programmer/tinyprog: Use the same function to parse meta json content

Use the same _parse_json function to handle parsing of json content
stored in flash. This allows for the _resolve_pointers function to read
out json data in the same way as the _read_metadata function, such that
0x00 and 0xff bytes are ignored. This allows for the bootmeta to
reference a section of flash instead of the exact content length.

Author: nathanrossi

programmer/tinyprog/__init__.py

@@ -158,7 +158,7 @@ def __init__(self, prog):
 
     def _parse_json(self, data):
         try:
-            return json.loads(bytes(data).decode("utf-8"))
+            return json.loads(bytes(data).replace(b"\x00", b"").replace(b"\xff", b"").decode("utf-8"))
         except BaseException:
             return None
 
@@ -176,7 +176,7 @@ def _resolve_pointers(self, meta):
             if m:
                 data = self.prog.read(
                     int(m.group("addr"), 16), int(m.group("len")))
-                return json.loads(bytes(data).decode("utf-8"))
+                return self._parse_json(data)
             else:
                 return meta
 
@@ -187,14 +187,12 @@ def _read_metadata(self):
         meta_roots = (
             [
                 self._parse_json(
-                    self.prog.read_security_register_page(p).replace(
-                        b"\x00", b"").replace(b"\xff", b""))
+                    self.prog.read_security_register_page(p))
                 for p in [1, 2, 3]
             ] + [
                 self._parse_json(
                     self.prog.read(
-                        int(math.pow(2, p) - (4 * 1024)), (4 * 1024)).replace(
-                            b"\x00", b"").replace(b"\xff", b""))
+                        int(math.pow(2, p) - (4 * 1024)), (4 * 1024)))
                 for p in [17, 18, 19, 20, 21, 22, 23, 24]
             ])
         meta_roots = [root for root in meta_roots if root is not None]