1 files changed, 35 insertions, 0 deletions
diff --git a/node_modules/concordance/lib/Circular.js b/node_modules/concordance/lib/Circular.js
new file mode 100644
index 000000000..c5c020267
--- /dev/null
+++ b/node_modules/concordance/lib/Circular.js
@@ -0,0 +1,35 @@
+'use strict'
+
+class Circular {
+  constructor () {
+    this.stack = new Map()
+  }
+
+  add (descriptor) {
+    if (this.stack.has(descriptor)) throw new Error('Already in stack')
+
+    if (descriptor.isItem !== true && descriptor.isMapEntry !== true && descriptor.isProperty !== true) {
+      this.stack.set(descriptor, this.stack.size + 1)
+    }
+    return this
+  }
+
+  delete (descriptor) {
+    if (this.stack.has(descriptor)) {
+      if (this.stack.get(descriptor) !== this.stack.size) throw new Error('Not on top of stack')
+      this.stack.delete(descriptor)
+    }
+    return this
+  }
+
+  has (descriptor) {
+    return this.stack.has(descriptor)
+  }
+
+  get (descriptor) {
+    return this.stack.has(descriptor)
+      ? this.stack.get(descriptor)
+      : 0
+  }
+}
+module.exports = Circular