img: add _PngParser.parse()

Steve Canny · Steve Canny · commit 4edbb14130f2 · 2014-03-01T01:35:30.000-08:00
diff --git a/docx/image/png.py b/docx/image/png.py
@@ -172,7 +172,8 @@ def parse(cls, stream):
         Return a |_PngParser| instance containing the header properties
         parsed from the PNG image in *stream*.
         """
-        raise NotImplementedError
+        chunks = _Chunks.from_stream(stream)
+        return cls(chunks)
 
     @property
     def px_width(self):
@@ -203,3 +204,15 @@ def vert_dpi(self):
         when not present in the file, as is often the case.
         """
         raise NotImplementedError
+
+
+class _Chunks(object):
+    """
+    Collection of the chunks parsed from a PNG image stream
+    """
+    @classmethod
+    def from_stream(cls, stream):
+        """
+        Return a |_Chunks| instance containing the PNG chunks in *stream*.
+        """
+        raise NotImplementedError
diff --git a/tests/image/test_png.py b/tests/image/test_png.py
@@ -12,7 +12,7 @@
 from docx.image.constants import MIME_TYPE, TAG
 from docx.image.exceptions import InvalidImageStreamError
 from docx.image.helpers import BIG_ENDIAN, StreamReader
-from docx.image.png import Png, _PngParser
+from docx.image.png import _Chunks, Png, _PngParser
 
 from ..unitutil import (
     initializer_mock, class_mock, instance_mock, method_mock, test_file
@@ -249,3 +249,37 @@ def stream_(self, request):
     @pytest.fixture
     def stream_rdr_(self, request):
         return instance_mock(request, StreamReader)
+
+
+class DescribePngParser(object):
+
+    def it_can_parse_the_headers_of_a_PNG_stream(self, parse_fixture):
+        stream_, _Chunks_, _PngParser__init_, chunks_ = parse_fixture
+        png_parser = _PngParser.parse(stream_)
+        _Chunks_.from_stream.assert_called_once_with(stream_)
+        _PngParser__init_.assert_called_once_with(chunks_)
+        assert isinstance(png_parser, _PngParser)
+
+    # fixtures -------------------------------------------------------
+
+    @pytest.fixture
+    def _Chunks_(self, request, chunks_):
+        _Chunks_ = class_mock(request, 'docx.image.png._Chunks')
+        _Chunks_.from_stream.return_value = chunks_
+        return _Chunks_
+
+    @pytest.fixture
+    def chunks_(self, request):
+        return instance_mock(request, _Chunks)
+
+    @pytest.fixture
+    def parse_fixture(self, stream_, _Chunks_, _PngParser__init_, chunks_):
+        return stream_, _Chunks_, _PngParser__init_, chunks_
+
+    @pytest.fixture
+    def _PngParser__init_(self, request):
+        return initializer_mock(request, _PngParser)
+
+    @pytest.fixture
+    def stream_(self, request):
+        return instance_mock(request, BytesIO)
