merge: support 'identical' on overlapped data

When merging multiple .hex files, in case of overlap we sometimes need to
just 'ensure' that values are identical.

The new 'identical' mode ensures this.

Note: the behavior for start_addr is currently a 'identical' (i.e. the
overlap configuration is checked only when values differ). So we might
want to change the behavior for data too:
- if data is identical: silently bail out
- add a 'stricter' mode that corresponds to the current behavior

docs/manual/part2-6.txt

@@ -16,6 +16,7 @@ It can take three options:
 * ``error`` - stop and raise an exception (default)
 * ``ignore`` - keep data from the original that contains data at overlapped address
 * ``replace`` - use data from the new object that contains data at overlapped address
+* ``identical`` - raise an exception if data is different
 
 You can merge only part of other hex file by using slice index notation::
 

docs/manual/part3-4.txt

@@ -22,6 +22,8 @@ This is a script to merge two different hex files. It is a frontend for the
                                             contains data at overlapped address
                                 * replace -- use data from last file that
                                              contains data at overlapped address
+                                * identical -- raise error if data differ
+
 
     Arguments:
         FILES       list of hex files for merging

intelhex/__init__.py

@@ -853,7 +853,9 @@ def merge(self, other, overlap='error'):
                         - ignore: ignore other data and keep current data
                                   in overlapping region;
                         - replace: replace data with other data
-                                  in overlapping region.
+                                  in overlapping region;
+                        - identical: raising OverlapError if data is not
+                                  identical.
 
         @raise  TypeError       if other is not instance of IntelHex
         @raise  ValueError      if other is the same object as self 
@@ -866,9 +868,9 @@ def merge(self, other, overlap='error'):
             raise TypeError('other should be IntelHex object')
         if other is self:
             raise ValueError("Can't merge itself")
-        if overlap not in ('error', 'ignore', 'replace'):
+        if overlap not in ('error', 'ignore', 'replace', 'identical'):
             raise ValueError("overlap argument should be either "
-                "'error', 'ignore' or 'replace'")
+                "'error', 'ignore', 'replace' or 'identical'")
         # merge data
         this_buf = self._buf
         other_buf = other._buf
@@ -879,6 +881,9 @@ def merge(self, other, overlap='error'):
                         'Data overlapped at address 0x%X' % i)
                 elif overlap == 'ignore':
                     continue
+                elif overlap == 'identical' and this_buf[i] != other_buf[i]:
+                    raise AddressOverlapError(
+                        'Data at address 0x%X is different: 0x%X vs. 0x%X' % (i, this_buf[i], other_buf[i]))
             this_buf[i] = other_buf[i]
         # merge start_addr
         if self.start_addr != other.start_addr:

intelhex/scripts/hexmerge.py

@@ -57,6 +57,8 @@
                                         contains data at overlapped address
                             * replace -- use data from last file that
                                          contains data at overlapped address
+                            * identical -- if overlapped data verifies that values
+                                       are identical
 
 Arguments:
     FILES       list of hex files for merging
@@ -122,7 +124,7 @@ def main(args=None):
             elif o == '--no-start-addr':
                 write_start_addr = False
             elif o == '--overlap':
-                if a in ('error', 'ignore', 'replace'):
+                if a in ('error', 'ignore', 'replace', 'identical'):
                     overlap = a
                 else:
                     raise getopt.GetoptError('Bad overlap value')

intelhex/test.py

@@ -1171,7 +1171,7 @@ def test_merge_wrong_args(self):
             ih1.merge, ih1)
         ih2 = IntelHex()
         self.assertRaisesMsg(ValueError, "overlap argument should be either "
-            "'error', 'ignore' or 'replace'",
+            "'error', 'ignore', 'replace' or 'identical'",
             ih1.merge, ih2, overlap='spam')
 
     def test_merge_overlap(self):
@@ -1191,6 +1191,17 @@ def test_merge_overlap(self):
         ih2 = IntelHex({0:2})
         ih1.merge(ih2, overlap='replace')
         self.assertEqual({0:2}, ih1.todict())
+        # identical: same value: ok
+        ih1 = IntelHex({0:1})
+        ih2 = IntelHex({0:1})
+        ih1.merge(ih2, overlap='identical')
+        self.assertEqual({0:1}, ih1.todict())
+        # identical: different value: raise error
+        ih1 = IntelHex({0:1})
+        ih2 = IntelHex({0:2})
+        self.assertRaisesMsg(intelhex.AddressOverlapError,
+            'Data at address 0x0 is different: 0x1 vs. 0x2',
+            ih1.merge, ih2, overlap='identical')
 
     def test_merge_start_addr(self):
         # this, None