1// Copyright 2022 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
7import "cmd/internal/src"
8
9// from https://research.swtch.com/sparse
10// in turn, from Briggs and Torczon
11
12type sparseEntryPos struct {
13	key ID
14	val int32
15	pos src.XPos
16}
17
18type sparseMapPos struct {
19	dense  []sparseEntryPos
20	sparse []int32
21}
22
23// newSparseMapPos returns a sparseMapPos that can map
24// integers between 0 and n-1 to the pair <int32,src.XPos>.
25func newSparseMapPos(n int) *sparseMapPos {
26	return &sparseMapPos{dense: nil, sparse: make([]int32, n)}
27}
28
29func (s *sparseMapPos) cap() int {
30	return len(s.sparse)
31}
32
33func (s *sparseMapPos) size() int {
34	return len(s.dense)
35}
36
37func (s *sparseMapPos) contains(k ID) bool {
38	i := s.sparse[k]
39	return i < int32(len(s.dense)) && s.dense[i].key == k
40}
41
42// get returns the value for key k, or -1 if k does
43// not appear in the map.
44func (s *sparseMapPos) get(k ID) int32 {
45	i := s.sparse[k]
46	if i < int32(len(s.dense)) && s.dense[i].key == k {
47		return s.dense[i].val
48	}
49	return -1
50}
51
52func (s *sparseMapPos) set(k ID, v int32, a src.XPos) {
53	i := s.sparse[k]
54	if i < int32(len(s.dense)) && s.dense[i].key == k {
55		s.dense[i].val = v
56		s.dense[i].pos = a
57		return
58	}
59	s.dense = append(s.dense, sparseEntryPos{k, v, a})
60	s.sparse[k] = int32(len(s.dense)) - 1
61}
62
63func (s *sparseMapPos) remove(k ID) {
64	i := s.sparse[k]
65	if i < int32(len(s.dense)) && s.dense[i].key == k {
66		y := s.dense[len(s.dense)-1]
67		s.dense[i] = y
68		s.sparse[y.key] = i
69		s.dense = s.dense[:len(s.dense)-1]
70	}
71}
72
73func (s *sparseMapPos) clear() {
74	s.dense = s.dense[:0]
75}
76
77func (s *sparseMapPos) contents() []sparseEntryPos {
78	return s.dense
79}
80