diff options
Diffstat (limited to 'vendor/github.com/tchap/go-patricia')
| -rw-r--r-- | vendor/github.com/tchap/go-patricia/LICENSE | 20 | ||||
| -rw-r--r-- | vendor/github.com/tchap/go-patricia/README.md | 123 | ||||
| -rw-r--r-- | vendor/github.com/tchap/go-patricia/patricia/children.go | 325 | ||||
| -rw-r--r-- | vendor/github.com/tchap/go-patricia/patricia/patricia.go | 594 |
4 files changed, 1062 insertions, 0 deletions
diff --git a/vendor/github.com/tchap/go-patricia/LICENSE b/vendor/github.com/tchap/go-patricia/LICENSE new file mode 100644 index 000000000..e50d398e9 --- /dev/null +++ b/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. diff --git a/vendor/github.com/tchap/go-patricia/README.md b/vendor/github.com/tchap/go-patricia/README.md new file mode 100644 index 000000000..d9cbf624f --- /dev/null +++ b/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**: [](https://drone.io/github.com/tchap/go-patricia/latest)<br /> +**Test Coverage**: [](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.v2/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. + +[](https://www.gittip.com/tchap/ +"Gittip Badge") + +[](https://bitdeli.com/free +"Bitdeli Badge") diff --git a/vendor/github.com/tchap/go-patricia/patricia/children.go b/vendor/github.com/tchap/go-patricia/patricia/children.go new file mode 100644 index 000000000..a5677c335 --- /dev/null +++ b/vendor/github.com/tchap/go-patricia/patricia/children.go @@ -0,0 +1,325 @@ +// 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 ( + "fmt" + "io" + "sort" +) + +type childList interface { + length() int + head() *Trie + add(child *Trie) childList + remove(b byte) + replace(b byte, child *Trie) + next(b byte) *Trie + walk(prefix *Prefix, visitor VisitorFunc) error + print(w io.Writer, indent int) + total() int +} + +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, maxChildrenPerSparseNode), + } +} + +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) remove(b byte) { + for i, node := range list.children { + if node.prefix[0] == b { + list.children[i] = list.children[len(list.children)-1] + list.children[len(list.children)-1] = nil + list.children = list.children[:len(list.children)-1] + return + } + } + + // This is not supposed to be reached. + panic("removing non-existent child") +} + +func (list *sparseChildList) replace(b byte, child *Trie) { + // Make a consistency check. + if p0 := child.prefix[0]; p0 != b { + panic(fmt.Errorf("child prefix mismatch: %v != %v", p0, b)) + } + + // 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) 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 +} + +func (list *sparseChildList) total() int { + tot := 0 + for _, child := range list.children { + if child != nil { + tot = tot + child.total() + } + } + return tot +} + +func (list *sparseChildList) print(w io.Writer, indent int) { + for _, child := range list.children { + if child != nil { + child.print(w, indent) + } + } +} + +type denseChildList struct { + min int + max int + numChildren int + headIndex 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: min, + max: max, + numChildren: list.length() + 1, + headIndex: 0, + children: children, + } +} + +func (list *denseChildList) length() int { + return list.numChildren +} + +func (list *denseChildList) head() *Trie { + return list.children[list.headIndex] +} + +func (list *denseChildList) add(child *Trie) childList { + b := int(child.prefix[0]) + var i int + + switch { + case list.min <= b && b <= list.max: + if list.children[b-list.min] != nil { + panic("dense child list collision detected") + } + i = b - list.min + list.children[i] = child + + case b < list.min: + children := make([]*Trie, list.max-b+1) + i = 0 + children[i] = 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) + i = b - list.min + children[i] = child + copy(children, list.children) + list.children = children + list.max = b + } + + list.numChildren++ + if i < list.headIndex { + list.headIndex = i + } + return list +} + +func (list *denseChildList) remove(b byte) { + i := int(b) - list.min + if list.children[i] == nil { + // This is not supposed to be reached. + panic("removing non-existent child") + } + list.numChildren-- + list.children[i] = nil + + // Update head index. + if i == list.headIndex { + for ; i < len(list.children); i++ { + if list.children[i] != nil { + list.headIndex = i + return + } + } + } +} + +func (list *denseChildList) replace(b byte, child *Trie) { + // Make a consistency check. + if p0 := child.prefix[0]; p0 != b { + panic(fmt.Errorf("child prefix mismatch: %v != %v", p0, b)) + } + + // Replace the child. + list.children[int(b)-list.min] = child +} + +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 +} + +func (list *denseChildList) print(w io.Writer, indent int) { + for _, child := range list.children { + if child != nil { + child.print(w, indent) + } + } +} + +func (list *denseChildList) total() int { + tot := 0 + for _, child := range list.children { + if child != nil { + tot = tot + child.total() + } + } + return tot +} diff --git a/vendor/github.com/tchap/go-patricia/patricia/patricia.go b/vendor/github.com/tchap/go-patricia/patricia/patricia.go new file mode 100644 index 000000000..a1fc53d5d --- /dev/null +++ b/vendor/github.com/tchap/go-patricia/patricia/patricia.go @@ -0,0 +1,594 @@ +// 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 ( + "bytes" + "errors" + "fmt" + "io" + "strings" +) + +//------------------------------------------------------------------------------ +// 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) +} + +func (trie *Trie) size() int { + n := 0 + + trie.walk(nil, func(prefix Prefix, item Item) error { + n++ + return nil + }) + + return n +} + +func (trie *Trie) total() int { + return 1 + trie.children.total() +} + +// 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. + path, found, _ := trie.findSubtreePath(key) + if !found { + return false + } + + node := path[len(path)-1] + var parent *Trie + if len(path) != 1 { + parent = path[len(path)-2] + } + + // 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 + + // Initialise i before goto. + // Will be used later in a loop. + i := len(path) - 1 + + // In case there are some child nodes, we cannot drop the whole subtree. + // We can try to compact nodes, though. + if node.children.length() != 0 { + goto Compact + } + + // In case we are at the root, just reset it and we are done. + if parent == nil { + node.reset() + return true + } + + // We can drop a subtree. + // Find the first ancestor that has its value set or it has 2 or more child nodes. + // That will be the node where to drop the subtree at. + for ; i >= 0; i-- { + if current := path[i]; current.item != nil || current.children.length() >= 2 { + break + } + } + + // Handle the case when there is no such node. + // In other words, we can reset the whole tree. + if i == -1 { + path[0].reset() + return true + } + + // We can just remove the subtree here. + node = path[i] + if i == 0 { + parent = nil + } else { + parent = path[i-1] + } + // i+1 is always a valid index since i is never pointing to the last node. + // The loop above skips at least the last node since we are sure that the item + // is set to nil and it has no children, othewise we would be compacting instead. + node.children.remove(path[i+1].prefix[0]) + +Compact: + // The node is set to the first non-empty ancestor, + // so try to 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.reset() + return true + } + + // Otherwise remove the root node from its parent. + parent.children.remove(root.prefix[0]) + return true +} + +// Internal helper methods ----------------------------------------------------- + +func (trie *Trie) empty() bool { + return trie.item == nil && trie.children.length() == 0 +} + +func (trie *Trie) reset() { + trie.prefix = nil + trie.children = newSparseChildList(trie.maxPrefixPerNode) +} + +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) findSubtreePath(prefix Prefix) (path []*Trie, found bool, leftover Prefix) { + // Find the subtree matching prefix. + root := trie + var subtreePath []*Trie + for { + // Append the current root to the path. + subtreePath = append(subtreePath, root) + + // 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 { + path = subtreePath + 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 + } + + 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 +} + +func (trie *Trie) dump() string { + writer := &bytes.Buffer{} + trie.print(writer, 0) + return writer.String() +} + +func (trie *Trie) print(writer io.Writer, indent int) { + fmt.Fprintf(writer, "%s%s %v\n", strings.Repeat(" ", indent), string(trie.prefix), trie.item) + trie.children.print(writer, indent+2) +} + +// Errors ---------------------------------------------------------------------- + +var ( + SkipSubtree = errors.New("Skip this subtree") + ErrNilPrefix = errors.New("Nil prefix passed into a method call") +) |