update

Signed-off-by: hongming <talonwan@yunify.com>

vendor/github.com/open-policy-agent/opa/util/graph.go

@@ -0,0 +1,90 @@
+// Copyright 2016 The OPA Authors.  All rights reserved.
+// Use of this source code is governed by an Apache2
+// license that can be found in the LICENSE file.
+
+package util
+
+// Traversal defines a basic interface to perform traversals.
+type Traversal interface {
+
+	// Edges should return the neighbours of node "u".
+	Edges(u T) []T
+
+	// Visited should return true if node "u" has already been visited in this
+	// traversal. If the same traversal is used multiple times, the state that
+	// tracks visited nodes should be reset.
+	Visited(u T) bool
+}
+
+// Equals should return true if node "u" equals node "v".
+type Equals func(u T, v T) bool
+
+// Iter should return true to indicate stop.
+type Iter func(u T) bool
+
+// DFS performs a depth first traversal calling f for each node starting from u.
+// If f returns true, traversal stops and DFS returns true.
+func DFS(t Traversal, f Iter, u T) bool {
+	lifo := NewLIFO(u)
+	for lifo.Size() > 0 {
+		next, _ := lifo.Pop()
+		if t.Visited(next) {
+			continue
+		}
+		if f(next) {
+			return true
+		}
+		for _, v := range t.Edges(next) {
+			lifo.Push(v)
+		}
+	}
+	return false
+}
+
+// BFS performs a breadth first traversal calling f for each node starting from
+// u. If f returns true, traversal stops and BFS returns true.
+func BFS(t Traversal, f Iter, u T) bool {
+	fifo := NewFIFO(u)
+	for fifo.Size() > 0 {
+		next, _ := fifo.Pop()
+		if t.Visited(next) {
+			continue
+		}
+		if f(next) {
+			return true
+		}
+		for _, v := range t.Edges(next) {
+			fifo.Push(v)
+		}
+	}
+	return false
+}
+
+// DFSPath returns a path from node a to node z found by performing
+// a depth first traversal. If no path is found, an empty slice is returned.
+func DFSPath(t Traversal, eq Equals, a, z T) []T {
+	p := dfsRecursive(t, eq, a, z, []T{})
+	for i := len(p)/2 - 1; i >= 0; i-- {
+		o := len(p) - i - 1
+		p[i], p[o] = p[o], p[i]
+	}
+	return p
+}
+
+func dfsRecursive(t Traversal, eq Equals, u, z T, path []T) []T {
+	if t.Visited(u) {
+		return path
+	}
+	for _, v := range t.Edges(u) {
+		if eq(v, z) {
+			path = append(path, z)
+			path = append(path, u)
+			return path
+		}
+		if p := dfsRecursive(t, eq, v, z, path); len(p) > 0 {
+			path = append(p, u)
+			return path
+		}
+	}
+	return path
+}