swarming: add support for cipd on the server side

appengine/swarming/cipd.py

Index: appengine/swarming/cipd.py
diff --git a/appengine/swarming/cipd.py b/appengine/swarming/cipd.py
new file mode 100644
index 0000000000000000000000000000000000000000..3f33067ccbffbfa03d9f21b4ed9ef90de19e9ccf
--- /dev/null
+++ b/appengine/swarming/cipd.py
@@ -0,0 +1,43 @@
+# Copyright 2016 The LUCI Authors. All rights reserved.
+# Use of this source code is governed by the Apache v2.0 license that can be
+# found in the LICENSE file.
+
+"""CIPD-specific code is concentrated here."""
+
+import re
+
+# Regular expressions below are copied from
+# https://chromium.googlesource.com/infra/infra/+/468bb43/appengine/chrome_infra_packages/cipd/impl.py
+# https://chromium.googlesource.com/infra/infra/+/468bb43/appengine/chrome_infra_packages/cas/impl.py
+
+PACKAGE_NAME_RE = re.compile(r'^([a-z0-9_\-]+/)*[a-z0-9_\-]+$')
+INSTANCE_ID_RE = re.compile(r'^[0-9a-f]{40}$')
+TAG_KEY_RE = re.compile(r'^[a-z0-9_\-]$')
+REF_RE = re.compile(r'^[a-z0-9_\-]{1,100}$')
+TAG_MAX_LEN = 400
+
+
+def is_valid_package_name(package_name):
+  """Returns True if |package_name| is a valid CIPD package name."""
+  return bool(PACKAGE_NAME_RE.match(package_name))
+
+
+def is_valid_version(version):
+  """Returns True if |version| is a valid CIPD package version."""
+  return bool(
+      INSTANCE_ID_RE.match(version) or
+      is_valid_tag(version) or
+      REF_RE.match(version)
+  )
+
+def is_valid_tag(tag):
+  """True if string looks like a valid package instance tag."""
+  if not tag or ':' not in tag or len(tag) > TAG_MAX_LEN:
+    return False
+  # Care only about the key. Value can be anything (including empty string).
+  return bool(TAG_KEY_RE.match(tag.split(':', 1)[0]))
+
+
+def is_pinned_version(version):
+  """Returns True if |version| is pinned."""
+  return bool(INSTANCE_ID_RE.match(version) or TAG_KEY_RE.match(version))