1 files changed, 100 insertions, 0 deletions
diff --git a/tools/code-coverage/tests/xpcshell/head.js b/tools/code-coverage/tests/xpcshell/head.js
new file mode 100644
index 0000000000..3642c5794c
--- /dev/null
+++ b/tools/code-coverage/tests/xpcshell/head.js
@@ -0,0 +1,100 @@
+/* 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 { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+function getFiles() {
+  // This is the directory where gcov is emitting the gcda files.
+  const jsCoveragePath = Services.env.get("JS_CODE_COVERAGE_OUTPUT_DIR");
+
+  const jsCoverageDir = Cc["@mozilla.org/file/local;1"].createInstance(
+    Ci.nsIFile
+  );
+  jsCoverageDir.initWithPath(jsCoveragePath);
+
+  let files = [];
+
+  let entries = jsCoverageDir.directoryEntries;
+  while (entries.hasMoreElements()) {
+    files.push(entries.nextFile);
+  }
+
+  return files;
+}
+
+function diffFiles(files_after, files_before) {
+  let files_before_set = new Set(files_before.map(file => file.leafName));
+  return files_after.filter(file => !files_before_set.has(file.leafName));
+}
+
+const BASENAME_RE = new RegExp("([^/\\\\]+)$");
+
+function parseRecords(files) {
+  let records = new Map();
+
+  for (let file of files) {
+    const lines = Cu.readUTF8File(file).split("\n");
+    let currentSF = null;
+
+    for (let line of lines) {
+      let [recordType, ...recordContent] = line.split(":");
+      recordContent = recordContent.join(":");
+
+      switch (recordType) {
+        case "FNDA": {
+          if (currentSF == null) {
+            throw new Error("SF missing");
+          }
+
+          let [hits, name] = recordContent.split(",");
+          currentSF.push({
+            type: "FNDA",
+            hits,
+            name,
+          });
+          break;
+        }
+
+        case "FN": {
+          if (currentSF == null) {
+            throw new Error("SF missing");
+          }
+
+          let name = recordContent.split(",")[1];
+          currentSF.push({
+            type: "FN",
+            name,
+          });
+          break;
+        }
+
+        case "SF": {
+          if (
+            recordContent.startsWith("resource:") ||
+            recordContent.startsWith("chrome:")
+          ) {
+            recordContent = recordContent.split("/").at(-1);
+          } else {
+            if (AppConstants.platform == "win") {
+              recordContent = recordContent.replace(/\//g, "\\");
+            }
+            const match = BASENAME_RE.exec(recordContent);
+            if (match.length) {
+              recordContent = match[0];
+            }
+          }
+
+          currentSF = [];
+
+          records.set(recordContent, currentSF);
+          break;
+        }
+      }
+    }
+  }
+
+  return records;
+}