1// Copyright 2015 The Go Authors. 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
5package ssa
6
7// from https://research.swtch.com/sparse
8// in turn, from Briggs and Torczon
9
10type sparseSet struct {
11	dense  []ID
12	sparse []int32
13}
14
15// newSparseSet returns a sparseSet that can represent
16// integers between 0 and n-1.
17func newSparseSet(n int) *sparseSet {
18	return &sparseSet{dense: nil, sparse: make([]int32, n)}
19}
20
21func (s *sparseSet) cap() int {
22	return len(s.sparse)
23}
24
25func (s *sparseSet) size() int {
26	return len(s.dense)
27}
28
29func (s *sparseSet) contains(x ID) bool {
30	i := s.sparse[x]
31	return i < int32(len(s.dense)) && s.dense[i] == x
32}
33
34func (s *sparseSet) add(x ID) {
35	i := s.sparse[x]
36	if i < int32(len(s.dense)) && s.dense[i] == x {
37		return
38	}
39	s.dense = append(s.dense, x)
40	s.sparse[x] = int32(len(s.dense)) - 1
41}
42
43func (s *sparseSet) addAll(a []ID) {
44	for _, x := range a {
45		s.add(x)
46	}
47}
48
49func (s *sparseSet) addAllValues(a []*Value) {
50	for _, v := range a {
51		s.add(v.ID)
52	}
53}
54
55func (s *sparseSet) remove(x ID) {
56	i := s.sparse[x]
57	if i < int32(len(s.dense)) && s.dense[i] == x {
58		y := s.dense[len(s.dense)-1]
59		s.dense[i] = y
60		s.sparse[y] = i
61		s.dense = s.dense[:len(s.dense)-1]
62	}
63}
64
65// pop removes an arbitrary element from the set.
66// The set must be nonempty.
67func (s *sparseSet) pop() ID {
68	x := s.dense[len(s.dense)-1]
69	s.dense = s.dense[:len(s.dense)-1]
70	return x
71}
72
73func (s *sparseSet) clear() {
74	s.dense = s.dense[:0]
75}
76
77func (s *sparseSet) contents() []ID {
78	return s.dense
79}
80