy(u, vv.views[i])
+		u = u[n:]
+	}
+	return v
+}
+
+// Views returns the slice containing the all views.
+func (vv *VectorisedView) Views() []View {
+	return vv.views
+}
+
+// ByteSlice returns a slice containing the all views as a []byte.
+func (vv *VectorisedView) ByteSlice() [][]byte {
+	s := make([][]byte, len(vv.views))
+	for i := range vv.views {
+		s[i] = []byte(vv.views[i])
+	}
+	return s
+}
+
+// copy returns a deep-copy of the vectorised view.
+// It is an expensive method that should be used only in tests.
+func (vv *VectorisedView) copy() *VectorisedView {
+	uu := &VectorisedView{
+		views: make([]View, len(vv.views)),
+		size:  vv.size,
+	}
+	for i, v := range vv.views {
+		uu.views[i] = make(View, len(v))
+		copy(uu.views[i], v)
+	}
+	return uu
+}