1 files changed, 62 insertions, 0 deletions
diff --git a/toolkit/modules/CanonicalJSON.jsm b/toolkit/modules/CanonicalJSON.jsm
new file mode 100644
index 000000000..ae754ff3a
--- /dev/null
+++ b/toolkit/modules/CanonicalJSON.jsm
@@ -0,0 +1,62 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+this.EXPORTED_SYMBOLS = ["CanonicalJSON"];
+
+const { classes: Cc, interfaces: Ci, utils: Cu } = Components;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "jsesc",
+                                  "resource://gre/modules/third_party/jsesc/jsesc.js");
+
+this.CanonicalJSON = {
+  /**
+   * Return the canonical JSON form of the passed source, sorting all the object
+   * keys recursively. Note that this method will cause an infinite loop if
+   * cycles exist in the source (bug 1265357).
+   *
+   * @param source
+   *        The elements to be serialized.
+   *
+   * The output will have all unicode chars escaped with the unicode codepoint
+   * as lowercase hexadecimal.
+   *
+   * @usage
+   *        CanonicalJSON.stringify(listOfRecords);
+   **/
+  stringify: function stringify(source) {
+    if (Array.isArray(source)) {
+      const jsonArray = source.map(x => typeof x === "undefined" ? null : x);
+      return `[${jsonArray.map(stringify).join(",")}]`;
+    }
+
+    if (typeof source === "number") {
+      if (source === 0) {
+        return (Object.is(source, -0)) ? "-0" : "0";
+      }
+    }
+
+    // Leverage jsesc library, mainly for unicode escaping.
+    const toJSON = (input) => jsesc(input, {lowercaseHex: true, json: true});
+
+    if (typeof source !== "object" || source === null) {
+      return toJSON(source);
+    }
+
+    // Dealing with objects, ordering keys.
+    const sortedKeys = Object.keys(source).sort();
+    const lastIndex = sortedKeys.length - 1;
+    return sortedKeys.reduce((serial, key, index) => {
+      const value = source[key];
+      // JSON.stringify drops keys with an undefined value.
+      if (typeof value === "undefined") {
+        return serial;
+      }
+      const jsonValue = value && value.toJSON ? value.toJSON() : value;
+      const suffix = index !== lastIndex ? "," : "";
+      const escapedKey = toJSON(key);
+      return serial + `${escapedKey}:${stringify(jsonValue)}${suffix}`;
+    }, "{") + "}";
+  },
+};