github.com/mymmsc/gox@v1.3.33/util/treeset/iterator.go (about)

     1  // Copyright (c) 2015, Emir Pasic. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package treeset
     6  
     7  import (
     8  	"github.com/mymmsc/gox/util"
     9  	rbt "github.com/mymmsc/gox/util/redblacktree"
    10  )
    11  
    12  func assertIteratorImplementation() {
    13  	var _ util.ReverseIteratorWithIndex = (*Iterator)(nil)
    14  }
    15  
    16  // Iterator returns a stateful iterator whose values can be fetched by an index.
    17  type Iterator struct {
    18  	index    int
    19  	iterator rbt.Iterator
    20  	tree     *rbt.Tree
    21  }
    22  
    23  // Iterator holding the iterator's state
    24  func (set *Set) Iterator() Iterator {
    25  	return Iterator{index: -1, iterator: set.tree.Iterator(), tree: set.tree}
    26  }
    27  
    28  // Next moves the iterator to the next element and returns true if there was a next element in the container.
    29  // If Next() returns true, then next element's index and value can be retrieved by Index() and Value().
    30  // If Next() was called for the first time, then it will point the iterator to the first element if it exists.
    31  // Modifies the state of the iterator.
    32  func (iterator *Iterator) Next() bool {
    33  	if iterator.index < iterator.tree.Size() {
    34  		iterator.index++
    35  	}
    36  	return iterator.iterator.Next()
    37  }
    38  
    39  // Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
    40  // If Prev() returns true, then previous element's index and value can be retrieved by Index() and Value().
    41  // Modifies the state of the iterator.
    42  func (iterator *Iterator) Prev() bool {
    43  	if iterator.index >= 0 {
    44  		iterator.index--
    45  	}
    46  	return iterator.iterator.Prev()
    47  }
    48  
    49  // Value returns the current element's value.
    50  // Does not modify the state of the iterator.
    51  func (iterator *Iterator) Value() interface{} {
    52  	return iterator.iterator.Key()
    53  }
    54  
    55  // Index returns the current element's index.
    56  // Does not modify the state of the iterator.
    57  func (iterator *Iterator) Index() int {
    58  	return iterator.index
    59  }
    60  
    61  // Begin resets the iterator to its initial state (one-before-first)
    62  // Call Next() to fetch the first element if any.
    63  func (iterator *Iterator) Begin() {
    64  	iterator.index = -1
    65  	iterator.iterator.Begin()
    66  }
    67  
    68  // End moves the iterator past the last element (one-past-the-end).
    69  // Call Prev() to fetch the last element if any.
    70  func (iterator *Iterator) End() {
    71  	iterator.index = iterator.tree.Size()
    72  	iterator.iterator.End()
    73  }
    74  
    75  // First moves the iterator to the first element and returns true if there was a first element in the container.
    76  // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
    77  // Modifies the state of the iterator.
    78  func (iterator *Iterator) First() bool {
    79  	iterator.Begin()
    80  	return iterator.Next()
    81  }
    82  
    83  // Last moves the iterator to the last element and returns true if there was a last element in the container.
    84  // If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
    85  // Modifies the state of the iterator.
    86  func (iterator *Iterator) Last() bool {
    87  	iterator.End()
    88  	return iterator.Prev()
    89  }