github.com/gopherd/gonum@v0.0.4/graph/set/uid/uid.go (about)

     1  // Copyright ©2014 The Gonum 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 uid implements unique ID provision for graphs.
     6  package uid
     7  
     8  import (
     9  	"math"
    10  
    11  	"github.com/gopherd/gonum/graph/internal/set"
    12  )
    13  
    14  // Max is the maximum ID value.
    15  const Max = math.MaxInt64
    16  
    17  // Set implements available ID storage.
    18  type Set struct {
    19  	maxID      int64
    20  	used, free set.Int64s
    21  }
    22  
    23  // NewSet returns a new Set.
    24  func NewSet() *Set {
    25  	return &Set{maxID: -1, used: make(set.Int64s), free: make(set.Int64s)}
    26  }
    27  
    28  // NewID returns a new unique ID. The ID returned is not considered used
    29  // until passed in a call to use.
    30  func (s *Set) NewID() int64 {
    31  	for id := range s.free {
    32  		return id
    33  	}
    34  	if s.maxID != math.MaxInt64 {
    35  		return s.maxID + 1
    36  	}
    37  	for id := int64(0); id <= s.maxID; id++ {
    38  		if !s.used.Has(id) {
    39  			return id
    40  		}
    41  	}
    42  	panic("unreachable")
    43  }
    44  
    45  // Use adds the id to the used IDs in the Set.
    46  func (s *Set) Use(id int64) {
    47  	s.used.Add(id)
    48  	s.free.Remove(id)
    49  	if id > s.maxID {
    50  		s.maxID = id
    51  	}
    52  }
    53  
    54  // Release frees the id for reuse.
    55  func (s *Set) Release(id int64) {
    56  	s.free.Add(id)
    57  	s.used.Remove(id)
    58  }