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// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ssa
import "cmd/internal/src"
// from https://research.swtch.com/sparse
// in turn, from Briggs and Torczon
type sparseEntryPos struct {
key ID
val int32
pos src.XPos
}
type sparseMapPos struct {
dense []sparseEntryPos
sparse []int32
}
// newSparseMapPos returns a sparseMapPos that can map
// integers between 0 and n-1 to the pair <int32,src.XPos>.
func newSparseMapPos(n int) *sparseMapPos {
return &sparseMapPos{dense: nil, sparse: make([]int32, n)}
}
func (s *sparseMapPos) cap() int {
return len(s.sparse)
}
func (s *sparseMapPos) size() int {
return len(s.dense)
}
func (s *sparseMapPos) contains(k ID) bool {
i := s.sparse[k]
return i < int32(len(s.dense)) && s.dense[i].key == k
}
// get returns the value for key k, or -1 if k does
// not appear in the map.
func (s *sparseMapPos) get(k ID) int32 {
i := s.sparse[k]
if i < int32(len(s.dense)) && s.dense[i].key == k {
return s.dense[i].val
}
return -1
}
func (s *sparseMapPos) set(k ID, v int32, a src.XPos) {
i := s.sparse[k]
if i < int32(len(s.dense)) && s.dense[i].key == k {
s.dense[i].val = v
s.dense[i].pos = a
return
}
s.dense = append(s.dense, sparseEntryPos{k, v, a})
s.sparse[k] = int32(len(s.dense)) - 1
}
func (s *sparseMapPos) remove(k ID) {
i := s.sparse[k]
if i < int32(len(s.dense)) && s.dense[i].key == k {
y := s.dense[len(s.dense)-1]
s.dense[i] = y
s.sparse[y.key] = i
s.dense = s.dense[:len(s.dense)-1]
}
}
func (s *sparseMapPos) clear() {
s.dense = s.dense[:0]
}
func (s *sparseMapPos) contents() []sparseEntryPos {
return s.dense
}
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