Get piping working on windows as well

src/calibre/utils/ipc/launch.py

@@ -187,9 +187,19 @@ class Worker:
             args['stderr'] = subprocess.STDOUT
 
         args['close_fds'] = True
-        if pass_fds:
-            args['pass_fds'] = pass_fds
-        self.child = subprocess.Popen(cmd, **args)
+        try:
+            if pass_fds:
+                if iswindows:
+                    for fd in pass_fds:
+                        os.set_handle_inheritable(fd, True)
+                    args['startupinfo'] = subprocess.STARTUPINFO(lpAttributeList={'handle_list':pass_fds})
+                else:
+                    args['pass_fds'] = pass_fds
+            self.child = subprocess.Popen(cmd, **args)
+        finally:
+            if iswindows and pass_fds:
+                for fd in pass_fds:
+                    os.set_handle_inheritable(fd, False)
         if 'stdin' in args:
             self.child.stdin.close()
 

src/calibre/utils/ipc/pool.py

@@ -387,7 +387,10 @@ def worker_main(conn):
 
 
 def run_main(client_fd, func):
-    from multiprocessing.connection import Connection
+    if iswindows:
+        from multiprocessing.connection import PipeConnection as Connection
+    else:
+        from multiprocessing.connection import Connection
     with Connection(client_fd) as conn:
         raise SystemExit(func(conn))
 

src/calibre/utils/ipc/simple_worker.py

@@ -146,19 +146,30 @@ def start_pipe_worker(command, env=None, priority='normal', **process_args):
     w = Worker(env or {})
     args = {'stdout':subprocess.PIPE, 'stdin':subprocess.PIPE, 'env':w.env, 'close_fds': True}
     args.update(process_args)
-    if iswindows:
-        priority = {
-                'high'   : subprocess.HIGH_PRIORITY_CLASS,
-                'normal' : subprocess.NORMAL_PRIORITY_CLASS,
-                'low'    : subprocess.IDLE_PRIORITY_CLASS}[priority]
-        args['creationflags'] = subprocess.CREATE_NO_WINDOW|priority
-    else:
-        niceness = {'normal' : 0, 'low'    : 10, 'high'   : 20}[priority]
-        args['env']['CALIBRE_WORKER_NICENESS'] = str(niceness)
+    pass_fds = None
+    try:
+        if iswindows:
+            priority = {
+                    'high'   : subprocess.HIGH_PRIORITY_CLASS,
+                    'normal' : subprocess.NORMAL_PRIORITY_CLASS,
+                    'low'    : subprocess.IDLE_PRIORITY_CLASS}[priority]
+            args['creationflags'] = subprocess.CREATE_NO_WINDOW|priority
+            pass_fds = args.pop('pass_fds', None)
+            if pass_fds:
+                for fd in pass_fds:
+                    os.set_handle_inheritable(fd, True)
+                args['startupinfo'] = subprocess.STARTUPINFO(lpAttributeList={'handle_list':pass_fds})
+        else:
+            niceness = {'normal' : 0, 'low'    : 10, 'high'   : 20}[priority]
+            args['env']['CALIBRE_WORKER_NICENESS'] = str(niceness)
 
-    exe = w.executable
-    cmd = [exe] if isinstance(exe, string_or_bytes) else exe
-    p = subprocess.Popen(cmd + ['--pipe-worker', command], **args)
+        exe = w.executable
+        cmd = [exe] if isinstance(exe, string_or_bytes) else exe
+        p = subprocess.Popen(cmd + ['--pipe-worker', command], **args)
+    finally:
+        if iswindows and pass_fds:
+            for fd in pass_fds:
+                os.set_handle_inheritable(fd, False)
     return p
 
 

src/calibre/utils/ipc/worker.py

@@ -6,17 +6,23 @@ __license__   = 'GPL v3'
 __copyright__ = '2009, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
-import os, sys, importlib
-from multiprocessing.connection import Connection
+import importlib
+import os
+import sys
 from threading import Thread
 from zipimport import ZipImportError
 
 from calibre import prints
-from calibre.constants import iswindows, ismacos
+from calibre.constants import ismacos, iswindows
 from calibre.utils.ipc import eintr_retry_call
 from calibre.utils.serialize import pickle_dumps
-from polyglot.queue import Queue
 from polyglot.binary import from_hex_unicode
+from polyglot.queue import Queue
+
+if iswindows:
+    from multiprocessing.connection import PipeConnection as Connection
+else:
+    from multiprocessing.connection import Connection
 
 PARALLEL_FUNCS = {
     'lrfviewer'    :