1 files changed, 51 insertions, 0 deletions
diff --git a/services/settings/SharedUtils.sys.mjs b/services/settings/SharedUtils.sys.mjs
new file mode 100644
index 0000000000..1eeaf0bed9
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+++ b/services/settings/SharedUtils.sys.mjs
@@ -0,0 +1,51 @@
+/* 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/. */
+
+/**
+ * Common logic shared by RemoteSettingsWorker.js (Worker) and the main thread.
+ */
+
+export var SharedUtils = {
+  /**
+   * Check that the specified content matches the expected size and SHA-256 hash.
+   * @param {ArrayBuffer} buffer binary content
+   * @param {Number} size expected file size
+   * @param {String} size expected file SHA-256 as hex string
+   * @returns {boolean}
+   */
+  async checkContentHash(buffer, size, hash) {
+    const bytes = new Uint8Array(buffer);
+    // Has expected size? (saves computing hash)
+    if (bytes.length !== size) {
+      return false;
+    }
+    // Has expected content?
+    const hashBuffer = await crypto.subtle.digest("SHA-256", bytes);
+    const hashBytes = new Uint8Array(hashBuffer);
+    const toHex = b => b.toString(16).padStart(2, "0");
+    const hashStr = Array.from(hashBytes, toHex).join("");
+    return hashStr == hash;
+  },
+
+  /**
+   * Load (from disk) the JSON file distributed with the release for this collection.
+   * @param {String}  bucket
+   * @param {String}  collection
+   */
+  async loadJSONDump(bucket, collection) {
+    // When using the preview bucket, we still want to load the main dump.
+    // But we store it locally in the preview bucket.
+    const jsonBucket = bucket.replace("-preview", "");
+    const fileURI = `resource://app/defaults/settings/${jsonBucket}/${collection}.json`;
+    let response;
+    try {
+      response = await fetch(fileURI);
+    } catch (e) {
+      // Return null if file is missing.
+      return { data: null, timestamp: null };
+    }
+    // Will throw if JSON is invalid.
+    return response.json();
+  },
+};