* morituri/common/task.py (added):

Add a task abstraction.

ChangeLog

@@ -0,0 +1,5 @@
+2009-02-28  Thomas Vander Stichele  <thomas at apestaart dot org>
+
+	* morituri/common/task.py (added):
+	  Add a task abstraction.
+

morituri/common/task.py

@@ -0,0 +1,149 @@
+# -*- Mode: Python; test-case-name: morituri.test.test_common_task -*-
+# vi:si:et:sw=4:sts=4:ts=4
+
+# Morituri - for those about to RIP
+
+# Copyright (C) 2009 Thomas Vander Stichele
+
+# This file is part of morituri.
+# 
+# morituri is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+# 
+# morituri is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with morituri.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+import zlib
+
+import gobject
+import gst
+
+class Task(object):
+    description = 'I am doing something.'
+
+    progress = 0.0
+    increment = 0.01
+    running = False
+
+    _listeners = None
+
+    def debug(self, *args, **kwargs):
+        print args, kwargs
+        pass
+
+    def start(self):
+        self.running = True
+        self._notifyListeners('start')
+
+    def stop(self):
+        self.debug('stopping')
+        self.running = False
+        self._notifyListeners('stop')
+
+    def setProgress(self, value):
+        if value - self.progress > self.increment or value == 1.0:
+            self.progress = value
+            self._notifyListeners('progress', value)
+            self.debug('notifying progress', value)
+        
+    def addListener(self, listener):
+        if not self._listeners:
+            self._listeners = []
+        self._listeners.append(listener)
+
+    def _notifyListeners(self, methodName, *args, **kwargs):
+            if self._listeners:
+                for l in self._listeners:
+                    getattr(l, methodName)(*args, **kwargs)
+
+class CRCTask(Task):
+    # this object needs a main loop to stop
+    description = 'Calculating CRC checksum...'
+
+    def __init__(self, path, frameStart=0, frameEnd=-1):
+        if not os.path.exists(path):
+            raise IndexError, '%s does not exist' % path
+
+        self._path = path
+        self._frameStart = frameStart
+        self._frameEnd = frameEnd
+        self._crc = 0
+        self._bytes = 0
+        self._first = None
+        self._last = None
+
+        self.crc = None # result
+
+    def start(self):
+        Task.start(self)
+        self._pipeline = gst.parse_launch('''
+            filesrc location="%s" !
+            decodebin ! audio/x-raw-int !
+            appsink name=sink sync=False emit-signals=True''' % self._path)
+        self.debug('pausing')
+        self._pipeline.set_state(gst.STATE_PAUSED)
+        self._pipeline.get_state()
+        self.debug('paused')
+
+        self.debug('query duration')
+        sink = self._pipeline.get_by_name('sink')
+
+        if self._frameEnd == -1:
+            (self._frameEnd, _) = sink.query_duration(gst.FORMAT_DEFAULT)
+
+        self.debug('event')
+
+
+        # the segment end only is respected since -good 0.10.14.1
+        event = gst.event_new_seek(1.0, gst.FORMAT_DEFAULT,
+            gst.SEEK_FLAG_FLUSH,
+            gst.SEEK_TYPE_SET, self._frameStart,
+            gst.SEEK_TYPE_SET, self._frameEnd)
+        result = sink.send_event(event)
+        self.debug('event sent')
+        self.debug(result)
+        sink.connect('new-buffer', self._new_buffer_cb)
+        sink.connect('eos', self._eos_cb)
+
+        self.debug('setting to play')
+        self._pipeline.set_state(gst.STATE_PLAYING)
+        self.debug('set to play')
+
+    def _new_buffer_cb(self, sink):
+        buffer = sink.emit('pull-buffer')
+        if self._first is None:
+            self._first = buffer.offset
+            self.debug('first sample is', self._first)
+        self._last = buffer
+
+        assert len(buffer) % 4 == 0, "buffer is not a multiple of 4 bytes"
+        self._bytes += len(buffer)
+        
+        # update progress
+        frame = self._first + self._bytes / 4
+        progress = float((frame - self._frameStart)) / float((self._frameEnd - self._frameStart))
+        self.setProgress(progress)
+
+        self._crc = zlib.crc32(buffer, self._crc)
+
+    def _eos_cb(self, sink):
+        self.debug('setting state to NULL')
+        gobject.timeout_add(0L, self.stop)
+
+    def stop(self):
+        self._pipeline.set_state(gst.STATE_NULL)
+        self.debug('stopping')
+        self._crc = self._crc % 2 ** 32
+        self.debug("last sample:", self._last.offset + len(self._last) / 4 - 1)
+        self.debug("CRC: %08X" % self._crc)
+        self.debug("bytes: %d" % self._bytes)
+        self.crc = self._crc
+        Task.stop(self)