From 64b2dab795e171e2ea0345732e96048cfb605466 Mon Sep 17 00:00:00 2001
From: Helmut Grohne <helmut@subdivi.de>
Date: Sat, 26 Oct 2024 20:22:36 +0200
Subject: add a method IDMapping.identity for convenience

---
 examples/cgroup.py          | 4 ++--
 examples/withallsubuids.py  | 4 ++--
 linuxnamespaces/__init__.py | 5 +++++
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/examples/cgroup.py b/examples/cgroup.py
index 219dc62..34bf01b 100755
--- a/examples/cgroup.py
+++ b/examples/cgroup.py
@@ -56,8 +56,8 @@ def main() -> None:
         | linuxnamespaces.CloneFlags.NEWCGROUP
     )
     linuxnamespaces.unshare_user_idmap(
-        [linuxnamespaces.IDMapping(os.getuid(), os.getuid(), 1)],
-        [linuxnamespaces.IDMapping(os.getgid(), os.getgid(), 1)],
+        [linuxnamespaces.IDMapping.identity(os.getuid())],
+        [linuxnamespaces.IDMapping.identity(os.getgid())],
         namespaces,
     )
     linuxnamespaces.populate_sys("/", "/", namespaces, mycgroup)
diff --git a/examples/withallsubuids.py b/examples/withallsubuids.py
index 3bed3bc..2a0c9d5 100755
--- a/examples/withallsubuids.py
+++ b/examples/withallsubuids.py
@@ -19,7 +19,7 @@ import linuxnamespaces
 def main() -> None:
     # Construct an identity mapping of all available user/group ids
     uidmap = [
-        linuxnamespaces.IDMapping(os.getuid(), os.getuid(), 1),
+        linuxnamespaces.IDMapping.identity(os.getuid()),
         *(
             linuxnamespaces.IDMapping(start, start, count)
             for start, count
@@ -27,7 +27,7 @@ def main() -> None:
         ),
     ]
     gidmap = [
-        linuxnamespaces.IDMapping(os.getgid(), os.getgid(), 1),
+        linuxnamespaces.IDMapping.identity(os.getgid()),
         *(
             linuxnamespaces.IDMapping(start, start, count)
             for start, count
diff --git a/linuxnamespaces/__init__.py b/linuxnamespaces/__init__.py
index 8c1def3..a2c7985 100644
--- a/linuxnamespaces/__init__.py
+++ b/linuxnamespaces/__init__.py
@@ -59,6 +59,11 @@ class IDMapping:
         if self.innerstart + self.count >= 1 << 64:
             raise ValueError("innerstart + count exceed 64bits")
 
+    @classmethod
+    def identity(cls, idn: int, count: int = 1) -> typing.Self:
+        """Construct an identity mapping for the given identifier."""
+        return cls(idn, idn, count)
+
 
 class IDAllocation:
     """This represents a subset of IDs (user or group). It can be used to
-- 
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