Update vendor

vendor/github.com/tchap/go-patricia/.gitignore

@@ -0,0 +1,25 @@
+# Swap files.
+*.swp
+
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe

vendor/github.com/tchap/go-patricia/AUTHORS

@@ -0,0 +1,3 @@
+This is the complete list of go-patricia copyright holders:
+
+Ondřej Kupka <ondra.cap@gmail.com>

vendor/github.com/tchap/go-patricia/LICENSE

@@ -0,0 +1,20 @@
+The MIT License (MIT)
+
+Copyright (c) 2014 The AUTHORS
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

vendor/github.com/tchap/go-patricia/README.md

@@ -0,0 +1,123 @@
+# go-patricia #
+
+**Documentation**: [GoDoc](http://godoc.org/github.com/tchap/go-patricia/patricia)<br />
+**Build Status**: [![Build
+Status](https://drone.io/github.com/tchap/go-patricia/status.png)](https://drone.io/github.com/tchap/go-patricia/latest)<br />
+**Test Coverage**: [![Coverage
+Status](https://coveralls.io/repos/tchap/go-patricia/badge.png)](https://coveralls.io/r/tchap/go-patricia)
+
+## About ##
+
+A generic patricia trie (also called radix tree) implemented in Go (Golang).
+
+The patricia trie as implemented in this library enables fast visiting of items
+in some particular ways:
+
+1. visit all items saved in the tree,
+2. visit all items matching particular prefix (visit subtree), or
+3. given a string, visit all items matching some prefix of that string.
+
+`[]byte` type is used for keys, `interface{}` for values.
+
+`Trie` is not thread safe. Synchronize the access yourself.
+
+### State of the Project ###
+
+Apparently some people are using this, so the API should not change often.
+Any ideas on how to make the library better are still welcome.
+
+More (unit) testing would be cool as well...
+
+## Usage ##
+
+Import the package from GitHub first.
+
+```go
+import "github.com/tchap/go-patricia/patricia"
+```
+
+You can as well use gopkg.in thingie:
+
+```go
+import "gopkg.in/tchap/go-patricia.v1/patricia"
+```
+
+Then you can start having fun.
+
+```go
+printItem := func(prefix patricia.Prefix, item patricia.Item) error {
+	fmt.Printf("%q: %v\n", prefix, item)
+	return nil
+}
+
+// Create a new default trie (using the default parameter values).
+trie := NewTrie()
+
+// Create a new custom trie.
+trie := NewTrie(MaxPrefixPerNode(16), MaxChildrenPerSparseNode(10))
+
+// Insert some items.
+trie.Insert(Prefix("Pepa Novak"), 1)
+trie.Insert(Prefix("Pepa Sindelar"), 2)
+trie.Insert(Prefix("Karel Macha"), 3)
+trie.Insert(Prefix("Karel Hynek Macha"), 4)
+
+// Just check if some things are present in the tree.
+key := Prefix("Pepa Novak")
+fmt.Printf("%q present? %v\n", key, trie.Match(key))
+// "Pepa Novak" present? true
+key = Prefix("Karel")
+fmt.Printf("Anybody called %q here? %v\n", key, trie.MatchSubtree(key))
+// Anybody called "Karel" here? true
+
+// Walk the tree in alphabetical order.
+trie.Visit(printItem)
+// "Karel Hynek Macha": 4
+// "Karel Macha": 3
+// "Pepa Novak": 1
+// "Pepa Sindelar": 2
+
+// Walk a subtree.
+trie.VisitSubtree(Prefix("Pepa"), printItem)
+// "Pepa Novak": 1
+// "Pepa Sindelar": 2
+
+// Modify an item, then fetch it from the tree.
+trie.Set(Prefix("Karel Hynek Macha"), 10)
+key = Prefix("Karel Hynek Macha")
+fmt.Printf("%q: %v\n", key, trie.Get(key))
+// "Karel Hynek Macha": 10
+
+// Walk prefixes.
+prefix := Prefix("Karel Hynek Macha je kouzelnik")
+trie.VisitPrefixes(prefix, printItem)
+// "Karel Hynek Macha": 10
+
+// Delete some items.
+trie.Delete(Prefix("Pepa Novak"))
+trie.Delete(Prefix("Karel Macha"))
+
+// Walk again.
+trie.Visit(printItem)
+// "Karel Hynek Macha": 10
+// "Pepa Sindelar": 2
+
+// Delete a subtree.
+trie.DeleteSubtree(Prefix("Pepa"))
+
+// Print what is left.
+trie.Visit(printItem)
+// "Karel Hynek Macha": 10
+```
+
+## License ##
+
+MIT, check the `LICENSE` file.
+
+[![Gittip
+Badge](http://img.shields.io/gittip/alanhamlett.png)](https://www.gittip.com/tchap/
+"Gittip Badge")
+
+[![Bitdeli
+Badge](https://d2weczhvl823v0.cloudfront.net/tchap/go-patricia/trend.png)](https://bitdeli.com/free
+"Bitdeli Badge")

vendor/github.com/tchap/go-patricia/patricia/children.go

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+// Copyright (c) 2014 The go-patricia AUTHORS
+//
+// Use of this source code is governed by The MIT License
+// that can be found in the LICENSE file.
+
+package patricia
+
+import "sort"
+
+type childList interface {
+	length() int
+	head() *Trie
+	add(child *Trie) childList
+	replace(b byte, child *Trie)
+	remove(child *Trie)
+	next(b byte) *Trie
+	walk(prefix *Prefix, visitor VisitorFunc) error
+}
+
+type tries []*Trie
+
+func (t tries) Len() int {
+	return len(t)
+}
+
+func (t tries) Less(i, j int) bool {
+	strings := sort.StringSlice{string(t[i].prefix), string(t[j].prefix)}
+	return strings.Less(0, 1)
+}
+
+func (t tries) Swap(i, j int) {
+	t[i], t[j] = t[j], t[i]
+}
+
+type sparseChildList struct {
+	children tries
+}
+
+func newSparseChildList(maxChildrenPerSparseNode int) childList {
+	return &sparseChildList{
+		children: make(tries, 0, DefaultMaxChildrenPerSparseNode),
+	}
+}
+
+func (list *sparseChildList) length() int {
+	return len(list.children)
+}
+
+func (list *sparseChildList) head() *Trie {
+	return list.children[0]
+}
+
+func (list *sparseChildList) add(child *Trie) childList {
+	// Search for an empty spot and insert the child if possible.
+	if len(list.children) != cap(list.children) {
+		list.children = append(list.children, child)
+		return list
+	}
+
+	// Otherwise we have to transform to the dense list type.
+	return newDenseChildList(list, child)
+}
+
+func (list *sparseChildList) replace(b byte, child *Trie) {
+	// Seek the child and replace it.
+	for i, node := range list.children {
+		if node.prefix[0] == b {
+			list.children[i] = child
+			return
+		}
+	}
+}
+
+func (list *sparseChildList) remove(child *Trie) {
+	for i, node := range list.children {
+		if node.prefix[0] == child.prefix[0] {
+			list.children = append(list.children[:i], list.children[i+1:]...)
+			return
+		}
+	}
+
+	// This is not supposed to be reached.
+	panic("removing non-existent child")
+}
+
+func (list *sparseChildList) next(b byte) *Trie {
+	for _, child := range list.children {
+		if child.prefix[0] == b {
+			return child
+		}
+	}
+	return nil
+}
+
+func (list *sparseChildList) walk(prefix *Prefix, visitor VisitorFunc) error {
+
+	sort.Sort(list.children)
+
+	for _, child := range list.children {
+		*prefix = append(*prefix, child.prefix...)
+		if child.item != nil {
+			err := visitor(*prefix, child.item)
+			if err != nil {
+				if err == SkipSubtree {
+					*prefix = (*prefix)[:len(*prefix)-len(child.prefix)]
+					continue
+				}
+				*prefix = (*prefix)[:len(*prefix)-len(child.prefix)]
+				return err
+			}
+		}
+
+		err := child.children.walk(prefix, visitor)
+		*prefix = (*prefix)[:len(*prefix)-len(child.prefix)]
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+type denseChildList struct {
+	min      int
+	max      int
+	children []*Trie
+}
+
+func newDenseChildList(list *sparseChildList, child *Trie) childList {
+	var (
+		min int = 255
+		max int = 0
+	)
+	for _, child := range list.children {
+		b := int(child.prefix[0])
+		if b < min {
+			min = b
+		}
+		if b > max {
+			max = b
+		}
+	}
+
+	b := int(child.prefix[0])
+	if b < min {
+		min = b
+	}
+	if b > max {
+		max = b
+	}
+
+	children := make([]*Trie, max-min+1)
+	for _, child := range list.children {
+		children[int(child.prefix[0])-min] = child
+	}
+	children[int(child.prefix[0])-min] = child
+
+	return &denseChildList{min, max, children}
+}
+
+func (list *denseChildList) length() int {
+	return list.max - list.min + 1
+}
+
+func (list *denseChildList) head() *Trie {
+	return list.children[0]
+}
+
+func (list *denseChildList) add(child *Trie) childList {
+	b := int(child.prefix[0])
+
+	switch {
+	case list.min <= b && b <= list.max:
+		if list.children[b-list.min] != nil {
+			panic("dense child list collision detected")
+		}
+		list.children[b-list.min] = child
+
+	case b < list.min:
+		children := make([]*Trie, list.max-b+1)
+		children[0] = child
+		copy(children[list.min-b:], list.children)
+		list.children = children
+		list.min = b
+
+	default: // b > list.max
+		children := make([]*Trie, b-list.min+1)
+		children[b-list.min] = child
+		copy(children, list.children)
+		list.children = children
+		list.max = b
+	}
+
+	return list
+}
+
+func (list *denseChildList) replace(b byte, child *Trie) {
+	list.children[int(b)-list.min] = nil
+	list.children[int(child.prefix[0])-list.min] = child
+}
+
+func (list *denseChildList) remove(child *Trie) {
+	i := int(child.prefix[0]) - list.min
+	if list.children[i] == nil {
+		// This is not supposed to be reached.
+		panic("removing non-existent child")
+	}
+	list.children[i] = nil
+}
+
+func (list *denseChildList) next(b byte) *Trie {
+	i := int(b)
+	if i < list.min || list.max < i {
+		return nil
+	}
+	return list.children[i-list.min]
+}
+
+func (list *denseChildList) walk(prefix *Prefix, visitor VisitorFunc) error {
+	for _, child := range list.children {
+		if child == nil {
+			continue
+		}
+		*prefix = append(*prefix, child.prefix...)
+		if child.item != nil {
+			if err := visitor(*prefix, child.item); err != nil {
+				if err == SkipSubtree {
+					*prefix = (*prefix)[:len(*prefix)-len(child.prefix)]
+					continue
+				}
+				*prefix = (*prefix)[:len(*prefix)-len(child.prefix)]
+				return err
+			}
+		}
+
+		err := child.children.walk(prefix, visitor)
+		*prefix = (*prefix)[:len(*prefix)-len(child.prefix)]
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

vendor/github.com/tchap/go-patricia/patricia/patricia.go

@@ -0,0 +1,467 @@
+// Copyright (c) 2014 The go-patricia AUTHORS
+//
+// Use of this source code is governed by The MIT License
+// that can be found in the LICENSE file.
+
+package patricia
+
+import (
+	"errors"
+)
+
+//------------------------------------------------------------------------------
+// Trie
+//------------------------------------------------------------------------------
+
+const (
+	DefaultMaxPrefixPerNode         = 10
+	DefaultMaxChildrenPerSparseNode = 8
+)
+
+type (
+	Prefix      []byte
+	Item        interface{}
+	VisitorFunc func(prefix Prefix, item Item) error
+)
+
+// Trie is a generic patricia trie that allows fast retrieval of items by prefix.
+// and other funky stuff.
+//
+// Trie is not thread-safe.
+type Trie struct {
+	prefix Prefix
+	item   Item
+
+	maxPrefixPerNode         int
+	maxChildrenPerSparseNode int
+
+	children childList
+}
+
+// Public API ------------------------------------------------------------------
+
+type Option func(*Trie)
+
+// Trie constructor.
+func NewTrie(options ...Option) *Trie {
+	trie := &Trie{}
+
+	for _, opt := range options {
+		opt(trie)
+	}
+
+	if trie.maxPrefixPerNode <= 0 {
+		trie.maxPrefixPerNode = DefaultMaxPrefixPerNode
+	}
+	if trie.maxChildrenPerSparseNode <= 0 {
+		trie.maxChildrenPerSparseNode = DefaultMaxChildrenPerSparseNode
+	}
+
+	trie.children = newSparseChildList(trie.maxChildrenPerSparseNode)
+	return trie
+}
+
+func MaxPrefixPerNode(value int) Option {
+	return func(trie *Trie) {
+		trie.maxPrefixPerNode = value
+	}
+}
+
+func MaxChildrenPerSparseNode(value int) Option {
+	return func(trie *Trie) {
+		trie.maxChildrenPerSparseNode = value
+	}
+}
+
+// Item returns the item stored in the root of this trie.
+func (trie *Trie) Item() Item {
+	return trie.item
+}
+
+// Insert inserts a new item into the trie using the given prefix. Insert does
+// not replace existing items. It returns false if an item was already in place.
+func (trie *Trie) Insert(key Prefix, item Item) (inserted bool) {
+	return trie.put(key, item, false)
+}
+
+// Set works much like Insert, but it always sets the item, possibly replacing
+// the item previously inserted.
+func (trie *Trie) Set(key Prefix, item Item) {
+	trie.put(key, item, true)
+}
+
+// Get returns the item located at key.
+//
+// This method is a bit dangerous, because Get can as well end up in an internal
+// node that is not really representing any user-defined value. So when nil is
+// a valid value being used, it is not possible to tell if the value was inserted
+// into the tree by the user or not. A possible workaround for this is not to use
+// nil interface as a valid value, even using zero value of any type is enough
+// to prevent this bad behaviour.
+func (trie *Trie) Get(key Prefix) (item Item) {
+	_, node, found, leftover := trie.findSubtree(key)
+	if !found || len(leftover) != 0 {
+		return nil
+	}
+	return node.item
+}
+
+// Match returns what Get(prefix) != nil would return. The same warning as for
+// Get applies here as well.
+func (trie *Trie) Match(prefix Prefix) (matchedExactly bool) {
+	return trie.Get(prefix) != nil
+}
+
+// MatchSubtree returns true when there is a subtree representing extensions
+// to key, that is if there are any keys in the tree which have key as prefix.
+func (trie *Trie) MatchSubtree(key Prefix) (matched bool) {
+	_, _, matched, _ = trie.findSubtree(key)
+	return
+}
+
+// Visit calls visitor on every node containing a non-nil item
+// in alphabetical order.
+//
+// If an error is returned from visitor, the function stops visiting the tree
+// and returns that error, unless it is a special error - SkipSubtree. In that
+// case Visit skips the subtree represented by the current node and continues
+// elsewhere.
+func (trie *Trie) Visit(visitor VisitorFunc) error {
+	return trie.walk(nil, visitor)
+}
+
+// VisitSubtree works much like Visit, but it only visits nodes matching prefix.
+func (trie *Trie) VisitSubtree(prefix Prefix, visitor VisitorFunc) error {
+	// Nil prefix not allowed.
+	if prefix == nil {
+		panic(ErrNilPrefix)
+	}
+
+	// Empty trie must be handled explicitly.
+	if trie.prefix == nil {
+		return nil
+	}
+
+	// Locate the relevant subtree.
+	_, root, found, leftover := trie.findSubtree(prefix)
+	if !found {
+		return nil
+	}
+	prefix = append(prefix, leftover...)
+
+	// Visit it.
+	return root.walk(prefix, visitor)
+}
+
+// VisitPrefixes visits only nodes that represent prefixes of key.
+// To say the obvious, returning SkipSubtree from visitor makes no sense here.
+func (trie *Trie) VisitPrefixes(key Prefix, visitor VisitorFunc) error {
+	// Nil key not allowed.
+	if key == nil {
+		panic(ErrNilPrefix)
+	}
+
+	// Empty trie must be handled explicitly.
+	if trie.prefix == nil {
+		return nil
+	}
+
+	// Walk the path matching key prefixes.
+	node := trie
+	prefix := key
+	offset := 0
+	for {
+		// Compute what part of prefix matches.
+		common := node.longestCommonPrefixLength(key)
+		key = key[common:]
+		offset += common
+
+		// Partial match means that there is no subtree matching prefix.
+		if common < len(node.prefix) {
+			return nil
+		}
+
+		// Call the visitor.
+		if item := node.item; item != nil {
+			if err := visitor(prefix[:offset], item); err != nil {
+				return err
+			}
+		}
+
+		if len(key) == 0 {
+			// This node represents key, we are finished.
+			return nil
+		}
+
+		// There is some key suffix left, move to the children.
+		child := node.children.next(key[0])
+		if child == nil {
+			// There is nowhere to continue, return.
+			return nil
+		}
+
+		node = child
+	}
+}
+
+// Delete deletes the item represented by the given prefix.
+//
+// True is returned if the matching node was found and deleted.
+func (trie *Trie) Delete(key Prefix) (deleted bool) {
+	// Nil prefix not allowed.
+	if key == nil {
+		panic(ErrNilPrefix)
+	}
+
+	// Empty trie must be handled explicitly.
+	if trie.prefix == nil {
+		return false
+	}
+
+	// Find the relevant node.
+	parent, node, _, leftover := trie.findSubtree(key)
+	if len(leftover) != 0 {
+		return false
+	}
+
+	// If the item is already set to nil, there is nothing to do.
+	if node.item == nil {
+		return false
+	}
+
+	// Delete the item.
+	node.item = nil
+
+	// Compact since that might be possible now.
+	if compacted := node.compact(); compacted != node {
+		if parent == nil {
+			*node = *compacted
+		} else {
+			parent.children.replace(node.prefix[0], compacted)
+			*parent = *parent.compact()
+		}
+	}
+
+	return true
+}
+
+// DeleteSubtree finds the subtree exactly matching prefix and deletes it.
+//
+// True is returned if the subtree was found and deleted.
+func (trie *Trie) DeleteSubtree(prefix Prefix) (deleted bool) {
+	// Nil prefix not allowed.
+	if prefix == nil {
+		panic(ErrNilPrefix)
+	}
+
+	// Empty trie must be handled explicitly.
+	if trie.prefix == nil {
+		return false
+	}
+
+	// Locate the relevant subtree.
+	parent, root, found, _ := trie.findSubtree(prefix)
+	if !found {
+		return false
+	}
+
+	// If we are in the root of the trie, reset the trie.
+	if parent == nil {
+		root.prefix = nil
+		root.children = newSparseChildList(trie.maxPrefixPerNode)
+		return true
+	}
+
+	// Otherwise remove the root node from its parent.
+	parent.children.remove(root)
+	return true
+}
+
+// Internal helper methods -----------------------------------------------------
+
+func (trie *Trie) put(key Prefix, item Item, replace bool) (inserted bool) {
+	// Nil prefix not allowed.
+	if key == nil {
+		panic(ErrNilPrefix)
+	}
+
+	var (
+		common int
+		node   *Trie = trie
+		child  *Trie
+	)
+
+	if node.prefix == nil {
+		if len(key) <= trie.maxPrefixPerNode {
+			node.prefix = key
+			goto InsertItem
+		}
+		node.prefix = key[:trie.maxPrefixPerNode]
+		key = key[trie.maxPrefixPerNode:]
+		goto AppendChild
+	}
+
+	for {
+		// Compute the longest common prefix length.
+		common = node.longestCommonPrefixLength(key)
+		key = key[common:]
+
+		// Only a part matches, split.
+		if common < len(node.prefix) {
+			goto SplitPrefix
+		}
+
+		// common == len(node.prefix) since never (common > len(node.prefix))
+		// common == len(former key) <-> 0 == len(key)
+		// -> former key == node.prefix
+		if len(key) == 0 {
+			goto InsertItem
+		}
+
+		// Check children for matching prefix.
+		child = node.children.next(key[0])
+		if child == nil {
+			goto AppendChild
+		}
+		node = child
+	}
+
+SplitPrefix:
+	// Split the prefix if necessary.
+	child = new(Trie)
+	*child = *node
+	*node = *NewTrie()
+	node.prefix = child.prefix[:common]
+	child.prefix = child.prefix[common:]
+	child = child.compact()
+	node.children = node.children.add(child)
+
+AppendChild:
+	// Keep appending children until whole prefix is inserted.
+	// This loop starts with empty node.prefix that needs to be filled.
+	for len(key) != 0 {
+		child := NewTrie()
+		if len(key) <= trie.maxPrefixPerNode {
+			child.prefix = key
+			node.children = node.children.add(child)
+			node = child
+			goto InsertItem
+		} else {
+			child.prefix = key[:trie.maxPrefixPerNode]
+			key = key[trie.maxPrefixPerNode:]
+			node.children = node.children.add(child)
+			node = child
+		}
+	}
+
+InsertItem:
+	// Try to insert the item if possible.
+	if replace || node.item == nil {
+		node.item = item
+		return true
+	}
+	return false
+}
+
+func (trie *Trie) compact() *Trie {
+	// Only a node with a single child can be compacted.
+	if trie.children.length() != 1 {
+		return trie
+	}
+
+	child := trie.children.head()
+
+	// If any item is set, we cannot compact since we want to retain
+	// the ability to do searching by key. This makes compaction less usable,
+	// but that simply cannot be avoided.
+	if trie.item != nil || child.item != nil {
+		return trie
+	}
+
+	// Make sure the combined prefixes fit into a single node.
+	if len(trie.prefix)+len(child.prefix) > trie.maxPrefixPerNode {
+		return trie
+	}
+
+	// Concatenate the prefixes, move the items.
+	child.prefix = append(trie.prefix, child.prefix...)
+	if trie.item != nil {
+		child.item = trie.item
+	}
+
+	return child
+}
+
+func (trie *Trie) findSubtree(prefix Prefix) (parent *Trie, root *Trie, found bool, leftover Prefix) {
+	// Find the subtree matching prefix.
+	root = trie
+	for {
+		// Compute what part of prefix matches.
+		common := root.longestCommonPrefixLength(prefix)
+		prefix = prefix[common:]
+
+		// We used up the whole prefix, subtree found.
+		if len(prefix) == 0 {
+			found = true
+			leftover = root.prefix[common:]
+			return
+		}
+
+		// Partial match means that there is no subtree matching prefix.
+		if common < len(root.prefix) {
+			leftover = root.prefix[common:]
+			return
+		}
+
+		// There is some prefix left, move to the children.
+		child := root.children.next(prefix[0])
+		if child == nil {
+			// There is nowhere to continue, there is no subtree matching prefix.
+			return
+		}
+
+		parent = root
+		root = child
+	}
+}
+
+func (trie *Trie) walk(actualRootPrefix Prefix, visitor VisitorFunc) error {
+	var prefix Prefix
+	// Allocate a bit more space for prefix at the beginning.
+	if actualRootPrefix == nil {
+		prefix = make(Prefix, 32+len(trie.prefix))
+		copy(prefix, trie.prefix)
+		prefix = prefix[:len(trie.prefix)]
+	} else {
+		prefix = make(Prefix, 32+len(actualRootPrefix))
+		copy(prefix, actualRootPrefix)
+		prefix = prefix[:len(actualRootPrefix)]
+	}
+
+	// Visit the root first. Not that this works for empty trie as well since
+	// in that case item == nil && len(children) == 0.
+	if trie.item != nil {
+		if err := visitor(prefix, trie.item); err != nil {
+			if err == SkipSubtree {
+				return nil
+			}
+			return err
+		}
+	}
+
+	// Then continue to the children.
+	return trie.children.walk(&prefix, visitor)
+}
+
+func (trie *Trie) longestCommonPrefixLength(prefix Prefix) (i int) {
+	for ; i < len(prefix) && i < len(trie.prefix) && prefix[i] == trie.prefix[i]; i++ {
+	}
+	return
+}
+
+// Errors ----------------------------------------------------------------------
+
+var (
+	SkipSubtree  = errors.New("Skip this subtree")
+	ErrNilPrefix = errors.New("Nil prefix passed into a method call")
+)