btree

Documentation

Overview

Package btree implements a B tree.

According to Knuth's definition, a B-tree of order m is a tree which satisfies the following properties: - Every node has at most m children. - Every non-leaf node (except root) has at least ⌈m/2⌉ children. - The root has at least two children if it is not a leaf node. - A non-leaf node with k children contains k−1 keys. - All leaves appear in the same level

Structure is not thread safe.

References: https://en.wikipedia.org/wiki/B-tree

Index

• type Entry
  • func (entry *Entry) String() string
• type Iterator
  • func (iterator *Iterator) Begin()
  • func (iterator *Iterator) End()
  • func (iterator *Iterator) First() bool
  • func (iterator *Iterator) Key() interface{}
  • func (iterator *Iterator) Last() bool
  • func (iterator *Iterator) Next() bool
  • func (iterator *Iterator) Prev() bool
  • func (iterator *Iterator) Value() interface{}
• type Node
• type Tree
  • func NewWith(order int, comparator util.Comparator) *Tree
  • func NewWithIntComparator(order int) *Tree
  • func NewWithStringComparator(order int) *Tree
  • func (tree *Tree) Clear()
  • func (tree *Tree) Empty() bool
  • func (tree *Tree) FromJSON(data []byte) error
  • func (tree *Tree) Get(key interface{}) (value interface{}, found bool)
  • func (tree *Tree) Height() int
  • func (tree *Tree) Iterator() Iterator
  • func (tree *Tree) Keys() []interface{}
  • func (tree *Tree) Left() *Node
  • func (tree *Tree) LeftKey() interface{}
  • func (tree *Tree) LeftValue() interface{}
  • func (tree *Tree) Put(key interface{}, value interface{})
  • func (tree *Tree) Remove(key interface{})
  • func (tree *Tree) Right() *Node
  • func (tree *Tree) RightKey() interface{}
  • func (tree *Tree) RightValue() interface{}
  • func (tree *Tree) Size() int
  • func (tree *Tree) String() string
  • func (tree *Tree) ToJSON() ([]byte, error)
  • func (tree *Tree) Values() []interface{}

Types

type Entry

type Entry struct {
	Key   interface{}
	Value interface{}
}

Entry represents the key-value pair contained within nodes

func (*Entry) String

func (entry *Entry) String() string

type Iterator

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

Iterator holding the iterator's state

func (*Iterator) Begin

func (iterator *Iterator) Begin()

Begin resets the iterator to its initial state (one-before-first) Call Next() to fetch the first element if any.

func (*Iterator) End

func (iterator *Iterator) End()

End moves the iterator past the last element (one-past-the-end). Call Prev() to fetch the last element if any.

func (*Iterator) First

func (iterator *Iterator) First() bool

First moves the iterator to the first element and returns true if there was a first element in the container. If First() returns true, then first element's key and value can be retrieved by Key() and Value(). Modifies the state of the iterator

func (*Iterator) Key

func (iterator *Iterator) Key() interface{}

Key returns the current element's key. Does not modify the state of the iterator.

func (*Iterator) Last

func (iterator *Iterator) Last() bool

Last moves the iterator to the last element and returns true if there was a last element in the container. If Last() returns true, then last element's key and value can be retrieved by Key() and Value(). Modifies the state of the iterator.

func (*Iterator) Next

func (iterator *Iterator) Next() bool

Next moves the iterator to the next element and returns true if there was a next element in the container. If Next() returns true, then next element's key and value can be retrieved by Key() and Value(). If Next() was called for the first time, then it will point the iterator to the first element if it exists. Modifies the state of the iterator.

func (*Iterator) Prev

func (iterator *Iterator) Prev() bool

Prev moves the iterator to the previous element and returns true if there was a previous element in the container. If Prev() returns true, then previous element's key and value can be retrieved by Key() and Value(). Modifies the state of the iterator.

func (*Iterator) Value

func (iterator *Iterator) Value() interface{}

Value returns the current element's value. Does not modify the state of the iterator.

type Node

type Node struct {
	Parent   *Node
	Entries  []*Entry // Contained keys in node
	Children []*Node  // Children nodes
}

Node is a single element within the tree

type Tree

type Tree struct {
	Root       *Node           // Root node
	Comparator util.Comparator // Key comparator
	// contains filtered or unexported fields
}

Tree holds elements of the B-tree

func NewWith

func NewWith(order int, comparator util.Comparator) *Tree

NewWith instantiates a B-tree with the order (maximum number of children) and a custom key comparator.

func NewWithIntComparator

func NewWithIntComparator(order int) *Tree

NewWithIntComparator instantiates a B-tree with the order (maximum number of children) and the IntComparator, i.e. keys are of type int.

func NewWithStringComparator

func NewWithStringComparator(order int) *Tree

NewWithStringComparator instantiates a B-tree with the order (maximum number of children) and the StringComparator, i.e. keys are of type string.

func (*Tree) Clear

func (tree *Tree) Clear()

Clear removes all nodes from the tree.

func (*Tree) Empty

func (tree *Tree) Empty() bool

Empty returns true if tree does not contain any nodes

func (*Tree) FromJSON

func (tree *Tree) FromJSON(data []byte) error

FromJSON populates the tree from the input JSON representation.

func (*Tree) Get

func (tree *Tree) Get(key interface{}) (value interface{}, found bool)

Get searches the node in the tree by key and returns its value or nil if key is not found in tree. Second return parameter is true if key was found, otherwise false. Key should adhere to the comparator's type assertion, otherwise method panics.

func (*Tree) Height

func (tree *Tree) Height() int

Height returns the height of the tree.

func (*Tree) Iterator

func (tree *Tree) Iterator() Iterator

Iterator returns a stateful iterator whose elements are key/value pairs.

func (*Tree) Keys

func (tree *Tree) Keys() []interface{}

Keys returns all keys in-order

func (*Tree) Left

func (tree *Tree) Left() *Node

Left returns the left-most (min) node or nil if tree is empty.

func (*Tree) LeftKey

func (tree *Tree) LeftKey() interface{}

LeftKey returns the left-most (min) key or nil if tree is empty.

func (*Tree) LeftValue

func (tree *Tree) LeftValue() interface{}

LeftValue returns the left-most value or nil if tree is empty.

func (*Tree) Put

func (tree *Tree) Put(key interface{}, value interface{})

Put inserts key-value pair node into the tree. If key already exists, then its value is updated with the new value. Key should adhere to the comparator's type assertion, otherwise method panics.

func (*Tree) Remove

func (tree *Tree) Remove(key interface{})

Remove remove the node from the tree by key. Key should adhere to the comparator's type assertion, otherwise method panics.

func (*Tree) Right

func (tree *Tree) Right() *Node

Right returns the right-most (max) node or nil if tree is empty.

func (*Tree) RightKey

func (tree *Tree) RightKey() interface{}

RightKey returns the right-most (max) key or nil if tree is empty.

func (*Tree) RightValue

func (tree *Tree) RightValue() interface{}

RightValue returns the right-most value or nil if tree is empty.

func (*Tree) Size

func (tree *Tree) Size() int

Size returns number of nodes in the tree.

func (*Tree) String

func (tree *Tree) String() string

String returns a string representation of container (for debugging purposes)

func (*Tree) ToJSON

func (tree *Tree) ToJSON() ([]byte, error)

ToJSON outputs the JSON representation of the tree.

func (*Tree) Values

func (tree *Tree) Values() []interface{}

Values returns all values in-order based on the key.