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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2019 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package strutil
// OrderedSet is a set of strings that maintains the order of insertion.
//
// The order of putting items into the set is retained. Putting items "a", "b"
// and then "a", results in order "a", "b".
//
// External synchronization is required for safe concurrent access.
type OrderedSet struct {
positionOf map[string]int
}
// Items returns a slice of strings representing insertion order.
//
// Items is O(N) in the size of the set.
func (o *OrderedSet) Items() []string {
if len(o.positionOf) == 0 {
return nil
}
items := make([]string, len(o.positionOf))
for item, idx := range o.positionOf {
items[idx] = item
}
return items
}
// Contains returns true if the set contains a given item.
//
// Contains is O(1) in the size of the set.
func (o *OrderedSet) Contains(item string) bool {
_, ok := o.positionOf[item]
return ok
}
// IndexOf returns the position of an item in the set.
func (o *OrderedSet) IndexOf(item string) (idx int, ok bool) {
idx, ok = o.positionOf[item]
return idx, ok
}
// Put adds an item into the set.
//
// If the item was not present then it is stored and ordered after all existing
// elements. If the item was already present its position is not changed.
//
// Put is O(1) in the size of the set.
func (o *OrderedSet) Put(item string) {
if o.positionOf == nil {
o.positionOf = make(map[string]int)
}
if _, ok := o.positionOf[item]; ok {
return
}
o.positionOf[item] = len(o.positionOf)
}
// Size returns the number of elements in the set.
func (o *OrderedSet) Size() int {
return len(o.positionOf)
}
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