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 sparseEntry struct {
11	key ID
12	val int32
13}
14
15type sparseMap struct {
16	dense  []sparseEntry
17	sparse []int32
18}
19
20// newSparseMap returns a sparseMap that can map
21// integers between 0 and n-1 to int32s.
22func newSparseMap(n int) *sparseMap {
23	return &sparseMap{dense: nil, sparse: make([]int32, n)}
24}
25
26func (s *sparseMap) cap() int {
27	return len(s.sparse)
28}
29
30func (s *sparseMap) size() int {
31	return len(s.dense)
32}
33
34func (s *sparseMap) contains(k ID) bool {
35	i := s.sparse[k]
36	return i < int32(len(s.dense)) && s.dense[i].key == k
37}
38
39// get returns the value for key k, or -1 if k does
40// not appear in the map.
41func (s *sparseMap) get(k ID) int32 {
42	i := s.sparse[k]
43	if i < int32(len(s.dense)) && s.dense[i].key == k {
44		return s.dense[i].val
45	}
46	return -1
47}
48
49func (s *sparseMap) set(k ID, v int32) {
50	i := s.sparse[k]
51	if i < int32(len(s.dense)) && s.dense[i].key == k {
52		s.dense[i].val = v
53		return
54	}
55	s.dense = append(s.dense, sparseEntry{k, v})
56	s.sparse[k] = int32(len(s.dense)) - 1
57}
58
59// setBit sets the v'th bit of k's value, where 0 <= v < 32
60func (s *sparseMap) setBit(k ID, v uint) {
61	if v >= 32 {
62		panic("bit index too large.")
63	}
64	i := s.sparse[k]
65	if i < int32(len(s.dense)) && s.dense[i].key == k {
66		s.dense[i].val |= 1 << v
67		return
68	}
69	s.dense = append(s.dense, sparseEntry{k, 1 << v})
70	s.sparse[k] = int32(len(s.dense)) - 1
71}
72
73func (s *sparseMap) remove(k ID) {
74	i := s.sparse[k]
75	if i < int32(len(s.dense)) && s.dense[i].key == k {
76		y := s.dense[len(s.dense)-1]
77		s.dense[i] = y
78		s.sparse[y.key] = i
79		s.dense = s.dense[:len(s.dense)-1]
80	}
81}
82
83func (s *sparseMap) clear() {
84	s.dense = s.dense[:0]
85}
86
87func (s *sparseMap) contents() []sparseEntry {
88	return s.dense
89}
90