trie

package module
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Published: Dec 24, 2022 License: MIT Imports: 1 Imported by: 0

README

Trie GoDoc Workflow

Package trie implements rune-wise and path-wise Tries optimized for Get performance and to allocate 0 bytes of heap memory (i.e. garbage) per Get.

A typical use case is to perform any Put or Delete operations upfront to populate the trie, then perform Get operations very quickly. The Tries do not synchronize access (not thread-safe).

When Tries are chosen over maps, it is typically for their space efficiency. However, in situations where direct key lookup is not possible (e.g. routers), tries can provide faster lookups and avoid key iteration.

Install

$ go get gomodules.xyz/trie

Documentation

Read Godoc

Performance

RuneTrie is a typical Trie which segments strings rune-wise (i.e. by unicode code point). These benchmarks perform Puts and Gets of random string keys that are 30 bytes long and of random '/' separated paths that have 3 parts and are 30 bytes long (longer if you count the '/' seps).

BenchmarkRuneTriePutStringKey-8   3000000    437 ns/op     9 B/op     1 allocs/op
BenchmarkRuneTrieGetStringKey-8   3000000    411 ns/op     0 B/op     0 allocs/op
BenchmarkRuneTriePutPathKey-8     3000000    464 ns/op     9 B/op     1 allocs/op
BenchmarkRuneTrieGetPathKey-8     3000000    429 ns/op     0 B/op     0 allocs/op

PathTrie segments strings by forward slash separators which can boost performance for some use cases. These benchmarks perform Puts and Gets of random string keys that are 30 bytes long and of random '/' separated paths that have 3 parts and are 30 bytes long (longer if you count the '/' seps).

BenchmarkPathTriePutStringKey-8   30000000   55.5 ns/op    8 B/op     1 allocs/op
BenchmarkPathTrieGetStringKey-8   50000000   37.9 ns/op    0 B/op     0 allocs/op
BenchmarkPathTriePutPathKey-8     20000000   88.7 ns/op    8 B/op     1 allocs/op
BenchmarkPathTrieGetPathKey-8     20000000   68.6 ns/op    0 B/op     0 allocs/op

Note that for random string Puts and Gets, the PathTrie is effectively a map as every node is a direct child of the root (except for strings that happen to have a slash).

This benchmark measures the performance of the PathSegmenter alone. It is used to segment random paths that have 3 '/' separated parts and are 30 bytes long.

BenchmarkPathSegmenter-8          50000000   32.0 ns/op    0 B/op     0 allocs/op

License

MIT License

Documentation

Overview

Package trie implements several types of performant Tries (e.g. rune-wise, path-wise).

The implementations are optimized for Get performance and to allocate 0 bytes of heap memory (i.e. garbage) per Get.

The Tries do not synchronize access (not thread-safe). A typical use case is to perform Puts and Deletes upfront to populate the Trie, then perform Gets very quickly.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func PathSegmenter

func PathSegmenter(path string, start int) (segment string, next int)

PathSegmenter segments string key paths by slash separators. For example, "/a/b/c" -> ("/a", 2), ("/b", 4), ("/c", -1) in successive calls. It does not allocate any heap memory.

Types

type PathTrie

type PathTrie struct {
	// contains filtered or unexported fields
}

PathTrie is a trie of string keys and interface{} values. Internal nodes have nil values so stored nil values cannot be distinguished and are excluded from walks. By default, PathTrie will segment keys by forward slashes with PathSegmenter (e.g. "/a/b/c" -> "/a", "/b", "/c"). A custom StringSegmenter may be used to customize how strings are segmented into nodes. A classic trie might segment keys by rune (i.e. unicode points).

func NewPathTrie

func NewPathTrie() *PathTrie

NewPathTrie allocates and returns a new *PathTrie.

func NewPathTrieWithConfig

func NewPathTrieWithConfig(config *PathTrieConfig) *PathTrie

NewPathTrieWithConfig allocates and returns a new *PathTrie with the given *PathTrieConfig

func (*PathTrie) Delete

func (trie *PathTrie) Delete(key string) bool

Delete removes the value associated with the given key. Returns true if a node was found for the given key. If the node or any of its ancestors becomes childless as a result, it is removed from the trie.

func (*PathTrie) Get

func (trie *PathTrie) Get(key string) interface{}

Get returns the value stored at the given key. Returns nil for internal nodes or for nodes with a value of nil.

func (*PathTrie) Put

func (trie *PathTrie) Put(key string, value interface{}) bool

Put inserts the value into the trie at the given key, replacing any existing items. It returns true if the put adds a new value, false if it replaces an existing value. Note that internal nodes have nil values so a stored nil value will not be distinguishable and will not be included in Walks.

func (*PathTrie) Walk

func (trie *PathTrie) Walk(walker WalkFunc) error

Walk iterates over each key/value stored in the trie and calls the given walker function with the key and value. If the walker function returns an error, the walk is aborted. The traversal is depth first with no guaranteed order.

func (*PathTrie) WalkPath

func (trie *PathTrie) WalkPath(key string, walker WalkFunc) error

WalkPath iterates over each key/value in the path in trie from the root to the node at the given key, calling the given walker function for each key/value. If the walker function returns an error, the walk is aborted.

func (*PathTrie) WalkPrefix

func (trie *PathTrie) WalkPrefix(key string, walker WalkFunc) error

WalkPrefix iterates over each key/value under the given key in the tree, calling the given walker function for each key/value. If the walker function returns an error, the walk is aborted.

type PathTrieConfig

type PathTrieConfig struct {
	Segmenter StringSegmenter
}

PathTrieConfig for building a path trie with different segmenter

type RuneTrie

type RuneTrie struct {
	// contains filtered or unexported fields
}

RuneTrie is a trie of runes with string keys and interface{} values. Note that internal nodes have nil values so a stored nil value will not be distinguishable and will not be included in Walks.

func NewRuneTrie

func NewRuneTrie() *RuneTrie

NewRuneTrie allocates and returns a new *RuneTrie.

func (*RuneTrie) Delete

func (trie *RuneTrie) Delete(key string) bool

Delete removes the value associated with the given key. Returns true if a node was found for the given key. If the node or any of its ancestors becomes childless as a result, it is removed from the trie.

func (*RuneTrie) Get

func (trie *RuneTrie) Get(key string) interface{}

Get returns the value stored at the given key. Returns nil for internal nodes or for nodes with a value of nil.

func (*RuneTrie) Put

func (trie *RuneTrie) Put(key string, value interface{}) bool

Put inserts the value into the trie at the given key, replacing any existing items. It returns true if the put adds a new value, false if it replaces an existing value. Note that internal nodes have nil values so a stored nil value will not be distinguishable and will not be included in Walks.

func (*RuneTrie) Walk

func (trie *RuneTrie) Walk(walker WalkFunc) error

Walk iterates over each key/value stored in the trie and calls the given walker function with the key and value. If the walker function returns an error, the walk is aborted. The traversal is depth first with no guaranteed order.

func (*RuneTrie) WalkPath

func (trie *RuneTrie) WalkPath(key string, walker WalkFunc) error

WalkPath iterates over each key/value in the path in trie from the root to the node at the given key, calling the given walker function for each key/value. If the walker function returns an error, the walk is aborted.

func (*RuneTrie) WalkPrefix

func (trie *RuneTrie) WalkPrefix(key string, walker WalkFunc) error

WalkPrefix iterates over each key/value under the given key in the tree, calling the given walker function for each key/value. If the walker function returns an error, the walk is aborted.

type StringSegmenter

type StringSegmenter func(key string, start int) (segment string, nextIndex int)

StringSegmenter takes a string key with a starting index and returns the first segment after the start and the ending index. When the end is reached, the returned nextIndex should be -1. Implementations should NOT allocate heap memory as Trie Segmenters are called upon Gets. See PathSegmenter.

type Trier

type Trier interface {
	Get(key string) interface{}
	Put(key string, value interface{}) bool
	Delete(key string) bool
	Walk(walker WalkFunc) error
	WalkPath(key string, walker WalkFunc) error
}

Trier exposes the Trie structure capabilities.

type WalkFunc

type WalkFunc func(key string, value interface{}) error

WalkFunc defines some action to take on the given key and value during a Trie Walk. Returning a non-nil error will terminate the Walk.

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