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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2025 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 bimap
// Bimap provides a bidirectional mapping between a value and an index in a
// slice. Lookups in either direction are O(1).
type Bimap[V comparable, I ~int] struct {
values []V
indexes map[V]I
}
// New returns an empty Bimap.
func New[V comparable, I ~int]() *Bimap[V, I] {
return &Bimap[V, I]{
indexes: make(map[V]I),
}
}
// Add inserts v into the map if it is not already present and returns the index
// associated with it. This method is idempotent.
func (bm *Bimap[V, I]) Add(v V) I {
if idx, exists := bm.indexes[v]; exists {
return idx
}
index := I(len(bm.values))
bm.values = append(bm.values, v)
bm.indexes[v] = index
return index
}
// IndexOf returns the index previously assigned to v by Add. We return the
// index and true if v exists, false otherwise.
func (bm *Bimap[V, I]) IndexOf(v V) (I, bool) {
idx, exists := bm.indexes[v]
return idx, exists
}
// Value returns the value stored at index i. This method panics if the index is
// not associated with a value in the map.
func (bm *Bimap[V, I]) Value(i I) V {
return bm.values[i]
}
// Values returns a slice containing all values in insertion order. Callers must
// not mutate the returned slice. Future calls to [Add] may invalidate the
// returned slice.
func (bm *Bimap[V, I]) Values() []V {
return bm.values
}
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