img: add _TiffParser.parse()

Steve Canny · Steve Canny · commit 2b6497b04e04 · 2014-02-27T12:08:35.000-08:00
diff --git a/docx/image/tiff.py b/docx/image/tiff.py
@@ -29,13 +29,20 @@ class _TiffParser(object):
     Parses a TIFF image stream to extract the image properties found in its
     main image file directory (IFD)
     """
+    def __init__(self, ifd):
+        super(_TiffParser, self).__init__()
+        self._ifd = ifd
+
     @classmethod
     def parse(cls, stream):
         """
         Return an instance of |_TiffParser| containing the properties parsed
         from the TIFF image in *stream*.
         """
-        raise NotImplementedError
+        stream_rdr = cls._make_stream_reader(stream)
+        ifd0_offset = stream_rdr.read_long(4)
+        ifd_entries = _IfdEntries.from_stream(stream_rdr, ifd0_offset)
+        return cls(ifd_entries)
 
     @property
     def horz_dpi(self):
@@ -72,3 +79,26 @@ def vert_dpi(self):
         present.
         """
         raise NotImplementedError
+
+    @classmethod
+    def _make_stream_reader(cls, stream):
+        """
+        Return a |StreamReader| instance with wrapping *stream* and having
+        "endian-ness" determined by the 'MM' or 'II' indicator in the TIFF
+        stream header.
+        """
+        raise NotImplementedError
+
+
+class _IfdEntries(object):
+    """
+    Image File Directory for a TIFF image, having mapping (dict) semantics
+    allowing "tag" values to be retrieved by tag code.
+    """
+    @classmethod
+    def from_stream(cls, stream, offset):
+        """
+        Return a new |_IfdEntries| instance parsed from *stream* starting at
+        *offset*.
+        """
+        raise NotImplementedError
diff --git a/tests/image/test_tiff.py b/tests/image/test_tiff.py
@@ -9,9 +9,12 @@
 import pytest
 
 from docx.compat import BytesIO
-from docx.image.tiff import Tiff, _TiffParser
+from docx.image.helpers import StreamReader
+from docx.image.tiff import _IfdEntries, Tiff, _TiffParser
 
-from ..unitutil import class_mock, initializer_mock, instance_mock
+from ..unitutil import (
+    initializer_mock, class_mock, instance_mock, method_mock
+)
 
 
 class DescribeTiff(object):
@@ -68,3 +71,64 @@ def tiff_parser_(self, request):
     @pytest.fixture
     def stream_(self, request):
         return instance_mock(request, BytesIO)
+
+
+class Describe_TiffParser(object):
+
+    def it_can_parse_the_properties_from_a_tiff_stream(
+            self, from_stream_fixture):
+        (stream_, _make_stream_reader_, _IfdEntries_, ifd0_offset_,
+         stream_rdr_, _TiffParser__init_, ifd_entries_) = from_stream_fixture
+        tiff_parser = _TiffParser.parse(stream_)
+        _make_stream_reader_.assert_called_once_with(stream_)
+        _IfdEntries_.from_stream.assert_called_once_with(
+            stream_rdr_, ifd0_offset_
+        )
+        _TiffParser__init_.assert_called_once_with(ifd_entries_)
+        assert isinstance(tiff_parser, _TiffParser)
+
+    # fixtures -------------------------------------------------------
+
+    @pytest.fixture
+    def from_stream_fixture(
+            self, stream_, _make_stream_reader_, _IfdEntries_, ifd0_offset_,
+            stream_rdr_, _TiffParser__init_, ifd_entries_):
+        return (
+            stream_, _make_stream_reader_, _IfdEntries_, ifd0_offset_,
+            stream_rdr_, _TiffParser__init_, ifd_entries_
+        )
+
+    @pytest.fixture
+    def _IfdEntries_(self, request, ifd_entries_):
+        _IfdEntries_ = class_mock(request, 'docx.image.tiff._IfdEntries')
+        _IfdEntries_.from_stream.return_value = ifd_entries_
+        return _IfdEntries_
+
+    @pytest.fixture
+    def ifd_entries_(self, request):
+        return instance_mock(request, _IfdEntries)
+
+    @pytest.fixture
+    def ifd0_offset_(self, request):
+        return instance_mock(request, int)
+
+    @pytest.fixture
+    def _make_stream_reader_(self, request, stream_rdr_):
+        return method_mock(
+            request, _TiffParser, '_make_stream_reader',
+            return_value=stream_rdr_
+        )
+
+    @pytest.fixture
+    def stream_(self, request):
+        return instance_mock(request, BytesIO)
+
+    @pytest.fixture
+    def stream_rdr_(self, request, ifd0_offset_):
+        stream_rdr_ = instance_mock(request, StreamReader)
+        stream_rdr_.read_long.return_value = ifd0_offset_
+        return stream_rdr_
+
+    @pytest.fixture
+    def _TiffParser__init_(self, request):
+        return initializer_mock(request, _TiffParser)
