second commit

env/lib/python3.11/site-packages/shellingham/posix/proc.py

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+import io
+import os
+import re
+import sys
+
+from ._core import Process
+
+# FreeBSD: https://www.freebsd.org/cgi/man.cgi?query=procfs
+# NetBSD: https://man.netbsd.org/NetBSD-9.3-STABLE/mount_procfs.8
+# DragonFlyBSD: https://www.dragonflybsd.org/cgi/web-man?command=procfs
+BSD_STAT_PPID = 2
+
+# See https://docs.kernel.org/filesystems/proc.html
+LINUX_STAT_PPID = 3
+
+STAT_PATTERN = re.compile(r"\(.+\)|\S+")
+
+
+def detect_proc():
+    """Detect /proc filesystem style.
+
+    This checks the /proc/{pid} directory for possible formats. Returns one of
+    the following as str:
+
+    * `stat`: Linux-style, i.e. ``/proc/{pid}/stat``.
+    * `status`: BSD-style, i.e. ``/proc/{pid}/status``.
+    """
+    pid = os.getpid()
+    for name in ("stat", "status"):
+        if os.path.exists(os.path.join("/proc", str(pid), name)):
+            return name
+    raise ProcFormatError("unsupported proc format")
+
+
+def _use_bsd_stat_format():
+    try:
+        return os.uname().sysname.lower() in ("freebsd", "netbsd", "dragonfly")
+    except Exception:
+        return False
+
+
+def _get_ppid(pid, name):
+    path = os.path.join("/proc", str(pid), name)
+    with io.open(path, encoding="ascii", errors="replace") as f:
+        parts = STAT_PATTERN.findall(f.read())
+    # We only care about TTY and PPID -- both are numbers.
+    if _use_bsd_stat_format():
+        return parts[BSD_STAT_PPID]
+    return parts[LINUX_STAT_PPID]
+
+
+def _get_cmdline(pid):
+    path = os.path.join("/proc", str(pid), "cmdline")
+    encoding = sys.getfilesystemencoding() or "utf-8"
+    with io.open(path, encoding=encoding, errors="replace") as f:
+        # XXX: Command line arguments can be arbitrary byte sequences, not
+        # necessarily decodable. For Shellingham's purpose, however, we don't
+        # care. (pypa/pipenv#2820)
+        # cmdline appends an extra NULL at the end, hence the [:-1].
+        return tuple(f.read().split("\0")[:-1])
+
+
+class ProcFormatError(EnvironmentError):
+    pass
+
+
+def iter_process_parents(pid, max_depth=10):
+    """Try to look up the process tree via the /proc interface."""
+    stat_name = detect_proc()
+
+    # Inner generator function so we correctly throw an error eagerly if proc
+    # is not supported, rather than on the first call to the iterator. This
+    # allows the call site detects the correct implementation.
+    def _iter_process_parents(pid, max_depth):
+        for _ in range(max_depth):
+            ppid = _get_ppid(pid, stat_name)
+            args = _get_cmdline(pid)
+            yield Process(args=args, pid=pid, ppid=ppid)
+            if ppid == "0":
+                break
+            pid = ppid
+
+    return _iter_process_parents(pid, max_depth)