github.com/mymmsc/gox@v1.3.33/util/linkedhashset/linkedhashset.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 linkedhashset is a set that preserves insertion-order.
     6  //
     7  // It is backed by a hash table to store values and doubly-linked list to store ordering.
     8  //
     9  // Note that insertion-order is not affected if an element is re-inserted into the set.
    10  //
    11  // Structure is not thread safe.
    12  //
    13  // References: http://en.wikipedia.org/wiki/Set_%28abstract_data_type%29
    14  package linkedhashset
    15  
    16  import (
    17  	"fmt"
    18  	"github.com/mymmsc/gox/util"
    19  	"github.com/mymmsc/gox/util/doublylinkedlist"
    20  	"strings"
    21  )
    22  
    23  func assertSetImplementation() {
    24  	var _ util.Set = (*Set)(nil)
    25  }
    26  
    27  // Set holds elements in go's native map
    28  type Set struct {
    29  	table    map[interface{}]struct{}
    30  	ordering *doublylinkedlist.List
    31  }
    32  
    33  var itemExists = struct{}{}
    34  
    35  // New instantiates a new empty set and adds the passed values, if any, to the set
    36  func New(values ...interface{}) *Set {
    37  	set := &Set{
    38  		table:    make(map[interface{}]struct{}),
    39  		ordering: doublylinkedlist.New(),
    40  	}
    41  	if len(values) > 0 {
    42  		set.Add(values...)
    43  	}
    44  	return set
    45  }
    46  
    47  // Add adds the items (one or more) to the set.
    48  // Note that insertion-order is not affected if an element is re-inserted into the set.
    49  func (set *Set) Add(items ...interface{}) {
    50  	for _, item := range items {
    51  		if _, contains := set.table[item]; !contains {
    52  			set.table[item] = itemExists
    53  			set.ordering.Append(item)
    54  		}
    55  	}
    56  }
    57  
    58  // Remove removes the items (one or more) from the set.
    59  // Slow operation, worst-case O(n^2).
    60  func (set *Set) Remove(items ...interface{}) {
    61  	for _, item := range items {
    62  		if _, contains := set.table[item]; contains {
    63  			delete(set.table, item)
    64  			index := set.ordering.IndexOf(item)
    65  			set.ordering.Remove(index)
    66  		}
    67  	}
    68  }
    69  
    70  // Contains check if items (one or more) are present in the set.
    71  // All items have to be present in the set for the method to return true.
    72  // Returns true if no arguments are passed at all, i.e. set is always superset of empty set.
    73  func (set *Set) Contains(items ...interface{}) bool {
    74  	for _, item := range items {
    75  		if _, contains := set.table[item]; !contains {
    76  			return false
    77  		}
    78  	}
    79  	return true
    80  }
    81  
    82  // Empty returns true if set does not contain any elements.
    83  func (set *Set) Empty() bool {
    84  	return set.Size() == 0
    85  }
    86  
    87  // Size returns number of elements within the set.
    88  func (set *Set) Size() int {
    89  	return set.ordering.Size()
    90  }
    91  
    92  // Clear clears all values in the set.
    93  func (set *Set) Clear() {
    94  	set.table = make(map[interface{}]struct{})
    95  	set.ordering.Clear()
    96  }
    97  
    98  // Values returns all items in the set.
    99  func (set *Set) Values() []interface{} {
   100  	values := make([]interface{}, set.Size())
   101  	it := set.Iterator()
   102  	for it.Next() {
   103  		values[it.Index()] = it.Value()
   104  	}
   105  	return values
   106  }
   107  
   108  // String returns a string representation of container
   109  func (set *Set) String() string {
   110  	str := "LinkedHashSet\n"
   111  	items := []string{}
   112  	it := set.Iterator()
   113  	for it.Next() {
   114  		items = append(items, fmt.Sprintf("%v", it.Value()))
   115  	}
   116  	str += strings.Join(items, ", ")
   117  	return str
   118  }