--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/CSP2/CSP2_env/env-d9b9114564458d9d-741b3de822f2aaca6c6caa4325c4afce/lib/python3.8/multiprocessing/forkserver.py	Tue Mar 18 17:55:14 2025 -0400
@@ -0,0 +1,352 @@
+import errno
+import os
+import selectors
+import signal
+import socket
+import struct
+import sys
+import threading
+import warnings
+
+from . import connection
+from . import process
+from .context import reduction
+from . import resource_tracker
+from . import spawn
+from . import util
+
+__all__ = ['ensure_running', 'get_inherited_fds', 'connect_to_new_process',
+           'set_forkserver_preload']
+
+#
+#
+#
+
+MAXFDS_TO_SEND = 256
+SIGNED_STRUCT = struct.Struct('q')     # large enough for pid_t
+
+#
+# Forkserver class
+#
+
+class ForkServer(object):
+
+    def __init__(self):
+        self._forkserver_address = None
+        self._forkserver_alive_fd = None
+        self._forkserver_pid = None
+        self._inherited_fds = None
+        self._lock = threading.Lock()
+        self._preload_modules = ['__main__']
+
+    def _stop(self):
+        # Method used by unit tests to stop the server
+        with self._lock:
+            self._stop_unlocked()
+
+    def _stop_unlocked(self):
+        if self._forkserver_pid is None:
+            return
+
+        # close the "alive" file descriptor asks the server to stop
+        os.close(self._forkserver_alive_fd)
+        self._forkserver_alive_fd = None
+
+        os.waitpid(self._forkserver_pid, 0)
+        self._forkserver_pid = None
+
+        os.unlink(self._forkserver_address)
+        self._forkserver_address = None
+
+    def set_forkserver_preload(self, modules_names):
+        '''Set list of module names to try to load in forkserver process.'''
+        if not all(type(mod) is str for mod in self._preload_modules):
+            raise TypeError('module_names must be a list of strings')
+        self._preload_modules = modules_names
+
+    def get_inherited_fds(self):
+        '''Return list of fds inherited from parent process.
+
+        This returns None if the current process was not started by fork
+        server.
+        '''
+        return self._inherited_fds
+
+    def connect_to_new_process(self, fds):
+        '''Request forkserver to create a child process.
+
+        Returns a pair of fds (status_r, data_w).  The calling process can read
+        the child process's pid and (eventually) its returncode from status_r.
+        The calling process should write to data_w the pickled preparation and
+        process data.
+        '''
+        self.ensure_running()
+        if len(fds) + 4 >= MAXFDS_TO_SEND:
+            raise ValueError('too many fds')
+        with socket.socket(socket.AF_UNIX) as client:
+            client.connect(self._forkserver_address)
+            parent_r, child_w = os.pipe()
+            child_r, parent_w = os.pipe()
+            allfds = [child_r, child_w, self._forkserver_alive_fd,
+                      resource_tracker.getfd()]
+            allfds += fds
+            try:
+                reduction.sendfds(client, allfds)
+                return parent_r, parent_w
+            except:
+                os.close(parent_r)
+                os.close(parent_w)
+                raise
+            finally:
+                os.close(child_r)
+                os.close(child_w)
+
+    def ensure_running(self):
+        '''Make sure that a fork server is running.
+
+        This can be called from any process.  Note that usually a child
+        process will just reuse the forkserver started by its parent, so
+        ensure_running() will do nothing.
+        '''
+        with self._lock:
+            resource_tracker.ensure_running()
+            if self._forkserver_pid is not None:
+                # forkserver was launched before, is it still running?
+                pid, status = os.waitpid(self._forkserver_pid, os.WNOHANG)
+                if not pid:
+                    # still alive
+                    return
+                # dead, launch it again
+                os.close(self._forkserver_alive_fd)
+                self._forkserver_address = None
+                self._forkserver_alive_fd = None
+                self._forkserver_pid = None
+
+            cmd = ('from multiprocessing.forkserver import main; ' +
+                   'main(%d, %d, %r, **%r)')
+
+            if self._preload_modules:
+                desired_keys = {'main_path', 'sys_path'}
+                data = spawn.get_preparation_data('ignore')
+                data = {x: y for x, y in data.items() if x in desired_keys}
+            else:
+                data = {}
+
+            with socket.socket(socket.AF_UNIX) as listener:
+                address = connection.arbitrary_address('AF_UNIX')
+                listener.bind(address)
+                os.chmod(address, 0o600)
+                listener.listen()
+
+                # all client processes own the write end of the "alive" pipe;
+                # when they all terminate the read end becomes ready.
+                alive_r, alive_w = os.pipe()
+                try:
+                    fds_to_pass = [listener.fileno(), alive_r]
+                    cmd %= (listener.fileno(), alive_r, self._preload_modules,
+                            data)
+                    exe = spawn.get_executable()
+                    args = [exe] + util._args_from_interpreter_flags()
+                    args += ['-c', cmd]
+                    pid = util.spawnv_passfds(exe, args, fds_to_pass)
+                except:
+                    os.close(alive_w)
+                    raise
+                finally:
+                    os.close(alive_r)
+                self._forkserver_address = address
+                self._forkserver_alive_fd = alive_w
+                self._forkserver_pid = pid
+
+#
+#
+#
+
+def main(listener_fd, alive_r, preload, main_path=None, sys_path=None):
+    '''Run forkserver.'''
+    if preload:
+        if '__main__' in preload and main_path is not None:
+            process.current_process()._inheriting = True
+            try:
+                spawn.import_main_path(main_path)
+            finally:
+                del process.current_process()._inheriting
+        for modname in preload:
+            try:
+                __import__(modname)
+            except ImportError:
+                pass
+
+    util._close_stdin()
+
+    sig_r, sig_w = os.pipe()
+    os.set_blocking(sig_r, False)
+    os.set_blocking(sig_w, False)
+
+    def sigchld_handler(*_unused):
+        # Dummy signal handler, doesn't do anything
+        pass
+
+    handlers = {
+        # unblocking SIGCHLD allows the wakeup fd to notify our event loop
+        signal.SIGCHLD: sigchld_handler,
+        # protect the process from ^C
+        signal.SIGINT: signal.SIG_IGN,
+        }
+    old_handlers = {sig: signal.signal(sig, val)
+                    for (sig, val) in handlers.items()}
+
+    # calling os.write() in the Python signal handler is racy
+    signal.set_wakeup_fd(sig_w)
+
+    # map child pids to client fds
+    pid_to_fd = {}
+
+    with socket.socket(socket.AF_UNIX, fileno=listener_fd) as listener, \
+         selectors.DefaultSelector() as selector:
+        _forkserver._forkserver_address = listener.getsockname()
+
+        selector.register(listener, selectors.EVENT_READ)
+        selector.register(alive_r, selectors.EVENT_READ)
+        selector.register(sig_r, selectors.EVENT_READ)
+
+        while True:
+            try:
+                while True:
+                    rfds = [key.fileobj for (key, events) in selector.select()]
+                    if rfds:
+                        break
+
+                if alive_r in rfds:
+                    # EOF because no more client processes left
+                    assert os.read(alive_r, 1) == b'', "Not at EOF?"
+                    raise SystemExit
+
+                if sig_r in rfds:
+                    # Got SIGCHLD
+                    os.read(sig_r, 65536)  # exhaust
+                    while True:
+                        # Scan for child processes
+                        try:
+                            pid, sts = os.waitpid(-1, os.WNOHANG)
+                        except ChildProcessError:
+                            break
+                        if pid == 0:
+                            break
+                        child_w = pid_to_fd.pop(pid, None)
+                        if child_w is not None:
+                            if os.WIFSIGNALED(sts):
+                                returncode = -os.WTERMSIG(sts)
+                            else:
+                                if not os.WIFEXITED(sts):
+                                    raise AssertionError(
+                                        "Child {0:n} status is {1:n}".format(
+                                            pid,sts))
+                                returncode = os.WEXITSTATUS(sts)
+                            # Send exit code to client process
+                            try:
+                                write_signed(child_w, returncode)
+                            except BrokenPipeError:
+                                # client vanished
+                                pass
+                            os.close(child_w)
+                        else:
+                            # This shouldn't happen really
+                            warnings.warn('forkserver: waitpid returned '
+                                          'unexpected pid %d' % pid)
+
+                if listener in rfds:
+                    # Incoming fork request
+                    with listener.accept()[0] as s:
+                        # Receive fds from client
+                        fds = reduction.recvfds(s, MAXFDS_TO_SEND + 1)
+                        if len(fds) > MAXFDS_TO_SEND:
+                            raise RuntimeError(
+                                "Too many ({0:n}) fds to send".format(
+                                    len(fds)))
+                        child_r, child_w, *fds = fds
+                        s.close()
+                        pid = os.fork()
+                        if pid == 0:
+                            # Child
+                            code = 1
+                            try:
+                                listener.close()
+                                selector.close()
+                                unused_fds = [alive_r, child_w, sig_r, sig_w]
+                                unused_fds.extend(pid_to_fd.values())
+                                code = _serve_one(child_r, fds,
+                                                  unused_fds,
+                                                  old_handlers)
+                            except Exception:
+                                sys.excepthook(*sys.exc_info())
+                                sys.stderr.flush()
+                            finally:
+                                os._exit(code)
+                        else:
+                            # Send pid to client process
+                            try:
+                                write_signed(child_w, pid)
+                            except BrokenPipeError:
+                                # client vanished
+                                pass
+                            pid_to_fd[pid] = child_w
+                            os.close(child_r)
+                            for fd in fds:
+                                os.close(fd)
+
+            except OSError as e:
+                if e.errno != errno.ECONNABORTED:
+                    raise
+
+
+def _serve_one(child_r, fds, unused_fds, handlers):
+    # close unnecessary stuff and reset signal handlers
+    signal.set_wakeup_fd(-1)
+    for sig, val in handlers.items():
+        signal.signal(sig, val)
+    for fd in unused_fds:
+        os.close(fd)
+
+    (_forkserver._forkserver_alive_fd,
+     resource_tracker._resource_tracker._fd,
+     *_forkserver._inherited_fds) = fds
+
+    # Run process object received over pipe
+    parent_sentinel = os.dup(child_r)
+    code = spawn._main(child_r, parent_sentinel)
+
+    return code
+
+
+#
+# Read and write signed numbers
+#
+
+def read_signed(fd):
+    data = b''
+    length = SIGNED_STRUCT.size
+    while len(data) < length:
+        s = os.read(fd, length - len(data))
+        if not s:
+            raise EOFError('unexpected EOF')
+        data += s
+    return SIGNED_STRUCT.unpack(data)[0]
+
+def write_signed(fd, n):
+    msg = SIGNED_STRUCT.pack(n)
+    while msg:
+        nbytes = os.write(fd, msg)
+        if nbytes == 0:
+            raise RuntimeError('should not get here')
+        msg = msg[nbytes:]
+
+#
+#
+#
+
+_forkserver = ForkServer()
+ensure_running = _forkserver.ensure_running
+get_inherited_fds = _forkserver.get_inherited_fds
+connect_to_new_process = _forkserver.connect_to_new_process
+set_forkserver_preload = _forkserver.set_forkserver_preload