RF: refactor find_private_element

Neater and more readable version of find_private_element, extend tests.

nibabel/nicom/tests/test_utils.py

@@ -4,7 +4,7 @@
 
 from nibabel.optpkg import optional_package
 
-from ..utils import find_private_section
+from ..utils import find_private_section as fps
 from .test_dicomwrappers import DATA, DATA_PHILIPS
 
 pydicom, _, setup_module = optional_package('pydicom')
@@ -13,37 +13,53 @@
 def test_find_private_section_real():
     # Find section containing named private creator information
     # On real data first
-    assert find_private_section(DATA, 0x29, 'SIEMENS CSA HEADER') == 0x1000
-    assert find_private_section(DATA, 0x29, 'SIEMENS MEDCOM HEADER2') == 0x1100
-    assert find_private_section(DATA_PHILIPS, 0x29, 'SIEMENS CSA HEADER') == None
-    # Make fake datasets
+    assert fps(DATA, 0x29, 'SIEMENS CSA HEADER') == 0x1000
+    assert fps(DATA, 0x29, b'SIEMENS CSA HEADER') == 0x1000
+    assert fps(DATA, 0x29, re.compile('SIEMENS CSA HEADER')) == 0x1000
+    assert fps(DATA, 0x29, 'NOT A HEADER') is None
+    assert fps(DATA, 0x29, 'SIEMENS MEDCOM HEADER2') == 0x1100
+    assert fps(DATA_PHILIPS, 0x29, 'SIEMENS CSA HEADER') == None
+
+
+def test_find_private_section_fake():
+    # Make and test fake datasets
     ds = pydicom.dataset.Dataset({})
+    assert fps(ds, 0x11, 'some section') is None
     ds.add_new((0x11, 0x10), 'LO', b'some section')
-    assert find_private_section(ds, 0x11, 'some section') == 0x1000
-    ds.add_new((0x11, 0x11), 'LO', b'anther section')
+    assert fps(ds, 0x11, 'some section') == 0x1000
+    ds.add_new((0x11, 0x11), 'LO', b'another section')
     ds.add_new((0x11, 0x12), 'LO', b'third section')
-    assert find_private_section(ds, 0x11, 'third section') == 0x1200
-    # Wrong 'OB' is acceptable for VM (should be 'LO')
+    assert fps(ds, 0x11, 'third section') == 0x1200
+    # Technically incorrect 'OB' is acceptable for VM (should be 'LO')
     ds.add_new((0x11, 0x12), 'OB', b'third section')
-    assert find_private_section(ds, 0x11, 'third section') == 0x1200
+    assert fps(ds, 0x11, 'third section') == 0x1200
     # Anything else not acceptable
     ds.add_new((0x11, 0x12), 'PN', b'third section')
-    assert find_private_section(ds, 0x11, 'third section') is None
+    assert fps(ds, 0x11, 'third section') is None
     # The input (DICOM value) can be a string insteal of bytes
     ds.add_new((0x11, 0x12), 'LO', 'third section')
-    assert find_private_section(ds, 0x11, 'third section') == 0x1200
+    assert fps(ds, 0x11, 'third section') == 0x1200
     # Search can be bytes as well as string
     ds.add_new((0x11, 0x12), 'LO', b'third section')
-    assert find_private_section(ds, 0x11, b'third section') == 0x1200
+    assert fps(ds, 0x11, b'third section') == 0x1200
     # Search with string or bytes must be exact
-    assert find_private_section(ds, 0x11, b'third sectio') is None
-    assert find_private_section(ds, 0x11, 'hird sectio') is None
+    assert fps(ds, 0x11, b'third sectio') is None
+    assert fps(ds, 0x11, 'hird sectio') is None
     # The search can be a regexp
-    assert find_private_section(ds, 0x11, re.compile(r'third\Wsectio[nN]')) == 0x1200
+    assert fps(ds, 0x11, re.compile(r'third\Wsectio[nN]')) == 0x1200
     # No match -> None
-    assert find_private_section(ds, 0x11, re.compile(r'not third\Wsectio[nN]')) is None
+    assert fps(ds, 0x11, re.compile(r'not third\Wsectio[nN]')) is None
     # If there are gaps in the sequence before the one we want, that is OK
     ds.add_new((0x11, 0x13), 'LO', b'near section')
-    assert find_private_section(ds, 0x11, 'near section') == 0x1300
+    assert fps(ds, 0x11, 'near section') == 0x1300
     ds.add_new((0x11, 0x15), 'LO', b'far section')
-    assert find_private_section(ds, 0x11, 'far section') == 0x1500
+    assert fps(ds, 0x11, 'far section') == 0x1500
+    # More than one match - find the first.
+    assert fps(ds, 0x11, re.compile('(another|third) section')) == 0x1100
+    # The signalling element number must be <= 0xFF
+    ds = pydicom.dataset.Dataset({})
+    ds.add_new((0x11, 0xFF), 'LO', b'some section')
+    assert fps(ds, 0x11, 'some section') == 0xFF00
+    ds = pydicom.dataset.Dataset({})
+    ds.add_new((0x11, 0x100), 'LO', b'some section')
+    assert fps(ds, 0x11, 'some section') is None

nibabel/nicom/utils.py

@@ -27,26 +27,20 @@ def find_private_section(dcm_data, group_no, creator):
     Returns
     -------
     element_start : int
-        Element number at which named section starts
+        Element number at which named section starts.
     """
-    is_regex = hasattr(creator, 'search')
-    if not is_regex:  # assume string / bytes
+    if hasattr(creator, 'search'):
+        match_func = lambda x : creator.search(x)
+    else:  # assume string / bytes
         creator = asstr(creator)
-    for element in dcm_data:  # Assumed ordered by tag (groupno, elno)
-        grpno, elno = element.tag.group, element.tag.elem
-        if grpno > group_no:
-            break
-        if grpno != group_no:
-            continue
+        match_func = lambda x : x == creator
+    # Group elements assumed ordered by tag (groupno, elno)
+    for element in dcm_data.group_dataset(group_no):
+        elno = element.tag.elem
         if elno > 0xFF:
             break
         if element.VR not in ('LO', 'OB'):
             continue
-        name = asstr(element.value)
-        if is_regex:
-            if creator.search(name) is not None:
-                return elno * 0x100
-        else:  # string - needs exact match
-            if creator == name:
-                return elno * 0x100
+        if match_func(asstr(element.value)):
+            return elno * 0x100
     return None