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vendor/github.com/tidwall/btree/README.md
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BTree implementation for Go
===========================
# btree
![Travis CI Build Status](https://api.travis-ci.org/tidwall/btree.svg?branch=master)
[![GoDoc](https://godoc.org/github.com/tidwall/btree?status.svg)](https://godoc.org/github.com/tidwall/btree)
This package provides an in-memory B-Tree implementation for Go, useful as
an ordered, mutable data structure.
An efficient [B-tree](https://en.wikipedia.org/wiki/B-tree) implementation in Go.
This is a fork of the wonderful [google/btree](https://github.com/google/btree) package. It's has all the same great features and adds a few more.
## Features
- Descend* functions for iterating backwards.
- Iteration performance boost.
- User defined context.
- Support for [Generics](#generics) (Go 1.18+).
- `Map` and `Set` types for ordered key-value maps and sets,
- Fast bulk loading for pre-ordered data using the `Load()` method.
- `Copy()` method with copy-on-write support.
- Thread-safe operations.
- [Path hinting](PATH_HINT.md) optimization for operations with nearby keys.
User defined context
--------------------
This is a great new feature that allows for entering the same item into multiple B-trees, and each B-tree have a different ordering formula.
## Using
For example:
To start using this package, install Go and run:
```sh
$ go get github.com/tidwall/btree
```
## B-tree types
This package includes the following types of B-trees:
- [`btree.Map`](#btreemap):
A fast B-tree for storing ordered key value pairs.
Go 1.18+
- [`btree.Set`](#btreeset):
Like `Map`, but only for storing keys.
Go 1.18+
- [`btree.BTreeG`](#btreegeneric):
A feature-rich B-tree for storing data using a custom comparator.
Go 1.18+
- [`btree.BTree`](#btreebtree):
Like `BTreeG` but uses the `interface{}` type for data. Backwards compatible.
Go 1.16+
### btree.Map
```go
// Basic
Set(key, value) // insert or replace an item
Get(key, value) // get an existing item
Delete(key) // delete an item
Len() // return the number of items in the map
// Iteration
Scan(iter) // scan items in ascending order
Reverse(iter) // scan items in descending order
Ascend(key, iter) // scan items in ascending order that are >= to key
Descend(key, iter) // scan items in descending order that are <= to key.
Iter() // returns a read-only iterator for for-loops.
// Array-like operations
GetAt(index) // returns the item at index
DeleteAt(index) // deletes the item at index
// Bulk-loading
Load(key, value) // load presorted items into tree
```
#### Example
```go
package main
import (
"fmt"
"github.com/tidwall/btree"
)
func main() {
// create a map
var users btree.Map[string, string]
// add some users
users.Set("user:4", "Andrea")
users.Set("user:6", "Andy")
users.Set("user:2", "Andy")
users.Set("user:1", "Jane")
users.Set("user:5", "Janet")
users.Set("user:3", "Steve")
// Iterate over the maps and print each user
users.Scan(func(key, value string) bool {
fmt.Printf("%s %s\n", key, value)
return true
})
fmt.Printf("\n")
// Delete a couple
users.Delete("user:5")
users.Delete("user:1")
// print the map again
users.Scan(func(key, value string) bool {
fmt.Printf("%s %s\n", key, value)
return true
})
fmt.Printf("\n")
// Output:
// user:1 Jane
// user:2 Andy
// user:3 Steve
// user:4 Andrea
// user:5 Janet
// user:6 Andy
//
// user:2 Andy
// user:3 Steve
// user:4 Andrea
// user:6 Andy
}
```
### btree.Set
```go
// Basic
Insert(key) // insert an item
Contains(key) // test if item exists
Delete(key) // delete an item
Len() // return the number of items in the set
// Iteration
Scan(iter) // scan items in ascending order
Reverse(iter) // scan items in descending order
Ascend(key, iter) // scan items in ascending order that are >= to key
Descend(key, iter) // scan items in descending order that are <= to key.
Iter() // returns a read-only iterator for for-loops.
// Array-like operations
GetAt(index) // returns the item at index
DeleteAt(index) // deletes the item at index
// Bulk-loading
Load(key) // load presorted item into tree
```
#### Example
```go
package main
import (
"fmt"
"github.com/tidwall/btree"
)
func main() {
// create a set
var names btree.Set[string]
// add some names
names.Insert("Jane")
names.Insert("Andrea")
names.Insert("Steve")
names.Insert("Andy")
names.Insert("Janet")
names.Insert("Andy")
// Iterate over the maps and print each user
names.Scan(func(key string) bool {
fmt.Printf("%s\n", key)
return true
})
fmt.Printf("\n")
// Delete a couple
names.Delete("Steve")
names.Delete("Andy")
// print the map again
names.Scan(func(key string) bool {
fmt.Printf("%s\n", key)
return true
})
fmt.Printf("\n")
// Output:
// Andrea
// Andy
// Jane
// Janet
// Steve
//
// Andrea
// Jane
// Janet
}
```
### btree.BTreeG
```go
// Basic
Set(item) // insert or replace an item
Get(item) // get an existing item
Delete(item) // delete an item
Len() // return the number of items in the btree
// Iteration
Scan(iter) // scan items in ascending order
Reverse(iter) // scan items in descending order
Ascend(key, iter) // scan items in ascending order that are >= to key
Descend(key, iter) // scan items in descending order that are <= to key.
Iter() // returns a read-only iterator for for-loops.
// Array-like operations
GetAt(index) // returns the item at index
DeleteAt(index) // deletes the item at index
// Bulk-loading
Load(item) // load presorted items into tree
// Path hinting
SetHint(item, *hint) // insert or replace an existing item
GetHint(item, *hint) // get an existing item
DeleteHint(item, *hint) // delete an item
// Copy-on-write
Copy() // copy the btree
```
#### Example
```go
package main
@@ -32,30 +241,154 @@ type Item struct {
Key, Val string
}
func (i1 *Item) Less(item btree.Item, ctx interface{}) bool {
i2 := item.(*Item)
switch tag := ctx.(type) {
case string:
if tag == "vals" {
if i1.Val < i2.Val {
return true
} else if i1.Val > i2.Val {
return false
}
// Both vals are equal so we should fall though
// and let the key comparison take over.
}
// byKeys is a comparison function that compares item keys and returns true
// when a is less than b.
func byKeys(a, b Item) bool {
return a.Key < b.Key
}
// byVals is a comparison function that compares item values and returns true
// when a is less than b.
func byVals(a, b Item) bool {
if a.Val < b.Val {
return true
}
return i1.Key < i2.Key
if a.Val > b.Val {
return false
}
// Both vals are equal so we should fall though
// and let the key comparison take over.
return byKeys(a, b)
}
func main() {
// Create a tree for keys and a tree for values.
// The "keys" tree will be sorted on the Keys field.
// The "values" tree will be sorted on the Values field.
keys := btree.New(16, "keys")
vals := btree.New(16, "vals")
keys := btree.NewBTreeG[Item](byKeys)
vals := btree.NewBTreeG[Item](byVals)
// Create some items.
users := []Item{
Item{Key: "user:1", Val: "Jane"},
Item{Key: "user:2", Val: "Andy"},
Item{Key: "user:3", Val: "Steve"},
Item{Key: "user:4", Val: "Andrea"},
Item{Key: "user:5", Val: "Janet"},
Item{Key: "user:6", Val: "Andy"},
}
// Insert each user into both trees
for _, user := range users {
keys.Set(user)
vals.Set(user)
}
// Iterate over each user in the key tree
keys.Scan(func(item Item) bool {
fmt.Printf("%s %s\n", item.Key, item.Val)
return true
})
fmt.Printf("\n")
// Iterate over each user in the val tree
vals.Scan(func(item Item) bool {
fmt.Printf("%s %s\n", item.Key, item.Val)
return true
})
// Output:
// user:1 Jane
// user:2 Andy
// user:3 Steve
// user:4 Andrea
// user:5 Janet
// user:6 Andy
//
// user:4 Andrea
// user:2 Andy
// user:6 Andy
// user:1 Jane
// user:5 Janet
// user:3 Steve
}
```
### btree.BTree
```go
// Basic
Set(item) // insert or replace an item
Get(item) // get an existing item
Delete(item) // delete an item
Len() // return the number of items in the btree
// Iteration
Scan(iter) // scan items in ascending order
Reverse(iter) // scan items in descending order
Ascend(key, iter) // scan items in ascending order that are >= to key
Descend(key, iter) // scan items in descending order that are <= to key.
Iter() // returns a read-only iterator for for-loops.
// Array-like operations
GetAt(index) // returns the item at index
DeleteAt(index) // deletes the item at index
// Bulk-loading
Load(item) // load presorted items into tree
// Path hinting
SetHint(item, *hint) // insert or replace an existing item
GetHint(item, *hint) // get an existing item
DeleteHint(item, *hint) // delete an item
// Copy-on-write
Copy() // copy the btree
```
#### Example
```go
package main
import (
"fmt"
"github.com/tidwall/btree"
)
type Item struct {
Key, Val string
}
// byKeys is a comparison function that compares item keys and returns true
// when a is less than b.
func byKeys(a, b interface{}) bool {
i1, i2 := a.(*Item), b.(*Item)
return i1.Key < i2.Key
}
// byVals is a comparison function that compares item values and returns true
// when a is less than b.
func byVals(a, b interface{}) bool {
i1, i2 := a.(*Item), b.(*Item)
if i1.Val < i2.Val {
return true
}
if i1.Val > i2.Val {
return false
}
// Both vals are equal so we should fall though
// and let the key comparison take over.
return byKeys(a, b)
}
func main() {
// Create a tree for keys and a tree for values.
// The "keys" tree will be sorted on the Keys field.
// The "values" tree will be sorted on the Values field.
keys := btree.New(byKeys)
vals := btree.New(byVals)
// Create some items.
users := []*Item{
@@ -69,12 +402,12 @@ func main() {
// Insert each user into both trees
for _, user := range users {
keys.ReplaceOrInsert(user)
vals.ReplaceOrInsert(user)
keys.Set(user)
vals.Set(user)
}
// Iterate over each user in the key tree
keys.Ascend(func(item btree.Item) bool {
keys.Ascend(nil, func(item interface{}) bool {
kvi := item.(*Item)
fmt.Printf("%s %s\n", kvi.Key, kvi.Val)
return true
@@ -82,26 +415,37 @@ func main() {
fmt.Printf("\n")
// Iterate over each user in the val tree
vals.Ascend(func(item btree.Item) bool {
vals.Ascend(nil, func(item interface{}) bool {
kvi := item.(*Item)
fmt.Printf("%s %s\n", kvi.Key, kvi.Val)
return true
})
// Output:
// user:1 Jane
// user:2 Andy
// user:3 Steve
// user:4 Andrea
// user:5 Janet
// user:6 Andy
//
// user:4 Andrea
// user:2 Andy
// user:6 Andy
// user:1 Jane
// user:5 Janet
// user:3 Steve
}
// Should see the results
/*
user:1 Jane
user:2 Andy
user:3 Steve
user:4 Andrea
user:5 Janet
user:6 Andy
user:4 Andrea
user:2 Andy
user:6 Andy
user:1 Jane
user:3 Steve
*/
```
## Performance
See [tidwall/btree-benchmark](https://github.com/tidwall/btree-benchmark) for benchmark numbers.
## Contact
Josh Baker [@tidwall](http://twitter.com/tidwall)
## License
Source code is available under the MIT [License](/LICENSE).