Fix progressive task output when it contains entity-escaped characters

If an update task's output contains a single quote for example (') then
this will be escaped to an HTML entity before it gets sent as a
response. However, that means that the length of the data in the response
will be greater than the length of the original data, resulting in
characters getting missed out when we read the next chunk - so we
can't use the escaped length to set the next position to read from. The
easiest thing to do is have the Django view send us the actual position
we're at and then we don't have to try to calculate it on the JS side.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

layerindex/views.py

@@ -1537,16 +1537,18 @@ def task_log_view(request, task_id):
         raise Http404
 
     result = AsyncResult(task_id)
-    start = request.GET.get('start', 0)
+    start = int(request.GET.get('start', 0))
     try:
         f = open(os.path.join(settings.TASK_LOG_DIR, 'task_%s.log' % task_id), 'rb')
     except FileNotFoundError:
         raise Http404
     try:
-        f.seek(int(start))
+        f.seek(start)
         # We need to escape this or else things that look like tags in the output
         # will be interpreted as such by the browser
-        data = escape(f.read())
+        datastr = f.read()
+        origlen = len(datastr)
+        data = escape(datastr)
         response = HttpResponse(data)
         if result.ready():
             response['Task-Done'] = '1'
@@ -1562,6 +1564,7 @@ def task_log_view(request, task_id):
             response['Task-Done'] = '0'
             preader = utils.ProgressReader(settings.TASK_LOG_DIR, task_id)
             response['Task-Progress'] = preader.read()
+        response['Task-Log-Position'] = start + origlen
     finally:
         f.close()
     return response

templates/layerindex/task.html

@@ -80,7 +80,7 @@
                 if(scrolling) {
                     task_log.animate({ scrollTop: task_log.prop('scrollHeight') }, "slow");
                 }
-                posn += data.length
+                posn = xhr.getResponseHeader('Task-Log-Position');
                 done = xhr.getResponseHeader('Task-Done')
                 duration = xhr.getResponseHeader('Task-Duration')
                 progress = parseInt(xhr.getResponseHeader('Task-Progress')) || 0;