sparseset.go

Documentation: cmd/compile/internal/ssa

     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  
     5  package ssa
     6  
     7  // from https://research.swtch.com/sparse
     8  // in turn, from Briggs and Torczon
     9  
    10  type 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.
    17  func newSparseSet(n int) *sparseSet {
    18  	return &sparseSet{dense: nil, sparse: make([]int32, n)}
    19  }
    20  
    21  func (s *sparseSet) cap() int {
    22  	return len(s.sparse)
    23  }
    24  
    25  func (s *sparseSet) size() int {
    26  	return len(s.dense)
    27  }
    28  
    29  func (s *sparseSet) contains(x ID) bool {
    30  	i := s.sparse[x]
    31  	return i < int32(len(s.dense)) && s.dense[i] == x
    32  }
    33  
    34  func (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  
    43  func (s *sparseSet) addAll(a []ID) {
    44  	for _, x := range a {
    45  		s.add(x)
    46  	}
    47  }
    48  
    49  func (s *sparseSet) addAllValues(a []*Value) {
    50  	for _, v := range a {
    51  		s.add(v.ID)
    52  	}
    53  }
    54  
    55  func (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.
    67  func (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  
    73  func (s *sparseSet) clear() {
    74  	s.dense = s.dense[:0]
    75  }
    76  
    77  func (s *sparseSet) contents() []ID {
    78  	return s.dense
    79  }
    80
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