1 files changed, 58 insertions, 0 deletions
diff --git a/taskcluster/taskgraph/util/hash.py b/taskcluster/taskgraph/util/hash.py
new file mode 100644
index 0000000000..04b946be71
--- /dev/null
+++ b/taskcluster/taskgraph/util/hash.py
@@ -0,0 +1,58 @@
+# 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/.
+
+from __future__ import absolute_import, print_function, unicode_literals
+from mozbuild.util import memoize
+import mozpack.path as mozpath
+from mozversioncontrol import get_repository_object
+import hashlib
+import io
+import six
+
+
+@memoize
+def hash_path(path):
+    """Hash a single file.
+
+    Returns the SHA-256 hash in hex form.
+    """
+    with io.open(path, mode="rb") as fh:
+        return hashlib.sha256(fh.read()).hexdigest()
+
+
+@memoize
+def get_file_finder(base_path):
+    return get_repository_object(base_path).get_tracked_files_finder()
+
+
+def hash_paths(base_path, patterns):
+    """
+    Give a list of path patterns, return a digest of the contents of all
+    the corresponding files, similarly to git tree objects or mercurial
+    manifests.
+
+    Each file is hashed. The list of all hashes and file paths is then
+    itself hashed to produce the result.
+    """
+    finder = get_file_finder(base_path)
+    h = hashlib.sha256()
+    files = {}
+    for pattern in patterns:
+        found = list(finder.find(pattern))
+        if found:
+            files.update(found)
+        else:
+            raise Exception("%s did not match anything" % pattern)
+    for path in sorted(files.keys()):
+        if path.endswith((".pyc", ".pyd", ".pyo")):
+            continue
+        h.update(
+            six.ensure_binary(
+                "{} {}\n".format(
+                    hash_path(mozpath.abspath(mozpath.join(base_path, path))),
+                    mozpath.normsep(path),
+                )
+            )
+        )
+    return h.hexdigest()