Add (poor) support for conditionals

generate/templates/dissect.j2

@@ -1,4 +1,8 @@
+  {% if field.if %}
+  if values["{{ field.if_field }}"] {{field.if_operator}} "{{field.if_value}}" then
+  {% endif %}
   {% if field.primitive %}
+
   tree:{{ field.add_fn }}({{ field.variable }}, tvb({% if field.pos %}{{ field.pos }}{% else %}offset{% endif %}, {{ field.size }}))
   values["{{ field.id }}"] = tvb(offset, {{ field.size }}){{ field.value_fn }}
   offset = offset + {{ field.size }}
@@ -8,3 +12,6 @@
   {{ field.id }}_tree:set_len({{ field.id }}_size)
   offset = offset + {{ field.id }}_size
   {% endif %}
+  {% if field.if %}
+  end
+  {% endif %}

transpile/field_extractor.py

@@ -11,6 +11,7 @@ def build_field(item):
                 "id": item["id"],
                 "type": item["type"] if "type" in item else None,
                 "size": item["size"] if "size" in item else None,
+                "if": item["if"] if "if" in item else None,
                 "contents": item["contents"] if "contents" in item else None,
                 "path": []
             }
@@ -19,13 +20,15 @@ def build_field(item):
             return []
         return list(map(build_field, self.definition["seq"]))
 
+    # {'id': 'body', 'type': 'body', 'if': 'msg_type == [0x19, 0x0b]'}]
     def _collect_type_fields(self, type_name: str) -> []:
         def build_field(item):
             return {
                 "id": item["id"],
                 "type": item["type"] if "type" in item else None,
                 "size": item["size"] if "size" in item else None,
                 "contents": item["contents"] if "contents" in item else None,
+                "if": item["if"] if "if" in item else None,
                 "path": [type_name]
             }
         return list(map(build_field, self.definition["types"][type_name]["seq"]))
@@ -51,6 +54,7 @@ def _collect_instance_fields(self) -> []:
                 "contents": instance["contents"] if "contents" in instance else None,
                 "pos": instance["pos"] if "pos" in instance else None,
                 "value": instance["value"] if "value" in instance else None,
+                # "if": instance["if"] if "if" in instance else None,
                 "path": []
             })
         return fields

transpile/kaitai_wireshark_transpiler.py

@@ -1,5 +1,5 @@
 from utils.names import for_human
-from utils.types import is_primitive, calculate_size, get_wireshark_type, get_add_fn, get_value_fn
+from utils.types import is_primitive, get_conditional, calculate_size, get_wireshark_type, get_add_fn, get_value_fn
 from transpile.field_extractor import FieldExtractor
 
 class KaitaiToWiresharkTranspiler:
@@ -34,6 +34,11 @@ def _generate_fields(self):
         for field in fields:
             field["title"] = for_human(field["id"])
             field["primitive"] = is_primitive(field)
+            if field["if"]:
+                (field["if_field"], field["if_operator"], field["if_value"]) = get_conditional(field["if"])
+                field["if"] = True
+            else:
+                field["if"] = False
 
         self.result["fields"] = {}
         self.result["fields"]["primitive"] = list(filter(lambda item: item["primitive"], fields))

utils/types.py

@@ -34,14 +34,31 @@ def is_primitive(field):
     if "contents" in field and field["contents"] != None:
         return True
 
-    if field["type"] is None and field["value"] != None:
+    if field["type"] is None and "value" in field and field["value"] != None:
         return True
 
     return False
 
-def get_wireshark_type(value):
-
+class UnsupportedConditional(Exception):
+    pass
+
+def get_conditional(field):
+    tokens = field.strip().split(" ")
+    tokens = [tokens[0], tokens[1], " ".join(tokens[2:])]
+    if_field,if_operator,if_value = tokens
 
+    if if_operator == "!=":
+        if_operator = "~="
+
+    if '[' in if_value:
+        if_value = eval(if_value) # lol
+        if_value = bytes(if_value).hex().upper()
+    else:
+        raise UnsupportedConditional()
+
+    return if_field,if_operator,if_value
+
+def get_wireshark_type(value):
     if value in TYPES:
         return TYPES[value]
     elif value == None:
@@ -70,7 +87,7 @@ def calculate_size(field):
             return field["size"]
         else:
             return "values[\"" + field["size"] + "\"]"
-    
+
 
     if "contents" in field and field["contents"] != None:
         return len(field["contents"])