img: add _MarkerParser.from_stream()

Steve Canny · Steve Canny · commit 6456d8666ce3 · 2014-02-27T12:08:34.000-08:00
diff --git a/docx/image/jpeg.py b/docx/image/jpeg.py
@@ -8,6 +8,7 @@
 from __future__ import absolute_import, division, print_function
 
 from .constants import JPEG_MARKER_CODE
+from .helpers import BIG_ENDIAN, StreamReader
 from .image import Image
 
 
@@ -104,23 +105,41 @@ class _MarkerParser(object):
     Service class that knows how to parse a JFIF stream and iterate over its
     markers.
     """
+    def __init__(self, stream_reader):
+        super(_MarkerParser, self).__init__()
+        self._stream = stream_reader
+
     @classmethod
     def from_stream(cls, stream):
         """
         Return a |_MarkerParser| instance to parse JFIF markers from
         *stream*.
         """
-        raise NotImplementedError
+        stream_reader = StreamReader(stream, BIG_ENDIAN)
+        return cls(stream_reader)
 
     def iter_markers(self):
         """
-        Generate a (marker_code, segment_offset) 3-tuple for each marker in
-        the JPEG byte stream in *stream*, in the order they occur in the
-        stream.
+        Generate a (marker_code, segment_offset) 2-tuple for each marker in
+        the JPEG *stream*, in the order they occur in the stream.
         """
         raise NotImplementedError
 
 
+class _MarkerFinder(object):
+    """
+    Service class that knows how to find the next JFIF marker in a stream.
+    """
+
+
+def _MarkerFactory(marker_code, stream, offset):
+    """
+    Return |_Marker| or subclass instance appropriate for marker at *offset*
+    in *stream* having *marker_code*.
+    """
+    raise NotImplementedError
+
+
 class _Marker(object):
     """
     Base class for JFIF marker classes. Represents a marker and its segment
diff --git a/tests/image/test_jpeg.py b/tests/image/test_jpeg.py
@@ -10,6 +10,7 @@
 
 from docx.compat import BytesIO
 from docx.image.constants import JPEG_MARKER_CODE
+from docx.image.helpers import BIG_ENDIAN, StreamReader
 from docx.image.jpeg import (
     _App0Marker, Jfif, _JfifMarkers, _Marker, _MarkerParser, _SofMarker
 )
@@ -145,3 +146,42 @@ def sos_(self, request):
     @pytest.fixture
     def stream_(self, request):
         return instance_mock(request, BytesIO)
+
+
+class Describe_MarkerParser(object):
+
+    def it_can_construct_from_a_jfif_stream(self, from_stream_fixture):
+        stream_, StreamReader_, _MarkerParser__init_, stream_reader_ = (
+            from_stream_fixture
+        )
+        marker_parser = _MarkerParser.from_stream(stream_)
+        StreamReader_.assert_called_once_with(stream_, BIG_ENDIAN)
+        _MarkerParser__init_.assert_called_once_with(stream_reader_)
+        assert isinstance(marker_parser, _MarkerParser)
+
+    # fixtures -------------------------------------------------------
+
+    @pytest.fixture
+    def from_stream_fixture(
+            self, stream_, StreamReader_, _MarkerParser__init_,
+            stream_reader_):
+        return stream_, StreamReader_, _MarkerParser__init_, stream_reader_
+
+    @pytest.fixture
+    def _MarkerParser__init_(self, request):
+        return initializer_mock(request, _MarkerParser)
+
+    @pytest.fixture
+    def stream_(self, request):
+        return instance_mock(request, BytesIO)
+
+    @pytest.fixture
+    def StreamReader_(self, request, stream_reader_):
+        return class_mock(
+            request, 'docx.image.jpeg.StreamReader',
+            return_value=stream_reader_
+        )
+
+    @pytest.fixture
+    def stream_reader_(self, request):
+        return instance_mock(request, StreamReader)
