Use shared memory for IPC with toc editor

src/calibre/gui2/actions/toc_edit.py

@@ -6,6 +6,7 @@ __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 import os
+from itertools import count
 from collections import OrderedDict
 from qt.core import (
     QCheckBox, QDialog, QDialogButtonBox, QGridLayout, QIcon, QLabel, QTimer
@@ -100,6 +101,7 @@ class ToCEditAction(InterfaceAction):
             self.do_edit(book_id_map)
 
     def genesis(self):
+        self.shm_count = count()
         self.qaction.triggered.connect(self.edit_books)
         self.jobs = []
 
@@ -146,34 +148,51 @@ class ToCEditAction(InterfaceAction):
                 self.do_one(book_id, fmt)
 
     def do_one(self, book_id, fmt):
+        import struct, json, atexit
+        from calibre.utils.shm import SharedMemory
         db = self.gui.current_db
         path = db.format(book_id, fmt, index_is_id=True, as_path=True)
         title = db.title(book_id, index_is_id=True) + ' [%s]'%fmt
-        data = {'path': path, 'title': title}
+        job = {'path': path, 'title': title}
-        self.gui.job_manager.launch_gui_app('toc-dialog', kwargs=data)
+        data = json.dumps(job).encode('utf-8')
-        job = data.copy()
+        header = struct.pack('>II', 0, 0)
-        job.update({'book_id': book_id, 'fmt': fmt, 'library_id': db.new_api.library_id, 'started': False, 'start_time': monotonic()})
+        shm = SharedMemory(prefix=f'c{os.getpid()}-{next(self.shm_count)}-', size=len(data) + len(header) + SharedMemory.num_bytes_for_size)
+        shm.write(header)
+        shm.write_data_with_size(data)
+        shm.flush()
+        atexit.register(shm.close)
+        self.gui.job_manager.launch_gui_app('toc-dialog', kwargs={'shm_name': shm.name})
+        job.update({
+            'book_id': book_id, 'fmt': fmt, 'library_id': db.new_api.library_id, 'shm': shm, 'started': False, 'start_time': monotonic()})
         self.jobs.append(job)
         self.check_for_completions()
 
     def check_for_completions(self):
-        from calibre.utils.filenames import retry_on_fail
+        import struct
+
+        def remove_job(job):
+            job['shm'].close()
+            self.jobs.remove(job)
+
         for job in tuple(self.jobs):
             path = job['path']
-            started_path = path + '.started'
+            shm = job['shm']
-            result_path = path + '.result'
+            shm.seek(0)
-            if job['started'] and os.path.exists(result_path):
+            state, ok = struct.unpack('>II', shm.read(struct.calcsize('>II')))
-                self.jobs.remove(job)
+            if state == 0:
-                ret = -1
+                # not started
-
+                if monotonic() - job['start_time'] > 120:
-                def read(result_path):
+                    remove_job(job)
-                    nonlocal ret
+                    error_dialog(self.gui, _('Failed to start editor'), _(
-                    with open(result_path) as f:
+                        'Could not edit: {}. The Table of Contents editor did not start in two minutes').format(job['title']), show=True)
-                        ret = int(f.read().strip())
+            elif state == 1:
-
+                # running
-                retry_on_fail(read, result_path)
+                pass
-                retry_on_fail(os.remove, result_path)
+            elif state == 2:
-                if ret == 0:
+                # finished
+                job['shm'].already_unlinked = True
+                remove_job(job)
+                if ok == 1:
                     db = self.gui.current_db
                     if db.new_api.library_id != job['library_id']:
                         error_dialog(self.gui, _('Library changed'), _(
@@ -181,16 +200,6 @@ class ToCEditAction(InterfaceAction):
                             ' the calibre library has changed.').format(job['title']), show=True)
                     else:
                         db.new_api.add_format(job['book_id'], job['fmt'], path, run_hooks=False)
-                retry_on_fail(os.remove, path)
-            elif not job['started']:
-                if monotonic() - job['start_time'] > 120:
-                    self.jobs.remove(job)
-                    error_dialog(self.gui, _('Failed to start editor'), _(
-                        'Could not edit: {}. The Table of Contents editor did not start in two minutes').format(job['title']), show=True)
-                    continue
-                if os.path.exists(started_path):
-                    job['started'] = True
-                    retry_on_fail(os.remove, started_path)
         if self.jobs:
             QTimer.singleShot(100, self.check_for_completions)
 

src/calibre/gui2/toc/main.py

@@ -1145,7 +1145,11 @@ class TOCEditor(QDialog):  # {{{
 # }}}
 
 
-def main(path=None, title=None):
+def main(shm_name=None):
+    import json
+    import struct
+    from calibre.utils.shm import SharedMemory
+
     # Ensure we can continue to function if GUI is closed
     os.environ.pop('CALIBRE_WORKER_TEMP_DIR', None)
     reset_base_dir()
@@ -1154,19 +1158,28 @@ def main(path=None, title=None):
         # prevents them from being grouped with viewer/editor process when
         # launched from within calibre, as both use calibre-parallel.exe
         set_app_uid(TOC_DIALOG_APP_UID)
+    with SharedMemory(name=shm_name) as shm:
+        pos = struct.calcsize('>II')
+        state, ok = struct.unpack('>II', shm.read(pos))
+        data = json.loads(shm.read_data_with_size())
+        title = data['title']
+        path = data['path']
+        s = struct.pack('>I', 1)
+        shm.seek(0), shm.write(s), shm.flush()
+
+        override = 'calibre-gui' if islinux else None
+        app = Application([], override_program_name=override)
+        d = TOCEditor(path, title=title, write_result_to=path + '.result')
+        d.start()
+        ok = 0
+        if d.exec() == QDialog.DialogCode.Accepted:
+            ok = 1
+        s = struct.pack('>II', 2, ok)
+        shm.seek(0), shm.write(s), shm.flush()
 
-    with open(path + '.started', 'w'):
-        pass
-    override = 'calibre-gui' if islinux else None
-    app = Application([], override_program_name=override)
-    d = TOCEditor(path, title=title, write_result_to=path + '.result')
-    d.start()
-    ret = 1
-    if d.exec() == QDialog.DialogCode.Accepted:
-        ret = 0
     del d
     del app
-    raise SystemExit(ret)
+    raise SystemExit(0 if ok else 1)
 
 
 if __name__ == '__main__':