img: add _MarkerFactory()

Steve Canny · Steve Canny · commit 79efb67cec5b · 2014-02-27T12:08:35.000-08:00
diff --git a/docx/image/jpeg.py b/docx/image/jpeg.py
@@ -215,14 +215,27 @@ def _MarkerFactory(marker_code, stream, offset):
     Return |_Marker| or subclass instance appropriate for marker at *offset*
     in *stream* having *marker_code*.
     """
-    raise NotImplementedError
+    if marker_code == JPEG_MARKER_CODE.APP0:
+        return _App0Marker.from_stream(stream, marker_code, offset)
+    elif marker_code in JPEG_MARKER_CODE.SOF_MARKER_CODES:
+        return _SofMarker.from_stream(stream, marker_code, offset)
+    else:
+        return _Marker.from_stream(stream, marker_code, offset)
 
 
 class _Marker(object):
     """
     Base class for JFIF marker classes. Represents a marker and its segment
     occuring in a JPEG byte stream.
     """
+    @classmethod
+    def from_stream(cls, stream, marker_code, offset):
+        """
+        Return a generic |_Marker| instance for the marker at *offset* in
+        *stream* having *marker_code*.
+        """
+        raise NotImplementedError
+
     @property
     def marker_code(self):
         """
@@ -243,9 +256,23 @@ class _App0Marker(_Marker):
     """
     Represents a JFIF APP0 marker segment.
     """
+    @classmethod
+    def from_stream(cls, stream, marker_code, offset):
+        """
+        Return an |_App0Marker| instance for the APP0 marker at *offset* in
+        *stream*.
+        """
+        raise NotImplementedError
 
 
 class _SofMarker(_Marker):
     """
     Represents a JFIF start of frame (SOFx) marker segment.
     """
+    @classmethod
+    def from_stream(cls, stream, marker_code, offset):
+        """
+        Return an |_SofMarker| instance for the SOFn marker at *offset* in
+        stream.
+        """
+        raise NotImplementedError
diff --git a/tests/image/test_jpeg.py b/tests/image/test_jpeg.py
@@ -14,8 +14,8 @@
 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, _MarkerFinder, _MarkerParser,
-    _SofMarker
+    _App0Marker, Jfif, _JfifMarkers, _Marker, _MarkerFactory, _MarkerFinder,
+    _MarkerParser, _SofMarker
 )
 
 from ..unitutil import class_mock, initializer_mock, instance_mock
@@ -151,6 +151,57 @@ def stream_(self, request):
         return instance_mock(request, BytesIO)
 
 
+class Describe_MarkerFactory(object):
+
+    def it_constructs_the_appropriate_marker_object(self, call_fixture):
+        marker_code, stream_, offset_, marker_cls_ = call_fixture
+        marker = _MarkerFactory(marker_code, stream_, offset_)
+        marker_cls_.from_stream.assert_called_once_with(
+            stream_, marker_code, offset_
+        )
+        assert marker is marker_cls_.from_stream.return_value
+
+    # fixtures -------------------------------------------------------
+
+    @pytest.fixture(params=[
+        JPEG_MARKER_CODE.APP0,
+        JPEG_MARKER_CODE.SOF0,
+        JPEG_MARKER_CODE.SOF7,
+        JPEG_MARKER_CODE.SOS,
+    ])
+    def call_fixture(
+            self, request, stream_, offset_, _App0Marker_, _SofMarker_,
+            _Marker_):
+        marker_code = request.param
+        if marker_code == JPEG_MARKER_CODE.APP0:
+            marker_cls_ = _App0Marker_
+        elif marker_code in JPEG_MARKER_CODE.SOF_MARKER_CODES:
+            marker_cls_ = _SofMarker_
+        else:
+            marker_cls_ = _Marker_
+        return marker_code, stream_, offset_, marker_cls_
+
+    @pytest.fixture
+    def _App0Marker_(self, request):
+        return class_mock(request, 'docx.image.jpeg._App0Marker')
+
+    @pytest.fixture
+    def _Marker_(self, request):
+        return class_mock(request, 'docx.image.jpeg._Marker')
+
+    @pytest.fixture
+    def offset_(self, request):
+        return instance_mock(request, int)
+
+    @pytest.fixture
+    def _SofMarker_(self, request):
+        return class_mock(request, 'docx.image.jpeg._SofMarker')
+
+    @pytest.fixture
+    def stream_(self, request):
+        return instance_mock(request, BytesIO)
+
+
 class Describe_MarkerFinder(object):
 
     def it_can_construct_from_a_stream(self, from_stream_fixture):
