Add dependencies for code generator

vendor/gonum.org/v1/gonum/graph/internal/uid/uid.go

@@ -0,0 +1,54 @@
+// Copyright ©2014 The Gonum 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 uid implements unique ID provision for graphs.
+package uid
+
+import "gonum.org/v1/gonum/graph/internal/set"
+
+// Max is the maximum value of int64.
+const Max = int64(^uint64(0) >> 1)
+
+// Set implements available ID storage.
+type Set struct {
+	maxID      int64
+	used, free set.Int64s
+}
+
+// NewSet returns a new Set. The returned value should not be passed except by pointer.
+func NewSet() Set {
+	return Set{maxID: -1, used: make(set.Int64s), free: make(set.Int64s)}
+}
+
+// NewID returns a new unique ID. The ID returned is not considered used
+// until passed in a call to use.
+func (s *Set) NewID() int64 {
+	for id := range s.free {
+		return id
+	}
+	if s.maxID != Max {
+		return s.maxID + 1
+	}
+	for id := int64(0); id <= s.maxID+1; id++ {
+		if !s.used.Has(id) {
+			return id
+		}
+	}
+	panic("unreachable")
+}
+
+// Use adds the id to the used IDs in the Set.
+func (s *Set) Use(id int64) {
+	s.used.Add(id)
+	s.free.Remove(id)
+	if id > s.maxID {
+		s.maxID = id
+	}
+}
+
+// Release frees the id for reuse.
+func (s *Set) Release(id int64) {
+	s.free.Add(id)
+	s.used.Remove(id)
+}