img: add _Chunks.from_stream()

Steve Canny · Steve Canny · commit 279fb9f59317 · 2014-03-01T01:35:30.000-08:00
diff --git a/docx/image/png.py b/docx/image/png.py
@@ -215,4 +215,26 @@ def from_stream(cls, stream):
         """
         Return a |_Chunks| instance containing the PNG chunks in *stream*.
         """
+        chunk_parser = _ChunkParser.from_stream(stream)
+        chunk_lst = [chunk for chunk in chunk_parser.iter_chunks()]
+        return cls(chunk_lst)
+
+
+class _ChunkParser(object):
+    """
+    Extracts chunks from a PNG image stream
+    """
+    @classmethod
+    def from_stream(cls, stream):
+        """
+        Return a |_ChunkParser| instance that can extract the chunks from the
+        PNG image in *stream*.
+        """
+        raise NotImplementedError
+
+    def iter_chunks(self):
+        """
+        Generate a |_Chunk| subclass instance for each chunk in this parser's
+        PNG stream, in the order encountered in the 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 _Chunks, Png, _PngParser
+from docx.image.png import _Chunks, _ChunkParser, Png, _PngParser
 
 from ..unitutil import (
     initializer_mock, class_mock, instance_mock, method_mock, test_file
@@ -251,7 +251,7 @@ def stream_rdr_(self, request):
         return instance_mock(request, StreamReader)
 
 
-class DescribePngParser(object):
+class Describe_PngParser(object):
 
     def it_can_parse_the_headers_of_a_PNG_stream(self, parse_fixture):
         stream_, _Chunks_, _PngParser__init_, chunks_ = parse_fixture
@@ -283,3 +283,45 @@ def _PngParser__init_(self, request):
     @pytest.fixture
     def stream_(self, request):
         return instance_mock(request, BytesIO)
+
+
+class Describe_Chunks(object):
+
+    def it_can_construct_from_a_stream(self, from_stream_fixture):
+        stream_, _ChunkParser_, chunk_parser_, _Chunks__init_, chunk_lst = (
+            from_stream_fixture
+        )
+        chunks = _Chunks.from_stream(stream_)
+        _ChunkParser_.from_stream.assert_called_once_with(stream_)
+        chunk_parser_.iter_chunks.assert_called_once_with()
+        _Chunks__init_.assert_called_once_with(chunk_lst)
+        assert isinstance(chunks, _Chunks)
+
+    # fixtures -------------------------------------------------------
+
+    @pytest.fixture
+    def from_stream_fixture(
+            self, stream_, _ChunkParser_, chunk_parser_, _Chunks__init_):
+        chunk_lst = [1, 2]
+        chunk_parser_.iter_chunks.return_value = iter(chunk_lst)
+        return (
+            stream_, _ChunkParser_, chunk_parser_, _Chunks__init_, chunk_lst
+        )
+
+    @pytest.fixture
+    def _ChunkParser_(self, request, chunk_parser_):
+        _ChunkParser_ = class_mock(request, 'docx.image.png._ChunkParser')
+        _ChunkParser_.from_stream.return_value = chunk_parser_
+        return _ChunkParser_
+
+    @pytest.fixture
+    def chunk_parser_(self, request):
+        return instance_mock(request, _ChunkParser)
+
+    @pytest.fixture
+    def _Chunks__init_(self, request):
+        return initializer_mock(request, _Chunks)
+
+    @pytest.fixture
+    def stream_(self, request):
+        return instance_mock(request, BytesIO)
