VOL-1395: Common shared libraries needed for Python based device adapters.

This is an initial check-in of code from the master branch.  Additional work
is expected on a few items to work with the new go-core and will be covered
by separate JIRAs and commits.

Change-Id: I0856ec6b79b8d3e49082c609eb9c7eedd75b1708
diff --git a/python/adapters/extensions/omci/tasks/file_download_task.py b/python/adapters/extensions/omci/tasks/file_download_task.py
new file mode 100755
index 0000000..63da427
--- /dev/null
+++ b/python/adapters/extensions/omci/tasks/file_download_task.py
@@ -0,0 +1,108 @@
+#
+# Copyright 2017 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+from task import Task
+from twisted.internet.defer import inlineCallbacks, TimeoutError, failure, AlreadyCalledError
+from twisted.internet import reactor
+from voltha.extensions.omci.omci_defs import ReasonCodes
+import requests
+import os
+import time
+
+class FileDownloadTask(Task):
+    name = "Image File Download Task"
+    CHUNK_SIZE = 1024
+    
+    def __init__(self, omci_agent, img_dnld, clock= None): #device_id, url, local_path)
+        super(FileDownloadTask, self).__init__(FileDownloadTask.name, omci_agent, img_dnld.id,
+                                               exclusive=False,
+                                               watchdog_timeout=45)
+        # self.url = url
+        # self.local_path = local_path
+        self._image_download = img_dnld
+        self.reactor = clock if clock is not None else reactor
+        self._local_deferred = None
+        # self._request = None
+        # self._file = None
+        # self.log.debug('{} running'.format(FileDownloadTask.name))
+
+    # def __save_data(self):
+    #     chunk = self._request.iter_content(chunk_size=FileDownloadTask.CHUNK_SIZE)
+    #     if len(chunk) == 0:
+    #         self._file.close()
+    #         self.deferred.callback(self._image_download)
+    #     else:
+    #         self._file.write(chunk)
+    #         self._image_download.downloaded_bytes += len(chunk)
+    #         self.reactor.callLater(0, self.__save_data)        
+
+    @inlineCallbacks
+    def perform_download_data(self):
+        try:
+            r = requests.get(self._image_download.url, stream=True)
+            with open(self._image_download.local_dir + '/' + self._image_download.name, 'wb') as f:
+                for chunk in r.iter_content(chunk_size=FileDownloadTask.CHUNK_SIZE):
+                    self.strobe_watchdog()
+                    if chunk: # filter out keep-alive new chunks
+                        yield f.write(chunk)
+                        self._image_download.file_size += len(chunk)
+                        # yield time.sleep(1)
+            self.deferred.callback(self._image_download)
+        except Exception as e:
+            self.deferred.errback(failure.Failure(e))
+        
+    def start(self):
+        super(FileDownloadTask, self).start()
+        if not os.path.exists(self._image_download.local_dir):
+            os.makedirs(self._image_download.local_dir)
+
+        self.strobe_watchdog()
+        self._image_download.file_size = 0
+        self._local_deferred = self.reactor.callLater(0, self.perform_download_data)
+        # try:
+        #     if not os.path.exists(self._image_download.local_dir):
+        #         os.makedirs(self._image_download.local_dir)
+
+        #     self.strobe_watchdog()
+        #     self._image_download.downloaded_bytes = 0
+        #     self.reactor.callLater(0, self.perform_download_data)
+            
+            # self._request = requests.get(self._image_download.url, stream=True)
+            # with open(self._image_download.local_dir + '/' + self._image_download.name, 'wb') as f:
+            #     for chunk in r.iter_content(chunk_size=FileDownloadTask.CHUNK_SIZE):
+            #         self.strobe_watchdog()
+            #         if chunk: # filter out keep-alive new chunks
+            #             f.write(chunk)
+            #             self._image_download.downloaded_bytes += len(chunk)
+            
+            # self.deferred.callback(self._image_download)
+        # except Exception as e:
+        #     self.deferred.errback(failure.Failure(e))
+            
+    # def stop(self):
+    #     # self.cancel_deferred()
+    #     super(FileDownloadTask, self).stop()
+
+    def cancel_deferred(self):
+        self.log.debug('FileDownloadTask cancel_deferred')
+        super(FileDownloadTask, self).cancel_deferred()
+
+        d, self._local_deferred = self._local_deferred, None
+        try:
+            if d is not None and not d.called:
+                d.cancel()
+        except:
+            pass
+