Added append capability, #103

glymur/jp2k.py

@@ -432,6 +432,42 @@ class Jp2k(Jp2kBox):
         # Refresh the metadata.
         self.parse()
 
+    def append(self, box):
+        """Append a JP2 box to the file in-place.
+
+        Parameters
+        ----------
+        box : Jp2Box
+            Instance of a JP2 box.  Currently only XML boxes are allowed.
+        """
+        if self._codec_format == opj2.CODEC_J2K:
+            msg = "Only JP2 files can currently have boxes appended to them."
+            raise IOError(msg)
+
+        if box.box_id != 'xml ':
+            raise IOError("Only XML boxes can currently be appended.")
+
+        # Check the last box.  If the length field is zero, then rewrite
+        # the length field to reflect the true length of the box.
+        with open(self.filename, 'rb') as ifile:
+            offset = self.box[-1].offset
+            ifile.seek(offset)
+            read_buffer = ifile.read(4)
+            box_length, = struct.unpack('>I', read_buffer)
+            if box_length == 0:
+                # Reopen the file in write mode and rewrite the length field.
+                true_box_length = os.path.getsize(ifile.name) - offset
+                with open(self.filename, 'r+b') as ofile:
+                    ofile.seek(offset)
+                    write_buffer = struct.pack('>I', true_box_length)
+                    ofile.write(write_buffer)
+
+        # Can now safely append the box.
+        with open(self.filename, 'ab') as ofile:
+            box.write(ofile)
+
+        self.parse()
+
     def wrap(self, filename, boxes=None):
         """Write the codestream back out to file, wrapped in new JP2 jacket.
 
@@ -1133,6 +1169,7 @@ def _unpack_colorspace(colorspace, img_array, cparams):
 
     return colorspace
 
+
 def _populate_comptparms(img_array, cparams):
     """Instantiate and populate comptparms structure.
 
@@ -1171,6 +1208,7 @@ def _populate_comptparms(img_array, cparams):
 
     return comptparms
 
+
 def _populate_image_struct(cparams, image, imgdata):
     """Populates image struct needed for compression.
 
@@ -1203,6 +1241,7 @@ def _populate_image_struct(cparams, image, imgdata):
 
     return image
 
+
 def _validate_compression_params(img_array, cparams):
     """Check that the compression parameters are valid.
 
@@ -1313,4 +1352,3 @@ class LibraryNotFoundError(IOError):
     """
     def __init__(self, msg):
         IOError.__init__(self, msg)
-

glymur/test/test_jp2box.py

@@ -18,8 +18,11 @@ Test suite specifically targeting JP2 box layout.
 
 import doctest
 import os
+import shutil
+import struct
 import sys
 import tempfile
+import uuid
 import xml.etree.cElementTree as ET
 
 if sys.hexversion < 0x02070000:
@@ -502,6 +505,100 @@ class TestColourSpecificationBox(unittest.TestCase):
                                                  approximation=approx)
 
 
+@unittest.skipIf(glymur.lib.openjp2.OPENJP2 is None,
+                 "Missing openjp2 library.")
+class TestAppend(unittest.TestCase):
+    """Tests for append method."""
+
+    def setUp(self):
+        self.j2kfile = glymur.data.goodstuff()
+        self.jp2file = glymur.data.nemo()
+
+    def tearDown(self):
+        pass
+
+    def test_append_xml(self):
+        """Should be able to append an XML box."""
+        with tempfile.NamedTemporaryFile(suffix=".jp2") as tfile:
+            shutil.copyfile(self.jp2file, tfile.name)
+
+            jp2 = Jp2k(tfile.name)
+            the_xml = ET.fromstring('<?xml version="1.0"?><data>0</data>')
+            xmlbox = glymur.jp2box.XMLBox(xml=the_xml)
+            jp2.append(xmlbox)
+
+            # The sequence of box IDs should be the same as before, but with an
+            # xml box at the end.
+            box_ids = [box.box_id for box in jp2.box]
+            expected = ['jP  ', 'ftyp', 'jp2h', 'uuid', 'uuid', 'jp2c', 'xml ']
+            self.assertEqual(box_ids, expected)
+            self.assertEqual(ET.tostring(jp2.box[-1].xml.getroot()),
+                             b'<data>0</data>')
+
+    def test_only_jp2_allowed_to_append(self):
+        """Only JP2 files are allowed to be appended."""
+        with tempfile.NamedTemporaryFile(suffix=".j2k") as tfile:
+            shutil.copyfile(self.j2kfile, tfile.name)
+
+            jp2 = Jp2k(tfile.name)
+
+            # Make a UUID box.
+            uuid_instance = uuid.UUID('00000000-0000-0000-0000-000000000000')
+            data = b'0123456789'
+            uuidbox = glymur.jp2box.UUIDBox(uuid_instance, data)
+            with self.assertRaises(IOError):
+                jp2.append(uuidbox)
+
+    def test_length_field_is_zero(self):
+        """L=0 (length field in box header) is handled.
+
+        L=0 implies that the containing box is the last box.  If this is not
+        handled properly, the appended box is never seen.
+        """
+        baseline_jp2 = Jp2k(self.jp2file)
+        with tempfile.NamedTemporaryFile(suffix='.jp2') as tfile:
+            with open(self.jp2file, 'rb') as ifile:
+                # Everything up until the jp2c box.
+                offset = baseline_jp2.box[-1].offset
+                tfile.write(ifile.read(offset))
+
+                # Write the L, T fields of the jp2c box such that L == 0
+                write_buffer = struct.pack('>I4s', int(0), b'jp2c')
+                tfile.write(write_buffer)
+
+                # Write out the rest of the codestream.
+                ifile.seek(offset+8)
+                tfile.write(ifile.read())
+                tfile.flush()
+
+            jp2 = Jp2k(tfile.name)
+            the_xml = ET.fromstring('<?xml version="1.0"?><data>0</data>')
+            xmlbox = glymur.jp2box.XMLBox(xml=the_xml)
+            jp2.append(xmlbox)
+
+            # The sequence of box IDs should be the same as before, but with an
+            # xml box at the end.
+            box_ids = [box.box_id for box in jp2.box]
+            expected = ['jP  ', 'ftyp', 'jp2h', 'uuid', 'uuid', 'jp2c', 'xml ']
+            self.assertEqual(box_ids, expected)
+            self.assertEqual(ET.tostring(jp2.box[-1].xml.getroot()),
+                             b'<data>0</data>')
+
+    def test_only_xml_allowed_to_append(self):
+        """Only XML boxes are allowed to be appended."""
+        with tempfile.NamedTemporaryFile(suffix=".jp2") as tfile:
+            shutil.copyfile(self.jp2file, tfile.name)
+
+            jp2 = Jp2k(tfile.name)
+
+            # Make a UUID box.
+            uuid_instance = uuid.UUID('00000000-0000-0000-0000-000000000000')
+            data = b'0123456789'
+            uuidbox = glymur.jp2box.UUIDBox(uuid_instance, data)
+            with self.assertRaises(IOError):
+                jp2.append(uuidbox)
+
+
 @unittest.skipIf(glymur.lib.openjp2.OPENJP2 is None,
                  "Missing openjp2 library.")
 class TestWrap(unittest.TestCase):