make use of range requests if available in werkzeug (#2031)

* make use of range requests if available in werkzeug

* different logic for testing werkzeug functionality

CHANGES

@@ -18,6 +18,7 @@ Version 0.12
 - Correctly invoke response handlers for both regular request dispatching as
   well as error handlers.
 - Disable logger propagation by default for the app logger.
+- Add support for range requests in ``send_file``.
 
 Version 0.11.2
 --------------

flask/helpers.py

@@ -25,8 +25,9 @@ try:
 except ImportError:
     from urlparse import quote as url_quote
 
-from werkzeug.datastructures import Headers
-from werkzeug.exceptions import BadRequest, NotFound
+from werkzeug.datastructures import Headers, Range
+from werkzeug.exceptions import BadRequest, NotFound, \
+    RequestedRangeNotSatisfiable
 
 # this was moved in 0.7
 try:
@@ -446,6 +447,10 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
     ETags will also be attached automatically if a `filename` is provided. You
     can turn this off by setting `add_etags=False`.
 
+    If `conditional=True` and `filename` is provided, this method will try to
+    upgrade the response stream to support range requests.  This will allow
+    the request to be answered with partial content response.
+
     Please never pass filenames to this function from user sources;
     you should use :func:`send_from_directory` instead.
 
@@ -500,6 +505,7 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
         If a file was passed, this overrides its mtime.
     """
     mtime = None
+    fsize = None
     if isinstance(filename_or_fp, string_types):
         filename = filename_or_fp
         if not os.path.isabs(filename):
@@ -535,13 +541,15 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
         if file is not None:
             file.close()
         headers['X-Sendfile'] = filename
-        headers['Content-Length'] = os.path.getsize(filename)
+        fsize = os.path.getsize(filename)
+        headers['Content-Length'] = fsize
         data = None
     else:
         if file is None:
             file = open(filename, 'rb')
             mtime = os.path.getmtime(filename)
-            headers['Content-Length'] = os.path.getsize(filename)
+            fsize = os.path.getsize(filename)
+            headers['Content-Length'] = fsize
         data = wrap_file(request.environ, file)
 
     rv = current_app.response_class(data, mimetype=mimetype, headers=headers,
@@ -576,6 +584,16 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
                  'headers' % filename, stacklevel=2)
 
     if conditional:
+        if callable(getattr(Range, 'to_content_range_header', None)):
+            # Werkzeug supports Range Requests
+            # Remove this test when support for Werkzeug <0.12 is dropped
+            try:
+                rv = rv.make_conditional(request, accept_ranges=True,
+                                         complete_length=fsize)
+            except RequestedRangeNotSatisfiable:
+                file.close()
+                raise
+        else:
             rv = rv.make_conditional(request)
         # make sure we don't send x-sendfile for servers that
         # ignore the 304 status code for x-sendfile.

tests/test_helpers.py

@@ -14,8 +14,10 @@ import pytest
 import os
 import uuid
 import datetime
+
 import flask
 from logging import StreamHandler
+from werkzeug.datastructures import Range
 from werkzeug.exceptions import BadRequest, NotFound
 from werkzeug.http import parse_cache_control_header, parse_options_header
 from werkzeug.http import http_date
@@ -462,6 +464,69 @@ class TestSendfile(object):
             assert 'x-sendfile' not in rv.headers
             rv.close()
 
+    @pytest.mark.skipif(
+        not callable(getattr(Range, 'to_content_range_header', None)),
+        reason="not implement within werkzeug"
+    )
+    def test_send_file_range_request(self):
+        app = flask.Flask(__name__)
+
+        @app.route('/')
+        def index():
+            return flask.send_file('static/index.html', conditional=True)
+
+        c = app.test_client()
+
+        rv = c.get('/', headers={'Range': 'bytes=4-15'})
+        assert rv.status_code == 206
+        with app.open_resource('static/index.html') as f:
+            assert rv.data == f.read()[4:16]
+        rv.close()
+
+        rv = c.get('/', headers={'Range': 'bytes=4-'})
+        assert rv.status_code == 206
+        with app.open_resource('static/index.html') as f:
+            assert rv.data == f.read()[4:]
+        rv.close()
+
+        rv = c.get('/', headers={'Range': 'bytes=4-1000'})
+        assert rv.status_code == 206
+        with app.open_resource('static/index.html') as f:
+            assert rv.data == f.read()[4:]
+        rv.close()
+
+        rv = c.get('/', headers={'Range': 'bytes=-10'})
+        assert rv.status_code == 206
+        with app.open_resource('static/index.html') as f:
+            assert rv.data == f.read()[-10:]
+        rv.close()
+
+        rv = c.get('/', headers={'Range': 'bytes=1000-'})
+        assert rv.status_code == 416
+        rv.close()
+
+        rv = c.get('/', headers={'Range': 'bytes=-'})
+        assert rv.status_code == 416
+        rv.close()
+
+        rv = c.get('/', headers={'Range': 'somethingsomething'})
+        assert rv.status_code == 416
+        rv.close()
+
+        last_modified = datetime.datetime.fromtimestamp(os.path.getmtime(
+            os.path.join(app.root_path, 'static/index.html'))).replace(
+            microsecond=0)
+
+        rv = c.get('/', headers={'Range': 'bytes=4-15',
+                                 'If-Range': http_date(last_modified)})
+        assert rv.status_code == 206
+        rv.close()
+
+        rv = c.get('/', headers={'Range': 'bytes=4-15', 'If-Range': http_date(
+            datetime.datetime(1999, 1, 1))})
+        assert rv.status_code == 200
+        rv.close()
+
     def test_attachment(self):
         app = flask.Flask(__name__)
         with app.test_request_context():