improvements to s7util

prevent writing data to read only part of spec
add row_offset, to add more write protection
add key checking, ignoring empty rows
prevent writing data to read only part of spec
better check parameters when setting data

Author: spreeker

snap7/util.py

@@ -9,6 +9,7 @@
 
 from collections import OrderedDict
 import struct
+import logging
 
 
 def parse_specification(db_specification):
@@ -61,6 +62,8 @@ def set_int(_bytearray, byte_index, _int):
     """
     Set value in bytearray to int
     """
+    # make sure were dealing with an int
+    _int = int(_int)
     # int needs two be two bytes.
     byte0 = _int >> 8
     byte1 = _int - (byte0 << 8)
@@ -109,6 +112,7 @@ def set_string(_bytearray, byte_index, value):
     :params value: string data
     :params size: total possible string size
     """
+    assert isinstance(value, (str, unicode))
     # set len count
     _bytearray[byte_index + 1] = len(value)
     i = 0
@@ -137,6 +141,7 @@ def get_dword(_bytearray, byte_index):
 
 
 def set_dword(_bytearray, byte_index, dword):
+    dword = int(dword)
     _bytes = struct.unpack('4B', struct.pack('I', dword))
     for i, b in enumerate(_bytes):
         _bytearray[byte_index + i] = b
@@ -153,11 +158,14 @@ class DB(object):
     layout_offset = None   # at which byte in row specification should
                            # we start reading the data
     db_offset = None       # at which byte in db should we start reading?
-                           # first fields could be used for something else
+                           # first fields could be be status data.
+                           # and only the last part could be control data
+                           # now you can be sure you will never overwrite
+                           # critical parts of db
 
     def __init__(self, db_number, _bytearray,
                  specification, row_size, size, id_field=None,
-                 db_offset=0, layout_offset=0):
+                 db_offset=0, layout_offset=0, row_offset=0):
 
         self.db_number = db_number
         self.size = size
@@ -166,6 +174,8 @@ def __init__(self, db_number, _bytearray,
 
         self.db_offset = db_offset
         self.layout_offset = layout_offset
+        self.row_offset = row_offset
+
         self._bytearray = _bytearray
         self.specification = specification
         # loop over bytearray. make rowObjects
@@ -187,10 +197,15 @@ def make_rows(self):
                          specification,
                          row_size=row_size,
                          db_offset=db_offset,
-                         layout_offset=layout_offset)
+                         layout_offset=layout_offset,
+                         row_offset=self.row_offset)
 
             # store row object
             key = row[id_field] if id_field else i
+            if key and key in self.index:
+                msg = '%s not unique!' % key
+                logging.error(msg)
+                print msg
             self.index[key] = row
 
     def __getitem__(self, key, default=None):
@@ -216,11 +231,12 @@ class DB_Row(object):
     _specification = None  # row specification
 
     def __init__(self, _bytearray, _specification, row_size=0,
-                 db_offset=0, layout_offset=0):
+                 db_offset=0, layout_offset=0, row_offset=0):
 
         self.db_offset = db_offset          # start point of row data in db
         self.layout_offset = layout_offset  # start point of row data in layout
         self.row_size = row_size
+        self.row_offset = row_offset        # start of writable part of row
 
         assert(isinstance(_bytearray, (bytearray, DB)))
         self._bytearray = _bytearray
@@ -335,8 +351,15 @@ def write(self, client):
 
         db_nr = self._bytearray.db_number
         offset = self.db_offset
-	data = self.get_bytearray()[offset:offset+self.row_size]
-	client.db_write(db_nr, self.db_offset, data)
+        data = self.get_bytearray()[offset:offset+self.row_size]
+        db_offset = self.db_offset
+
+        # indicate start of write only area of row!
+        if self.row_offset:
+            data = data[self.row_offset:]
+            db_offset += self.row_offset
+
+        client.db_write(db_nr, db_offset, data)
 
     def read(self, client):
         """