github.com/mymmsc/gox@v1.3.33/util/singlylinkedlist/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 singlylinkedlist
     6  
     7  import "github.com/mymmsc/gox/util"
     8  
     9  func assertIteratorImplementation() {
    10  	var _ util.IteratorWithIndex = (*Iterator)(nil)
    11  }
    12  
    13  // Iterator holding the iterator's state
    14  type Iterator struct {
    15  	list    *List
    16  	index   int
    17  	element *element
    18  }
    19  
    20  // Iterator returns a stateful iterator whose values can be fetched by an index.
    21  func (list *List) Iterator() Iterator {
    22  	return Iterator{list: list, index: -1, element: nil}
    23  }
    24  
    25  // Next moves the iterator to the next element and returns true if there was a next element in the container.
    26  // If Next() returns true, then next element's index and value can be retrieved by Index() and Value().
    27  // If Next() was called for the first time, then it will point the iterator to the first element if it exists.
    28  // Modifies the state of the iterator.
    29  func (iterator *Iterator) Next() bool {
    30  	if iterator.index < iterator.list.size {
    31  		iterator.index++
    32  	}
    33  	if !iterator.list.withinRange(iterator.index) {
    34  		iterator.element = nil
    35  		return false
    36  	}
    37  	if iterator.index == 0 {
    38  		iterator.element = iterator.list.first
    39  	} else {
    40  		iterator.element = iterator.element.next
    41  	}
    42  	return true
    43  }
    44  
    45  // Value returns the current element's value.
    46  // Does not modify the state of the iterator.
    47  func (iterator *Iterator) Value() interface{} {
    48  	return iterator.element.value
    49  }
    50  
    51  // Index returns the current element's index.
    52  // Does not modify the state of the iterator.
    53  func (iterator *Iterator) Index() int {
    54  	return iterator.index
    55  }
    56  
    57  // Begin resets the iterator to its initial state (one-before-first)
    58  // Call Next() to fetch the first element if any.
    59  func (iterator *Iterator) Begin() {
    60  	iterator.index = -1
    61  	iterator.element = nil
    62  }
    63  
    64  // First moves the iterator to the first element and returns true if there was a first element in the container.
    65  // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
    66  // Modifies the state of the iterator.
    67  func (iterator *Iterator) First() bool {
    68  	iterator.Begin()
    69  	return iterator.Next()
    70  }