103 lines
3.1 KiB
Go
103 lines
3.1 KiB
Go
// Copyright (c) 2017, Benjamin Scher Purcell. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package plist
|
|
|
|
// Iterator holding the iterator's state
|
|
type Iterator struct {
|
|
tree *Tree
|
|
node *AvlNode
|
|
position position
|
|
}
|
|
|
|
type position byte
|
|
|
|
const (
|
|
begin, between, end position = 0, 1, 2
|
|
)
|
|
|
|
// Iterator returns a stateful iterator whose elements are key/value pairs.
|
|
func (tree *Tree) Iterator() *Iterator {
|
|
return &Iterator{tree: tree, node: nil, position: begin}
|
|
}
|
|
|
|
// 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 *Iterator) Next() bool {
|
|
switch iterator.position {
|
|
case begin:
|
|
iterator.position = between
|
|
iterator.node = iterator.tree.Left()
|
|
case between:
|
|
iterator.node = iterator.node.Next()
|
|
}
|
|
|
|
if iterator.node == nil {
|
|
iterator.position = end
|
|
return false
|
|
}
|
|
return true
|
|
}
|
|
|
|
// Prev moves the iterator to the next element and returns true if there was a previous element in the container.
|
|
// If Prev() returns true, then next element's key and value can be retrieved by Key() and Value().
|
|
// If Prev() 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 *Iterator) Prev() bool {
|
|
switch iterator.position {
|
|
case end:
|
|
iterator.position = between
|
|
iterator.node = iterator.tree.Right()
|
|
case between:
|
|
iterator.node = iterator.node.Prev()
|
|
}
|
|
|
|
if iterator.node == nil {
|
|
iterator.position = begin
|
|
return false
|
|
}
|
|
return true
|
|
}
|
|
|
|
// Value returns the current element's Value.
|
|
// Does not modify the state of the iterator.
|
|
func (iterator *Iterator) Value() []interface{} {
|
|
if iterator.node == nil {
|
|
return nil
|
|
}
|
|
return iterator.node.Value
|
|
}
|
|
|
|
// Begin resets the iterator to its initial state (one-before-first)
|
|
// Call Next() to fetch the first element if any.
|
|
func (iterator *Iterator) Begin() {
|
|
iterator.node = nil
|
|
iterator.position = begin
|
|
}
|
|
|
|
// End moves the iterator past the last element (one-past-the-end).
|
|
// Call Prev() to fetch the last element if any.
|
|
func (iterator *Iterator) End() {
|
|
iterator.node = nil
|
|
iterator.position = end
|
|
}
|
|
|
|
// 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 *Iterator) First() bool {
|
|
iterator.Begin()
|
|
return iterator.Next()
|
|
}
|
|
|
|
// 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 *Iterator) Last() bool {
|
|
iterator.End()
|
|
return iterator.Prev()
|
|
}
|