3 files changed, 470 insertions, 0 deletions
diff --git a/pkg/ilist/BUILD b/pkg/ilist/BUILD
new file mode 100644
index 000000000..937ac3876
--- /dev/null
+++ b/pkg/ilist/BUILD
@@ -0,0 +1,66 @@
+package(licenses = ["notice"])  # BSD
+
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+load("//tools/go_generics:defs.bzl", "go_template", "go_template_instance")
+load("//tools/go_stateify:defs.bzl", "go_stateify")
+
+go_stateify(
+    name = "list_state",
+    srcs = [
+        "interface_list.go",
+    ],
+    out = "interface_list_state.go",
+    package = "ilist",
+)
+
+go_library(
+    name = "ilist",
+    srcs = [
+        "interface_list.go",
+        "interface_list_state.go",
+    ],
+    importpath = "gvisor.googlesource.com/gvisor/pkg/ilist",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//pkg/state",
+    ],
+)
+
+go_template_instance(
+    name = "interface_list",
+    out = "interface_list.go",
+    package = "ilist",
+    template = ":generic_list",
+    types = {},
+)
+
+# This list is used for benchmarking.
+go_template_instance(
+    name = "test_list",
+    out = "test_list.go",
+    package = "ilist",
+    prefix = "direct",
+    template = ":generic_list",
+    types = {
+        "Linker": "*direct",
+    },
+)
+
+go_test(
+    name = "list_test",
+    size = "small",
+    srcs = [
+        "list_test.go",
+        "test_list.go",
+    ],
+    embed = [":ilist"],
+)
+
+go_template(
+    name = "generic_list",
+    srcs = [
+        "list.go",
+    ],
+    opt_types = ["Linker"],
+    visibility = ["//visibility:public"],
+)
diff --git a/pkg/ilist/list.go b/pkg/ilist/list.go
new file mode 100644
index 000000000..739575f17
--- /dev/null
+++ b/pkg/ilist/list.go
@@ -0,0 +1,171 @@
+// 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 ilist provides the implementation of intrusive linked lists.
+package ilist
+
+// Linker is the interface that objects must implement if they want to be added
+// to and/or removed from List objects.
+//
+// N.B. When substituted in a template instantiation, Linker doesn't need to
+// be an interface, and in most cases won't be.
+type Linker interface {
+	Next() Linker
+	Prev() Linker
+	SetNext(Linker)
+	SetPrev(Linker)
+}
+
+// List is an intrusive list. Entries can be added to or removed from the list
+// in O(1) time and with no additional memory allocations.
+//
+// The zero value for List is an empty list ready to use.
+//
+// To iterate over a list (where l is a List):
+//      for e := l.Front(); e != nil; e = e.Next() {
+// 		// do something with e.
+//      }
+type List struct {
+	head Linker
+	tail Linker
+}
+
+// Reset resets list l to the empty state.
+func (l *List) Reset() {
+	l.head = nil
+	l.tail = nil
+}
+
+// Empty returns true iff the list is empty.
+func (l *List) Empty() bool {
+	return l.head == nil
+}
+
+// Front returns the first element of list l or nil.
+func (l *List) Front() Linker {
+	return l.head
+}
+
+// Back returns the last element of list l or nil.
+func (l *List) Back() Linker {
+	return l.tail
+}
+
+// PushFront inserts the element e at the front of list l.
+func (l *List) PushFront(e Linker) {
+	e.SetNext(l.head)
+	e.SetPrev(nil)
+
+	if l.head != nil {
+		l.head.SetPrev(e)
+	} else {
+		l.tail = e
+	}
+
+	l.head = e
+}
+
+// PushBack inserts the element e at the back of list l.
+func (l *List) PushBack(e Linker) {
+	e.SetNext(nil)
+	e.SetPrev(l.tail)
+
+	if l.tail != nil {
+		l.tail.SetNext(e)
+	} else {
+		l.head = e
+	}
+
+	l.tail = e
+}
+
+// PushBackList inserts list m at the end of list l, emptying m.
+func (l *List) PushBackList(m *List) {
+	if l.head == nil {
+		l.head = m.head
+		l.tail = m.tail
+	} else if m.head != nil {
+		l.tail.SetNext(m.head)
+		m.head.SetPrev(l.tail)
+
+		l.tail = m.tail
+	}
+
+	m.head = nil
+	m.tail = nil
+}
+
+// InsertAfter inserts e after b.
+func (l *List) InsertAfter(b, e Linker) {
+	a := b.Next()
+	e.SetNext(a)
+	e.SetPrev(b)
+	b.SetNext(e)
+
+	if a != nil {
+		a.SetPrev(e)
+	} else {
+		l.tail = e
+	}
+}
+
+// InsertBefore inserts e before a.
+func (l *List) InsertBefore(a, e Linker) {
+	b := a.Prev()
+	e.SetNext(a)
+	e.SetPrev(b)
+	a.SetPrev(e)
+
+	if b != nil {
+		b.SetNext(e)
+	} else {
+		l.head = e
+	}
+}
+
+// Remove removes e from l.
+func (l *List) Remove(e Linker) {
+	prev := e.Prev()
+	next := e.Next()
+
+	if prev != nil {
+		prev.SetNext(next)
+	} else {
+		l.head = next
+	}
+
+	if next != nil {
+		next.SetPrev(prev)
+	} else {
+		l.tail = prev
+	}
+}
+
+// Entry is a default implementation of Linker. Users can add anonymous fields
+// of this type to their structs to make them automatically implement the
+// methods needed by List.
+type Entry struct {
+	next Linker
+	prev Linker
+}
+
+// Next returns the entry that follows e in the list.
+func (e *Entry) Next() Linker {
+	return e.next
+}
+
+// Prev returns the entry that precedes e in the list.
+func (e *Entry) Prev() Linker {
+	return e.prev
+}
+
+// SetNext assigns 'entry' as the entry that follows e in the list.
+func (e *Entry) SetNext(entry Linker) {
+	e.next = entry
+}
+
+// SetPrev assigns 'entry' as the entry that precedes e in the list.
+func (e *Entry) SetPrev(entry Linker) {
+	e.prev = entry
+}
diff --git a/pkg/ilist/list_test.go b/pkg/ilist/list_test.go
new file mode 100644
index 000000000..7f2b90e0c
--- /dev/null
+++ b/pkg/ilist/list_test.go
@@ -0,0 +1,233 @@
+// 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 ilist
+
+import (
+	"runtime"
+	"testing"
+)
+
+type testEntry struct {
+	Entry
+	value int
+}
+
+type direct struct {
+	directEntry
+	value int
+}
+
+func verifyEquality(t *testing.T, entries []testEntry, l *List) {
+	i := 0
+	for it := l.Front(); it != nil; it = it.Next() {
+		e := it.(*testEntry)
+		if e != &entries[i] {
+			_, file, line, _ := runtime.Caller(1)
+			t.Errorf("Wrong entry at index (%s:%d): %v", file, line, i)
+			return
+		}
+		i++
+	}
+
+	if i != len(entries) {
+		_, file, line, _ := runtime.Caller(1)
+		t.Errorf("Wrong number of entries (%s:%d)", file, line)
+		return
+	}
+
+	i = 0
+	for it := l.Back(); it != nil; it = it.Prev() {
+		e := it.(*testEntry)
+		if e != &entries[len(entries)-1-i] {
+			_, file, line, _ := runtime.Caller(1)
+			t.Errorf("Wrong entry at index (%s:%d): %v", file, line, i)
+			return
+		}
+		i++
+	}
+
+	if i != len(entries) {
+		_, file, line, _ := runtime.Caller(1)
+		t.Errorf("Wrong number of entries (%s:%d)", file, line)
+		return
+	}
+}
+
+func TestZeroEmpty(t *testing.T) {
+	var l List
+	if l.Front() != nil {
+		t.Error("Front is non-nil")
+	}
+	if l.Back() != nil {
+		t.Error("Back is non-nil")
+	}
+}
+
+func TestPushBack(t *testing.T) {
+	var l List
+
+	// Test single entry insertion.
+	var entry testEntry
+	l.PushBack(&entry)
+
+	e := l.Front().(*testEntry)
+	if e != &entry {
+		t.Error("Wrong entry returned")
+	}
+
+	// Test inserting 100 entries.
+	l.Reset()
+	var entries [100]testEntry
+	for i := range entries {
+		l.PushBack(&entries[i])
+	}
+
+	verifyEquality(t, entries[:], &l)
+}
+
+func TestPushFront(t *testing.T) {
+	var l List
+
+	// Test single entry insertion.
+	var entry testEntry
+	l.PushFront(&entry)
+
+	e := l.Front().(*testEntry)
+	if e != &entry {
+		t.Error("Wrong entry returned")
+	}
+
+	// Test inserting 100 entries.
+	l.Reset()
+	var entries [100]testEntry
+	for i := range entries {
+		l.PushFront(&entries[len(entries)-1-i])
+	}
+
+	verifyEquality(t, entries[:], &l)
+}
+
+func TestRemove(t *testing.T) {
+	// Remove entry from single-element list.
+	var l List
+	var entry testEntry
+	l.PushBack(&entry)
+	l.Remove(&entry)
+	if l.Front() != nil {
+		t.Error("List is empty")
+	}
+
+	var entries [100]testEntry
+
+	// Remove single element from lists of lengths 2 to 101.
+	for n := 1; n <= len(entries); n++ {
+		for extra := 0; extra <= n; extra++ {
+			l.Reset()
+			for i := 0; i < n; i++ {
+				if extra == i {
+					l.PushBack(&entry)
+				}
+				l.PushBack(&entries[i])
+			}
+			if extra == n {
+				l.PushBack(&entry)
+			}
+
+			l.Remove(&entry)
+			verifyEquality(t, entries[:n], &l)
+		}
+	}
+}
+
+func TestReset(t *testing.T) {
+	var l List
+
+	// Resetting list of one element.
+	l.PushBack(&testEntry{})
+	if l.Front() == nil {
+		t.Error("List is empty")
+	}
+
+	l.Reset()
+	if l.Front() != nil {
+		t.Error("List is not empty")
+	}
+
+	// Resetting list of 10 elements.
+	for i := 0; i < 10; i++ {
+		l.PushBack(&testEntry{})
+	}
+
+	if l.Front() == nil {
+		t.Error("List is empty")
+	}
+
+	l.Reset()
+	if l.Front() != nil {
+		t.Error("List is not empty")
+	}
+
+	// Resetting empty list.
+	l.Reset()
+	if l.Front() != nil {
+		t.Error("List is not empty")
+	}
+}
+
+func BenchmarkIterateForward(b *testing.B) {
+	var l List
+	for i := 0; i < 1000000; i++ {
+		l.PushBack(&testEntry{value: i})
+	}
+
+	for i := b.N; i > 0; i-- {
+		tmp := 0
+		for e := l.Front(); e != nil; e = e.Next() {
+			tmp += e.(*testEntry).value
+		}
+	}
+}
+
+func BenchmarkIterateBackward(b *testing.B) {
+	var l List
+	for i := 0; i < 1000000; i++ {
+		l.PushBack(&testEntry{value: i})
+	}
+
+	for i := b.N; i > 0; i-- {
+		tmp := 0
+		for e := l.Back(); e != nil; e = e.Prev() {
+			tmp += e.(*testEntry).value
+		}
+	}
+}
+
+func BenchmarkDirectIterateForward(b *testing.B) {
+	var l directList
+	for i := 0; i < 1000000; i++ {
+		l.PushBack(&direct{value: i})
+	}
+
+	for i := b.N; i > 0; i-- {
+		tmp := 0
+		for e := l.Front(); e != nil; e = e.Next() {
+			tmp += e.value
+		}
+	}
+}
+
+func BenchmarkDirectIterateBackward(b *testing.B) {
+	var l directList
+	for i := 0; i < 1000000; i++ {
+		l.PushBack(&direct{value: i})
+	}
+
+	for i := b.N; i > 0; i-- {
+		tmp := 0
+		for e := l.Back(); e != nil; e = e.Prev() {
+			tmp += e.value
+		}
+	}
+}