1 files changed, 68 insertions, 0 deletions
diff --git a/toolkit/modules/CanonicalJSON.jsm b/toolkit/modules/CanonicalJSON.jsm
new file mode 100644
index 0000000000..b9c82c2c71
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+++ b/toolkit/modules/CanonicalJSON.jsm
@@ -0,0 +1,68 @@
+/* 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/. */
+
+var EXPORTED_SYMBOLS = ["CanonicalJSON"];
+
+var 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, jsescFn) {
+    if (typeof jsescFn != "function") {
+      const { jsesc } = ChromeUtils.import(
+        "resource://gre/modules/third_party/jsesc/jsesc.js"
+      );
+      jsescFn = jsesc;
+    }
+    if (Array.isArray(source)) {
+      const jsonArray = source.map(x => (typeof x === "undefined" ? null : x));
+      return (
+        "[" + jsonArray.map(item => stringify(item, jsescFn)).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 => jsescFn(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, jsescFn) + suffix
+        );
+      }, "{") + "}"
+    );
+  },
+};