08-27-周三_17-09-29

node_modules/dagre-layout/lib/data/list.js

@@ -0,0 +1,56 @@
+/*
+ * Simple doubly linked list implementation derived from Cormen, et al.,
+ * "Introduction to Algorithms".
+ */
+
+function List () {
+  const sentinel = {}
+  sentinel._next = sentinel._prev = sentinel
+  this._sentinel = sentinel
+}
+
+List.prototype.dequeue = function () {
+  const sentinel = this._sentinel
+  const entry = sentinel._prev
+  if (entry !== sentinel) {
+    unlink(entry)
+    return entry
+  }
+}
+
+List.prototype.enqueue = function (entry) {
+  const sentinel = this._sentinel
+  if (entry._prev && entry._next) {
+    unlink(entry)
+  }
+  entry._next = sentinel._next
+  sentinel._next._prev = entry
+  sentinel._next = entry
+  entry._prev = sentinel
+}
+
+List.prototype.toString = function () {
+  const strs = []
+  const sentinel = this._sentinel
+  let curr = sentinel._prev
+  while (curr !== sentinel) {
+    strs.push(JSON.stringify(curr, filterOutLinks))
+    curr = curr._prev
+  }
+  return '[' + strs.join(', ') + ']'
+}
+
+function unlink (entry) {
+  entry._prev._next = entry._next
+  entry._next._prev = entry._prev
+  delete entry._next
+  delete entry._prev
+}
+
+function filterOutLinks (k, v) {
+  if (k !== '_next' && k !== '_prev') {
+    return v
+  }
+}
+
+export default List